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Nanglu K, Ortega-Hernández J. Post-Cambrian survival of the tubicolous scalidophoran Selkirkia. Biol Lett 2024; 20:20240042. [PMID: 38531414 DOI: 10.1098/rsbl.2024.0042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2024] Open
Abstract
Scalidophoran worms represent common infaunal components of early and middle Cambrian Burgess Shale-type fossil biotas. Early scalidophorans resemble extant priapulids based on overall morphology, but the genus Selkirkia represents the earliest record of tube dwelling for the group. Despite its ubiquitous presence in exceptional marine deposits, whether the exclusively Cambrian occurrence of Selkirkia reflects its entire evolutionary history or is affected by taphonomic biases remains unresolved. Here, we demonstrate the post-Cambrian survival of Selkirkia based on new material from the Lower Ordovician Fezouata Shale biota of Morocco. The discovery of Selkirkia in the Fezouata Shale extends the biostratigraphic range of the genus by 25 million years and its palaeobiogeographic occurrence to the high latitudes of Gondwana, strengthens the evolutionary links between Cambrian and Ordovician Burgess Shale-type biotas and increases scalidophoran diversity for the Fezouata Shale biota otherwise consisting exclusively of the palaeoscolecid Palaeoscolex? tenensis. The tube of Selkirkia underwent negligible external change for over 40 million years, indicating a high degree of morphological stasis during the Early Palaeozoic. A tubicolous mode of life is rare among extant priapulids and expressed only in Maccabeus, which forms a delicate tube from agglutinated plant debris, unlike the macroscopic secreted cuticular tube of Selkirkia.
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Affiliation(s)
- Karma Nanglu
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
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2
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Losso SR, Affatato P, Nanglu K, Ortega-Hernández J. Convergent evolution of ventral adaptations for enrolment in trilobites and extant euarthropods. Proc Biol Sci 2023; 290:20232212. [PMID: 38113938 PMCID: PMC10730288 DOI: 10.1098/rspb.2023.2212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 11/24/2023] [Indexed: 12/21/2023] Open
Abstract
The ability to enrol for protection is an effective defensive strategy that has convergently evolved multiple times in disparate animal groups ranging from euarthropods to mammals. Enrolment is a staple habit of trilobites, and their biomineralized dorsal exoskeleton offered a versatile substrate for the evolution of interlocking devices. However, it is unknown whether trilobites also featured ventral adaptations for enrolment. Here, we report ventral exoskeletal adaptations that facilitate enrolment in exceptionally preserved trilobites from the Middle Ordovician Walcott-Rust Quarry in New York State, USA. Walcott-Rust trilobites reveal the intricate three-dimensional organization of the non-biomineralized ventral anatomy preserved as calcite casts, including the spatial relationship between the articulated sternites (i.e. ventral exoskeletal plates) and the wedge-shaped protopodites. Enrolment in trilobites is achieved by ventrally dipping the anterior margin of the sternites during trunk flexure, facilitated by the presence of flexible membranes, and with the close coupling of the wedge-shaped protopodites. Comparisons with the ventral morphology of extant glomerid millipedes and terrestrial isopods reveal similar mechanisms used for enrolment. The wedge-shaped protopodites of trilobites closely resemble the gnathobasic coxa/protopodite of extant horseshoe crabs. We propose that the trilobites' wedge-shaped protopodite simultaneously facilitated tight enrolment and gnathobasic feeding with the trunk appendages.
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Affiliation(s)
- Sarah R. Losso
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Pauline Affatato
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Karma Nanglu
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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3
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Wolfe JM, Ballou L, Luque J, Watson-Zink VM, Ahyong ST, Barido-Sottani J, Chan TY, Chu KH, Crandall KA, Daniels SR, Felder DL, Mancke H, Martin JW, Ng PKL, Ortega-Hernández J, Palacios Theil E, Pentcheff ND, Robles R, Thoma BP, Tsang LM, Wetzer R, Windsor AM, Bracken-Grissom HD. Convergent adaptation of true crabs (Decapoda: Brachyura) to a gradient of terrestrial environments. Syst Biol 2023:syad066. [PMID: 37941464 DOI: 10.1093/sysbio/syad066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Indexed: 11/10/2023] Open
Abstract
For much of terrestrial biodiversity, the evolutionary pathways of adaptation from marine ancestors are poorly understood, and have usually been viewed as a binary trait. True crabs, the decapod crustacean infraorder Brachyura, comprise over 7,600 species representing a striking diversity of morphology and ecology, including repeated adaptation to non-marine habitats. Here, we reconstruct the evolutionary history of Brachyura using new and published sequences of 10 genes for 344 tips spanning 88 of 109 brachyuran families. Using 36 newly vetted fossil calibrations, we infer that brachyurans most likely diverged in the Triassic, with family-level splits in the late Cretaceous and early Paleogene. By contrast, the root age is underestimated with automated sampling of 328 fossil occurrences explicitly incorporated into the tree prior, suggesting such models are a poor fit under heterogeneous fossil preservation. We apply recently defined trait-by-environment associations to classify a gradient of transitions from marine to terrestrial lifestyles. We estimate that crabs left the marine environment at least seven and up to 17 times convergently, and returned to the sea from non-marine environments at least twice. Although the most highly terrestrial- and many freshwater-adapted crabs are concentrated in Thoracotremata, Bayesian threshold models of ancestral state reconstruction fail to identify shifts to higher terrestrial grades due to the degree of underlying change required. Lineages throughout our tree inhabit intertidal and marginal marine environments, corroborating the inference that the early stages of terrestrial adaptation have a lower threshold to evolve. Our framework and extensive new fossil and natural history datasets will enable future comparisons of non-marine adaptation at the morphological and molecular level. Crabs provide an important window into the early processes of adaptation to novel environments, and different degrees of evolutionary constraint that might help predict these pathways.
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Affiliation(s)
- Joanna M Wolfe
- Museum of Comparative Zoology and Department of Organismic & Evolutionary Biology, Harvard University, 26 Oxford St, Cambridge, MA 02138, USA
| | - Lauren Ballou
- Institute of Environment and Department of Biological Sciences, Florida International University, Biscayne Bay Campus, North Miami, FL 33181, USA
| | - Javier Luque
- Museum of Comparative Zoology and Department of Organismic & Evolutionary Biology, Harvard University, 26 Oxford St, Cambridge, MA 02138, USA
- Institute of Environment and Department of Biological Sciences, Florida International University, Biscayne Bay Campus, North Miami, FL 33181, USA
| | | | - Shane T Ahyong
- Australian Museum, 1 William St, Sydney, NSW 2010, Australia
- School of Biological, Earth & Environmental Sciences, University of New South Wales, Kensington, NSW 2052, Australia
| | - Joëlle Barido-Sottani
- Institut de Biologie de l'École Normale Supérieure (IBENS), ENS, CNRS, INSERM, Université PSL (Paris Sciences & Lettres), Paris, France
| | - Tin-Yam Chan
- Institute of Marine Biology and Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung 202301, Taiwan, ROC
| | - Ka Hou Chu
- Simon F. S. Li Marine Science Laboratory, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
| | - Keith A Crandall
- Computational Biology Institute, Department of Biostatistics and Bioinformatics, Milken Institute School of Public Health, George Washington University, Washington, DC 20052, USA
- Department of Invertebrate Zoology, US National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
| | - Savel R Daniels
- Department of Botany and Zoology, University of Stellenbosch, Private Bag X1, Matieland, 7602, South Africa
| | - Darryl L Felder
- Department of Invertebrate Zoology, US National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
- Department of Biology and Laboratory for Crustacean Research, University of Louisiana at Lafayette, Lafayette, LA 70504, USA
| | - Harrison Mancke
- Institute of Environment and Department of Biological Sciences, Florida International University, Biscayne Bay Campus, North Miami, FL 33181, USA
| | - Joel W Martin
- Research and Collections, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, USA
| | - Peter K L Ng
- Lee Kong Chian Natural History Museum, Faculty of Science, National University of Singapore, 2 Conservatory Drive, 117377 Singapore, Singapore
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic & Evolutionary Biology, Harvard University, 26 Oxford St, Cambridge, MA 02138, USA
| | - Emma Palacios Theil
- Department of Invertebrate Zoology and Hydrobiology, University of Łódź, ul. Banacha 12/16, 90237 Łódź, Poland
| | - N Dean Pentcheff
- Research and Collections, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, USA
| | - Rafael Robles
- Department of Biology and Laboratory for Crustacean Research, University of Louisiana at Lafayette, Lafayette, LA 70504, USA
- Facultad de Ciencias Químico Biológicas, Universidad Autónoma de Campeche, San Francisco de Campeche, Campeche, México
| | - Brent P Thoma
- Department of Biology, Jackson State University, P.O. Box 18540, Jackson, MS 39217, USA
| | - Ling Ming Tsang
- Simon F. S. Li Marine Science Laboratory, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Regina Wetzer
- Research and Collections, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, USA
| | - Amanda M Windsor
- Department of Invertebrate Zoology, US National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
- United States Food and Drug Administration, Office of Regulatory Science, 5001 Campus Dr. College Park, MD 20740, USA
| | - Heather D Bracken-Grissom
- Institute of Environment and Department of Biological Sciences, Florida International University, Biscayne Bay Campus, North Miami, FL 33181, USA
- Department of Invertebrate Zoology, US National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
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Nanglu K, Waskom ME, Richards JC, Ortega-Hernández J. Rhabdopleurid epibionts from the Ordovician Fezouata Shale biota and the longevity of cross-phylum interactions. Commun Biol 2023; 6:1002. [PMID: 37821659 PMCID: PMC10567727 DOI: 10.1038/s42003-023-05377-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 09/18/2023] [Indexed: 10/13/2023] Open
Abstract
Evidence of interspecific interactions in the fossil record is rare but offers valuable insights into ancient ecologies. Exceptional fossiliferous sites can preserve complex ecological interactions involving non-biomineralized organisms, but most of these examples are restricted to Cambrian Lagerstätten. Here we report an exceptionally preserved cross-phylum interspecific interaction from the Tremadocian-aged Lower Fezouata Shale Formation of Morocco, which consists of the phragmocone of an orthocone cephalopod that has been extensively populated post-mortem by tubicolous epibionts. Well-preserved transverse bands in a zig-zag pattern and crenulations along the margin of the unbranched tubes indicate that they correspond to pterobranch hemichordates, with a close morphological similarity to rhabdopleurids based on the bush-like growth of the dense tubarium. The discovery of rhabdopleurid epibionts in the Fezouata Shale highlights the paucity of benthic graptolites, which also includes the rooted dendroids Didymograptus and Dictyonema, relative to the substantially more diverse and abundant planktic forms known from this biota. We propose that the rarity of Paleozoic rhabdopleurid epibionts is likely a consequence of their ecological requirement for hard substrates for initial settlement and growth. The Fezouata rhabdopleurid also reveals a 480-million-year-old association of pterobranchs as epibionts of molluscs that persist to the present day.
