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Chen A, Vannier J, Guo J, Wang D, Gąsiorek P, Han J, Ma W. Molting in early Cambrian armored lobopodians. Commun Biol 2024; 7:820. [PMID: 38969778 PMCID: PMC11226638 DOI: 10.1038/s42003-024-06440-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Accepted: 06/11/2024] [Indexed: 07/07/2024] Open
Abstract
Lobopodians represent a key step in the early history of ecdysozoans since they were the first animals to evolve legs within this clade. Their Cambrian representatives share a similar body plan with a typically cylindrical annulated trunk and a series of non-jointed legs. However, they do not form a monophyletic group and likely include ancestors of the three extant panarthropod lineages (Tardigrada, Onychophora, Euarthropoda). Some species display astonishing protective devices such as cuticular plates and spines. We describe here the armor and molting process of Microdictyon from the early Cambrian of China. Microdictyon secreted ovoid paired cuticular sclerites that were duplicated in a non-synchronous way along the animal's body. The reticulated pattern and cuticular architecture of these sclerites have similarities to extant armored tardigrades that recently served in hypothesizing that tardigrades are possibly miniaturized lobopodians. Ecdysis and hard cuticular protection are now well documented in the whole spectrum of early Cambrian ecdysozoans such as soft-bodied scalidophorans, lobopodians and fully articulated euarthropods. We hypothesize that the secretion of sclerotized cuticular elements periodically renewed via ecdysis was a key innovation that opened large-scale evolutionary opportunities to invertebrate animal life, specifically ecdysozoans, both in terms of anatomical functionalities and ecological success.
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Affiliation(s)
- Ailin Chen
- Research Centre of Palaeobiology, Yuxi Normal University, 653100, Yuxi, China.
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 210008, Nanjing, China.
| | - Jean Vannier
- Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement (CNRS-UMR 5276), Université de Lyon, Université Claude Bernard Lyon 1, ENS de Lyon, CNRS, Villeurbanne, 69622, France.
| | - Jin Guo
- Chengjiang Science Museum, Management Committee of the Chengjiang Fossil Site World Heritage, 652500, Chengjiang, China
| | - Deng Wang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, 710069, Xi'an, China
| | - Piotr Gąsiorek
- Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350, Universitetsparken 15, DK-2100, Copenhagen, Denmark
- Department of Invertebrate Evolution, Faculty of Biology, Jagiellonian University, Gronostajowa 9, 30-387, Kraków, Poland
| | - Jian Han
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, 710069, Xi'an, China
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2
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Smith FW, Game M, Mapalo MA, Chavarria RA, Harrison TR, Janssen R. Developmental and genomic insight into the origin of the tardigrade body plan. Evol Dev 2024; 26:e12457. [PMID: 37721221 DOI: 10.1111/ede.12457] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 08/11/2023] [Accepted: 08/29/2023] [Indexed: 09/19/2023]
Abstract
Tardigrada is an ancient lineage of miniaturized animals. As an outgroup of the well-studied Arthropoda and Onychophora, studies of tardigrades hold the potential to reveal important insights into body plan evolution in Panarthropoda. Previous studies have revealed interesting facets of tardigrade development and genomics that suggest that a highly compact body plan is a derived condition of this lineage, rather than it representing an ancestral state of Panarthropoda. This conclusion was based on studies of several species from Eutardigrada. We review these studies and expand on them by analyzing the publicly available genome and transcriptome assemblies of Echiniscus testudo, a representative of Heterotardigrada. These new analyses allow us to phylogenetically reconstruct important features of genome evolution in Tardigrada. We use available data from tardigrades to interrogate several recent models of body plan evolution in Panarthropoda. Although anterior segments of panarthropods are highly diverse in terms of anatomy and development, both within individuals and between species, we conclude that a simple one-to-one alignment of anterior segments across Panarthropoda is the best available model of segmental homology. In addition to providing important insight into body plan diversification within Panarthropoda, we speculate that studies of tardigrades may reveal generalizable pathways to miniaturization.
