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Wang D, Qiang Y, Guo J, Vannier J, Song Z, Peng J, Zhang B, Sun J, Yu Y, Zhang Y, Zhang T, Yang X, Han J. Early evolution of the ecdysozoan body plan. eLife 2024; 13:RP94709. [PMID: 38976315 PMCID: PMC11231812 DOI: 10.7554/elife.94709] [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] [Indexed: 07/09/2024] Open
Abstract
Extant ecdysozoans (moulting animals) are represented by a great variety of soft-bodied or articulated organisms that may or may not have appendages. However, controversies remain about the vermiform nature (i.e. elongated and tubular) of their ancestral body plan. We describe here Beretella spinosa gen. et sp. nov. a tiny (maximal length 3 mm) ecdysozoan from the lowermost Cambrian, Yanjiahe Formation, South China, characterized by an unusual sack-like appearance, single opening, and spiny ornament. Beretella spinosa gen. et sp. nov has no equivalent among animals, except Saccorhytus coronarius, also from the basal Cambrian. Phylogenetic analyses resolve both fossil species as a sister group (Saccorhytida) to all known Ecdysozoa, thus suggesting that ancestral ecdysozoans may have been non-vermiform animals. Saccorhytids are likely to represent an early off-shot along the stem-line Ecdysozoa. Although it became extinct during the Cambrian, this animal lineage provides precious insight into the early evolution of Ecdysozoa and the nature of the earliest representatives of the group.
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Affiliation(s)
- Deng Wang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi'an, China
| | - Yaqin Qiang
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Junfeng Guo
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Jean Vannier
- Université de Lyon, Université Claude Bernard Lyon 1, ENS de Lyon, CNRS, Laboratoire de Géologie de Lyon: Terre, Planètes, Environnement (CNRS-UMR 5276), Villeurbanne, France
| | - Zuchen Song
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Jiaxin Peng
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Boyao Zhang
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Jie Sun
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi'an, China
- School of Earth Science and Resources, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education, Chang'an University, Xi'an, China
| | - Yilun Yu
- Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yiheng Zhang
- School of Information Science and Technology, Northwest University, Xi'an, China
| | - Tao Zhang
- School of Information Science and Technology, Northwest University, Xi'an, China
| | - Xiaoguang Yang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi'an, China
| | - Jian Han
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, Xi'an, China
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Park TYS, Nielsen ML, Parry LA, Sørensen MV, Lee M, Kihm JH, Ahn I, Park C, de Vivo G, Smith MP, Harper DAT, Nielsen AT, Vinther J. A giant stem-group chaetognath. SCIENCE ADVANCES 2024; 10:eadi6678. [PMID: 38170772 PMCID: PMC10796117 DOI: 10.1126/sciadv.adi6678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 12/01/2023] [Indexed: 01/05/2024]
Abstract
Chaetognaths, with their characteristic grasping spines, are the oldest known pelagic predators, found in the lowest Cambrian (Terreneuvian). Here, we describe a large stem chaetognath, Timorebestia koprii gen. et sp. nov., from the lower Cambrian Sirius Passet Lagerstätte, which exhibits lateral and caudal fins, a distinct head region with long antennae and a jaw apparatus similar to Amiskwia sagittiformis. Amiskwia has previously been interpreted as a total-group chaetognathiferan, as either a stem-chaetognath or gnathostomulid. We show that T. koprii shares a ventral ganglion with chaetognaths to the exclusion of other animal groups, firmly placing these fossils on the chaetognath stem. The large size (up to 30 cm) and gut contents in T. koprii suggest that early chaetognaths occupied a higher trophic position in pelagic food chains than today.