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Affiliation(s)
- Karma Nanglu
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
| | - Madeleine E Waskom
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Jared C Richards
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
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5
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Del Mouro L, Becker-Kerber B, Janasi VA, de Araújo Carvalho M, Waichel BL, Lima EF, Rossetti LMM, Cruz V, Silva MS, Famelli N, Ortega-Hernández J. Organic walled microfossils in wet peperites from the early Cretaceous Paraná-Etendeka volcanism of Brazil. Sci Rep 2023; 13:15362. [PMID: 37717103 PMCID: PMC10505181 DOI: 10.1038/s41598-023-42483-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Accepted: 09/11/2023] [Indexed: 09/18/2023] Open
Abstract
Large igneous provinces (LIPs) are major magmatic events that have a significant impact on the global environment and the biosphere, for example as triggers of mass extinctions. LIPs provide an excellent sedimentological and geochemical record of short but intense periods of geological activity in the past, but their contribution towards understanding ancient life is much more restricted due to the destructive nature of their igneous origin. Here, we provide the first paleontological evidence for organic walled microfossils extracted from wet peperites from the Early Cretaceous Paraná-Etendeka intertrappean deposits of the Paraná basin in Brazil. Wet peperites are a volcaniclastic rock formed by the interaction of lava and subaqueous sediments.The Paraná-Etendeka was formed during the Valanginian (ca. 132 Ma) as a continental flood basalt in present day South America and Namibia, and released enormous amounts of carbon dioxide, sulfur dioxide, methane and hydrogen fluoride into the atmosphere. The organic walled microfossils recovered from the Paraná-Etendeka peperites include pollen grains, spores, acritarchs, and other remains of unidentifiable organic matter. In addition to the peperites, organic walled microfossils were also found in heterolithic sandstones and interpillow sandstones. Our findings represent the first insight into the biodiversity of the Paraná Basin during the Early Cretaceous during a period of intense magmatism, and the microfossil assemblages corroborate a regional paleoclimatic transition from arid to more humid conditions that were likely induced by the volcanic activity. We corroborate the potential of wet peperite rocks as a valuable source of paleobiological data and emphasize the importance of sampling volcaniclastic units that have been traditionally considered with lower fossiliferous potential due to their igneous origin.
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Affiliation(s)
- Lucas Del Mouro
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA, 02138, USA.
- Institute of Geosciences, University of São Paulo, São Paulo, Brazil.
| | | | - Valdecir A Janasi
- Institute of Geosciences, University of São Paulo, São Paulo, Brazil
| | | | - Breno L Waichel
- Espepetro, Federal University of Santa Catarina, Florianópolis, Brazil
| | - Evandro F Lima
- Federal University of Rio Grande Do Sul, Porto Alegre, Brazil
| | | | - Vinicius Cruz
- CODES - Centre for Ore Deposits and Earth Sciences, University of Tasmania, Hobart, 7001, Australia
| | | | - Natália Famelli
- Centro de Pesquisas e Desenvolvimento Leopoldo Américo Miguez de Mello - CENPES/PETROBRAS, Rio de Janeiro, Brazil
| | - Javier Ortega-Hernández
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA, 02138, USA
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6
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Nanglu K, Lerosey-Aubril R, Weaver JC, Ortega-Hernández J. A mid-Cambrian tunicate and the deep origin of the ascidiacean body plan. Nat Commun 2023; 14:3832. [PMID: 37414759 PMCID: PMC10325964 DOI: 10.1038/s41467-023-39012-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 05/25/2023] [Indexed: 07/08/2023] Open
Abstract
Tunicates are an evolutionarily significant subphylum of marine chordates, with their phylogenetic position as the sister-group to Vertebrata making them key to unraveling our own deep time origin. Tunicates greatly vary with regards to morphology, ecology, and life cycle, but little is known about the early evolution of the group, e.g. whether their last common ancestor lived freely in the water column or attached to the seafloor. Additionally, tunicates have a poor fossil record, which includes only one taxon with preserved soft-tissues. Here we describe Megasiphon thylakos nov., a 500-million-year-old tunicate from the Marjum Formation of Utah, which features a barrel-shaped body with two long siphons and prominent longitudinal muscles. The ascidiacean-like body of this new species suggests two alternative hypotheses for early tunicate evolution. The most likely scenario posits M. thylakos belongs to stem-group Tunicata, suggesting that a biphasic life cycle, with a planktonic larva and a sessile epibenthic adult, is ancestral for this entire subphylum. Alternatively, a position within the crown-group indicates that the divergence between appendicularians and all other tunicates occurred 50 million years earlier than currently estimated based on molecular clocks. Ultimately, M. thylakos demonstrates that fundamental components of the modern tunicate body plan were already established shortly after the Cambrian Explosion.
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Affiliation(s)
- Karma Nanglu
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
| | - Rudy Lerosey-Aubril
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
| | - James C Weaver
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA, 02138, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
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Zhang C, Liu Y, Ortega-Hernández J, Wolfe JM, Jin C, Mai H, Hou X, Guo J, Zhai D. Three-dimensional morphology of the biramous appendages in Isoxys from the early Cambrian of South China, and its implications for early euarthropod evolution. Proc Biol Sci 2023; 290:20230335. [PMID: 37072042 PMCID: PMC10113025 DOI: 10.1098/rspb.2023.0335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2023] Open
Abstract
Early euarthropod evolution involved a major transition from lobopodian-like taxa to organisms featuring a segmented, well-sclerotized trunk (arthrodization) and limbs (arthropodization). However, the precise origin of a completely arthrodized trunk and arthropodized ventral biramous appendages remain controversial, as well as the early onset of anterior-posterior limb differentiation in stem-group euarthropods. New fossil material and micro-computed tomography inform the detailed morphology of the arthropodized biramous appendages in the carapace-bearing euarthropod Isoxys curvirostratus from the early Cambrian Chengjiang biota. In addition to well-developed grasping frontal appendages, I. curvirostratus possesses two batches of morphologically and functionally distinct biramous limbs. The first batch consists of four pairs of short cephalic appendages with robust endites with a feeding function, whereas the second batch has more elongate trunk appendages for locomotion. Critically, our new material shows that the trunk of I. curvirostratus was not arthrodized. The results of our phylogenetic analyses recover isoxyids as some of the earliest branching sclerotized euarthropods, and strengthens the hypothesis that arthropodized biramous appendages evolved before full body arthrodization.
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Affiliation(s)
- Caixia Zhang
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming 650091, People's Republic of China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Waihuan South Road, Chenggong District, Kunming 650500, People's Republic of China
| | - Yu Liu
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming 650091, People's Republic of China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Waihuan South Road, Chenggong District, Kunming 650500, People's Republic of China
- Management Committee of the Chengjiang Fossil Site World Heritage, Chengjiang 652599, People's Republic of China
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Joanna M Wolfe
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Changfei Jin
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming 650091, People's Republic of China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Waihuan South Road, Chenggong District, Kunming 650500, People's Republic of China
| | - Huijuan Mai
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming 650091, People's Republic of China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Waihuan South Road, Chenggong District, Kunming 650500, People's Republic of China
| | - Xianguang Hou
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming 650091, People's Republic of China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Waihuan South Road, Chenggong District, Kunming 650500, People's Republic of China
| | - Jin Guo
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming 650091, People's Republic of China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Waihuan South Road, Chenggong District, Kunming 650500, People's Republic of China
- Management Committee of the Chengjiang Fossil Site World Heritage, Chengjiang 652599, People's Republic of China
| | - Dayou Zhai
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming 650091, People's Republic of China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Waihuan South Road, Chenggong District, Kunming 650500, People's Republic of China
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8
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Saleh F, Vaucher R, Vidal M, Hariri KE, Laibl L, Daley AC, Gutiérrez-Marco JC, Candela Y, Harper DAT, Ortega-Hernández J, Ma X, Rida A, Vizcaïno D, Lefebvre B. New fossil assemblages from the Early Ordovician Fezouata Biota. Sci Rep 2022; 12:20773. [PMID: 36513689 PMCID: PMC9747710 DOI: 10.1038/s41598-022-25000-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 11/23/2022] [Indexed: 12/15/2022] Open
Abstract
The Fezouata Biota (Morocco) is a unique Early Ordovician fossil assemblage. The discovery of this biota revolutionized our understanding of Earth's early animal diversifications-the Cambrian Explosion and the Ordovician Radiation-by suggesting an evolutionary continuum between both events. Herein, we describe Taichoute, a new fossil locality from the Fezouata Shale. This locality extends the temporal distribution of fossil preservation from this formation into the upper Floian, while also expanding the range of depositional environments to more distal parts of the shelf. In Taichoute, most animals were transported by density flows, unlike the in-situ preservation of animals recovered in previously investigated Fezouata sites. Taichoute is dominated by three-dimensionally preserved, and heavily sclerotized fragments of large euarthropods-possibly representing nektobenthic/nektic bivalved taxa and/or hurdiid radiodonts. Resolving whether this dominance reflects a legitimate aspect of the original ecosystem or a preservational bias requires an in-depth assessment of the environmental conditions at this site. Nevertheless, Taichoute provides novel preservational and palaeontological insights during a key evolutionary transition in the history of life on Earth.
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Affiliation(s)
- Farid Saleh
- grid.9851.50000 0001 2165 4204Institute of Earth Sciences (ISTE), University of Lausanne, Geopolis, 1015 Lausanne, Switzerland ,grid.440773.30000 0000 9342 2456Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, China ,grid.440773.30000 0000 9342 2456MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Institute of Palaeontology, Yunnan University, Kunming, China
| | - Romain Vaucher
- grid.9851.50000 0001 2165 4204Institute of Earth Sciences (ISTE), University of Lausanne, Geopolis, 1015 Lausanne, Switzerland
| | - Muriel Vidal
- Univ Brest, CNRS, Ifremer, Geo-Ocean, UMR 6538, Place Nicolas Copernic, F-29280 Plouzané, France
| | - Khadija El Hariri
- grid.411840.80000 0001 0664 9298Laboratoire de Géoressources, Géoenvironnement Et Génie Civil ‘L3G’, Faculté Des Sciences Et Techniques, Université Cadi-Ayyad, BP 549, 40000 Marrakesh, Morocco
| | - Lukáš Laibl
- grid.447909.70000 0001 2220 6788Czech Academy of Sciences, Institute of Geology, Rozvojová 269, 165 00 Prague 6, Czech Republic
| | - Allison C. Daley
- grid.9851.50000 0001 2165 4204Institute of Earth Sciences (ISTE), University of Lausanne, Geopolis, 1015 Lausanne, Switzerland
| | - Juan Carlos Gutiérrez-Marco
- grid.4711.30000 0001 2183 4846Instituto de Geociencias (CSIC, UCM), Departamento GEODESPAL, Facultad de Ciencias Geológicas, Spanish Research Council, José Antonio Novais 12, 28040 Madrid, Spain
| | - Yves Candela
- grid.422302.50000 0001 0943 6159Department of Natural Sciences, National Museums Scotland, Edinburgh, EH1 1JF UK
| | - David A. T. Harper
- grid.8250.f0000 0000 8700 0572Palaeoecosystems Group, Department of Earth Sciences, Durham University, Durham, DH1 3LE UK
| | - Javier Ortega-Hernández
- grid.38142.3c000000041936754XMuseum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138 USA
| | - Xiaoya Ma
- grid.440773.30000 0000 9342 2456Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, China ,grid.440773.30000 0000 9342 2456MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Institute of Palaeontology, Yunnan University, Kunming, China ,grid.8391.30000 0004 1936 8024Centre for Ecology and Conservation, University of Exeter, Penryn, UK
| | - Ariba Rida
- grid.411840.80000 0001 0664 9298Université Cadi Ayyad, École Normale Supérieure, Marrakech, Morocco
| | - Daniel Vizcaïno
- Independent, 7 rue Chardin, Maquens, 11090 Carcassonne, France
| | - Bertrand Lefebvre
- grid.7849.20000 0001 2150 7757Université Claude Bernard Lyon 1, École Normale Supérieure de Lyon, CNRS, UMR5276, LGL-TPE, Université de Lyon, Villeurbanne, France
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9
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Schmidt M, Hou X, Zhai D, Mai H, Belojević J, Chen X, Melzer RR, Ortega-Hernández J, Liu Y. Before trilobite legs: Pygmaclypeatus daziensis reconsidered and the ancestral appendicular organization of Cambrian artiopods. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210030. [PMID: 35125003 PMCID: PMC8819370 DOI: 10.1098/rstb.2021.0030] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The Cambrian Stage 3 Chengjiang biota in South China is one of the most influential Konservat-Lagerstätten worldwide thanks to the fossilization of diverse non-biomineralizing organisms through pyritization. Despite their contributions to understanding the evolution of early animals, several Chengjiang species remain poorly known owing to their scarcity and/or incomplete preservation. Here, we use micro-computed tomography to reveal in detail the ventral appendage organization of the enigmatic non-trilobite artiopod Pygmaclypeatus daziensis-one of the rarest euarthropods in Chengjiang-and explore its functional ecology and broader evolutionary significance. Pygmaclypeatus daziensis possesses a set of uniramous antennae and 14 pairs of post-antennal biramous appendages, the latter of which show an unexpectedly high degree of heteronomy based on the localized differentiation of the protopodite, endopodite and exopodite along with the antero-posterior body axis. The small body size (less than 2 cm), the presence of delicate spinose endites and well-developed exopodites with multiple paddle-shaped lamellae on the appendages of P. daziensis indicate a nekto-benthic mode of life and a scavenging/detritus feeding strategy. Pygmaclypeatus daziensis shows that appendage heteronomy is phylogenetically widespread within Artiopoda-the megadiverse clade that includes trilobites and their relatives with non-biomineralizing exoskeletons-and suggests that a single exopodite lobe with paddle-like lamellae is ancestral for this clade. This article is part of the theme issue 'The impact of Chinese palaeontology on evolutionary research'.