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Affiliation(s)
- Frank W Smith
- Biology Department, University of North Florida, Jacksonville, Florida, USA
| | - Mandy Game
- Biology Department, University of North Florida, Jacksonville, Florida, USA
| | - Marc A Mapalo
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Raul A Chavarria
- Biology Department, University of North Florida, Jacksonville, Florida, USA
| | - Taylor R Harrison
- Biology Department, University of North Florida, Jacksonville, Florida, USA
| | - Ralf Janssen
- Department of Earth Sciences, Palaeobiology, Uppsala University, Uppsala, Sweden
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3
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Kihm JH, Smith FW, Kim S, Rho HS, Zhang X, Liu J, Park TYS. Cambrian lobopodians shed light on the origin of the tardigrade body plan. Proc Natl Acad Sci U S A 2023; 120:e2211251120. [PMID: 37399417 PMCID: PMC10334802 DOI: 10.1073/pnas.2211251120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 05/22/2023] [Indexed: 07/05/2023] Open
Abstract
Phylum Tardigrada (water bears), well known for their cryptobiosis, includes small invertebrates with four paired limbs and is divided into two classes: Eutardigrada and Heterotardigrada. The evolutionary origin of Tardigrada is known to lie within the lobopodians, which are extinct soft-bodied worms with lobopodous limbs mostly discovered at sites of exceptionally well-preserved fossils. Contrary to their closest relatives, onychophorans and euarthropods, the origin of morphological characters of tardigrades remains unclear, and detailed comparison with the lobopodians has not been well explored. Here, we present detailed morphological comparison between tardigrades and Cambrian lobopodians, with a phylogenetic analysis encompassing most of the lobopodians and three panarthropod phyla. The results indicate that the ancestral tardigrades likely had a Cambrian lobopodian-like morphology and shared most recent ancestry with the luolishaniids. Internal relationships within Tardigrada indicate that the ancestral tardigrade had a vermiform body shape without segmental plates, but possessed cuticular structures surrounding the mouth opening, and lobopodous legs terminating with claws, but without digits. This finding is in contrast to the long-standing stygarctid-like ancestor hypothesis. The highly compact and miniaturized body plan of tardigrades evolved after the tardigrade lineage diverged from an ancient shared ancestor with the luolishaniids.
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Affiliation(s)
- Ji-Hoon Kihm
- Division of Earth Sciences, Korea Polar Research Institute, Yeonsu-gu, Incheon21990, Korea
| | - Frank W. Smith
- Department of Biology, University of North Florida, Jacksonville, FL32224
| | - Sanghee Kim
- Division of Life Sciences, Korea Polar Research Institute, Yeonsu-gu, Incheon21990, Korea
| | - Hyun Soo Rho
- East Sea Environment Research Center, East Sea Research Institute, Korea Institute of Ocean Science and Technology, Uljin, Gyeongsangbuk-do36315, Korea
| | - Xingliang Zhang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi’an710069, China
| | - Jianni Liu
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi’an710069, China
| | - Tae-Yoon S. Park
- Division of Earth Sciences, Korea Polar Research Institute, Yeonsu-gu, Incheon21990, Korea
- Polar Science, University of Science and Technology, Yuseong-gu, Daejeon34113, Korea
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Abstract
Panarthropoda, the clade comprising the phyla Onychophora, Tardigrada and Euarthropoda, encompasses the largest majority of animal biodiversity. The relationships among the phyla are contested and resolution is key to understanding the evolutionary assembly of panarthropod bodyplans. Molecular phylogenetic analyses generally support monophyly of Onychophora and Euarthropoda to the exclusion of Tardigrada (Lobopodia hypothesis), which is also supported by some analyses of morphological data. However, analyses of morphological data have also been interpreted to support monophyly of Tardigrada and Euarthropoda to the exclusion of Onychophora (Tactopoda hypothesis). Support has also been found for a clade of Onychophora and Tardigrada that excludes Euarthropoda (Protarthropoda hypothesis). Here we show, using a diversity of phylogenetic inference methods, that morphological datasets cannot discriminate statistically between the Lobopodia, Tactopoda and Protarthropoda hypotheses. Since the relationships among the living clades of panarthropod phyla cannot be discriminated based on morphological data, we call into question the accuracy of morphology-based phylogenies of Panarthropoda that include fossil species and the evolutionary hypotheses based upon them.
