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Briggs DEG, Siveter DJ, Siveter DJ, Sutton MD, Legg D, Lamsdell JC. A vicissicaudatan arthropod from the Silurian Herefordshire Lagerstätte, UK. R Soc Open Sci 2023; 10:230661. [PMID: 37538743 PMCID: PMC10394423 DOI: 10.1098/rsos.230661] [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] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 07/17/2023] [Indexed: 08/05/2023]
Abstract
A new arthropod, Carimersa neptuni gen. et sp. nov., is described from the Silurian (Wenlock Series) Herefordshire Konservat-Lagerstätte, UK. The head bears pedunculate eyes and five pairs of appendages. Triflagellate antennae are followed by two pairs of uniramous limbs each with an endopod bearing a pronounced gnathobasic basipod. The posterior two pairs of head limbs and all trunk limbs bear an endopod, exopod and filamentous exite. The trunk consists of 10 appendage-bearing segments followed by an apodous abdomen of four segments. The arthropod resolves as sister taxon to Kodymirus and Eozetetes + Aglaspidida. It is the first representative of Vicissicaudata reported from the Herefordshire Lagerstätte and the first Silurian example with well-preserved appendages. The preservation of a cluster of radiolarians apparently captured by the trunk appendages is the first direct association of predator and prey discovered in the Herefordshire fauna, and suggests that Carimersa was a nektobenthic form that used its gnathobasic basipods in microdurophagy.
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Affiliation(s)
- Derek E. G. Briggs
- Department of Earth and Planetary Sciences, and Yale Peabody Museum, Yale University, New Haven, CT 06520-8109, USA
| | - David J. Siveter
- School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK
| | - Derek J. Siveter
- Earth Collections, University Museum of Natural History, Oxford OX1 3PW, UK
- Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK
| | - Mark D. Sutton
- Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK
| | - David Legg
- Department of Earth and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK
| | - James C. Lamsdell
- Department of Geology and Geography, West Virginia University, 98 Beechurst Avenue, Brooks Hall, Morgantown, WV 26506, USA
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2
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McGairy A, Komatsu T, Williams M, Harvey THP, Miller CG, Nguyen PD, Legrand J, Yamada T, Siveter DJ, Bush H, Stocker CP. Ostracods had colonized estuaries by the late Silurian. Biol Lett 2021; 17:20210403. [PMID: 34847752 PMCID: PMC8633793 DOI: 10.1098/rsbl.2021.0403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [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: 08/01/2021] [Accepted: 11/01/2021] [Indexed: 11/12/2022] Open
Abstract
The fossil record of terrestrialization documents notable shifts in the environmental and physiological tolerances of many animal and plant groups. However, for certain significant components of modern freshwater and terrestrial environments, the transition out of marine settings remains largely unconstrained. Ostracod crustaceans occupy an exceptional range of modern aquatic environments and are invaluable palaeoenvironmental indicators in the fossil record. However, pre-Carboniferous records of supposed non-marine and marginal marine ostracods are sparse, and the timing of their marine to non-marine transition has proven elusive. Here, we reassess the early environmental history of ostracods in light of new assemblages from the late Silurian of Vietnam. Two, low diversity but distinct ostracod assemblages are associated with estuarine deposits. This occurrence is consistent with previous incidental reports of ostracods occupying marginal and brackish settings through the late Silurian and Devonian. Therefore, ostracods were pioneering the occupation of marginal marine and estuarine settings 60 Myr before the Carboniferous and they were a component of the early phase of transition from marine to non-marine environments.
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Affiliation(s)
- Anna McGairy
- School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK
| | - Toshifumi Komatsu
- Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, 860-8555, Japan
| | - Mark Williams
- School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK
| | - Thomas H. P. Harvey
- School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK
| | - C. Giles Miller
- The Natural History Museum, Cromwell Road, South Kensington, London SW7 5BD, UK
| | - Phong Duc Nguyen
- Department of Paleontology and Stratigraphy, Vietnam Institute of Geosciences and Mineral Resources, 100000 Hanoi, Vietnam
| | - Julien Legrand
- Department of Geosciences, Faculty of Science, Shizuoka University, Shizuoka, 422-8529, Japan
| | - Toshihiro Yamada
- Botanical Gardens, Faculty of Science, Osaka City University, Osaka, 576-0004, Japan
| | - David J. Siveter
- School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK
| | - Harrison Bush
- School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK
| | - Christopher P. Stocker
- School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK
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3
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Zhai D, Williams M, Siveter DJ, Harvey THP, Sansom RS, Gabbott SE, Siveter DJ, Ma X, Zhou R, Liu Y, Hou X. Variation in appendages in early Cambrian bradoriids reveals a wide range of body plans in stem-euarthropods. Commun Biol 2019; 2:329. [PMID: 31508504 PMCID: PMC6722085 DOI: 10.1038/s42003-019-0573-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [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: 03/28/2019] [Accepted: 08/02/2019] [Indexed: 11/08/2022] Open
Abstract
Traditionally, the origin and evolution of modern arthropod body plans has been revealed through increasing levels of appendage specialisation exhibited by Cambrian euarthropods. Here we show significant variation in limb morphologies and patterns of limb-tagmosis among three early Cambrian arthropod species conventionally assigned to the Bradoriida. These arthropods are recovered as a monophyletic stem-euarthropod group (and sister taxon to crown-group euarthropods, i.e. Chelicerata, Mandibulata and their extinct relatives), thus implying a radiation of stem-euarthropods where trends towards increasing appendage specialisation were explored convergently with other euarthropod groups. The alternative solution, where bradoriids are polyphyletic, representing several independent origins of a small, bivalved body plan in lineages from diverse regions of the euarthropod and mandibulate stems, is only marginally less parsimonious. The new data reveal a previously unknown disparity of body plans in stem-euarthropods and both solutions support remarkable evolutionary convergence, either of fundamental body plans or appendage specialization patterns.
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Affiliation(s)
- Dayou Zhai
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, 650091 Kunming, Yunnan China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, 650091 Kunming, Yunnan China
| | - Mark Williams
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, 650091 Kunming, Yunnan China
- Centre for Palaeobiology Research, School of Geography, Geology and the Environment, University of Leicester, Leicester, LE1 7RH UK
| | - David J. Siveter
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, 650091 Kunming, Yunnan China
- Centre for Palaeobiology Research, School of Geography, Geology and the Environment, University of Leicester, Leicester, LE1 7RH UK
| | - Thomas H. P. Harvey
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, 650091 Kunming, Yunnan China
- Centre for Palaeobiology Research, School of Geography, Geology and the Environment, University of Leicester, Leicester, LE1 7RH UK
| | - Robert S. Sansom
- School of Earth and Environmental Sciences, University of Manchester, Oxford Road, Oxford, M13 9PT UK
| | - Sarah E. Gabbott
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, 650091 Kunming, Yunnan China
- Centre for Palaeobiology Research, School of Geography, Geology and the Environment, University of Leicester, Leicester, LE1 7RH UK
| | - Derek J. Siveter
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, 650091 Kunming, Yunnan China
- Earth Collections, Oxford University Museum of Natural History, Parks Road, Oxford, OX1 3PW UK
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3PR UK
| | - Xiaoya Ma
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, 650091 Kunming, Yunnan China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, 650091 Kunming, Yunnan China
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE UK
| | - Runqing Zhou
- Institute of Geology and Geophysics, Chinese academy of Sciences, 19 Beituchengxi Road, 100029 Beijing, China
| | - Yu Liu
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, 650091 Kunming, Yunnan China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, 650091 Kunming, Yunnan China
| | - Xianguang Hou
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, 650091 Kunming, Yunnan China
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, 650091 Kunming, Yunnan China
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4
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Nadhira A, Sutton MD, Botting JP, Muir LA, Gueriau P, King A, Briggs DEG, Siveter DJ, Siveter DJ. Three-dimensionally preserved soft tissues and calcareous hexactins in a Silurian sponge: implications for early sponge evolution. R Soc Open Sci 2019; 6:190911. [PMID: 31417767 PMCID: PMC6689616 DOI: 10.1098/rsos.190911] [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] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Accepted: 07/09/2019] [Indexed: 06/10/2023]
Abstract
Sponges (Porifera), as one of the earliest-branching animal phyla, are crucial for understanding early metazoan phylogeny. Recent studies of Lower Palaeozoic sponges have revealed a variety of character states and combinations unknown in extant taxa, challenging our views of early sponge morphology. The Herefordshire Konservat-Lagerstätte yields an abundant, diverse sponge fauna with three-dimensional preservation of spicules and soft tissue. Carduispongia pedicula gen. et sp. nov. possesses a single layer of hexactine spicules arranged in a regular orthogonal network. This spicule type and arrangement is characteristic of the reticulosans, which have traditionally been interpreted as early members of the extant siliceous Class Hexactinellida. However, the unusual preservation of the spicules of C. pedicula reveals an originally calcareous composition, which would be diagnostic of the living Class Calcarea. The soft tissue architecture closely resembles the complex sylleibid or leuconid structure seen in some modern calcareans and homoscleromorphs. This combination of features strongly supports a skeletal continuum between primitive calcareans and hexactinellid siliceans, indicating that the last common ancestor of Porifera was a spiculate, solitary, vasiform animal with a thin skeletal wall.