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Affiliation(s)
- Michel Schmidt
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China.,Bavarian State Collection of Zoology, Bavarian Natural History Collections, Münchhausenstrasse 21, 81247 München, Germany.,Department Biology II, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany
| | - Xianguang Hou
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China.,Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China
| | - Dayou Zhai
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China.,Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China
| | - Huijuan Mai
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China.,Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China
| | - Jelena Belojević
- Bavarian State Collection of Zoology, Bavarian Natural History Collections, Münchhausenstrasse 21, 81247 München, Germany
| | - Xiaohan Chen
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China.,Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China
| | - Roland R Melzer
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China.,Bavarian State Collection of Zoology, Bavarian Natural History Collections, Münchhausenstrasse 21, 81247 München, Germany.,Department Biology II, Ludwig-Maximilians-Universität München, 82152 Planegg-Martinsried, Germany.,GeoBio-Center, Ludwig-Maximilians-Universität Munich, Luisenstrasse 37, 80333 München, Germany
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, 791 Cambridge, MA 02138, USA
| | - Yu Liu
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China.,Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, North Cuihu Road 2, Kunming 650091, People's Republic of China
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10
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Abstract
Once considered 'weird wonders' of the Cambrian, the emblematic Burgess Shale animals Anomalocaris and Opabinia are now recognized as lower stem-group euarthropods and have provided crucial data for constraining the polarity of key morphological characters in the group. Anomalocaris and its relatives (radiodonts) had worldwide distribution and survived until at least the Devonian. However, despite intense study, Opabinia remains the only formally described opabiniid to date. Here we reinterpret a fossil from the Wheeler Formation of Utah as a new opabiniid, Utaurora comosa nov. gen. et sp. By visualizing the sample of phylogenetic topologies in treespace, our results fortify support for the position of U. comosa beyond the nodal support traditionally applied. Our phylogenetic evidence expands opabiniids to multiple Cambrian stages. Our results underscore the power of treespace visualization for resolving imperfectly preserved fossils and expanding the known diversity and spatio-temporal ranges within the euarthropod lower stem group.
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Affiliation(s)
- Stephen Pates
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.,Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Joanna M Wolfe
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Rudy Lerosey-Aubril
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Allison C Daley
- Institute of Earth Sciences, University of Lausanne, Géopolis, 1015 Lausanne, Switzerland
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
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11
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Ortega-Hernández J, Lerosey-Aubril R, Losso SR, Weaver JC. Neuroanatomy in a middle Cambrian mollisoniid and the ancestral nervous system organization of chelicerates. Nat Commun 2022; 13:410. [PMID: 35058474 PMCID: PMC8776822 DOI: 10.1038/s41467-022-28054-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 12/17/2021] [Indexed: 11/09/2022] Open
Abstract
Recent years have witnessed a steady increase in reports of fossilized nervous tissues among Cambrian total-group euarthropods, which allow reconstructing the early evolutionary history of these animals. Here, we describe the central nervous system of the stem-group chelicerate Mollisonia symmetrica from the mid-Cambrian Burgess Shale. The fossilized neurological anatomy of M. symmetrica includes optic nerves connected to a pair of lateral eyes, a putative condensed cephalic synganglion, and a metameric ventral nerve cord. Each trunk tergite is associated with a condensed ganglion bearing lateral segmental nerves, and linked by longitudinal connectives. The nervous system is preserved as reflective carbonaceous films underneath the phosphatized digestive tract. Our results suggest that M. symmetrica illustrates the ancestral organization of stem-group Chelicerata before the evolution of the derived neuroanatomical characters observed in Cambrian megacheirans and extant representatives. Our findings reveal a conflict between the phylogenetic signals provided by neuroanatomical and appendicular data, which we interpret as evidence of mosaic evolution in the chelicerate stem-lineage.
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Affiliation(s)
- Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
| | - Rudy Lerosey-Aubril
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Sarah R Losso
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
| | - James C Weaver
- Wyss Institute for Biologically Inspired Engineering, Harvard University, 60 Oxford Street, Cambridge, MA, 02138, USA
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12
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Jiao DG, Pates S, Lerosey-Aubril R, Ortega-Hernández J, Yang J, Lan T, Zhang XG. New multipodomerous appendages of stem-group euarthropods from the Cambrian (Stage 4) Guanshan Konservat-Lagerstätte. R Soc Open Sci 2021; 8:211134. [PMID: 34804574 PMCID: PMC8580442 DOI: 10.1098/rsos.211134] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 10/04/2021] [Indexed: 05/13/2023]
Abstract
Stem-group euarthropods are important for understanding the early evolutionary and ecological history of the most species-rich animal phylum on Earth. Of particular interest are fossil taxa that occupy a phylogenetic position immediately crownwards of radiodonts, for this part of the euarthropod tree is associated with the appearance of several morphological features that characterize extant members of the group. Here, we report two new euarthropods from the Cambrian Stage 4 Guanshan Biota of South China. The fuxianhuiid Alacaris? sp. is represented by isolated appendages composed of a gnathobasic protopodite and an endite-bearing endopod of at least 20 podomeres. This material represents the youngest occurrence of the family Chengjiangocarididae, and its first record outside the Chengjiang and Xiaoshiba biotas. We also describe Lihuacaris ferox gen. et sp. nov. based on well-preserved and robust isolated appendages. Lihuacaris ferox exhibits an atypical combination of characters including an enlarged rectangular base, 11 endite-bearing podomeres and a hypertrophied distal element bearing 8-10 curved spines. Alacaris? sp. appendages display adaptations for macrophagy. Lihuacaris ferox appendages resemble the frontal appendages of radiodonts, as well as the post-oral endopods of chengjiangocaridid fuxianhuids and other deuteropods with well-documented raptorial/predatory habits. Lihuacaris ferox contributes towards the record of endemic biodiversity in the Guanshan Biota.
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Affiliation(s)
- De-guang Jiao
- Yuxi Normal University, Kunming, 134 Phoenix Road, Yuxi, Yunnan 653100, People's Republic of China
- Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, People's Republic of China
| | - Stephen Pates
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
- Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
| | - Rudy Lerosey-Aubril
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Jie Yang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, People's Republic of China
| | - Tian Lan
- College of Resources and Environmental Engineering, Guizhou University, Guiyang 550003, People's Republic of China
| | - Xi-guang Zhang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, People's Republic of China
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13
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Abstract
Tardigrades are a diverse group of charismatic microscopic invertebrates that are best known for their ability to survive extreme conditions. Despite their long evolutionary history and global distribution in both aquatic and terrestrial environments, the tardigrade fossil record is exceedingly sparse. Molecular clocks estimate that tardigrades diverged from other panarthropod lineages before the Cambrian, but only two definitive crown-group representatives have been described to date, both from Cretaceous fossil deposits in North America. Here, we report a third fossil tardigrade from Miocene age Dominican amber. Paradoryphoribius chronocaribbeus gen. et sp. nov. is the first unambiguous fossil representative of the diverse superfamily Isohypsibioidea, as well as the first tardigrade fossil described from the Cenozoic. We propose that the patchy tardigrade fossil record can be explained by the preferential preservation of these microinvertebrates as amber inclusions, coupled with the scarcity of fossiliferous amber deposits before the Cretaceous.
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Affiliation(s)
- Marc A. Mapalo
- Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Ninon Robin
- Directorate Earth and History of Life, Royal Belgian Institute of Natural Sciences, Brussels, Belgium
| | - Brendon E. Boudinot
- Institut für Spezielle Zoologie und Evolutionsforschung, Friedrich-Schiller-Universität Jena, Jena, Germany
- University of California, Davis, Department of Entomology, One Shields Avenue, Davis 94596, CA, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Phillip Barden
- Department of Biological Sciences, New Jersey Institute of Technology, Newark, USA
- Division of Invertebrate Zoology, American Museum of Natural History, New York City, USA
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14
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Abstract
Developmental gene expression suggests a cryptic subdivision of the anterior brain in euarthropods. A new study illustrates delicate details of the nervous system from exceptionally preserved 500-million-year-old Chinese fossils, supporting the bipartite origin of the anterior brain among Cambrian representatives.
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Affiliation(s)
- Joanna M Wolfe
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
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15
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Parry LA, Lerosey-Aubril R, Weaver JC, Ortega-Hernández J. Cambrian comb jellies from Utah illuminate the early evolution of nervous and sensory systems in ctenophores. iScience 2021; 24:102943. [PMID: 34522849 PMCID: PMC8426560 DOI: 10.1016/j.isci.2021.102943] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 06/01/2021] [Accepted: 07/30/2021] [Indexed: 12/11/2022] Open
Abstract
Ctenophores are a group of predatory macroinvertebrates whose controversial phylogenetic position has prompted several competing hypotheses regarding the evolution of animal organ systems. Although ctenophores date back at least to the Cambrian, they have a poor fossil record due to their gelatinous bodies. Here, we describe two ctenophore species from the Cambrian of Utah, which illuminate the early evolution of nervous and sensory features in the phylum. Thalassostaphylos elegans has 16 comb rows, an oral skirt, and an apical organ with polar fields. Ctenorhabdotus campanelliformis has 24 comb rows, an oral skirt, an apical organ enclosed by a capsule and neurological tissues preserved as carbonaceous films. These are concentrated around the apical organ and ciliated furrows, which connect to a circumoral nerve ring via longitudinal axons. C. campanelliformis deviates from the neuroanatomy of living ctenophores and demonstrates a substantial complexity in the nervous system of Cambrian ctenophores. Two species of rare fossil ctenophores are described from the Cambrian of Utah Fossil ctenophores preserve remains of nervous tissue and sensory structures Neurological structures include an oral nerve ring and giant longitudinal axons Cambrian ctenophores had a more complex neuroanatomy than living species
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Affiliation(s)
- Luke A Parry
- Department of Earth Sciences, University of Oxford, 3 South Parks Road, Oxford, OX1 3AN, UK.,Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT 06511, USA
| | - Rudy Lerosey-Aubril
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - James C Weaver
- Wyss Institute for Biologically Inspired Engineering, Harvard University, 60 Oxford Street, Cambridge, MA 02138, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
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16
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Zhu X, Lerosey-Aubril R, Ortega-Hernández J. Furongian (Jiangshanian) occurrences of radiodonts in Poland and South China and the fossil record of the Hurdiidae. PeerJ 2021; 9:e11800. [PMID: 34386302 PMCID: PMC8312493 DOI: 10.7717/peerj.11800] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 06/26/2021] [Indexed: 11/22/2022] Open
Abstract
The Furongian period represents an important gap in the fossil record of most groups of non-biomineralizing organisms, owing to a scarcity of Konservat-Lagerstätten of that age. The most significant of these deposits, the Jiangshanian strata of the Sandu Formation near Guole Township (Guangxi, South China), have yielded a moderately abundant, but taxonomically diverse soft-bodied fossil assemblage, which provides rare insights into the evolution of marine life at that time. In this contribution, we report the first discovery of a radiodont fossil from the Guole Konservat-Lagerstätte. The specimen is an incomplete frontal appendage of a possibly new representative of the family Hurdiidae. It is tentatively interpreted as composed of seven podomeres, six of which bearing laminiform endites. The best preserved of these endites is especially long, and it bears short auxiliary spines that greatly vary in size. This is the second occurrence of hurdiids and more generally radiodonts in the Furongian, the first being the external mould of an oral cone from Jiangshanian strata of the Wiśniówka Sandstone Formation in Poland. Restudy of this Polish specimen confirms that it belongs to a hurdiid radiodont and best compares to Peytoia. The family Hurdiidae includes the oldest (basal Cambrian Epoch 2) and youngest (Early Ordovician, possibly Early Devonian) representatives of the Radiodonta and as such, has the longest stratigraphical range of the group. Yet, hurdiids only became prominent components of marine ecosystems during the middle Cambrian (Miaolingian), and their fossil record in younger strata remains limited.