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Affiliation(s)
- Ruolin Wu
- Bristol Palaeobiology Group, University of Bristol, Tyndall Avenue, Bristol BS8 1TQ, UK,School of Earth Sciences, University of Bristol, Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Davide Pisani
- Bristol Palaeobiology Group, University of Bristol, Tyndall Avenue, Bristol BS8 1TQ, UK,School of Biological Sciences, Life Sciences Building, University of Bristol, Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Philip C. J. Donoghue
- Bristol Palaeobiology Group, University of Bristol, Tyndall Avenue, Bristol BS8 1TQ, UK,School of Earth Sciences, University of Bristol, Tyndall Avenue, Bristol BS8 1TQ, UK
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5
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Aria C. The origin and early evolution of arthropods. Biol Rev Camb Philos Soc 2022; 97:1786-1809. [PMID: 35475316 DOI: 10.1111/brv.12864] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Revised: 04/12/2022] [Accepted: 04/14/2022] [Indexed: 12/18/2022]
Abstract
The rise of arthropods is a decisive event in the history of life. Likely the first animals to have established themselves on land and in the air, arthropods have pervaded nearly all ecosystems and have become pillars of the planet's ecological networks. Forerunners of this saga, exceptionally well-preserved Palaeozoic fossils recently discovered or re-discovered using new approaches and techniques have elucidated the precocious appearance of extant lineages at the onset of the Cambrian explosion, and pointed to the critical role of the plankton and hard integuments in early arthropod diversification. The notion put forward at the beginning of the century that the acquisition of extant arthropod characters was stepwise and represented by the majority of Cambrian fossil taxa is being rewritten. Although some key traits leading to Euarthropoda are indeed well documented along a diversified phylogenetic stem, this stem led to several speciose and ecologically diverse radiations leaving descendants late into the Palaeozoic, and a large part, if not all of the Cambrian euarthropods can now be placed on either of the two extant lineages: Mandibulata and Chelicerata. These new observations and discoveries have altered our view on the nature and timing of the Cambrian explosion and clarified diagnostic characters at the origin of extant arthropods, but also raised new questions, especially with respect to cephalic plasticity. There is now strong evidence that early arthropods shared a homologous frontalmost appendage, coined here the cheira, which likely evolved into antennules and chelicerae, but other aspects, such as brain and labrum evolution, are still subject to active debate. The early evolution of panarthropods was generally driven by increased mastication and predation efficiency and sophistication, but a wealth of recent studies have also highlighted the prevalent role of suspension-feeding, for which early panarthropods developed their own adaptive feedback through both specialized appendages and the diversification of small, morphologically differentiated larvae. In a context of general integumental differentiation and hardening across Cambrian metazoans, arthrodization of body and limbs notably prompted two diverging strategies of basipod differentiation, which arguably became founding criteria in the divergence of total-groups Mandibulata and Chelicerata. The kinship of trilobites and their relatives remains a source of disagreement, but a recent topological solution, termed the 'deep split', could embed Artiopoda as sister taxa to chelicerates and constitute definitive support for Arachnomorpha. Although Cambrian fossils have been critical to all these findings, data of exceptional quality have also been accumulating from other Palaeozoic Konservat-Lagerstätten, and a better integration of this information promises a much more complete and elaborate picture of early arthropod evolution in the near future. From the broader perspective of a total-evidence approach to the understanding of life's history, and despite persisting systematic debates and new interpretative challenges, various advances based on palaeontological evidence open the prospect of finally using the full potential of the most diverse animal phylum to investigate macroevolutionary patterns and processes.