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Affiliation(s)
- Tae-Yoon S. Park
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
- University of Science and Technology, 217 Gajeong-ro, Daejeon 34113, Republic of Korea
| | - Morten Lunde Nielsen
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
- School of Earth Sciences, Palaeobiology Research Group, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
- British Geological Survey, Nicker Hill, Keyworth NG12 5GG, UK
| | - Luke A. Parry
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | | | - Mirinae Lee
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
| | - Ji-Hoon Kihm
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
- University of Science and Technology, 217 Gajeong-ro, Daejeon 34113, Republic of Korea
| | - Inhye Ahn
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
- University of Science and Technology, 217 Gajeong-ro, Daejeon 34113, Republic of Korea
| | - Changkun Park
- Division of Earth Sciences, Korea Polar Research Institute, 26 Songdomirae-ro Yeonsu-gu, Incheon 21990, Republic of Korea
| | - Giacinto de Vivo
- Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Napoli, Italy
| | - M. Paul Smith
- Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK
| | - David A. T. Harper
- Palaeoecosystems Group, Department of Earth Sciences, Durham University, Durham DH1 3LE, UK
| | - Arne T. Nielsen
- Department of Geoscience and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, Copenhagen DK-1350, Denmark
| | - Jakob Vinther
- School of Earth Sciences, Palaeobiology Research Group, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
- School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
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3
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Smith MR. Evolution: Assembling the deuterostome body plan. Curr Biol 2023; 33:R691-R694. [PMID: 37339599 DOI: 10.1016/j.cub.2023.05.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2023]
Abstract
Starfish, graptolites and humans look as different as can be, yet are more closely related to each other than to any other phylum. Disc-shaped Cambrian fossils join the dots between these disparate body plans to plot out their evolutionary origins.
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Affiliation(s)
- Martin R Smith
- Department of Earth Sciences, Durham University, Mountjoy Site, Durham DH1 3LE, UK.
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Li Y, Dunn FS, Murdock DJE, Guo J, Rahman IA, Cong P. Cambrian stem-group ambulacrarians and the nature of the ancestral deuterostome. Curr Biol 2023:S0960-9822(23)00530-4. [PMID: 37167976 DOI: 10.1016/j.cub.2023.04.048] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 02/17/2023] [Accepted: 04/19/2023] [Indexed: 05/13/2023]
Abstract
Deuterostomes are characterized by some of the most widely divergent body plans in the animal kingdom. These striking morphological differences have hindered efforts to predict ancestral characters, with the origin and earliest evolution of the group remaining ambiguous. Several iconic Cambrian fossils have been suggested to be early deuterostomes and hence could help elucidate ancestral character states. However, their phylogenetic relationships are controversial. Here, we describe new, exceptionally preserved specimens of the discoidal metazoan Rotadiscus grandis from the early Cambrian Chengjiang biota of China. These reveal a previously unknown double spiral structure, which we interpret as a chordate-like covering to a coelomopore, located adjacent to a horseshoe-shaped tentacle complex. The tentacles differ in key aspects from those seen in lophophorates and are instead more similar to the tentacular systems of extant pterobranchs and echinoderms. Thus, Rotadiscus exhibits a chimeric combination of ambulacrarian and chordate characters. Phylogenetic analyses recover Rotadiscus and closely related fossil taxa as stem ambulacrarians, filling a significant morphological gap in the deuterostome tree of life. These results allow us to reconstruct the ancestral body plans of major clades of deuterostomes, revealing that key traits of extant forms, such as a post-anal region, gill bars, and a U-shaped gut, evolved through convergence.
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Affiliation(s)
- Yujing Li
- Yunnan Normal University, Kunming 650500, China; Yunnan Key Laboratory for Palaeobiology & MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Institute of Palaeontology, Yunnan University, Kunming 650500, China; State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
| | - Frances S Dunn
- Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK
| | - Duncan J E Murdock
- Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK
| | - Jin Guo
- Yunnan Key Laboratory for Palaeobiology & MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Institute of Palaeontology, Yunnan University, Kunming 650500, China; Management Committee of the Chengjiang Fossil Site World Heritage, Chengjiang 652599, China
| | - Imran A Rahman
- Oxford University Museum of Natural History, University of Oxford, Oxford OX1 3PW, UK; The Natural History Museum, London SW7 5BD, UK.
| | - Peiyun Cong
- Yunnan Key Laboratory for Palaeobiology & MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Institute of Palaeontology, Yunnan University, Kunming 650500, China.
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Liu Y, Carlisle E, Zhang H, Yang B, Steiner M, Shao T, Duan B, Marone F, Xiao S, Donoghue PCJ. Saccorhytus is an early ecdysozoan and not the earliest deuterostome. Nature 2022; 609:541-546. [PMID: 35978194 DOI: 10.1038/s41586-022-05107-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 07/13/2022] [Indexed: 11/09/2022]
Abstract
The early history of deuterostomes, the group composed of the chordates, echinoderms and hemichordates1, is still controversial, not least because of a paucity of stem representatives of these clades2-5. The early Cambrian microscopic animal Saccorhytus coronarius was interpreted as an early deuterostome on the basis of purported pharyngeal openings, providing evidence for a meiofaunal ancestry6 and an explanation for the temporal mismatch between palaeontological and molecular clock timescales of animal evolution6-8. Here we report new material of S. coronarius, which is reconstructed as a millimetric and ellipsoidal meiobenthic animal with spinose armour and a terminal mouth but no anus. Purported pharyngeal openings in support of the deuterostome hypothesis6 are shown to be taphonomic artefacts. Phylogenetic analyses indicate that S. coronarius belongs to total-group Ecdysozoa, expanding the morphological disparity and ecological diversity of early Cambrian ecdysozoans.