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Affiliation(s)
- Xuejian Zhu
- Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing, China
| | - Rudy Lerosey-Aubril
- Harvard University, Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Cambridge, MA, USA
| | - Javier Ortega-Hernández
- Harvard University, Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Cambridge, MA, USA
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17
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Bicknell RDC, Holmes JD, Edgecombe GD, Losso SR, Ortega-Hernández J, Wroe S, Paterson JR. Biomechanical analyses of Cambrian euarthropod limbs reveal their effectiveness in mastication and durophagy. Proc Biol Sci 2021; 288:20202075. [PMID: 33499790 DOI: 10.1098/rspb.2020.2075] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Durophagy arose in the Cambrian and greatly influenced the diversification of biomineralized defensive structures throughout the Phanerozoic. Spinose gnathobases on protopodites of Cambrian euarthropod limbs are considered key innovations for shell-crushing, yet few studies have demonstrated their effectiveness with biomechanical models. Here we present finite-element analysis models of two Cambrian trilobites with prominent gnathobases-Redlichia rex and Olenoides serratus-and compare these to the protopodites of the Cambrian euarthropod Sidneyia inexpectans and the modern American horseshoe crab, Limulus polyphemus. Results show that L. polyphemus, S. inexpectans and R. rex have broadly similar microstrain patterns, reflecting effective durophagous abilities. Conversely, low microstrain values across the O. serratus protopodite suggest that the elongate gnathobasic spines transferred minimal strain, implying that this species was less well-adapted to masticate hard prey. These results confirm that Cambrian euarthropods with transversely elongate protopodites bearing short, robust gnathobasic spines were likely durophages. Comparatively, taxa with shorter protopodites armed with long spines, such as O. serratus, were more likely restricted to a soft food diet. The prevalence of Cambrian gnathobase-bearing euarthropods and their various feeding specializations may have accelerated the development of complex trophic relationships within early animal ecosystems, especially the 'arms race' between predators and biomineralized prey.
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Affiliation(s)
- Russell D C Bicknell
- Palaeoscience Research Centre, School of Environmental & Rural Science University of New England, Armidale, NSW 2351, Australia.,Function, Evolution and Anatomy Research Lab, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia
| | - James D Holmes
- School of Biological Sciences, University of Adelaide, North Terrace, Adelaide, SA 5005, Australia
| | - Gregory D Edgecombe
- Department of Earth Sciences, The Natural History Museum, London SW7 5BD, UK
| | - Sarah R Losso
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Stephen Wroe
- Palaeoscience Research Centre, School of Environmental & Rural Science University of New England, Armidale, NSW 2351, Australia.,Function, Evolution and Anatomy Research Lab, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia
| | - John R Paterson
- Palaeoscience Research Centre, School of Environmental & Rural Science University of New England, Armidale, NSW 2351, Australia
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18
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Pates S, Lerosey-Aubril R, Daley AC, Kier C, Bonino E, Ortega-Hernández J. The diverse radiodont fauna from the Marjum Formation of Utah, USA (Cambrian: Drumian). PeerJ 2021; 9:e10509. [PMID: 33552709 PMCID: PMC7821760 DOI: 10.7717/peerj.10509] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 11/16/2020] [Indexed: 11/20/2022] Open
Abstract
Radiodonts have long been known from Cambrian deposits preserving non-biomineralizing organisms. In Utah, the presence of these panarthropods in the Spence and Wheeler (House Range and Drum Mountains) biotas is now well-documented. Conversely, radiodont occurrences in the Marjum Formation have remained scarce. Despite the large amount of work undertaken on its diverse fauna, only one radiodont (Peytoia) has been reported from the Marjum Biota. In this contribution we quadruple the known radiodont diversity of the Marjum fauna, with the description of the youngest members of two genera, Caryosyntrips and Pahvantia, and that of a new taxon Buccaspinea cooperi gen. et sp. nov. This new taxon can be identified from its large oral cone bearing robust hooked teeth with one, two, or three cusps, and by the unique endite morphology and organisation of its frontal appendages. Appendages of at least 12 podomeres bear six recurved plate-like endites proximal to up to four spiniform distal endites. Pahvantia hastata specimens from the Marjum Formation are particularly large, but otherwise morphologically indistinguishable from the carapace elements of this species found in the Wheeler Formation. One of the two new Caryosyntrips specimens can be confidently assigned to C. camurus. The other bears the largest spines relative to appendage length recorded for this genus, and possesses endites of variable size and unequal spacing, making its taxonomic assignment uncertain. Caryosyntrips, Pahvantia, and Peytoia are all known from the underlying Wheeler Formation, whereas isolated appendages from the Spence Shale and the Wheeler Formation, previously assigned to Hurdia, are tentatively reidentified as Buccaspinea. Notably, none of these four genera occurs in the overlying Weeks Formation, providing supporting evidence of a faunal restructuring around the Drumian-Guzhangian boundary. The description of three additional nektonic taxa from the Marjum Formation further documents the higher relative proportion of free-swimming species in this biota compared to those of the Wheeler and Weeks Lagerstätten. This could be related to a moderate deepening of the basin and/or changing regional ocean circulation at this time.
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Affiliation(s)
- Stephen Pates
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Rudy Lerosey-Aubril
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Allison C. Daley
- Institut des sciences de la Terre (ISTE), Université de Lausanne, Lausanne, Vaud, Switzerland
| | - Carlo Kier
- Back to the Past Museum, Carretera Cancún, Quintana Roo, Mexico
| | - Enrico Bonino
- Back to the Past Museum, Carretera Cancún, Quintana Roo, Mexico
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
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19
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Hunter AW, Ortega-Hernández J. A new somasteroid from the Fezouata Lagerstätte in Morocco and the Early Ordovician origin of Asterozoa. Biol Lett 2021; 17:20200809. [PMID: 33465330 PMCID: PMC7876607 DOI: 10.1098/rsbl.2020.0809] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 12/21/2020] [Indexed: 11/12/2022] Open
Abstract
The somasteroids are Lower Palaeozoic star-shaped animals widely regarded as ancestors of Asterozoa, the group of echinoderms that includes brittle stars and starfish. However, the origin of asterozoans, the assembly of their distinctive body organization, and their relationships with other Cambrian and Ordovician echinoderms remain problematic owing to the difficulties of comparing the endoskeleton between disparate groups. Here, we describe the new somasteroid Cantabrigiaster fezouataensis, a primitive asterozoan from the Early Ordovician Fezouata Lagerstätte in Morocco. Cantabrigiaster shares with other somasteroids a unique endoskeletal arm organization and the presence of rod-like virgal ossicles that articulate with the ambulacrals, but differs from all other known asterozoans in the absence of adambulacral ossicles defining the arm margins, evoking parallels with non-asterozoan echinoderms. Developmentally informed Bayesian and parsimony phylogenetic analyses, which reflect the homology of the biserial ambulacral ossicles in Palaeozoic echinoderms according to the extraxial-axial theory, recover Cantabrigiaster as the earliest divergent stem-group asterozoan. Our results illuminate the ancestral morphology of Asterozoa, and clarify the affinities of problematic Ordovician Asterozoa. Bayesian inference and parsimony demonstrate that somasteroids represent a paraphyletic grade within stem- and crown-group Asterozoa, whereas stenuroids are paraphyletic within stem-group Ophiuroidea. Our results also offer potential insights on the evolutionary relationships between asterozoans, crinoids and potential Cambrian stem-group representatives.
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Affiliation(s)
- Aaron W. Hunter
- Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
- School of Earth Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
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Liu Y, Ortega-Hernández J, Zhai D, Hou X. A Reduced Labrum in a Cambrian Great-Appendage Euarthropod. Curr Biol 2020; 30:3057-3061.e2. [DOI: 10.1016/j.cub.2020.05.085] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 04/12/2020] [Accepted: 05/27/2020] [Indexed: 11/29/2022]
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Liu Y, Ortega-Hernández J, Chen H, Mai H, Zhai D, Hou X. Computed tomography sheds new light on the affinities of the enigmatic euarthropod Jianshania furcatus from the early Cambrian Chengjiang biota. BMC Evol Biol 2020; 20:62. [PMID: 32487135 PMCID: PMC7268425 DOI: 10.1186/s12862-020-01625-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 05/11/2020] [Indexed: 11/16/2022] Open
Abstract
Background The Chengjiang biota is one of the most species-rich Cambrian Konservat-Lagerstätten, and preserves a community dominated by non-biomineralized euarthropods. However, several Chengjiang euarthropods have an unfamiliar morphology, are extremely rare, or incompletely preserved. Results We employed micro-computed tomography to restudy the enigmatic euarthropod Jianshania furcatus. We reveal new morphological details, and demonstrate that the specimens assigned to this species represent two different taxa. The holotype of J. furcatus features a head shield with paired anterolateral notches, stalked lateral eyes, and an articulated tailspine with a bifurcate termination. The other specimen is formally redescribed as Xiaocaris luoi gen. et sp. nov., and is characterized by stalked eyes connected to an anterior sclerite, a subtrapezoidal head shield covering three small segments with reduced tergites, a trunk with 15 overlapping tergites with a well-developed dorsal keel, and paired tail flukes. Conclusions The presence of antennae, biramous appendages with endopods composed of 15 articles, and multiple appendage pairs associated with the trunk tergites identify X. luoi nov. as a representative of Fuxianhuiida, an early branching group of stem-group euarthropods endemic to the early Cambrian of Southwest China. X. luoi nov. represents the fifth fuxianhuiid species described from the Chengjiang biota, and its functional morphology illuminates the ecological diversity of this important clade for understanding the early evolutionary history of euarthropods.
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Affiliation(s)
- Yu Liu
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, 650500, China. .,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650500, China.
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
| | - Hong Chen
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, 650500, China.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650500, China
| | - Huijuan Mai
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, 650500, China.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650500, China
| | - Dayou Zhai
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, 650500, China.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650500, China
| | - Xianguang Hou
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming, 650500, China.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650500, China
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Lerosey-Aubril R, Skabelund J, Ortega-Hernández J. Revision of the mollisoniid chelicerate(?) Thelxiope, with a new species from the middle Cambrian Wheeler Formation of Utah. PeerJ 2020; 8:e8879. [PMID: 32296605 PMCID: PMC7151752 DOI: 10.7717/peerj.8879] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 03/10/2020] [Indexed: 11/29/2022] Open
Abstract
The recent re-interpretation of the Lower Palaeozoic euarthropod group Mollisonia as belonging to Chelicerata has triggered a renewed interest for the poorly known family Mollisoniidae. In this contribution, we revise the anatomy, taxonomic diversity, and systematics of Thelxiope, the sister-taxon of Mollisonia. This mollisoniid genus comprises four species, and is characterized by the presence of one cephalic, seven thoracic (one per tergite), and three pygidial long sagittal spines. The type species, T. palaeothalassia Simonetta & Delle Cave, is a rare taxon in the Wuliuan Burgess Shale Formation of Canada, which can be recognized by the hypertrophy of a single of its sagittal spines, the posteriomost one. T. spinosa (Conway Morris & Robison)–a species originally assigned to a distinct genus ‘Ecnomocaris’ herein synonymised with Thelxiope–is known from a single specimen found in the Drumian Wheeler Formation of the House Range of Utah. It differs from the type-species in the hypertrophy of both the anteriormost (cephalic) and the posteriormost (third pygidial) sagittal spines. The same Wheeler strata have also yielded a single specimen of a new taxon, T. holmani sp. nov., which lacks hypertrophied sagittal spines and features blunt thoracic tergopleural tips. A putative fourth species, referred to Thelxiope sp. nov. A, extends the stratigraphical range of Thelxiope to the Lower Ordovician (Tremadocian), and its palaeographic range to West Gondwana. Currently under study, this relatively common component of the lower Fezouata Shale fauna is only briefly discussed. Features characterizing the genus Thelxiope and its components almost exclusively pertain to the sagittal spines, for the scarcity and inconsistent preservation of the Cambrian materials as-yet available preclude a confident assessment of the variability of other morphological features. The pygidium in Thelxiope and Mollisonia is not composed of four, but three tergites essentially similar to thoracic ones, except for the lack of articulations.