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Affiliation(s)
- Cédric Aria
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Palaeoenvironment, Chinese Academy of Sciences, Nanjing, 210008, P. R. China.,Shaanxi Key Laboratory of Early Life and Environments, Northwest University, Xi'an, 710069, P.R. China
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6
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Tube-dwelling in early animals exemplified by Cambrian scalidophoran worms. BMC Biol 2021; 19:243. [PMID: 34772414 PMCID: PMC8588615 DOI: 10.1186/s12915-021-01172-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 10/22/2021] [Indexed: 11/17/2022] Open
Abstract
Background The radiation of ecdysozoans (moulting animals) during the Cambrian gave rise to panarthropods and various groups of worms including scalidophorans, which played an important role in the elaboration of early marine ecosystems. Although most scalidophorans were infaunal burrowers travelling through soft sediment at the bottom of the sea, Selkirkia lived inside a tube. Results We explore the palaeobiology of these tubicolous worms, and more generally the origin and evolutionary significance of tube-dwelling in early animals, based on exceptionally preserved fossils from the early Cambrian Chengjiang Lagerstätte (Stage 3, China) including a new species, Selkirkia transita sp. nov. We find that the best phylogenetic model resolves Selkirkia as a stem-group priapulid. Selkirkia secreted a protective cuticular thickening, the tube, inside which it was able to move during at least part of its life. Partly based on measured growth patterns, we construe that this tube was separated from the trunk during a moulting process that has no direct equivalent in other scalidophorans. Although the ontogeny of Selkirkia is currently unknown, we hypothesize that its conical tube might have had the same ecological function and possibly even deep development origin as the lorica, a protective cuticular thickening found in larval priapulids and adult loriciferans. Selkirkia is seen as a semi-sedentary animal capable of very shallow incursions below the water/sediment interface, possibly for feeding or during the tube-secreting phase. Brachiopod epibionts previously reported from the Xiaoshiba Lagerstätte (ca. 514 Ma) also presumably occur in Selkirkia sinica from Chengjiang (ca. 518 Ma). Conclusions Our critical and model-based approach provides a new phylogenetic framework for Scalidophora, upon which to improve in order to study the evolution of morphological characters in this group. Tube-dwelling is likely to have offered Selkirkia better protection and anchoring to sediment and has developed simultaneously in other Cambrian animals such as hemichordates, annelids or panarthropods. Often lost in modern representatives in favour of active infaunal lifestyles, tube-dwelling can be regarded as an early evolutionary response of various metazoans to increasing environmental and biological pressure in Cambrian marine ecosystems. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-021-01172-4.
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7
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Edgecombe GD. Arthropod Origins: Integrating Paleontological and Molecular Evidence. ANNUAL REVIEW OF ECOLOGY, EVOLUTION, AND SYSTEMATICS 2020. [DOI: 10.1146/annurev-ecolsys-011720-124437] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Phylogenomics underpins a stable and mostly well-resolved hypothesis for the interrelationships of extant arthropods. Exceptionally preserved fossils are integrated into this framework by coding their morphological characters, as exemplified by total-evidence dating approaches that treat fossils as dated tips in analyses numerically dominated by molecular data. Cambrian fossils inform on the sequence of character acquisition in the arthropod stem group and in the stems of its main extant clades. The arthropod head problem incorporates unique appendage combinations and remains of the nervous system in fossils into a scheme mostly based on neuroanatomy and Hox expression domains for extant forms. Molecular estimates of arthropod origins in the Cryogenian or Ediacaran predate a coherent picture from the arthropod fossil record, which commences as trace fossils in the earliest Cambrian. Probabilistic morphological clock analysis of trilobites, which exemplify the earliest arthropod body fossils, supports a Cambrian origin, without the need to posit an unfossilized Ediacaran history.