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Affiliation(s)
- Ardianty Nadhira
- Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK
| | - Mark D. Sutton
- Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK
| | - Joseph P. Botting
- Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, People's Republic of China
- Department of Natural Sciences, Amgueddfa Cymru—National Museum Wales, Cathays Park, Cardiff CF10 3NP, UK
| | - Lucy A. Muir
- Department of Natural Sciences, Amgueddfa Cymru—National Museum Wales, Cathays Park, Cardiff CF10 3NP, UK
| | - Pierre Gueriau
- IPANEMA, CNRS, Ministère de la Culture, UVSQ, USR 3461, Université Paris-Saclay, 91192 Gif-sur-Yvette, France
- Institute of Earth Sciences, University of Lausanne, Géopolis, CH-1015 Lausanne, Switzerland
| | - Andrew King
- SOLEIL synchrotron, 91192 Gif-sur-Yvette, France
| | - Derek E. G. Briggs
- Department of Geology & 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
| | - Derek J. Siveter
- Earth Collections, University Museum of Natural History, Oxford OX1 3PW, UK
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
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5
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Cong PY, Harvey THP, Williams M, Siveter DJ, Siveter DJ, Gabbott SE, Li YJ, Wei F, Hou XG. Naked chancelloriids from the lower Cambrian of China show evidence for sponge-type growth. Proc Biol Sci 2019; 285:rspb.2018.0296. [PMID: 29925613 DOI: 10.1098/rspb.2018.0296] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 05/25/2018] [Indexed: 11/12/2022] Open
Abstract
Chancelloriids are an extinct group of spiny Cambrian animals of uncertain phylogenetic position. Despite their sponge-like body plan, their spines are unlike modern sponge spicules, but share several features with the sclerites of certain Cambrian bilaterians, notably halkieriids. However, a proposed homology of these 'coelosclerites' implies complex transitions in body plan evolution. A new species of chancelloriid, Allonnia nuda, from the lower Cambrian (Stage 3) Chengjiang Lagerstätte is distinguished by its large size and sparse spination, with modified apical sclerites surrounding an opening into the body cavity. The sclerite arrangement in A. nuda and certain other chancelloriids indicates that growth involved sclerite addition in a subapical region, thus maintaining distinct zones of body sclerites and apical sclerites. This pattern is not seen in halkieriids, but occurs in some modern calcarean sponges. With scleritome assembly consistent with a sponge affinity, and in the absence of cnidarian- or bilaterian-grade features, it is possible to interpret chancelloriids as sponges with an unusually robust outer epithelium, strict developmental control of body axis formation, distinctive spicule-like structures and, by implication, minute ostia too small to be resolved in fossils. In this light, chancelloriids may contribute to the emerging picture of high disparity among early sponges.
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Affiliation(s)
- Pei-Yun Cong
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, People's Republic of China .,Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming 650091, People's Republic of China
| | - Thomas H P Harvey
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming 650091, People's Republic of China .,School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester, LE1 7RH, UK
| | - Mark Williams
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming 650091, People's Republic of China.,School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester, LE1 7RH, UK
| | - David J Siveter
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming 650091, People's Republic of China.,School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester, LE1 7RH, UK
| | - Derek J Siveter
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming 650091, People's Republic of China.,Earth Collections, Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK.,Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3PR, UK
| | - Sarah E Gabbott
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming 650091, People's Republic of China.,School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester, LE1 7RH, UK
| | - Yu-Jing Li
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, People's Republic of China.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming 650091, People's Republic of China.,School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester, LE1 7RH, UK
| | - Fan Wei
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, People's Republic of China.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming 650091, People's Republic of China
| | - Xian-Guang Hou
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, People's Republic of China.,MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming 650091, People's Republic of China
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6
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Rahman IA, Thompson JR, Briggs DEG, Siveter DJ, Siveter DJ, Sutton MD. A new ophiocistioid with soft-tissue preservation from the Silurian Herefordshire Lagerstätte, and the evolution of the holothurian body plan. Proc Biol Sci 2019; 286:20182792. [PMID: 30966985 DOI: 10.1098/rspb.2018.2792] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [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
Reconstructing the evolutionary assembly of animal body plans is challenging when there are large morphological gaps between extant sister taxa, as in the case of echinozoans (echinoids and holothurians). However, the inclusion of extinct taxa can help bridge these gaps. Here we describe a new species of echinozoan, Sollasina cthulhu, from the Silurian Herefordshire Lagerstätte, UK. Sollasina cthulhu belongs to the ophiocistioids, an extinct group that shares characters with both echinoids and holothurians. Using physical-optical tomography and computer reconstruction, we visualize the internal anatomy of S. cthulhu in three dimensions, revealing inner soft tissues that we interpret as the ring canal, a key part of the water vascular system that was previously unknown in fossil echinozoans. Phylogenetic analyses strongly suggest that Sollasina and other ophiocistioids represent a paraphyletic group of stem holothurians, as previously hypothesized. This allows us to reconstruct the stepwise reduction of the skeleton during the assembly of the holothurian body plan, which may have been controlled by changes in the expression of biomineralization genes.