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Affiliation(s)
- Rudy Lerosey-Aubril
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA
| | | | - Javier Ortega-Hernández
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA
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Mángano MG, Ortega-Hernández J, Piñuela L, Buatois LA, Rodríguez-Tovar FJ, García-Ramos JC. Trace fossil evidence for infaunal moulting in a Middle Devonian non-trilobite euarthropod. Sci Rep 2020; 10:5316. [PMID: 32210261 PMCID: PMC7093436 DOI: 10.1038/s41598-020-62019-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 03/04/2020] [Indexed: 11/17/2022] Open
Abstract
Trace fossils represent the primary source of information on the evolution of animal behaviour through deep time, and provide exceptional insights into complex life strategies that would be otherwise impossible to infer from the study of body parts alone. Here, we describe unusual trace fossils found in marginal-marine, storm- and river-flood deposits from the Middle Devonian Naranco Formation of Asturias (northern Spain) that constitute the first evidence for infaunal moulting in a non-trilobite euarthropod. The trace fossils are preserved in convex hyporelief, and include two main morphological variants that reflect a behavioural continuum. Morphotype 1 consists of a structure that superficially resembles a Rusophycus with an oval outline that possesses a distinctly three lobed axis with an elevated central ridge and regularly spaced transverse furrows that convey the appearance of discrete body segments. The anterior part is the most irregular region of the structure, and it is not always recorded. Morphotype 2 displays more elongated, tubular morphology. Careful observation, however, reveals that it comprises up to three successive morphotype 1 specimens organised in a linear fashion and partially truncating each other. Trilobate morphology and effaced transverse furrows are locally evident, but the predominant morphological feature is the continuous, elevated ridge. The detailed morphology of morphotype 1 and well-preserved, discrete segments of morphotype 2 closely resemble the dorsal exoskeleton of the enigmatic late Carboniferous euarthropod Camptophyllia, suggesting the possible affinities of the producer. Comparisons with patterns of Devonian phacopid trilobite exuviation suggest that the Naranco Formation trace fossils may have been produced by the infaunal activities of an euarthropod that anchored its dorsal exoskeleton in the firm sediment during the body inversion moult procedure. Our findings expand the phylogenetic and environmental occurrence of infaunal moulting in Palaeozoic euarthropods, and suggest a defensive strategy against predation, previously only known from trilobites preserved in open-marine deposits.
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Affiliation(s)
- M Gabriela Mángano
- Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, SK, S7N 5E2, Canada.
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Laura Piñuela
- Museo del Jurásico de Asturias (MUJA), 33328, Colunga, Asturias, Spain
| | - Luis A Buatois
- Department of Geological Sciences, University of Saskatchewan, 114 Science Place, Saskatoon, SK, S7N 5E2, Canada
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Abstract
Recent investigations on neurological tissues preserved in Cambrian fossils have clarified the phylogenetic affinities and head segmentation in pivotal members of stem-group Euarthropoda. However, palaeoneuroanatomical features are often incomplete or described from single exceptional specimens, raising concerns about the morphological interpretation of fossilized neurological structures and their significance for early euarthropod evolution. Here, we describe the central nervous system (CNS) of the short great-appendage euarthropod Alalcomenaeus based on material from two Cambrian Burgess Shale-type deposits of the American Great Basin, the Pioche Formation (Stage 4) and the Marjum Formation (Drumian). The specimens reveal complementary ventral and lateral views of the CNS, preserved as a dark carbonaceous compression throughout the body. The head features a dorsal brain connected to four stalked ventral eyes, and four pairs of segmental nerves. The first to seventh trunk tergites overlie a ventral nerve cord with seven ganglia, each associated with paired sets of segmental nerve bundles. Posteriorly, the nerve cord features elongate thread-like connectives. The Great Basin fossils strengthen the original description—and broader evolutionary implications—of the CNS in Alalcomenaeus from the early Cambrian (Stage 3) Chengjiang deposit of South China. The spatio-temporal recurrence of fossilized neural tissues in Cambrian Konservat-Lagerstätten across North America (Pioche, Burgess Shale, Marjum) and South China (Chengjiang, Xiaoshiba) indicates that their preservation is consistent with the mechanism of Burgess Shale-type fossilization, without the need to invoke alternative taphonomic pathways or the presence of microbial biofilms.
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Affiliation(s)
- Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Rudy Lerosey-Aubril
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
| | - Stephen Pates
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
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Lerosey-Aubril R, Ortega-Hernández J. Appendicular anatomy of the artiopod Emeraldella brutoni from the middle Cambrian (Drumian) of western Utah. PeerJ 2019; 7:e7945. [PMID: 31687274 PMCID: PMC6825744 DOI: 10.7717/peerj.7945] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 09/24/2019] [Indexed: 11/25/2022] Open
Abstract
The non-biomineralized artiopod Emeraldella brutoni Stein, Church & Robison, from the middle Cambrian (Drumian) Wheeler Formation in Utah represents the only confirmed occurrence of the genus Emeraldella outside of the stratigraphically older (Wuliuan) Burgess Shale Konservat-Lagerstätte in British Columbia. The hitherto known sole specimen of this species is preserved in dorsal view and lacks critical information on the ventral appendages. Here, we redescribe E. brutoni based on a new completely articulated specimen that illustrates the appendage organization in exceptional detail. The main body consists of a cephalic region covered by a semicircular head shield, a trunk including 10 tergites with expanded pleurae plus a cylindrical terminal segment, and a long articulated tailspine. The head carries a pair of elongate and flexible antennae, a pair of lateral eyes, and three pairs of post-antennal appendages. We report the presence of eyes in Emeraldella for the first time. The first post-antennal limb solely consists of an endopod with well-developed paired spiniform endites. The remaining cephalic appendages and those associated with all but the last trunk segments possess exopods terminating in paddle-shaped, distal lobes fringed with robust setae. The cylindrical terminal segment bears a pair of posteriorly oriented caudal flaps reminiscent of trunk exopods, and a styliform, possibly uniarticulate tailspine longer than the main body. The new data on E. brutoni suggests an exopodal origin for the paired caudal structures in Vicissicaudata, and improve our understanding of the fundamental organization of this major clade within Artiopoda.
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Affiliation(s)
- Rudy Lerosey-Aubril
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
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26
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Abstract
Ortega-Hernández et al. introduce fuxianhuiids, Cambrian arthropods that are important for our understaindg how the largest animal phylum evolved.
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Affiliation(s)
- Javier Ortega-Hernández
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK; Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
| | - Jie Yang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China
| | - Xi-Guang Zhang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China.
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27
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Chen X, Ortega-Hernández J, Wolfe JM, Zhai D, Hou X, Chen A, Mai H, Liu Y. The appendicular morphology of Sinoburius lunaris and the evolution of the artiopodan clade Xandarellida (Euarthropoda, early Cambrian) from South China. BMC Evol Biol 2019; 19:165. [PMID: 31387545 PMCID: PMC6685191 DOI: 10.1186/s12862-019-1491-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 07/29/2019] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Artiopodan euarthropods represent common and abundant faunal components in sites with exceptional preservation during the Cambrian. The Chengjiang biota in South China contains numerous taxa that are exclusively known from this deposit, and thus offer a unique perspective on euarthropod diversity during the early Cambrian. One such endemic taxon is the non-trilobite artiopodan Sinoburius lunaris, which has been known for approximately three decades, but few details of its anatomy are well understood due to its rarity within the Chengjiang, as well as technical limitations for the study of these fossils. Furthermore, the available material does not provide clear information on the ventral organization of this animal, obscuring our understanding of phylogenetically significant details such as the appendages. RESULTS We employed X-ray computed tomography to study the non-biomineralized morphology of Sinoburius lunaris. Due to the replacement of the delicate anatomy with pyrite typical of Chengjiang fossils, computed tomography reveals substantial details of the ventral anatomy of Sinoburius lunaris, and allow us to observe in detail the three-dimensionally preserved appendicular organization of this taxon for the first time. The dorsal exoskeleton consists of a crescent-shaped head shield with well-developed genal spines, a thorax with seven freely articulating tergites, and a fused pygidium with lateral and median spines. The head bears a pair of ventral stalked eyes that are accommodated by dorsal exoskeletal bulges, and an oval elongate ventral hypostome. The appendicular organization of the head is unique among Artiopoda. The deutocerebral antennae are reduced, consisting of only five podomeres, and bear an antennal scale on the second podomere that most likely represents an exite rather than a true ramus. The head includes four post-antennal biramous limb pairs. The first two biramous appendages are differentiated from the rest. The first appendage pair consists of a greatly reduced endopod coupled with a greatly elongated exopod with a potentially sensorial function. The second appendage pair carries a more conventionally sized endopod, but also has an enlarged exopod. The remaining biramous appendages are homonomous in their construction, but decrease in size towards the posterior end of the body. They consist of a basipodite with ridge-like crescentic endites, an endopod with seven podomeres and a terminal claw, and a lamellae-bearing exopod with a slender shaft. Contrary to previous reports, we confirm the presence of segmental mismatch in Sinoburius lunaris, expressed as diplotergites in the thorax. Maximum parsimony and Bayesian phylogenetic analyses support the monophyly of Xandarellida within Artiopoda, and illuminate the internal relationships within this enigmatic clade. Our results allow us to propose a transformation series explaining the origin of archetypical xandarellid characters, such as the evolution of eye slits in Xandarella spectaculum and Phytophilaspis pergamena as derivates from the anterolateral notches in the head shield observed in Cindarella eucalla and Luohuilinella species. In this context, Sinoburius lunaris is found to feature several derived characters within the group, such as the secondary loss of eye slits and a high degree of appendicular tagmosis. Contrary to previous findings, our analyses strongly support close affinities between Sinoburius lunaris, Xandarella spectaculum and Phytophilaspis pergamena, although the precise relationships between these taxa are sensitive to different methodologies. CONCLUSIONS The revised morphology of Sinoburius lunaris, made possible through the use of computed tomography to resolve details of its three-dimensionally preserved appendicular anatomy, contributes towards an improved understanding of the morphology of this taxon and the evolution of Xandarellida more broadly. Our results indicate that Sinoburius lunaris possesses an unprecedented degree of appendicular tagmosis otherwise unknown within Artiopoda, with the implication that this iconic group of Palaeozoic euarthropods likely had a more complex ecology and functional morphology than previously considered. The application of computer tomographic techniques to the study of Chengjiang euarthropods holds exceptional promise for understanding the morphological diversity of these organisms, and also better reconstructing their phylogenetic relationships and evolutionary history.
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Affiliation(s)
- Xiaohan Chen
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, North Cuihu Road 2, Kunming, 650091, China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650091, China
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
| | - Joanna M Wolfe
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Dayou Zhai
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, North Cuihu Road 2, Kunming, 650091, China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650091, China
| | - Xianguang Hou
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, North Cuihu Road 2, Kunming, 650091, China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650091, China
| | - Ailin Chen
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650091, China
- Research Center of Paleobiology, Yuxi Normal University, Yuxi, 653100, Yunnan, China
| | - Huijuan Mai
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, North Cuihu Road 2, Kunming, 650091, China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650091, China
| | - Yu Liu
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, North Cuihu Road 2, Kunming, 650091, China.
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, 650091, China.