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Affiliation(s)
- Gregory D. Edgecombe
- Department of Earth Sciences, The Natural History Museum, London SW7 5BD, United Kingdom
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Howard RJ, Hou X, Edgecombe GD, Salge T, Shi X, Ma X. A Tube-Dwelling Early Cambrian Lobopodian. Curr Biol 2020; 30:1529-1536.e2. [PMID: 32109391 DOI: 10.1016/j.cub.2020.01.075] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Revised: 12/09/2019] [Accepted: 01/24/2020] [Indexed: 01/27/2023]
Abstract
Facivermis yunnanicus [1, 2] is an enigmatic worm-like animal from the early Cambrian Chengjiang Biota of Yunnan Province, China. It is a small (<10 cm) bilaterian with five pairs of spiny anterior arms, an elongated body, and a swollen posterior end. The unusual morphology of Facivermis has prompted a history of diverse taxonomic interpretations, including among annelids [1, 3], lophophorates [4], and pentastomids [5]. However, in other studies, Facivermis is considered to be more similar to lobopodians [2, 6-8]-the fossil grade from which modern panarthropods (arthropods, onychophorans, and tardigrades) are derived. In these studies, Facivermis is thought to be intermediate between cycloneuralian worms and lobopodians. Facivermis has therefore been suggested to represent an early endobenthic-epibenthic panarthropod transition [6] and to provide crucial insights into the origin of paired appendages [2]. However, the systematic affinity of Facivermis was poorly supported in a previous phylogeny [6], partially due to incomplete understanding of its morphology. Therefore, the evolutionary significance of Facivermis remains unresolved. In this study, we re-examine Facivermis from new material and the holotype, leading to the discovery of several new morphological features, such as paired eyes on the head and a dwelling tube. Comprehensive phylogenetic analyses using parsimony, Bayesian inference, and maximum likelihood all support Facivermis as a luolishaniid in a derived position within the onychophoran stem group rather than as a basal panarthropod. In contrast to previous studies, we therefore conclude that Facivermis provides a rare early Cambrian example of secondary loss to accommodate a highly specialized tube-dwelling lifestyle.
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Affiliation(s)
- Richard J Howard
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming 650500, China; Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9TA, UK; Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - Xianguang Hou
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming 650500, China; Yunnan Key Laboratory for Palaeobiology, Yunnan University, Chenggong Campus, Kunming 650500, China.
| | - Gregory D Edgecombe
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming 650500, China; Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - Tobias Salge
- Imaging and Analysis Centre, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - Xiaomei Shi
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming 650500, China; Yunnan Key Laboratory for Palaeobiology, Yunnan University, Chenggong Campus, Kunming 650500, China
| | - Xiaoya Ma
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming 650500, China; Yunnan Key Laboratory for Palaeobiology, Yunnan University, Chenggong Campus, Kunming 650500, China; Centre for Ecology and Conservation, University of Exeter, Penryn Campus, Cornwall TR10 9TA, UK.
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9
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Aria C, Zhao F, Zeng H, Guo J, Zhu M. Fossils from South China redefine the ancestral euarthropod body plan. BMC Evol Biol 2020; 20:4. [PMID: 31914921 PMCID: PMC6950928 DOI: 10.1186/s12862-019-1560-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 12/12/2019] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND Early Cambrian Lagerstätten from China have greatly enriched our perspective on the early evolution of animals, particularly arthropods. However, recent studies have shown that many of these early fossil arthropods were more derived than previously thought, casting uncertainty on the ancestral euarthropod body plan. In addition, evidence from fossilized neural tissues conflicts with external morphology, in particular regarding the homology of the frontalmost appendage. RESULTS Here we redescribe the multisegmented megacheirans Fortiforceps and Jianfengia and describe Sklerolibyon maomima gen. et sp. nov., which we place in Jianfengiidae, fam. nov. (in Megacheira, emended). We find that jianfengiids show high morphological diversity among megacheirans, both in trunk ornamentation and head anatomy, which encompasses from 2 to 4 post-frontal appendage pairs. These taxa are also characterized by elongate podomeres likely forming seven-segmented endopods, which were misinterpreted in their original descriptions. Plesiomorphic traits also clarify their connection with more ancestral taxa. The structure and position of the "great appendages" relative to likely sensory antero-medial protrusions, as well as the presence of optic peduncles and sclerites, point to an overall homology with the anterior head of radiodontans. This is confirmed by our Bayesian phylogeny, which places jianfengiids as the basalmost euarthropods, paraphyletic with other megacheirans, and in contiguity with isoxyids and radiodontans. CONCLUSIONS Sklerolibyon and other jianfengiids expand the disparity of megacheirans and suggest that the common euarthropod ancestor possessed a remarkable phenotypic variability associated with the externalized cephalon, as well as endopods that were already heptopodomerous, which differs from previous hypotheses and observations. These animals also demonstrate that the frontalmost pair of arthrodized appendage is homologous between radiodontans and megacheirans, refuting the claim that the radiodontan frontal appendages evolved into the euarthropod labrum, and questioning its protocerebral identity. This evidence based on external anatomy now constitutes a solid benchmark upon which we should address issues of homology, with the help of carefully examined palaeoneurological data.