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Affiliation(s)
- Imran A Rahman
- 1 Oxford University Museum of Natural History , Oxford OX1 3PW , UK
| | - Jeffrey R Thompson
- 2 Department of Earth Sciences, University of Southern California , Los Angeles, CA 90089-0740 , USA
| | - Derek E G Briggs
- 3 Department of Geology and Geophysics and Yale Peabody Museum of Natural History, Yale University , New Haven, CT 06520-8109 , USA
| | - David J Siveter
- 4 School of Geography, Geology and the Environment, University of Leicester , Leicester LE1 7RH , UK
| | - Derek J Siveter
- 1 Oxford University Museum of Natural History , Oxford OX1 3PW , UK.,5 Department of Earth Sciences, University of Oxford , South Parks Road, Oxford OX1 3AN , UK
| | - Mark D Sutton
- 6 Department of Earth Sciences and Engineering, Imperial College London , London SW7 2BP , UK
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7
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Siveter DJ, Briggs DEG, Siveter DJ, Sutton MD. A well-preserved respiratory system in a Silurian ostracod. Biol Lett 2018; 14:rsbl.2018.0464. [PMID: 30404865 PMCID: PMC6283931 DOI: 10.1098/rsbl.2018.0464] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [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: 07/02/2018] [Accepted: 10/12/2018] [Indexed: 11/13/2022] Open
Abstract
Ostracod crustaceans are diverse and ubiquitous in aqueous environments today but relatively few known species have gills. Ostracods are the most abundant fossil arthropods but examples of soft-part preservation, especially of gills, are exceptionally rare. A new ostracod, Spiricopia aurita (Myodocopa), from the marine Silurian Herefordshire Lagerstätte (430 Mya), UK, preserves appendages, lateral eyes and gills. The respiratory system includes five pairs of gill lamellae with hypobranchial and epibranchial canals that conveyed haemolymph. A heart and associated vessels had likely evolved in ostracods by the Mid-Silurian.
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Affiliation(s)
- David J Siveter
- School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, 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
| | - Derek J Siveter
- Earth Collections, University Museum of Natural History, Oxford OX1 3PW, UK.,Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - Mark D Sutton
- Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK
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8
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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. R Soc Open Sci 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] [What about the content of this article? (0)] [Affiliation(s)] [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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9
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Tanaka G, Zhou B, Zhang Y, Siveter DJ, Parker AR. Rods and cones in an enantiornithine bird eye from the Early Cretaceous Jehol Biota. Heliyon 2017; 3:e00479. [PMID: 29387816 PMCID: PMC5772835 DOI: 10.1016/j.heliyon.2017.e00479] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [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: 05/05/2017] [Revised: 08/22/2017] [Accepted: 11/29/2017] [Indexed: 12/02/2022] Open
Abstract
Extant birds have an extensive spectral range of colour vision among vertebrates, but evidence of colour vision among extinct birds has hitherto been lacking. An exceptionally well-preserved extinct enantiornithine fossil bird from the Early Cretaceous Jiufotang Formation (120 Ma) of Liaoning, China, provides the first report of mineralised soft tissue of a bird eye. Cone cells are identified, which have preserved oil droplets falling between wide ranges of size that can be compared with an extant house sparrow. The size distribution of oil droplets of extant birds demonstrates good correlation between size and the detectable wavelength range of the cone cells: UV-sensitive cones contain the smallest oil droplets, while red-sensitive cones possess the largest. The data suggests that this Early Cretaceous bird could have possessed colour vision.
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Affiliation(s)
- Gengo Tanaka
- Institute of Liberal Arts and Science, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Baochun Zhou
- Shanghai Natural History Museum, 510 West Beijing Road, Shanghai 200041, China
| | - Yunfei Zhang
- Shanghai Natural History Museum, 510 West Beijing Road, Shanghai 200041, China
| | - David J. Siveter
- School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK
| | - Andrew R. Parker
- Green Templeton College, University of Oxford, 43 Woodstock Road, Oxford OX2 6HG, UK
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10
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Briggs DEG, Siveter DJ, Siveter DJ, Sutton MD, Rahman IA. An edrioasteroid from the Silurian Herefordshire Lagerstätte of England reveals the nature of the water vascular system in an extinct echinoderm. Proc Biol Sci 2017; 284:rspb.2017.1189. [PMID: 28904139 DOI: 10.1098/rspb.2017.1189] [Citation(s) in RCA: 7] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 08/01/2017] [Indexed: 11/12/2022] Open
Abstract
Echinoderms are unique in having a water vascular system with tube feet, which perform a variety of functions in living forms. Here, we report the first example of preserved tube feet in an extinct group of echinoderms. The material, from the Silurian Herefordshire Lagerstätte, UK, is assigned to a new genus and species of rhenopyrgid edrioasteroid, Heropyrgus disterminus The tube feet attach to the inner surface of compound interradial plates and form two sets, an upper and a lower, an arrangement never reported previously in an extant or extinct echinoderm. Cover plates are absent and floor plates are separated creating a large permanent entrance to the interior of the oral area. The tube feet may have captured food particles that entered the oral area and/or enhanced respiration. The pentameral symmetry of the oral surface transitions to eight columns in which the plates are vertically offset resulting in a spiral appearance. This change in symmetry may reflect flexibility in the evolutionary development of the axial and extraxial zones in early echinoderm evolution.
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Affiliation(s)
- 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
| | - Derek J Siveter
- Oxford University Museum of Natural History, Oxford OX1 3PW, UK.,Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - David J Siveter
- Department of Geology, University of Leicester, Leicester LE1 7RH, UK
| | - Mark D Sutton
- Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK
| | - Imran A Rahman
- Oxford University Museum of Natural History, Oxford OX1 3PW, UK
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Cong P, Ma X, Williams M, Siveter DJ, Siveter DJ, Gabbott SE, Zhai D, Goral T, Edgecombe GD, Hou X. Host-specific infestation in early Cambrian worms. Nat Ecol Evol 2017; 1:1465-1469. [PMID: 29185506 DOI: 10.1038/s41559-017-0278-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 07/11/2017] [Indexed: 11/09/2022]
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12
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Siveter DJ, Briggs DEG, Siveter DJ, Sutton MD, Legg D. A new crustacean from the Herefordshire (Silurian) Lagerstätte, UK, and its significance in malacostracan evolution. Proc Biol Sci 2017; 284:20170279. [PMID: 28330926 PMCID: PMC5378094 DOI: 10.1098/rspb.2017.0279] [Citation(s) in RCA: 17] [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: 02/10/2017] [Accepted: 03/07/2017] [Indexed: 12/25/2022] Open
Abstract
Cascolus ravitis gen. et sp. nov. is a three-dimensionally preserved fossil crustacean with soft parts from the Herefordshire (Silurian) Lagerstätte, UK. It is characterized by a head with a head shield and five limb pairs, and a thorax (pereon) with nine appendage-bearing segments followed by an apodous abdomen (pleon). All the appendages except the first are biramous and have a gnathobase. The post-mandibular appendages are similar one to another, and bear petal-shaped epipods that probably functioned as a part of the respiratory-circulatory system. Cladistic analysis resolves the new taxon as a stem-group leptostracan (Malacostraca). This well-preserved arthropod provides novel insights into the evolution of appendage morphology, tagmosis and the possible respiratory-circulatory physiology of a basal malacostracan.
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Affiliation(s)
- David J Siveter
- Department of Geology, University of Leicester, Leicester LE1 7RH, 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
| | - Derek J Siveter
- Earth Collections, University Museum of Natural History, Oxford OX1 3PW, UK
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - Mark D Sutton
- Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK
| | - David Legg
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
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Briggs DEG, Siveter DJ, Siveter DJ, Sutton MD, Legg D. Tiny individuals attached to a new Silurian arthropod suggest a unique mode of brood care. Proc Natl Acad Sci U S A 2016; 113:4410-5. [PMID: 27044103 PMCID: PMC4843443 DOI: 10.1073/pnas.1600489113] [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] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The ∼430-My-old Herefordshire, United Kingdom, Lagerstätte has yielded a diversity of remarkably preserved invertebrates, many of which provide fundamental insights into the evolutionary history and ecology of particular taxa. Here we report a new arthropod with 10 tiny arthropods tethered to its tergites by long individual threads. The head of the host, which is covered by a shield that projects anteriorly, bears a long stout uniramous antenna and a chelate limb followed by two biramous appendages. The trunk comprises 11 segments, all bearing limbs and covered by tergites with long slender lateral spines. A short telson bears long parallel cerci. Our phylogenetic analysis resolves the new arthropod as a stem-group mandibulate. The evidence suggests that the tethered individuals are juveniles and the association represents a complex brooding behavior. Alternative possibilities-that the tethered individuals represent a different epizoic or parasitic arthropod-appear less likely.