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Abstract
Abstract
Vision allows animals to interact with their environment. Aquatic chelicerates dominate the early record of lateral compound eyes among non-biomineralizing crown-group euarthropods. Although the conservative morphology of lateral eyes in Xiphosura is potentially plesiomorphic for Euarthropoda, synziphosurine eye organization has received little attention despite their early diverging phylogenetic position. Here, we re-evaluate the fossil evidence for lateral compound eyes in the synziphosurines Bunodes sp., Cyamocephalus loganensis, Legrandella lombardii, Limuloides limuloides, Pseudoniscus clarkei, Pseudoniscus falcatus and Pseudoniscus roosevelti. We compare these data with lateral eyes in the euchelicerates Houia yueya, Kasibelinurus amicorum and Lunataspis aurora. We find no convincing evidence for lateral eyes in most studied taxa, and Pseudoniscus roosevelti and Legrandella lombardii are the only synziphosurines with this feature. Our findings support two scenarios for euchelicerate lateral eye evolution. The elongate-crescentic lateral eyes of Legrandella lombardii might represent the ancestral organization, as suggested by the phylogenetic position of this taxon in stem-group Euchelicerata. Alternatively, the widespread occurrence of kidney-shaped lateral eyes in stem-group Xiphosura and stem-group Arachnida could represent the plesiomorphic condition; Legrandella lombardii eyes would therefore be derived. Both evolutionary scenarios support the interpretation that kidney-shaped lateral eyes are ancestral for crown-group Euchelicerata and morphologically conserved in extant Limulus polyphemus.
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Affiliation(s)
- Russell D C Bicknell
- Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia
| | - Lisa Amati
- Paleontology, New York State Museum, Albany, NY, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
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Abstract
The euarthropod body consists of serially repeated segments with various degrees of functional specialization and regionalization [1]. Some representatives exhibit deviant metameric patterns expressed as an indirect correspondence between components of the exoskeleton, usually the number or position of dorsoventral sclerotized plates and walking legs (Supplemental Information) [1-3]. Segmental mismatch in the form of supernumerary walking legs per tergite (i.e. dorsal exoskeletal plate) is characteristic of fuxianhuiids, Cambrian euarthropods widely regarded as critical for understanding the origin of this phylum [4,5]. The broader significance of this organization remains obscure, however, due to the difficulty of distinguishing which components of the fuxianhuiid trunk reflect ancestral or derived traits. Here, we describe for the first time the presence of metameric midgut diverticulae in Fuxianhuia protensa from the Chengjiang Konservat-Lagerstätte and demonstrate that these digestive structures follow the segmentation pattern of the dorsal exoskeleton. Midgut diverticulae signal a predatory or scavenging ecology [6,7], falsifying the view of fuxianhuiids as simple mud-feeders [4]. Comparison with other euarthropods [1-3,5] indicates that fuxianhuiids possessed a unique mode of exoskeletal and visceral segmental mismatch, in which the tergites and midgut were segmentally patterned independently from the walking legs and ventral nerve cord. Our findings provide direct evidence of substantial developmental flexibility among stem-group euarthropods during the Cambrian.
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Affiliation(s)
- Javier Ortega-Hernández
- State Key Laboratory of Continental Dynamics, Early Life Institute and Department of Geology, Northwest University, Xian 710069, P.R. China; Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK; Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
| | - Dongjing Fu
- State Key Laboratory of Continental Dynamics, Early Life Institute and Department of Geology, Northwest University, Xian 710069, P.R. China.
| | - Xingliang Zhang
- State Key Laboratory of Continental Dynamics, Early Life Institute and Department of Geology, Northwest University, Xian 710069, P.R. China
| | - Degan Shu
- State Key Laboratory of Continental Dynamics, Early Life Institute and Department of Geology, Northwest University, Xian 710069, P.R. China
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Du KS, Ortega-Hernández J, Yang J, Zhang XG. A soft-bodied euarthropod from the early Cambrian Xiaoshiba Lagerstätte of China supports a new clade of basal artiopodans with dorsal ecdysial sutures. Cladistics 2019; 35:269-281. [PMID: 34622993 DOI: 10.1111/cla.12344] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/17/2018] [Indexed: 11/28/2022] Open
Abstract
We describe the exceptionally well-preserved non-trilobite artiopodan Zhiwenia coronata gen. et sp. nov. from the Cambrian Stage 3 Xiaoshiba Lagerstätte in Yunnan, China. The exoskeleton consists of a cephalic shield with dorsal sutures expressed as lateral notches that accommodate stalked lateral eyes, an elongate trunk composed of 20 tergites-the first of which is reduced-and a short tailspine with marginal spines. Appendicular data include a pair of multi-segmented antennae, and homonomous biramous trunk limbs consisting of an endopod with at least seven podomeres and a flattened exopod with lamellae. Although the presence of cephalic notches and a reduced first trunk tergite invites comparisons with the petalopleurans Xandarella, Luohiniella and Cindarella, the proportions and exoskeletal tagmosis of Zhiwenia do not closely resemble those of any major group within Trilobitomorpha. Parsimony and Bayesian phylogenetic analyses consistently support Zhiwenia as sister-taxon to the Emu Bay Shale artiopodan Australimicola spriggi, and both of them as closely related to Acanthomeridion from the Chengjiang. This new monophyletic clade, Protosutura nov., occupies a basal phylogenetic position within Artiopoda as sister-group to Trilobitomorpha and Vicissicaudata, illuminates the ancestral organization of these successful euarthropods, and leads to a re-evaluation of the evolution of ecdysial dorsal sutures within the group.
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Affiliation(s)
- Kun-Sheng Du
- Key Laboratory for Palaeobiology, Yunnan University, Kunming, 650091, China.,MEC International Joint Laboratory for Palaeoenvironment, Yunnan University, Kunming, 650091, China
| | - Javier Ortega-Hernández
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK.,Museum of Comparative Zoology and, Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Jie Yang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming, 650091, China.,MEC International Joint Laboratory for Palaeoenvironment, Yunnan University, Kunming, 650091, China
| | - Xi-Guang Zhang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming, 650091, China.,MEC International Joint Laboratory for Palaeoenvironment, Yunnan University, Kunming, 650091, China
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31
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Yang J, Ortega-Hernández J, Drage HB, Du KS, Zhang XG. Ecdysis in a stem-group euarthropod from the early Cambrian of China. Sci Rep 2019; 9:5709. [PMID: 30952888 PMCID: PMC6450865 DOI: 10.1038/s41598-019-41911-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 03/20/2019] [Indexed: 11/26/2022] Open
Abstract
Moulting is a fundamental component of the ecdysozoan life cycle, but the fossil record of this strategy is susceptible to preservation biases, making evidence of ecdysis in soft-bodied organisms extremely rare. Here, we report an exceptional specimen of the fuxianhuiid Alacaris mirabilis preserved in the act of moulting from the Cambrian (Stage 3) Xiaoshiba Lagerstätte, South China. The specimen displays a flattened and wrinkled head shield, inverted overlap of the trunk tergites over the head shield, and duplication of exoskeletal elements including the posterior body margins and telson. We interpret this fossil as a discarded exoskeleton overlying the carcass of an emerging individual. The moulting behaviour of A. mirabilis evokes that of decapods, in which the carapace is separated posteriorly and rotated forward from the body, forming a wide gape for the emerging individual. A. mirabilis illuminates the moult strategy of stem-group Euarthropoda, offers the stratigraphically and phylogenetically earliest direct evidence of ecdysis within total-group Euarthropoda, and represents one of the oldest examples of this growth strategy in the evolution of Ecdysozoa.
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Affiliation(s)
- Jie Yang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming, 650091, China
- MEC International Joint Laboratory for Palaeoenvironment, Yunnan University, Kunming, 650091, China
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
| | - Harriet B Drage
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK
- Institute of Earth Sciences, University of Lausanne, Géopolis, CH-1015, Lausanne, Switzerland
| | - Kun-Sheng Du
- Key Laboratory for Palaeobiology, Yunnan University, Kunming, 650091, China
- MEC International Joint Laboratory for Palaeoenvironment, Yunnan University, Kunming, 650091, China
| | - Xi-Guang Zhang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming, 650091, China.
- MEC International Joint Laboratory for Palaeoenvironment, Yunnan University, Kunming, 650091, China.
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Ortega-Hernández J, Janssen R, Budd GE. The last common ancestor of Ecdysozoa had an adult terminal mouth. Arthropod Struct Dev 2019; 49:155-158. [PMID: 30458236 DOI: 10.1016/j.asd.2018.11.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 11/09/2018] [Indexed: 06/09/2023]
Abstract
The Ecdysozoa is a major animal clade whose main uniting feature is a distinctive growth strategy that requires the periodical moulting of the external cuticle. The staggering diversity within Ecdysozoa has prompted substantial efforts to reconstruct their origin and early evolution. Based on palaentological and developmental data, we proposed a scenario for the early evolution of the ecdysozoan clade Panarthropoda (Onychophora, Tardigrada, Euarthropoda), and postulated that a terminal mouth is ancestral for this lineage. In light of the accompanying comment by Claus Nielsen, we take this opportunity to clarify the significance of our argumentation for Panarthropoda in the phylogenetic context of Ecdysozoa, and Bilateria more broadly. We conclude that the ancestral ecdysozoan most likely had an adult terminal mouth, and that the last common ancestors of all the phyla that constitute Ecdysozoa almost certainly also had an adult terminal mouth. The occurrence of a ventral-facing mouth in various adult ecdysozoans - particularly panarthropods - is the result of convergence. Despite the paucity of embryological data on fossil taxa, we contemplate the likelihood that a developmentally early ventral mouth opening could be ancestral for Ecdysozoa, and if so, then this would represent a symplesiomorphy of Bilateria as a whole.
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Affiliation(s)
- Javier Ortega-Hernández
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK; Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
| | - Ralf Janssen
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, Uppsala se 752 36, Sweden
| | - Graham E Budd
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, Uppsala se 752 36, Sweden
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Zhai D, Ortega-Hernández J, Wolfe JM, Hou X, Cao C, Liu Y. Three-Dimensionally Preserved Appendages in an Early Cambrian Stem-Group Pancrustacean. Curr Biol 2019; 29:171-177.e1. [DOI: 10.1016/j.cub.2018.11.060] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Revised: 09/06/2018] [Accepted: 11/28/2018] [Indexed: 10/27/2022]
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Yang J, Ortega-Hernández J, Legg DA, Lan T, Hou JB, Zhang XG. Early Cambrian fuxianhuiids from China reveal origin of the gnathobasic protopodite in euarthropods. Nat Commun 2018; 9:470. [PMID: 29391458 PMCID: PMC5794847 DOI: 10.1038/s41467-017-02754-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2017] [Accepted: 12/26/2017] [Indexed: 11/13/2022] Open
Abstract
Euarthropods owe their evolutionary and ecological success to the morphological plasticity of their appendages. Although this variability is partly expressed in the specialization of the protopodite for a feeding function in the post-deutocerebral limbs, the origin of the former structure among Cambrian representatives remains uncertain. Here, we describe Alacaris mirabilis gen. et sp. nov. from the early Cambrian Xiaoshiba Lagerstätte in China, which reveals the proximal organization of fuxianhuiid appendages in exceptional detail. Proximally, the post-deutocerebral limbs possess an antero-posteriorly compressed protopodite with robust spines. The protopodite is attached to an endopod with more than a dozen podomeres, and an oval flap-shaped exopod. The gnathal edges of the protopodites form an axial food groove along the ventral side of the body, indicating a predatory/scavenging autecology. A cladistic analysis indicates that the fuxianhuiid protopodite represents the phylogenetically earliest occurrence of substantial proximal differentiation within stem-group Euarthropoda illuminating the origin of gnathobasic feeding.
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Affiliation(s)
- Jie Yang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming, 650091, China
| | - Javier Ortega-Hernández
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - David A Legg
- Department of Earth, Atmospheric, and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
| | - Tian Lan
- College of Resources and Environmental Engineering, Guizhou University, Guiyang, 550003, China
| | - Jin-Bo Hou
- Key Laboratory for Palaeobiology, Yunnan University, Kunming, 650091, China
| | - Xi-Guang Zhang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming, 650091, China.