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Affiliation(s)
- Cédric Aria
- State Key Laboratory of Palaeobiology and Stratigraphy & Center for Excellence in Life and Palaeoenvironment, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Fangchen Zhao
- State Key Laboratory of Palaeobiology and Stratigraphy & Center for Excellence in Life and Palaeoenvironment, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Han Zeng
- State Key Laboratory of Palaeobiology and Stratigraphy & Center for Excellence in Life and Palaeoenvironment, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Jin Guo
- Management Committee of the Chengjiang Fossil Site World Heritage, Chengjiang, 652599, China
| | - Maoyan Zhu
- State Key Laboratory of Palaeobiology and Stratigraphy & Center for Excellence in Life and Palaeoenvironment, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China. .,College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
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10
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Moysiuk J, Caron JB. A new hurdiid radiodont from the Burgess Shale evinces the exploitation of Cambrian infaunal food sources. Proc Biol Sci 2019; 286:20191079. [PMID: 31362637 PMCID: PMC6710600 DOI: 10.1098/rspb.2019.1079] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 07/05/2019] [Indexed: 11/12/2022] Open
Abstract
Radiodonts, a clade of Cambro-Devonian stem group euarthropods, have classically been regarded as nektonic apex predators. However, many aspects of radiodont morphology and ecology have remained unclear because of the typically fragmentary nature of fossil material. Here, we describe a new hurdiid radiodont based on abundant and exceptionally well-preserved fossils from the Burgess Shale (Marble Canyon area, British Columbia, Canada). Cambroraster falcatus gen. et sp. nov. is characterized by an extra-large horseshoe-shaped head carapace, bearing conspicuous posterolateral spinous processes, and partially covering a short trunk with eight pairs of lateral flaps. Each of the pair of frontal appendages possess five mesially curving rake-like endites equipped with a series of anteriorly directed hooked spines, altogether surrounding the oral cone. This feeding apparatus suggests a micro to macrophagous sediment-sifting feeding ecology. Cambroraster illuminates the evolution of Hurdiidae and evinces the exploitation of the diversifying infauna by these large and specialized nektobenthic carnivores in the aftermath of the Cambrian explosion.
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Affiliation(s)
- J. Moysiuk
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, CanadaM5S 3B2
- Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, CanadaM5S 2C6
| | - J.-B. Caron
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, CanadaM5S 3B2
- Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, CanadaM5S 2C6
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11
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Ou Q, Mayer G. A Cambrian unarmoured lobopodian, †Lenisambulatrix humboldti gen. et sp. nov., compared with new material of †Diania cactiformis. Sci Rep 2018; 8:13667. [PMID: 30237414 PMCID: PMC6147921 DOI: 10.1038/s41598-018-31499-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 08/14/2018] [Indexed: 11/09/2022] Open
Abstract
Cambrian marine lobopodians are generally considered as predecessors of modern panarthropods (onychophorans, tardigrades, and arthropods). Hence, further study of their morphological diversity and early radiation may enhance our understanding of the ground pattern and evolutionary history of panarthropods. Here, we report a rare lobopodian species, †Lenisambulatrix humboldti gen. et sp. nov. ("Humboldt lobopodian"), from the early Cambrian Chengjiang Lagerstätte and describe new morphological features of †Diania cactiformis, a coeval armoured lobopodian nicknamed "walking cactus". Both lobopodian species were similar in possessing rather thick, elongate lobopods without terminal claws. However, in contrast to †Diania cactiformis, the body of which was heavily armored with spines, the trunk and limbs of the Humboldt lobopodian were entirely unarmored. Our study augments the morphological diversity of Cambrian lobopodians and presents two evolutionary extremes of cuticular ornamentation: one represented by the Humboldt lobopodian, which was most likely entirely "naked", the other epitomized by †D. cactiformis, which was highly "armoured".