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Affiliation(s)
- Derek E G Briggs
- Department of Geology and Geophysics, Yale University, New Haven, CT 06520-8109; Yale Peabody Museum of Natural History, Yale University, New Haven, CT 06520-8109;
| | - Derek J Siveter
- Oxford University Museum of Natural History, Oxford OX1 3PW, United Kingdom; Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, United Kingdom
| | - David J Siveter
- Department of Geology, University of Leicester, Leicester LE1 7RH, United Kingdom
| | - Mark D Sutton
- Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, United Kingdom
| | - David Legg
- Oxford University Museum of Natural History, Oxford OX1 3PW, United Kingdom
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Tanaka G, Parker AR, Hasegawa Y, Siveter DJ, Yamamoto R, Miyashita K, Takahashi Y, Ito S, Wakamatsu K, Mukuda T, Matsuura M, Tomikawa K, Furutani M, Suzuki K, Maeda H. Mineralized rods and cones suggest colour vision in a 300 Myr-old fossil fish. Nat Commun 2014; 5:5920. [DOI: 10.1038/ncomms6920] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 11/21/2014] [Indexed: 11/09/2022] Open
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16
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Abstract
A new arthropod, Enalikter aphson gen. et sp. nov., is described from the Silurian (Wenlock Series) Herefordshire Lagerstätte of the UK. It belongs to the Megacheira (=short-great-appendage group), which is recognized here, for the first time, in strata younger than mid-Cambrian age. Discovery of this new Silurian taxon allows us to identify a Devonian megacheiran representative, Bundenbachiellus giganteus from the Hunsrück Slate of Germany. The phylogenetic position of megacheirans is controversial: they have been interpreted as stem chelicerates, or stem euarthropods, but when Enalikter and Bundenbachiellus are added to the most comprehensive morphological database available, a stem euarthropod position is supported. Enalikter represents the only fully three-dimensionally preserved stem-group euarthropod, it falls in the sister clade to the crown-group euarthropods, and it provides new insights surrounding the origin and early evolution of the euarthropods. Recognition of Enalikter and Bundenbachiellus as megacheirans indicates that this major arthropod group survived for nearly 100 Myr beyond the mid-Cambrian.
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Affiliation(s)
- Derek J Siveter
- Earth Collections, University Museum of Natural History, , Parks Road, Oxford OX1 3PW, UK, Department of Earth Sciences, University of Oxford, , South Parks Road, Oxford OX1 3PR, UK, Department of Geology and Geophysics and Yale Peabody Museum of Natural History, Yale University, , PO Box 208109, New Haven, CT 06520-8109, USA, Department of Geology, University of Leicester, , Leicester LE1 7RH, UK, Department of Earth Sciences and Engineering, Imperial College London, , London SW7 2BP, UK
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Siveter DJ, Briggs DEG, Siveter DJ, Sutton MD, Joomun SC. A Silurian myodocope with preserved soft-parts: cautioning the interpretation of the shell-based ostracod record. Proc Biol Sci 2012; 280:20122664. [PMID: 23235709 DOI: 10.1098/rspb.2012.2664] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Ostracod crustaceans are the most abundant fossil arthropods. The Silurian Pauline avibella gen. et sp. nov., from the Herefordshire Lagerstätte, UK, is an extremely rare Palaeozoic example with soft-part preservation. Based on its soft-part morphology, especially the exceptionally preserved limbs and presence of lateral eyes, it is assigned to the myodocopid myodocopes. The ostracod is very large, with an epipod on the fifth limb pair, as well as gills implying the presence of a heart and an integrated respiratory-circulatory system as in living cylindroleberidid myodocopids. Features of its shell morphology, however, recall halocyprid myodocopes and palaeocopes, encouraging caution in classifying ostracods based on the carapace alone and querying the interpretation of their shell-based fossil record, especially for the Palaeozoic, where some 500 genera are presently assigned to the Palaeocopida.
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Affiliation(s)
- David J Siveter
- Department of Geology, University of Leicester, Leicester LE1 7RH, UK.
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Sutton MD, Briggs DEG, Siveter DJ, Siveter DJ, Sigwart JD. A Silurian armoured aplacophoran and implications for molluscan phylogeny. Nature 2012; 490:94-7. [PMID: 23038472 DOI: 10.1038/nature11328] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 06/14/2012] [Indexed: 11/09/2022]
Abstract
The Mollusca is one of the most diverse, important and well-studied invertebrate phyla; however, relationships among major molluscan taxa have long been a subject of controversy. In particular, the position of the shell-less vermiform Aplacophora and its relationship to the better-known Polyplacophora (chitons) have been problematic: Aplacophora has been treated as a paraphyletic or monophyletic group at the base of the Mollusca, proximate to other derived clades such as Cephalopoda, or as sister group to the Polyplacophora, forming the clade Aculifera. Resolution of this debate is required to allow the evolutionary origins of Mollusca to be reconstructed with confidence. Recent fossil finds support the Aculifera hypothesis, demonstrating that the Palaeozoic-era palaeoloricate 'chitons' included taxa combining certain polyplacophoran and aplacophoran characteristics. However, fossils combining an unambiguously aplacophoran-like body with chiton-like valves have remained elusive. Here we describe such a fossil, Kulindroplax perissokomos gen. et sp. nov., from the Herefordshire Lagerstätte (about 425 million years bp), a Silurian deposit preserving a marine biota in unusual three-dimensional detail. The specimen is reconstructed three-dimensionally through physical-optical tomography. Phylogenetic analysis indicates that this and many other palaeoloricate chitons are crown-group aplacophorans.
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Affiliation(s)
- Mark D Sutton
- Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK.
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Briggs DEG, Siveter DJ, Siveter DJ, Sutton MD, Garwood RJ, Legg D. Silurian horseshoe crab illuminates the evolution of arthropod limbs. Proc Natl Acad Sci U S A 2012; 109:15702-5. [PMID: 22967511 PMCID: PMC3465403 DOI: 10.1073/pnas.1205875109] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [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] [Indexed: 11/18/2022] Open
Abstract
The basic arrangement of limbs in euarthropods consists of a uniramous head appendage followed by a series of biramous appendages. The body is divided into functional units or tagmata which are usually distinguished by further differentiation of the limbs. The living horseshoe crabs are remnants of a much larger diversity of aquatic chelicerates. The limbs of the anterior and posterior divisions of the body of living horseshoe crabs differ in the loss of the outer and inner ramus, respectively, of an ancestral biramous limb. Here we report a new fossil horseshoe crab from the mid-Silurian Lagerstätte in Herefordshire, United Kingdom (approximately 425 Myr B.P.), a site that has yielded a remarkably preserved assemblage of soft-bodied fossils. The limbs of the new form can be homologized with those of living Limulus, but retain an ancestral biramous morphology. Remarkably, however, the two limb branches originate separately, providing fossil evidence to suggest that repression or loss of gene expression might have given rise to the appendage morphology of Limulus. Both branches of the prosomal limbs of this new fossil are robust and segmented in contrast to their morphology in Cambrian arthropods, revealing that a true biramous limb was once present in chelicerates as well as in the mandibulates.
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Affiliation(s)
- Derek E G Briggs
- Department of Geology and Geophysics, and Yale Peabody Museum of Natural History, Yale University, New Haven, CT 06520-8109, USA.