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Lerosey-Aubril R, Zhu X, Ortega-Hernández J. The Vicissicaudata revisited - insights from a new aglaspidid arthropod with caudal appendages from the Furongian of China. Sci Rep 2017; 7:11117. [PMID: 28894246 PMCID: PMC5593897 DOI: 10.1038/s41598-017-11610-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 08/25/2017] [Indexed: 11/09/2022] Open
Abstract
Cambrian marine ecosystems were dominated by arthropods, and more specifically artiopods. Aglaspidids represent an atypical group amongst them, not the least because they evolved and rapidly diversified during the late Cambrian, a time interval between the two diversification events of the Early Palaeozoic. Recent phylogenetic analyses have retrieved aglaspidids within the Vicissicaudata, a potentially important, but difficult to define clade of artiopods. Here we describe a new aglaspidid from the Furongian Guole Konservat-Lagerstätte of South China. This taxon displays a pretelsonic segment bearing non-walking appendages, features as-yet known in all vicissicaudatans, but aglaspidids. A new comprehensive phylogenetic analysis provides strong support for the legitimacy of a monophyletic clade Vicissicaudata, and demonstrates the pertinence of new characters to define Aglaspidida. It also motivates important changes to the systematics of the phylum, including the elevation of Artiopoda to the rank of subphylum, and the establishment of a new superclass Vicissicaudata and a new aglaspidid family Tremaglaspididae. Two diversification pulses can be recognized in the early history of artiopods - one in the early Cambrian (trilobitomorphs) and the other in the late Cambrian (vicissicaudatans). The discrepancy between this pattern and that traditionally depicted for marine invertebrates in the Early Palaeozoic is discussed.
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Affiliation(s)
- Rudy Lerosey-Aubril
- Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia
| | - Xuejian Zhu
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China.
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Ortega-Hernández J, Janssen R, Budd GE. Origin and evolution of the panarthropod head - A palaeobiological and developmental perspective. Arthropod Struct Dev 2017; 46:354-379. [PMID: 27989966 DOI: 10.1016/j.asd.2016.10.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2016] [Revised: 09/15/2016] [Accepted: 10/25/2016] [Indexed: 05/14/2023]
Abstract
The panarthropod head represents a complex body region that has evolved through the integration and functional specialization of the anterior appendage-bearing segments. Advances in the developmental biology of diverse extant organisms have led to a substantial clarity regarding the relationships of segmental homology between Onychophora (velvet worms), Tardigrada (water bears), and Euarthropoda (e.g. arachnids, myriapods, crustaceans, hexapods). The improved understanding of the segmental organization in panarthropods offers a novel perspective for interpreting the ubiquitous Cambrian fossil record of these successful animals. A combined palaeobiological and developmental approach to the study of the panarthropod head through deep time leads us to propose a consensus hypothesis for the intricate evolutionary history of this important tagma. The contribution of exceptionally preserved brains in Cambrian fossils - together with the recognition of segmentally informative morphological characters - illuminate the polarity for major anatomical features. The euarthropod stem-lineage provides a detailed view of the step-wise acquisition of critical characters, including the origin of a multiappendicular head formed by the fusion of several segments, and the transformation of the ancestral protocerebral limb pair into the labrum, following the postero-ventral migration of the mouth opening. Stem-group onychophorans demonstrate an independent ventral migration of the mouth and development of a multisegmented head, as well as the differentiation of the deutocerebral limbs as expressed in extant representatives. The anterior organization of crown-group Tardigrada retains several ancestral features, such as an anterior-facing mouth and one-segmented head. The proposed model aims to clarify contentious issues on the evolution of the panarthropod head, and lays the foundation from which to further address this complex subject in the future.
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Affiliation(s)
| | - Ralf Janssen
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, Uppsala SE-752 36, Sweden
| | - Graham E Budd
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, Uppsala SE-752 36, Sweden
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Ortega-Hernández J, Azizi A, Hearing TW, Harvey THP, Edgecombe GD, Hafid A, El Hariri K. A xandarellid artiopodan from Morocco - a middle Cambrian link between soft-bodied euarthropod communities in North Africa and South China. Sci Rep 2017; 7:42616. [PMID: 28211461 PMCID: PMC5314411 DOI: 10.1038/srep42616] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 01/11/2017] [Indexed: 11/09/2022] Open
Abstract
Xandarellida is a well-defined clade of Lower Palaeozoic non-biomineralized artiopodans that is exclusively known from the early Cambrian (Stage 3) Chengjiang biota of South China. Here we describe a new member of this group, Xandarella mauretanica sp. nov., from the middle Cambrian (Stage 5) Tatelt Formation of Morocco, making this the first non-trilobite Cambrian euarthropod known from North Africa. X. mauretanica sp. nov. represents the youngest occurrence of Xandarellida - extending its stratigraphic range by approximately 10 million years - and expands the palaeobiogeographic distribution of the group to the high southern palaeolatitudes of West Gondwana. The new species provides insights into the lightly sclerotized ventral anatomy of Xandarellida, and offers stratigraphically older evidence for a palaeobiogeographic connection between Burgess Shale-type euarthropod communities in North Africa and South China, relative to the (Tremadocian) Fezouata biota.
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Affiliation(s)
| | - Abdelfattah Azizi
- Département Sciences de la Terre, Faculté des Sciences et Techniques-Guéliz, Université Cadi Ayyad, Avenue Abdelkrim el Khattabi BP 549, 40000 Marrakech, Morocco
| | - Thomas W. Hearing
- Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK
- British Geological Survey, Keyworth, NG12 5GG, UK
| | - Thomas H. P. Harvey
- Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK
| | - Gregory D. Edgecombe
- Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - Ahmid Hafid
- Département Sciences de la Terre, Faculté des Sciences et Techniques-Guéliz, Université Cadi Ayyad, Avenue Abdelkrim el Khattabi BP 549, 40000 Marrakech, Morocco
| | - Khadija El Hariri
- Département Sciences de la Terre, Faculté des Sciences et Techniques-Guéliz, Université Cadi Ayyad, Avenue Abdelkrim el Khattabi BP 549, 40000 Marrakech, Morocco
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38
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Affiliation(s)
- Javier Ortega-Hernández
- Department of Earth Sciences, Downing Street, University of Cambridge, Cambridge CB2 3EQ, UK.
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Yang J, Ortega-Hernández J, Lan T, Hou JB, Zhang XG. A predatory bivalved euarthropod from the Cambrian (Stage 3) Xiaoshiba Lagerstätte, South China. Sci Rep 2016; 6:27709. [PMID: 27283406 PMCID: PMC4901283 DOI: 10.1038/srep27709] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 05/24/2016] [Indexed: 11/08/2022] Open
Abstract
Bivalved euarthropods represent a conspicuous component of exceptionally-preserved fossil biotas throughout the Lower Palaeozoic. However, most of these taxa are known from isolated valves, and thus there is a limited understanding of their morphological organization and palaeoecology in the context of early animal-dominated communities. The bivalved euarthropod Clypecaris serrata sp. nov., recovered from the Cambrian (Stage 3) Hongjingshao Formation in Kunming, southern China, is characterized by having a robust first pair of raptorial appendages that bear well-developed ventral-facing spines, paired dorsal spines on the trunk, and posteriorly oriented serrations on the anteroventral margins of both valves. The raptorial limbs of C. serrata were adapted for grasping prey employing a descending stroke for transporting it close the mouth, whereas the backwards-facing marginal serrations of the bivalved carapace may have helped to secure the food items during feeding. The new taxon offers novel insights on the morphology of the enigmatic genus Clypecaris, and indicates that the possession of paired dorsal spines is a diagnostic trait of the Family Clypecarididae within upper stem-group Euarthropoda. C. serrata evinces functional adaptations for an active predatory lifestyle within the context of Cambrian bivalved euarthropods, and contributes towards the better understanding of feeding diversity in early ecosystems.
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Affiliation(s)
- Jie Yang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China
| | | | - Tian Lan
- College of Resources and Environmental Engineering, Guizhou University, Guiyang 550003, China
| | - Jin-bo Hou
- Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China
| | - Xi-guang Zhang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China
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Yang J, Ortega-Hernández J, Butterfield NJ, Liu Y, Boyan GS, Hou JB, Lan T, Zhang XG. Fuxianhuiid ventral nerve cord and early nervous system evolution in Panarthropoda. Proc Natl Acad Sci U S A 2016; 113:2988-93. [PMID: 26933218 PMCID: PMC4801254 DOI: 10.1073/pnas.1522434113] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Panarthropods are typified by disparate grades of neurological organization reflecting a complex evolutionary history. The fossil record offers a unique opportunity to reconstruct early character evolution of the nervous system via exceptional preservation in extinct representatives. Here we describe the neurological architecture of the ventral nerve cord (VNC) in the upper-stem group euarthropod Chengjiangocaris kunmingensis from the early Cambrian Xiaoshiba Lagerstätte (South China). The VNC of C. kunmingensis comprises a homonymous series of condensed ganglia that extend throughout the body, each associated with a pair of biramous limbs. Submillimetric preservation reveals numerous segmental and intersegmental nerve roots emerging from both sides of the VNC, which correspond topologically to the peripheral nerves of extant Priapulida and Onychophora. The fuxianhuiid VNC indicates that ancestral neurological features of Ecdysozoa persisted into derived members of stem-group Euarthropoda but were later lost in crown-group representatives. These findings illuminate the VNC ground pattern in Panarthropoda and suggest the independent secondary loss of cycloneuralian-like neurological characters in Tardigrada and Euarthropoda.
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Affiliation(s)
- Jie Yang
- Yunnan Key Laboratory for Paleobiology, Yunnan University, Kunming 650091, China
| | | | - Nicholas J Butterfield
- Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom
| | - Yu Liu
- Yunnan Key Laboratory for Paleobiology, Yunnan University, Kunming 650091, China; Developmental Neurobiology Group, Biocenter, Ludwig-Maximilians-Universität, 82152 Martinsried, Germany; GeoBio-Center Ludwig-Maximilians-Universität, Munich 80333, Germany
| | - George S Boyan
- Developmental Neurobiology Group, Biocenter, Ludwig-Maximilians-Universität, 82152 Martinsried, Germany
| | - Jin-Bo Hou
- Yunnan Key Laboratory for Paleobiology, Yunnan University, Kunming 650091, China
| | - Tian Lan
- College of Resources and Environmental Engineering, Guizhou University, Guiyang 550003, China
| | - Xi-Guang Zhang
- Yunnan Key Laboratory for Paleobiology, Yunnan University, Kunming 650091, China;
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Ortega-Hernández J, Budd GE. The nature of non-appendicular anterior paired projections in Palaeozoic total-group Euarthropoda. Arthropod Struct Dev 2016; 45:185-199. [PMID: 26802876 DOI: 10.1016/j.asd.2016.01.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 01/12/2016] [Indexed: 05/14/2023]
Abstract
Recent studies have clarified the segmental organization of appendicular and exoskeletal structures in the anterior region of Cambrian stem-group Euarthropoda, and thus led to better understanding of the deep evolutionary origins of the head region in this successful animal group. However, there are aspects of the anterior organization of Palaeozoic euarthropods that remain problematic, such as the morphological identity and significance of minute limb-like projections on the anterior region in stem and crown-group representatives. Here, we draw attention to topological and morphological similarities between the frontal filaments of extant Crustacea and the embryonic frontal processes of Onychophora, and distinctive anterior paired projections observed in several extinct total-group Euarthropoda. Anterior paired projections are redescribed in temporally and phylogenetically distant fossil taxa, including the gilled lobopodians Kerygmachela kierkegaardi and Pambdelurion whittingtoni, the bivalved stem-euarthropod Canadaspis perfecta, the larval pycnogonid Cambropycnogon klausmuelleri, and the mandibulate Tanazios dokeron. Developmental data supporting the homology of the 'primary antennae' of Onychophora, the 'frontal appendages' of lower-stem Euarthropoda, and the hypostome/labrum complex of Deuteropoda, argue against the morphological identity of the anterior paired projections of extant and extinct panarthropods as a pair of pre-ocular appendages. Instead, we regard the paired projections of fossil total-group euarthropods as non-appendicular evaginations with a likely protocerebral segmental association, and a possible sensorial function. The widespread occurrence of pre-ocular paired projections among extant and extinct taxa suggests their potential homology as fundamentally ancestral features of the anterior body organization in Panarthropoda. Non-appendicular paired projections with a sensorial function may reflect a critical--yet previously overlooked--component of the panarthropod ground pattern.