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Affiliation(s)
- Qiang Ou
- Early Life Evolution Laboratory, State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), Beijing, 100083, China. .,Department of Zoology, University of Kassel, 34132, Kassel, Germany.
| | - Georg Mayer
- Department of Zoology, University of Kassel, 34132, Kassel, Germany
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Siveter DJ, Briggs DEG, Siveter DJ, Sutton MD, Legg D. A three-dimensionally preserved lobopodian from the Herefordshire (Silurian) Lagerstätte, UK. ROYAL SOCIETY OPEN SCIENCE 2018; 5:172101. [PMID: 30224988 PMCID: PMC6124121 DOI: 10.1098/rsos.172101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 07/06/2018] [Indexed: 06/08/2023]
Abstract
The Herefordshire (Silurian) Lagerstätte (approx. 430 Myr BP) has yielded, among many exceptionally preserved invertebrates, a wide range of new genera belonging to crown-group Panarthropoda. Here, we increase this panarthropod diversity with the lobopodian Thanahita distos, a new total-group panarthropod genus and species. This new lobopodian preserves at least nine paired, long, slender appendages, the anterior two in the head region and the posterior seven representing trunk lobopods. The body ends in a short post-appendicular extension. Some of the trunk lobopods bear two claws, others a single claw. The body is covered by paired, tuft-like papillae. Thanahita distos joins only seven other known three-dimensionally preserved lobopodian or onychophoran (velvet worm) fossil specimens and is the first lobopodian to be formally described from the Silurian. Phylogenetic analysis recovered it, together with all described Hallucigenia species, in a sister-clade to crown-group panarthropods. Its placement in a redefined Hallucigeniidae, an iconic Cambrian clade, indicates the survival of this clade to Silurian times.
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Affiliation(s)
- Derek J. Siveter
- Earth Collections, University Museum of Natural History, Oxford OX1 3PW, UK
- Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3AN, UK
| | - Derek E. G. Briggs
- Department of Geology and Geophysics and Yale Peabody Museum of Natural History, Yale University, PO Box 208109, New Haven, CT 06520-8109, USA
| | - David J. Siveter
- School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK
| | - Mark D. Sutton
- Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK
| | - David Legg
- School of Earth and Environmental Sciences, University of Manchester, Williamson Building, Oxford Road, Manchester M13 9PL, UK
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Vannier J, Aria C, Taylor RS, Caron JB. Waptia fieldensis Walcott, a mandibulate arthropod from the middle Cambrian Burgess Shale. ROYAL SOCIETY OPEN SCIENCE 2018; 5:172206. [PMID: 30110460 PMCID: PMC6030330 DOI: 10.1098/rsos.172206] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 05/04/2018] [Indexed: 05/12/2023]
Abstract
Waptia fieldensis Walcott, 1912 is one of the iconic animals from the middle Cambrian Burgess Shale biota that had lacked a formal description since its discovery at the beginning of the twentieth century. This study, based on over 1800 specimens, finds that W. fieldensis shares general characteristics with pancrustaceans, as previous authors had suggested based mostly on its overall aspect. The cephalothorax is covered by a flexible, bivalved carapace and houses a pair of long multisegmented antennules, palp-bearing mandibles, maxillules, and four pairs of appendages with five-segmented endopods-the anterior three pairs with long and robust enditic basipods, the fourth pair with proximal annulations and lamellae. The post-cephalothorax has six pairs of lamellate and fully annulated appendages which appear to be extensively modified basipods rather than exopods. The front part of the body bears a pair of stalked eyes with the first ommatidia preserved in a Burgess Shale arthropod, and a median 'labral' complex flanked by lobate projections with possible affinities to hemi-ellipsoid bodies. Waptia confirms the mandibulate affinity of hymenocarines, retrieved here as part of an expanded Pancrustacea, thereby providing a novel perspective on the evolutionary history of this hyperdiverse group. We construe that Waptia was an active swimming predator of soft prey items, using its anterior appendages for food capture and manipulation, and also potentially for clinging to epibenthic substrates.