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Ma X, Hou X, Aldridge RJ, Siveter DJ, Siveter DJ, Gabbott SE, Purnell MA, Parker AR, Edgecombe GD. Morphology of Cambrian lobopodian eyes from the Chengjiang Lagerstätte and their evolutionary significance. Arthropod Struct Dev 2012; 41:495-504. [PMID: 22484085 DOI: 10.1016/j.asd.2012.03.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 03/21/2012] [Accepted: 03/22/2012] [Indexed: 05/31/2023]
Abstract
Visual organs are widely distributed throughout the animal kingdom and exhibit a great diversity of morphologies. Compound eyes consisting of numerous visual units (ommatidia) are the oldest preserved visual systems of arthropods, but their origins are obscure and hypothetical models for their evolution have been difficult to test in the absence of unequivocal fossil evidence. Here we reveal the detailed eye structures of well-preserved Early Cambrian lobopodians Luolishania longicruris and Hallucigenia fortis from the Chengjiang Lagerstätte, China. These animals possess a pair of eyes composed of at least two visual units, interpreted as pigment cups. Contrary to previous suggestions that Cambrian lobopodians possessed ocellus-like eyes comparable to those of extant onychophorans, this multi-component structure is more similar to the lateral eyes of arthropods. Morphological comparison and phylogenetic analyses indicate that these lobopodian eyes may represent an early stage in the evolution of the ancestral visual system of euarthropods.
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Affiliation(s)
- Xiaoya Ma
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, 2 North Cuihu Road, Kunming 650091, China.
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21
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Abstract
Soft-bodied taxa comprise an important component of the extant lophophorate fauna, but convincing fossils of soft-bodied lophophorates are extremely rare. A small fossil lophophorate, attached to a brachiopod dorsal valve, is described from the Silurian (Wenlock Series) Herefordshire Lagerstätte of England. This unmineralized organism was bilaterally symmetrical and comprised a subconical body attached basally to the host and partially enclosed by a broad 'hood'; the body bore a small, coiled lophophore. Where the hood attached laterally, there is a series of transverse ridges and furrows. The affinities of this organism probably lie with Brachiopoda; the hood is interpreted as the homologue of a dorsal valve/mantle lobe, and the attachment as the homologue of the ventral valve and/or pedicle. The ridges are arranged in a manner that suggests constructional serial repetition, indicating that they are unlikely to represent mantle canals. Extant brachiopods are not serially structured, but morphological and molecular evidence suggests that their ancestors were. The new organism may belong to the brachiopod stem group, and might also represent a significant element of the Palaeozoic lophophorate fauna.
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Affiliation(s)
- M D Sutton
- Department of Earth Sciences and Engineering, South Kensington Campus, Imperial College London, London SW7 2AZ, UK.
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Zhang XG, Maas A, Haug JT, Siveter DJ, Waloszek D. A eucrustacean metanauplius from the Lower Cambrian. Curr Biol 2010; 20:1075-9. [PMID: 20493703 DOI: 10.1016/j.cub.2010.04.026] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 04/09/2010] [Accepted: 04/09/2010] [Indexed: 11/17/2022]
Abstract
A new eucrustacean arthropod, Wujicaris muelleri gen. et sp. nov, is represented by a Lower Cambrian early metanauplius of strikingly modern morphology despite being the oldest known fossil of such an early immature crustacean larva. The morphology of the metanauplius closely mirrors that of corresponding developmental stages of living barnacles and copepods, and it is likely that its appendages had a similar function for feeding and locomotion. The metanauplius larva demonstrates remarkable stasis in morphology, life history, and lifestyle of (small) eucrustaceans over 525 million years, probably as a result of adaptation to a long-lasting physical niche and regime involving low Reynolds numbers and laminar current flow.
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Affiliation(s)
- Xi-guang Zhang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China.
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Hou X, Williams M, Siveter DJ, Siveter DJ, Aldridge RJ, Sansom RS. Soft-part anatomy of the Early Cambrian bivalved arthropods Kunyangella and Kunmingella: significance for the phylogenetic relationships of Bradoriida. Proc Biol Sci 2010; 277:1835-41. [PMID: 20181565 DOI: 10.1098/rspb.2009.2194] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Bradoriids are small bivalved marine arthropods that are widespread in rocks of Cambrian to Early Ordovician age. They comprise seven families and about 70 genera based on shield ('carapace') morphology. New bradoriid specimens with preserved soft-part anatomy of Kunmingella douvillei (Kunmingellidae) are reported from the Early Cambrian Chengjiang Lagerstätte of China together with, for the first time to our knowledge, a second bradoriid species with preserved soft parts, Kunyangella cheni (Comptalutidae). Kunmingella douvillei has a 10-segmented limb-bearing body with uniramous ninth and tenth appendages and a series of homogeneous, apparently (proximal parts not preserved) unspecialized post-antennal biramous limbs with setose leaf-shaped exopods. Each endopod consists of five podomeres. A presumed penultimate instar of Ky. cheni preserves remnants of three head and two trunk appendages, and the adult is reconstructed as having four head appendages. This material allows testing of the affinity of the Bradoriida. Kunmingella is identified as a stem crustacean in character-based analyses, through both morphological comparisons and cladistic reconstructions. Global parsimony analysis recovers a monophyletic Bradoriida as the sister group to crown crustaceans.
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Affiliation(s)
- Xianguang Hou
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming, Yunnan Province, People's Republic of China.
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Siveter DJ, Briggs DEG, Siveter DJ, Sutton MD. An exceptionally preserved myodocopid ostracod from the Silurian of Herefordshire, UK. Proc Biol Sci 2010; 277:1539-44. [PMID: 20106847 DOI: 10.1098/rspb.2009.2122] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
An exceptionally preserved new ostracod crustacean from the Silurian of Herefordshire, UK, represents only the third fully documented Palaeozoic ostracod with soft-part preservation. Appendages, gills, gut system, lateral compound eyes and even a medial eye with a Bellonci organ are preserved, allowing assignment of the fossil to a new genus and species of cylindroleberidid myodocope (Myodocopida, Cylindroleberididae). The Bellonci organ is recorded for the first time in fossil ostracods. The find also represents a rare occurrence of gills in fossil ostracods and confirms the earliest direct evidence of a respiratory-cum-circulatory system in the group. The species demonstrates remarkably conserved morphology within myodocopes over a period of 425 Myr. Its shell morphology more closely resembles several families of myodocopes other than the Cylindroleberididae, especially the Cypridinidae and Sarsiellidae, thus questioning the utility of the carapace alone in establishing the affinity of fossil ostracods.
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Affiliation(s)
- David J Siveter
- Department of Geology, University of Leicester, Leicester, UK.
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Tanaka G, Smith RJ, Siveter DJ, Parker AR. Three-Dimensionally Preserved Decapod Larval Compound Eyes from the Cretaceous Santana Formation of Brazil. Zoolog Sci 2009; 26:846-50. [DOI: 10.2108/zsj.26.846] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Tanaka G, Parker AR, Siveter DJ, Maeda H, Furutani M. An exceptionally well-preserved Eocene dolichopodid fly eye: function and evolutionary significance. Proc Biol Sci 2009; 276:1015-9. [PMID: 19129103 DOI: 10.1098/rspb.2008.1467] [Citation(s) in RCA: 21] [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] [Indexed: 11/12/2022] Open
Abstract
The exceptionally preserved eyes of an Eocene dolichopodid fly contained in Baltic amber show remarkable detail, including features at micrometre and submicrometre levels. Based on this material, we establish that it is likely that the neural superposition compound eye existed as far back as 45 Ma. The ommatidia have an open rhabdom with a trapezoidal arrangement of seven rhabdomeres. Such a structure is uniquely characteristic of the neural superposition compound eye of present-day flies. Optical analysis reveals that the fossil eyes had a sophisticated and efficient optical system.