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Affiliation(s)
- Javier Ortega-Hernández
- Department of Earth Sciences, Downing Street, University of Cambridge, Cambridge CB2 3EQ, UK.
| | - Graham E Budd
- Department of Earth Sciences, Palaeobiology, Uppsala University, Norbyvägen 22, Uppsala SE 752 36, Sweden
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Yang J, Ortega-Hernández J, Gerber S, Butterfield NJ, Hou JB, Lan T, Zhang XG. A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora. Proc Natl Acad Sci U S A 2015; 112:8678-83. [PMID: 26124122 PMCID: PMC4507230 DOI: 10.1073/pnas.1505596112] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstätte in South China, an armored lobopodian with a remarkable degree of limb differentiation including a pair of antenna-like appendages, six pairs of elongate setiferous limbs for suspension feeding, and nine pairs of clawed annulated legs with an anchoring function. Collinsium belongs to a highly derived clade of lobopodians within stem group Onychophora, distinguished by a substantial dorsal armature of supernumerary and biomineralized spines (Family Luolishaniidae). As demonstrated here, luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Despite having higher disparity and appendage complexity than other lobopodians and extant velvet worms, the specialized mode of life embodied by luolishaniids became extinct during the Early Paleozoic. Collinsium and other superarmored lobopodians exploited a unique paleoecological niche during the Cambrian explosion.
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Affiliation(s)
- Jie Yang
- Yunnan Key Laboratory for Paleobiology, Yunnan University, Kunming 650091, China
| | | | - Sylvain Gerber
- Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom
| | - Nicholas J Butterfield
- Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom
| | - Jin-Bo Hou
- Yunnan Key Laboratory for Paleobiology, Yunnan University, Kunming 650091, China
| | - Tian Lan
- Yunnan Key Laboratory for Paleobiology, Yunnan University, Kunming 650091, China
| | - Xi-guang Zhang
- Yunnan Key Laboratory for Paleobiology, Yunnan University, Kunming 650091, China;
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Abstract
The Cambrian fossil record of euarthropods (extant arachnids, myriapods, crustaceans, hexapods) has played a major role in understanding the origins of these successful animals and indicates that early ancestors underwent an evolutionary transition from soft-bodied taxa (lobopodians) to more familiar sclerotized forms with jointed appendages [1-3]. Recent advances in paleoneurology and developmental biology show that this major transformation is reflected by substantial changes in the head region of early euarthropods, as informed by the segmental affinity of the cephalic appendages [1, 4-6]. However, data on the implications of this reorganization for non-appendicular exoskeletal structures are lacking, given the difficulty of inferring the precise segmental affinities of these features. Here, I report neurological remains associated with the stalked eyes and "anterior sclerite" in the (middle Cambrian) Burgess Shale euarthropods Helmetia expansa and Odaraia alata and provide evidence that these features are associated with nerve traces originating from the anterior brain region, the protocerebrum. The position of the protocerebral ganglia in exceptionally preserved Cambrian euarthropods indicates the homology of the anterior sclerite in extinct groups (e.g., fuxianhuiids, bivalved forms, artiopodans [7, 8]) and allows new comparisons with the dorsal cephalic plate of radiodontans, large nektonic predators whose anterior segmental organization bears fundamental similarities to that of Paleozoic lobopodians [1, 6, 9, 10]. These observations allow reconstruction of the segmental architecture of the head region in the earliest sclerotized euarthropods and demonstrate the deep homology between exoskeletal features in an evolutionary continuum of taxa with distinct types of body organization.
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Affiliation(s)
- Javier Ortega-Hernández
- Department of Earth Sciences, Downing Street, University of Cambridge, Cambridge CB2 3EQ, UK.
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Ortega-Hernández J. Making sense of 'lower' and 'upper' stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848. Biol Rev Camb Philos Soc 2014; 91:255-73. [PMID: 25528950 DOI: 10.1111/brv.12168] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Revised: 11/07/2014] [Accepted: 11/18/2014] [Indexed: 11/30/2022]
Abstract
The ever-increasing number of studies that address the origin and evolution of Euarthropoda - whose extant representatives include chelicerates, myriapods, crustaceans and hexapods - are gradually reaching a consensus with regard to the overall phylogenetic relationships of some of the earliest representatives of this phylum. The stem-lineage of Euarthropoda includes numerous forms that reflect the major morphological transition from a lobopodian-type to a completely arthrodized body organization. Several methods of classification that aim to reflect such a complex evolutionary history have been proposed as a consequence of this taxonomic diversity. Unfortunately, this has also led to a saturation of nomenclatural schemes, often in conflict with each other, some of which are incompatible with cladistic-based methodologies. Here, I review the convoluted terminology associated with the classification of stem-group Euarthropoda, and propose a synapomorphy-based distinction that allows 'lower stem-Euarthropoda' (e.g. lobopodians, radiodontans) to be separated from 'upper stem-Euarthropoda' (e.g. fuxianhuiids, Cambrian bivalved forms) in terms of the structural organization of the head region and other aspects of overall body architecture. The step-wise acquisition of morphological features associated with the origins of the crown-group indicate that the node defining upper stem-Euarthropoda is phylogenetically stable, and supported by numerous synapomorphic characters; these include the presence of a deutocerebral first appendage pair, multisegmented head region with one or more pairs of post-ocular differentiated limbs, complete body arthrodization, posterior-facing mouth associated with the hypostome/labrum complex, and post-oral biramous arthropodized appendages. The name 'Deuteropoda' nov. is proposed for the scion (monophyletic group including the crown-group and an extension of the stem-group) that comprises upper stem-Euarthropoda and Euarthropoda. A brief account of common terminological inaccuracies in recent palaeontological studies evinces the utility of Deuteropoda nov. as a reference point for discussing aspects of early euarthropod phylogeny.
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Affiliation(s)
- Javier Ortega-Hernández
- Department of Earth Sciences, University of Cambridge, Downing Site, Cambridge, CB2 3EQ, U.K
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Smith MR, Ortega-Hernández J. Hallucigenia’s onychophoran-like claws and the case for Tactopoda. Nature 2014; 514:363-6. [DOI: 10.1038/nature13576] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 06/11/2014] [Indexed: 01/25/2023]
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Ortega-Hernández J, Esteve J, Butterfield NJ. Humble origins for a successful strategy: complete enrolment in early Cambrian olenellid trilobites. Biol Lett 2013; 9:20130679. [PMID: 24068021 DOI: 10.1098/rsbl.2013.0679] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Trilobites are typified by the behavioural and morphological ability to enrol their bodies, most probably as a defence mechanism against adverse environmental conditions or predators. Although most trilobites could enrol at least partially, there is uncertainty about whether olenellids-among the most phylogenetically and stratigraphically basal representatives-could perform this behaviour because of their poorly caudalized trunk and scarcity of coaptative devices. Here, we report complete-but not encapsulating-enrolment for the olenellid genus Mummaspis from the early Cambrian Mural Formation in Alberta, the earliest direct evidence of this strategy in the fossil record of polymerid trilobites. Complete enrolment in olenellids was achieved through a combination of ancestral morphological features, and thus provides new information on the character polarity associated with this key trilobite adaptation.
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Affiliation(s)
- Javier Ortega-Hernández
- Department of Earth Sciences, University of Cambridge, , Downing Site, Cambridge CB2 3EQ, UK
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Yang J, Ortega-Hernández J, Butterfield NJ, Zhang XG. Specialized appendages in fuxianhuiids and the head organization of early euarthropods. Nature 2013; 494:468-71. [PMID: 23446418 DOI: 10.1038/nature11874] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Accepted: 12/21/2012] [Indexed: 11/09/2022]
Abstract
The organization of the head provides critical data for resolving the phylogenetic relationships and evolutionary history of extinct and extant euarthropods. The early Cambrian-period fuxianhuiids are regarded as basal representatives of stem-group Euarthropoda, and their anterior morphology therefore offers key insights for reconstructing the ancestral condition of the euarthropod head. However, the paired post-antennal structures in Fuxianhuia protensa remain controversial; they have been interpreted as both 'great appendages' and as gut diverticulae. Here we describe Chengjiangocaris kunmingensis sp. nov. and Fuxianhuia xiaoshibaensis sp. nov. from a new early Cambrian (Stage 3) fossil Lagerstätte in Yunnan, China. Numerous specimens of both species show a unique 'taphonomic dissection' of the anterodorsal head shield, revealing the cephalic organization in detail. We demonstrate the presence of a pair of specialized post-antennal appendages (SPAs) in the fuxianhuiid head, which attach at either side of the posteriorly directed mouth, behind the hypostome. Preserved functional articulations indicate a well-defined but restricted range of limb movement, suggestive of a simple type of sweep feeding. The organization of the SPAs in fuxianhuiids is incompatible with the (deutocerebral) anterior raptorial appendages of megacheirans, and argue against the presence of protocerebral limbs in the fuxianhuiids. The positions of the fuxianhuiid antennae and SPAs indicate that they are segmentally homologous to the deutocerebral and tritocerebral appendages of crown-group Euarthropoda respectively. These findings indicate that antenniform deutocerebral appendages with many podomeres are a plesiomorphic feature of the ancestral euarthropod head.
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Affiliation(s)
- Jie Yang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China
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Ortega-Hernández J, Brena C. Ancestral patterning of tergite formation in a centipede suggests derived mode of trunk segmentation in trilobites. PLoS One 2012; 7:e52623. [PMID: 23285116 PMCID: PMC3532300 DOI: 10.1371/journal.pone.0052623] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 11/19/2012] [Indexed: 12/05/2022] Open
Abstract
Trilobites have a rich and abundant fossil record, but little is known about the intrinsic mechanisms that orchestrate their body organization. To date, there is disagreement regarding the correspondence, or lack thereof, of the segmental units that constitute the trilobite trunk and their associated exoskeletal elements. The phylogenetic position of trilobites within total-group Euarthropoda, however, allows inferences about the underlying organization in these extinct taxa to be made, as some of the fundamental genetic processes for constructing the trunk segments are remarkably conserved among living arthropods. One example is the expression of the segment polarity gene engrailed, which at embryonic and early postembryonic stages is expressed in extant panarthropods (i.e. tardigrades, onychophorans, euarthropods) as transverse stripes that define the posteriormost region of each trunk segment. Due to its conservative morphology and allegedly primitive trunk tagmosis, we have utilized the centipede Strigamia maritima to study the correspondence between the expression of engrailed during late embryonic to postembryonic stages, and the development of the dorsal exoskeletal plates (i.e. tergites). The results corroborate the close correlation between the formation of the tergite borders and the dorsal expression of engrailed, and suggest that this association represents a symplesiomorphy within Euarthropoda. This correspondence between the genetic and phenetic levels enables making accurate inferences about the dorsoventral expression domains of engrailed in the trunk of exceptionally preserved trilobites and their close relatives, and is suggestive of the widespread occurrence of a distinct type of genetic segmental mismatch in these extinct arthropods. The metameric organization of the digestive tract in trilobites provides further support to this new interpretation. The wider evolutionary implications of these findings suggest the presence of a derived morphogenetic patterning mechanism responsible for the reiterated occurrence of different types of trunk dorsoventral segmental mismatch in several phylogenetically distant, extinct and extant, arthropod groups.
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Ortega-Hernández J, Legg DA, Braddy SJ. The phylogeny of aglaspidid arthropods and the internal relationships within Artiopoda. Cladistics 2012; 29:15-45. [DOI: 10.1111/j.1096-0031.2012.00413.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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