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Affiliation(s)
- Yunhuan Liu
- School of Earth Science and Resources, Chang'an University, Xi'an, China
| | - Emily Carlisle
- Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Bristol, UK
| | - Huaqiao Zhang
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing, China.
| | - Ben Yang
- MNR Key Laboratory of Stratigraphy and Palaeontology, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China
| | - Michael Steiner
- College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, China.,Department of Earth Sciences, Freie Universität Berlin, Berlin, Germany
| | - Tiequan Shao
- School of Earth Science and Resources, Chang'an University, Xi'an, China
| | - Baichuan Duan
- Key Laboratory of Marine Geology and Metallogeny, First Institute of Oceanography, Ministry of Natural Resource, Qingdao, China
| | - Federica Marone
- Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland
| | - Shuhai Xiao
- Department of Geosciences, Virginia Tech, Blacksburg, VA, USA.
| | - Philip C J Donoghue
- Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Bristol, UK.
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6
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Howard RJ, Edgecombe GD, Shi X, Hou X, Ma X. Ancestral morphology of Ecdysozoa constrained by an early Cambrian stem group ecdysozoan. BMC Evol Biol 2020; 20:156. [PMID: 33228518 PMCID: PMC7684930 DOI: 10.1186/s12862-020-01720-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 11/08/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Ecdysozoa are the moulting protostomes, including arthropods, tardigrades, and nematodes. Both the molecular and fossil records indicate that Ecdysozoa is an ancient group originating in the terminal Proterozoic, and exceptional fossil biotas show their dominance and diversity at the beginning of the Phanerozoic. However, the nature of the ecdysozoan common ancestor has been difficult to ascertain due to the extreme morphological diversity of extant Ecdysozoa, and the lack of early diverging taxa in ancient fossil biotas. RESULTS Here we re-describe Acosmia maotiania from the early Cambrian Chengjiang Biota of Yunnan Province, China and assign it to stem group Ecdysozoa. Acosmia features a two-part body, with an anterior proboscis bearing a terminal mouth and muscular pharynx, and a posterior annulated trunk with a through gut. Morphological phylogenetic analyses of the protostomes using parsimony, maximum likelihood and Bayesian inference, with coding informed by published experimental decay studies, each placed Acosmia as sister taxon to Cycloneuralia + Panarthropoda-i.e. stem group Ecdysozoa. Ancestral state probabilities were calculated for key ecdysozoan nodes, in order to test characters inferred from fossils to be ancestral for Ecdysozoa. Results support an ancestor of crown group ecdysozoans sharing an annulated vermiform body with a terminal mouth like Acosmia, but also possessing the pharyngeal armature and circumoral structures characteristic of Cambrian cycloneuralians and lobopodians. CONCLUSIONS Acosmia is the first taxon placed in the ecdysozoan stem group and provides a constraint to test hypotheses on the early evolution of Ecdysozoa. Our study suggests acquisition of pharyngeal armature, and therefore a change in feeding strategy (e.g. predation), may have characterised the origin and radiation of crown group ecdysozoans from Acosmia-like ancestors.
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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
| | - 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
| | - Xiaomei Shi
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming, 650500, China
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Chenggong Campus, Kunming, 650500, China
| | - Xianguang Hou
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Chenggong Campus, Kunming, 650500, China.
- Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, 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, Institute of Palaeontology, 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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7
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Affiliation(s)
- Martin R Smith
- Department of Earth Sciences, Durham University, UK
- Reviewer of NSR
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8
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9
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Laumer CE, Fernández R, Lemer S, Combosch D, Kocot KM, Riesgo A, Andrade SCS, Sterrer W, Sørensen MV, Giribet G. Revisiting metazoan phylogeny with genomic sampling of all phyla. Proc Biol Sci 2019; 286:20190831. [PMID: 31288696 PMCID: PMC6650721 DOI: 10.1098/rspb.2019.0831] [Citation(s) in RCA: 123] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 06/17/2019] [Indexed: 11/21/2022] Open
Abstract
Proper biological interpretation of a phylogeny can sometimes hinge on the placement of key taxa-or fail when such key taxa are not sampled. In this light, we here present the first attempt to investigate (though not conclusively resolve) animal relationships using genome-scale data from all phyla. Results from the site-heterogeneous CAT + GTR model recapitulate many established major clades, and strongly confirm some recent discoveries, such as a monophyletic Lophophorata, and a sister group relationship between Gnathifera and Chaetognatha, raising continued questions on the nature of the spiralian ancestor. We also explore matrix construction with an eye towards testing specific relationships; this approach uniquely recovers support for Panarthropoda, and shows that Lophotrochozoa (a subclade of Spiralia) can be constructed in strongly conflicting ways using different taxon- and/or orthologue sets. Dayhoff-6 recoding sacrifices information, but can also reveal surprising outcomes, e.g. full support for a clade of Lophophorata and Entoprocta + Cycliophora, a clade of Placozoa + Cnidaria, and raising support for Ctenophora as sister group to the remaining Metazoa, in a manner dependent on the gene and/or taxon sampling of the matrix in question. Future work should test the hypothesis that the few remaining uncertainties in animal phylogeny might reflect violations of the various stationarity assumptions used in contemporary inference methods.
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Affiliation(s)
- Christopher E. Laumer
- Museum of Comparative Zoology (MCZ) and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
- EMBL-European Bioinformatics Institute (EBI), Wellcome Genome Campus, Hinxton CB10 1SD, UK
| | - Rosa Fernández
- Museum of Comparative Zoology (MCZ) and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
- Bioinformatics & Genomics Unit, Center for Genomic Regulation, Carrer del Dr. Aiguader 88, 08003 Barcelona (Spain)
| | - Sarah Lemer
- Museum of Comparative Zoology (MCZ) and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
- Marine Laboratory, University of Guam, UOG Station, Mangilao, Guam 96923, USA
| | - David Combosch
- Museum of Comparative Zoology (MCZ) and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
- Marine Laboratory, University of Guam, UOG Station, Mangilao, Guam 96923, USA
| | - Kevin M. Kocot
- Department of Biological Sciences and Alabama Museum of Natural History, The University of Alabama, Campus Box 870344, Tuscaoosa, AL 35487, USA
| | - Ana Riesgo
- Department of Life Sciences, Natural History Museum of London, Cromwell Road, London SW7 5BD, UK
| | - Sónia C. S. Andrade
- Departamento de Genética e Biologia Evolutiva, IB, Universidade de São Paulo, 05508090 São Paulo, SP, Brazil
| | - Wolfgang Sterrer
- Bermuda Natural History Museum, PO Box FL 145, Flatts, FLBX, Bermuda
| | - Martin V. Sørensen
- Natural History Museum of Denmark, Universitetsparken 15, 2100 Copenhagen, Denmark
| | - Gonzalo Giribet
- Museum of Comparative Zoology (MCZ) and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA
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Caron JB, Cheung B. Amiskwia is a large Cambrian gnathiferan with complex gnathostomulid-like jaws. Commun Biol 2019; 2:164. [PMID: 31069273 PMCID: PMC6499802 DOI: 10.1038/s42003-019-0388-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 03/15/2019] [Indexed: 11/12/2022] Open
Abstract
Phylogenomic studies have greatly improved our understanding of the animal tree of life but the relationships of many clades remain ambiguous. Here we show that the rare soft-bodied animal Amiskwia from the Cambrian of Canada and China, which has variously been considered a chaetognath, a nemertine, allied to molluscs, or a problematica, is related to gnathiferans. New specimens from the Burgess Shale (British Columbia, Canada) preserve a complex pharyngeal jaw apparatus composed of a pair of elements with teeth most similar to gnathostomulids. Amiskwia demonstrates that primitive spiralians were large and unsegmented, had a coelom, and were probably active nekto-benthic scavengers or predators. Secondary simplification and miniaturisation events likely occurred in response to shifting ecologies and adaptations to specialised planktonic habitats.
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Affiliation(s)
- Jean-Bernard Caron
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2 Canada
- Department of Natural History—Palaeobiology, Royal Ontario Museum, 100 Queen’s Park, Toronto, ON M5S 2C6 Canada
- Department of Earth Sciences, University of Toronto, Toronto, ON M5S 3B1 Canada
| | - Brittany Cheung
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2 Canada
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