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Affiliation(s)
- Gengo Tanaka
- Gunma Museum of Natural History, 1674-1 Kamikuroiwa, Tomioka, Gunma 370-2345, Japan.
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Williams M, Siveter DJ, Ashworth AC, Wilby PR, Horne DJ, Lewis AR, Marchant DR. Exceptionally preserved lacustrine ostracods from the Middle Miocene of Antarctica: implications for high-latitude palaeoenvironment at 77 degrees south. Proc Biol Sci 2008; 275:2449-54. [PMID: 18647723 PMCID: PMC2603191 DOI: 10.1098/rspb.2008.0396] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A newly discovered Konservat-Lagerstätte from the Middle Miocene of the western Olympus Range, Dry Valleys, Antarctica, yields cypridoidean ostracods complete with preserved body and appendages. This is the first record of three-dimensionally fossilized animal soft tissues from the continent. The ostracods are preserved in goethite, secondary after pyrite, representing a novel mode of exceptional preservation. They signal a high-latitude (greater than 77 degrees south) lake setting (Palaeolake Boreas) viable for benthic animal colonization prior to 14 Myr ago. Their presence supports the notion of warmer, tundra-like environmental conditions persisting in the Dry Valleys until the Middle Miocene.
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Affiliation(s)
- Mark Williams
- Department of Geology, University of Leicester, Leicester LE1 7RH, UK.
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Abstract
Examples that indicate collective behavior in the fossil record are rare. A group association of specimens that belong to a previously unknown arthropod from the Chengjiang Lagerstätte, China, provides evidence that such behavior was present in the early Cambrian (about 525 million years ago), coincident with the earliest extensive diversification of the Metazoa, the so-called Cambrian explosion event. The chainlike form of these specimens is unique for any arthropod, fossil or living, and most likely represents behavior associated with migration.
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Affiliation(s)
- Xian-Guang Hou
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, Kunming, Yunnan Province, People's Republic of China.
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Williams M, Siveter DJ, Salas MJ, Vannier J, Popov LE, Ghobadi Pour M. The earliest ostracods: the geological evidence. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/bf03043974] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Siveter DJ, Sutton MD, Briggs DEG, Siveter DJ. Correction for Siveter
et al.
, A new probable stem lineage crustacean with three-dimensionally preserved soft parts from the Herefordshire (Silurian) Lagerstätte, UK. Proc Biol Sci 2007. [DOI: 10.1098/rspb.2007.2002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Correction for ‘A new probable stem lineage crustacean with three-dimensionally preserved soft parts from the Herefordshire (Silurian) Lagerstätte, UK’ by Derek J. Siveter, Mark D. Sutton, Derek E. G. Briggs and David J. Siveter (Proc. R. Soc. B
274
, 2099–2107.
(doi:
10.1098/rspb.2007.0429
)).
Figures 1 and 2 were incorrectly sized and the magnifications in the legend of figure 3 were incorrectly stated. The online version of the article has now been corrected.
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Abstract
Xylokorys chledophilia, a new arthropod with three-dimensionally preserved soft tissues, is described from the Herefordshire (Silurian) Lagerstätte of England. The head and trunk are covered by a relatively featureless ovoid carapace, which comprises a domed central part and a flange-like border. The head bears five pairs of appendages. The first is uniramous, with dorsal and ventral projections distally. Appendages two to four are biramous and each endopod terminates in two projections. Appendage five is possibly biramous. The hypostome is very long and subrectangular in outline. There are approximately 35 pairs of biramous trunk appendages. Each exopod comprises a long slender shaft bearing numerous fine filaments; each endopod comprises a ribbon-like shaft bearing paddle-like endites. Morphological comparisons and cladistic analyses of X. chledophilia indicate affinity with Vachonisia rogeri from the Lower Devonian Hunsrück Slate, within the marrellomorphs, but assignment to Marrellomorpha is provisional pending revision of other members of this clade. Xylokorys is the first 'marrellomorph' to be reported from the Silurian. It is interpreted as a benthic particle filter feeder, which may also have consumed prey items.
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Affiliation(s)
- Derek J Siveter
- Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK.
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Siveter DJ, Sutton MD, Briggs DEG, Siveter DJ. A new probable stem lineage crustacean with three-dimensionally preserved soft parts from the Herefordshire (Silurian) Lagerstätte, UK. Proc Biol Sci 2007; 274:2099-107. [PMID: 17609185 PMCID: PMC2706188 DOI: 10.1098/rspb.2007.0429] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A new arthropod with three-dimensionally preserved soft parts, Tanazios dokeron, is described from the Wenlock Series (Silurian) of Herefordshire, England, UK. Serial grinding, digital photographic and computer rendering techniques yielded 'virtual fossils' in the round for study. The body tagmata of T. dokeron comprise a head shield and a long trunk. The head shield bears six pairs of horn-like spines and the head bears five pairs of appendages. The antennule, antenna and mandible are all uniramous, and the mandible includes a gnathobasic coxa. Appendages four and five are biramous and similar to those of the trunk: each comprises a limb base with an endite, an enditic membrane, and two epipodites, plus an endopod and exopod. The hypostome bears a large cone-like projection centrally, and there may be a short labrum. The trunk has some 64 segments and at least 60 appendage pairs. A very small telson has the anus sited ventrally in its posterior part and also bears a caudal furca. Comparative morphological and cladistic analyses of T. dokeron indicate a crustacean affinity, with a probable position in the eucrustacean stem group. As such the epipodites in T. dokeron are the first recorded in a eucrustacean stem taxon. The new species is interpreted as a benthic or nektobenthic scavenger.
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Affiliation(s)
- Derek J Siveter
- Geological Collections, University Museum of Natural History, Oxford OX1 3PW, UK.
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Zhang XG, Siveter DJ, Waloszek D, Maas A. An epipodite-bearing crown-group crustacean from the Lower Cambrian. Nature 2007; 449:595-8. [PMID: 17914395 DOI: 10.1038/nature06138] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Accepted: 07/30/2007] [Indexed: 11/09/2022]
Abstract
Crown-group crustaceans (Eucrustacea) are common in the fossil record of the past 500 million years back to the early Ordovician period, and very rare representatives are also known from the late Middle and Late Cambrian periods. Finds in Lower Cambrian rocks of the Phosphatocopina, the fossil sister group to eucrustaceans, imply that members of the eucrustacean stem lineage co-occurred, but it remained unclear whether crown-group members were also present at that time. 'Orsten'-type fossils are typically tiny embryos and cuticle-bearing animals, of which the cuticle is phosphatized and the material is three-dimensional and complete with soft parts. Such fossils are found predominantly in the Cambrian and Ordovician and provide detailed morphological and phylogenetic information on the early evolution of metazoans. Here we report an Orsten-type Konservat-Lagerstätte from the Lower Cambrian of China that contains at least three new arthropod species, of which we describe the most abundant form on the basis of exceptionally well preserved material of several growth stages. The limb morphology and other details of this new species are markedly similar to those of living cephalocarids, branchiopods and copepods and it is assigned to the Eucrustacea, thus representing the first undoubted crown-group crustacean from the early Cambrian. Its stratigraphical position provides substantial support to the proposition that the main cladogenic event that gave rise to the Arthropoda was before the Cambrian. Small leaf-shaped structures on the outer limb base of the new species provide evidence on the long-debated issue of the origin of epipodites: they occur in a set of three, derive from setae and are a ground-pattern feature of Eucrustacea.
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Affiliation(s)
- Xi-guang Zhang
- Key Laboratory for Palaeobiology, Yunnan University, Kunming 650091, China.