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Affiliation(s)
- Jean Vannier
- Université de Lyon, Université Lyon 1, ENS de Lyon, CNRS, UMR 5276 LGL-TPE, Bâtiment Géode, 2, rue Raphaël Dubois, Villeurbanne 69622, France
| | - Cédric Aria
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39, East Beijing Road, Nanjing 210008, People's Republic of China
- Department of Natural History (Palaeobiology Section), Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, CanadaM5S 2C6
| | - Rod S. Taylor
- Manuels River Hibernia Interpretation Centre, 7 Conception Bay South Highway, CBS, Newfoundland, CanadaA1W 3A2
- Department of Earth Sciences, Memorial University of Newfoundland, St John's, Newfoundland, CanadaA1B 3X5
| | - Jean-Bernard Caron
- Department of Natural History (Palaeobiology Section), Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, CanadaM5S 2C6
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, CanadaM5S 3B2, Toronto, Ontario, CanadaM5S 3B2
- Department of Earth Sciences, University of Toronto, Toronto, Ontario, CanadaM5S 3B1
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Aria C, Caron JB. Mandibulate convergence in an armoured Cambrian stem chelicerate. BMC Evol Biol 2017; 17:261. [PMID: 29262772 PMCID: PMC5738823 DOI: 10.1186/s12862-017-1088-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 11/21/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Chelicerata represents a vast clade of mostly predatory arthropods united by a distinctive body plan throughout the Phanerozoic. Their origins, however, with respect to both their ancestral morphological features and their related ecologies, are still poorly understood. In particular, it remains unclear whether their major diagnostic characters were acquired early on, and their anatomical organization rapidly constrained, or if they emerged from a stem lineage encompassing an array of structural variations, based on a more labile "panchelicerate" body plan. RESULTS In this study, we reinvestigated the problematic middle Cambrian arthropod Habelia optata Walcott from the Burgess Shale, and found that it was a close relative of Sanctacaris uncata Briggs and Collins (in Habeliida, ord. nov.), both retrieved in our Bayesian phylogeny as stem chelicerates. Habelia possesses an exoskeleton covered in numerous spines and a bipartite telson as long as the rest of the body. Segments are arranged into three tagmata. The prosoma includes a reduced appendage possibly precursor to the chelicera, raptorial endopods connected to five pairs of outstandingly large and overlapping gnathobasic basipods, antennule-like exopods seemingly dissociated from the main limb axis, and, posteriorly, a pair of appendages morphologically similar to thoracic ones. While the head configuration of habeliidans anchors a seven-segmented prosoma as the chelicerate ground pattern, the peculiar size and arrangement of gnathobases and the presence of sensory/tactile appendages also point to an early convergence with the masticatory head of mandibulates. CONCLUSIONS Although habeliidans illustrate the early appearance of some diagnostic chelicerate features in the evolution of euarthropods, the unique convergence of their cephalons with mandibulate anatomies suggests that these traits retained an unusual variability in these taxa. The common involvement of strong gnathal appendages across non-megacheirans Cambrian taxa also illustrates that the specialization of the head as the dedicated food-processing tagma was critical to the emergence of both lineages of extant euarthropods-Chelicerata and Mandibulata-and implies that this diversification was facilitated by the expansion of durophagous niches.
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Affiliation(s)
- Cédric Aria
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S3B2, Canada.
- Present address: State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, 210008, China.
| | - Jean-Bernard Caron
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, M5S3B2, Canada
- Department of Natural History (Palaeobiology Section), Royal Ontario Museum, Toronto, ON, M5S2C6, Canada
- Department of Earth Sciences, University of Toronto, Toronto, ON, M5S3B1, Canada
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Giribet G, Edgecombe GD. Current Understanding of Ecdysozoa and its Internal Phylogenetic Relationships. Integr Comp Biol 2017; 57:455-466. [DOI: 10.1093/icb/icx072] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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