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Abstract
An exceptionally preserved new ostracod crustacean from the Silurian of Herefordshire, England, preserves eggs and possible juveniles within its carapace, providing an unequivocal and unique view of parental brood care in the invertebrate fossil record. The female fossil is assigned to a new family and superfamily of myodocopids based on its soft-part anatomy. It demonstrates a remarkably conserved egg-brooding reproductive strategy within these ostracods over 425 Myr. The soft-tissue anatomy urges extreme caution in classifying 'straight-hinged' Palaeozoic ostracods based on the carapace alone and fundamentally questions the nature of the shell-based Palaeozoic ostracod record.
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Affiliation(s)
- David J Siveter
- Department of Geology, University of Leicester, Leicester LE1 7RH, UK.
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Abstract
Gastropod shells are common in the fossil record, but their fossil soft tissues are almost unknown, and have not been reported previously from the Palaeozoic. Here, we describe a Silurian (approx. 425 Myr) platyceratid gastropod from the Herefordshire Lagerstätte that preserves the oldest soft tissues yet reported from an undoubted crown-group mollusc. The digestive system is preserved in detail, and morphological data on the gonads, digestive gland, pedal muscle, radula, mouth and foot are also available. The specimen is preserved three-dimensionally, and has been reconstructed digitally following serial grinding. Platyceratids are often found attached to echinoderms, and have been interpreted as either commensal coprophages or kleptoparasites. The new data provide support for an attached mode of life, and are suggestive of a coprophagous feeding strategy. The affinities of the platyceratids are uncertain; they have been compared to both the patellogastropods and the neritopsines. Analysis of the new material suggests that a patellogastropod affinity is the more plausible of these hypotheses.
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Affiliation(s)
- M D Sutton
- Department of Earth Sciences and Engineering, South Kensington Campus, Imperial College London, SW7 2AZ, UK.
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Abstract
Exceptionally preserved fossils from the Wenlock Series (Silurian) of Herefordshire, UK, provide unique evidence of metamorphosis from free-swimming cyprid larva to attached juvenile in a Palaeozoic barnacle. The larva had large brush-like anterior limbs. The juvenile shows the head transformed into a stalk and the development of the primordial condition of five mineralized plates within the carapace. The discovery of a cyprid larva indicates that crown group cirripedes had evolved by the Silurian.
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Affiliation(s)
- Derek E G Briggs
- Yale University, Department of Geology and Geophysics, PO Box 208109, New Haven, CT 06520-8109, USA.
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Abstract
'Articulated' rhynchonelliformean brachiopods are abundant shelly fossils, but the direct fossil record of their soft parts was hitherto confined to a single pyritized trace possibly representing a lophophore. Anatomical knowledge of extinct rhynchonelliformeans relies heavily on analogies to extant species; these analogies are untested for stem-group clades. The Silurian Herefordshire (UK) Konservat-Lagerstätte (about 425 Myr bp) yields exceptionally preserved three-dimensional fossils that provide unrivalled insights into the palaeobiology of a variety of invertebrates. The fossils are preserved as calcitic void in-fills in carbonate concretions within a volcaniclastic horizon, and are reconstructed digitally. Here we describe a stem-group rhynchonelliformean specimen from this deposit; it most probably belongs in the order Orthida. A robust ridged pedicle with distal rootlets is preserved, together with a lophophore and other soft-tissue structures. The pedicle morphology is novel, urging caution in inferring stem-group rhynchonelliformean anatomy from that of crown-group species. Smaller brachiopods are attached to the specimen; these include a probable atrypide, with pedicle and marginal setae preserved.
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Affiliation(s)
- Mark D Sutton
- Department of Earth Science and Engineering, Imperial College, London SW7 2AZ, UK.
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Sutton MD, Briggs DEG, Siveter DJ, Siveter DJ, Gladwell DJ. A starfish with three-dimensionally preserved soft parts from the Silurian of England. Proc Biol Sci 2005; 272:1001-6. [PMID: 16024357 PMCID: PMC1599871 DOI: 10.1098/rspb.2004.2951] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Palaeozoic asteroids represent a stem-group to the monophyletic post-Palaeozoic Neoasteroidea, but many aspects of their anatomy are poorly known. Using serial grinding and computer reconstruction, we describe fully articulated Silurian (ca 425 Myr) specimens from the Herefordshire Lagerstätte, preserved in three dimensions complete with soft tissues. The material belongs to a species of Bdellacoma, a genus previously assigned to the ophiuroids, but has characters that suggest an asteroid affinity. These include a pyloric system in the gut, and the presence of large bivalved pedicellariae, the latter originally described under the name Bursulella from isolated valves. Ampullae are external and occur within podial basins; the radial canal is also external. Podia are elongate and lack terminal suckers. The peristome is large relative to the mouth. Aspects of the morphology are comparable to that of the extant Paxillosida, supporting phylogenetic schemes that place this order at the base of the asteroid crown group.
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Affiliation(s)
- M D Sutton
- Department of Earth Sciences and Engineering, South Kensington Campus, Imperial College London, London SW7 2AZ, UK.
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Abstract
Pycnogonids (sea spiders) are marine arthropods numbering some 1,160 extant species. They are globally distributed in depths of up to 6,000 metres, and locally abundant; however, their typically delicate form and non-biomineralized cuticle has resulted in an extremely sparse fossil record that is not accepted universally. There are two opposing views of their phylogenetic position: either within Chelicerata as sister group to the euchelicerates, or as a sister taxon to all other euarthropods. The Silurian Herefordshire Konservat-Lagerstatte in England (approximately 425 million years (Myr) bp) yields exceptionally preserved three-dimensional fossils that provide unrivalled insights into the palaeobiology of a variety of invertebrates. The fossils are preserved as calcitic void in-fills in carbonate concretions within a volcaniclastic horizon, and are reconstructed digitally. Here we describe a new pycnogonid from this deposit, which is the oldest adult sea spider by approximately 35 Myr and the most completely known fossil species. The large chelate first appendage is consistent with a chelicerate affinity for the pycnogonids. Cladistic analyses place the new species near the base of the pycnogonid crown group, implying that the latter had arisen by the Silurian period.
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Affiliation(s)
- Derek J Siveter
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
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Briggs DEG, Sutton MD, Siveter DJ, Siveter DJ. A new phyllocarid (Crustacea: Malacostraca) from the Silurian Fossil-Lagerstätte of Herefordshire, UK. Proc Biol Sci 2004; 271:131-8. [PMID: 15058388 PMCID: PMC1691579 DOI: 10.1098/rspb.2003.2593] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A new three-dimensionally preserved arthropod, Cinerocaris magnifica, from the Wenlock Series (Silurian) of Herefordshire, UK, is described and assigned to the Phyllocarida (Crustacea). The description and reconstruction are based on specimens that have been serially ground, reconstructed by computer and rendered in three dimensions as coloured virtual models. Cinerocaris magnifica displayed the tagmosis characteristic of phyllocarids, with eight thoracic and seven abdominal somites, terminating in a telson with furca. The remarkable preservation of the appendages makes this the earliest completely known malacostracan crustacean. Two pairs of antennae (the first with two flagella) were followed by a mandible and first maxilla, each with a slender palp-like ramus. The second maxilla consisted of a limb stem with endites and an endopod that tapered distally. There was no exopod. The thoracopods comprised a limb stem with six or seven endites, an arrangement previously known only in entomostracans, and an endopod with about five endites. Flap-like outer rami correspond to an exopod and epipods. The pleopods bore two long slender oar-blade-like rami. Cladistic analysis places C. magnifica as a plesion within the Echinocaridina. It provides critical evidence of the limb morphology of an early malacostracan, which will be important in understanding crustacean evolution.
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Affiliation(s)
- Derek E G Briggs
- Department of Geology and Geophysics, Yale University, PO Box 208109, New Haven, CT 06520-8109, USA.
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Abstract
An exceptionally well-preserved ostracode from the Silurian of Herefordshire, United Kingdom, provides a rare view of the fossilized soft-part anatomy of this important group of living crustaceans and confirms that Ostracoda were extant in the Paleozoic. The fossil has striking similarity to the extant myodocopid family Cylindroleberididae, to which it is assigned, and demonstrates remarkable evolutionary stasis over 425 million years. The fossil is identified as a male on the basis of its copulatory organ.
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Affiliation(s)
- David J Siveter
- Department of Geology, University of Leicester, Leicester LE1 7RH, UK.
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Abstract
We report the discovery of a new agnathan specimen from the Lower Cambrian Chengjiang Lagerstätte of China and thereby provide new evidence on the myomeres (V-shaped), the branchial apparatus (gill filaments and arches), the dorsal fin and the gonads (24-26) of the earliest vertebrates. The new specimen and the co-occurring Myllokunmingia fengjiaoa and Haikouichthys ercaicunensis represent a single species, which is a primitive member of the crown group craniates (vertebrates) and post-dates the origin of the myxinoids (hagfish). The origin of the vertebrate clade is at least as old as Early Cambrian.
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Affiliation(s)
- Hou Xian-guang
- Yunnan Research Centre for Chengjiang Biota, Yunnan University, Kunming 650091, Yunnan Province, People's Republic of China.
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Sutton MD, Briggs DEG, Siveter DJ, Siveter DJ, Orr PJ. The arthropod Offacolus kingi (Chelicerata) from the Silurian of Herefordshire, England: computer based morphological reconstructions and phylogenetic affinities. Proc Biol Sci 2002; 269:1195-203. [PMID: 12065034 PMCID: PMC1691018 DOI: 10.1098/rspb.2002.1986] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The small, non-biomineralized, three-dimensionally preserved arthropod Offacolus kingi Orr et al. from the Wenlock Series (Silurian) of Herefordshire, England, is re-evaluated, and the new family Offacolidae erected. This new study is based on specimens which have been serially ground, reconstructed by computer and rendered in the round as coloured models. Offacolus possesses a prosomal appendage array similar to that of Limulus, but also bears robust and setose exopods on appendages II-V which are unlike those found in any other arthropods. Opisthosomal appendages are similar in number and morphology to the book-gills of Limulus. Cladistic analysis places Offacolus basally within the Chelicerata, as a sister taxon to the eurypterids and extant chelicerates, but more derived than the Devonian Weinbergina.
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Affiliation(s)
- Mark D Sutton
- Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK
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Sutton MD, Briggs DE, Siveter DJ, Siveter DJ. A three-dimensionally preserved fossil polychaete worm from the Silurian of Herefordshire, England. Proc Biol Sci 2001; 268:2355-63. [PMID: 11703876 PMCID: PMC1088887 DOI: 10.1098/rspb.2001.1788] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Polychaete body fossils are rare, and are almost invariably compressed and too poorly preserved for meaningful comparison with extant forms. We here describe Kenostrychus clementsi gen. et sp. nov. from the Silurian Herefordshire Konservat-Lagerstätte of England, in which three-dimensional external morphology is preserved with a fidelity unprecedented among fossil polychaetes. The fossils, which are preserved in calcite, were serially ground and photographed at 30 microm intervals to produce computer-generated reconstructions of the original external surface. The new genus has a generalized polychaete morphology with large biramous parapodia, unspecialized anterior segments and a small prostomium with median and lateral antennae and ventral prostomial palps. Cirriform branchiae arise from the ventral surface of each notopodium, and may be homologous with the inter-ramal branchiae of the extant nephtyids. Through cladistic analysis, Kenostrychus is interpreted as a member of a stem group of either the Phyllodocida or the Aciculata (Phyllodocida + Eunicida). Direct comparison with other fossil forms is difficult, but hints that inter-ramal respiratory structures may be primitive within the Phyllodocida and/or the Aciculata.
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Affiliation(s)
- M D Sutton
- Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK
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Abstract
Here we describe a phosphatocopid arthropod with preserved soft anatomy from Lower Cambrian rocks of Shropshire, England, which provides evidence for the occurrence of Crustacea, including Eucrustacea, in the Early Cambrian. The find identifies an important, stratigraphically early source of well-preserved fossils (Konservat-Lagerstätte).
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Affiliation(s)
- D J Siveter
- Department of Geology, University of Leicester, Leicester LE1 7RH, UK.
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Abstract
Studies of the origin and radiation of the molluscs have yet to resolve many issues regarding their nearest relatives, phylogeny and ancestral characters. The Polyplacophora (chitons) and the Aplacophora are widely interpreted as the most primitive extant molluscs, but Lower Palaeozoic fossils of the former lack soft parts, and the latter were hitherto unrecognized as fossils. The Herefordshire Lagerstätte is a Silurian (about 425 Myr bp) deposit that preserves a marine biota in remarkable three-dimensional detail. The external surface of even non-biomineralized cuticle was preserved by entombment in volcanic ash, subsequent incorporation into concretions, and infilling of the fossils with sparry calcite. Here we describe, from this deposit, a complete vermiform mollusc, which we interpret as a plated aplacophoran. Serial grinding at intervals of tens of micrometres, combined with computer-based reconstruction methods, renders the fossils in the round.
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Affiliation(s)
- M D Sutton
- Earth Sciences Department, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
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Abstract
A small, non-biomineralized, macrophagous arthropod with chelicerate affinities, Offacolus kingi gen. et sp. nov., from the Silurian (Wenlock Series) of Herefordshire, UK, is described. The dorsal exoskeleton comprises an arch-like cephalic shield, a thorax of three free tergites and a triangular posterior tagma of five fused tergites, the last with a stout postero-dorsally directed medial spine. Seven pairs of appendages beneath the cephalic shield surround a postero-medially sited oral cavity on the ventral surface of the head. Appendages I and, probably II are uniramous and project antero-ventrally; I was sensory and II sensory and/or ambulatory. Appendages III-VI are biramous, each with an antero-ventrally projecting ramus and a robust, highly geniculate, horizontally oriented ramus that projects through an anterior gape. The former rami were ambulatory and the latter have spinose terminal podomeres and functioned as a unit for trapping food and transferring it towards the oral cavity. Appendage VII, which is probably uniramous, is posteroventrally directed and flap like. Each tergite of the thorax and posterior tagma covers at least a pair (probably two pairs) of probably biramous appendages with each ramus flap like and setose.
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Affiliation(s)
- P J Orr
- Department of Earth Sciences, University of Oxford, UK
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Siveter DJ, Lane PD. The myodocope ostracode Entomozoe from an early Silurian (Telychian, Llandovery) carbonate mound of the Samuelsen Høj Formation, North Greenland. ACTA ACUST UNITED AC 1999. [DOI: 10.34194/ggub.v184.5225] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Entomozoe aff. Entomozoe tuberosa (Jones 1861), from carbonate mounds of the Samuelsen Høj Formation, represents one of the few ostracodes documented from the Silurian of Greenland and a rare occurrence of Entomozoe from outside Scotland. Like its coeval, congeneric Scottish counterparts, the Greenland Entomozoe lived on a shallow-water shelf dominated by epibenthonic fauna and probably had a benthonic, swimming(?) lifestyle. Its environmental, ecological and geographical setting is consistent with the idea that these earliest, Lower Silurian myodocopes were benthonic and, therefore, that Upper Silurian pelagic representatives must have resulted from an ecological shift in the group.
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