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Phylogeny, classification and character polarity of the Osteostraci (Vertebrata)

  • Robert S. Sansom (a1)
Abstract
SYNOPSIS

The jawless Osteostraci are the sister taxon to jawed vertebrates and, thus, are integral to understanding the evolution of gnathostomes from a jawless ancestor. Our understanding of this episode is currently hampered by incomplete knowledge of osteostracan phylogenetics and character polarity. Previous hypotheses of osteostracan intrarelations are reviewed and synthesised into two conflicting hypotheses – ‘Tremataspis-basal’ versus ‘Ateleaspis-basal’ models, both related to the ancestral morphotype of the group. Previous analyses are shown to be limited in three main regards – taxonomic scope, phylogenetic methodology and character polarity. To address this problem, direct observations and reconstructions were made for every osteostracan genus. This enabled a taxonomically comprehensive analysis, utilising global parsimony and out-group analysis. The inclusion of a morphological range of taxa from both extant and extinct osteostracan-related clades (pteraspidomorphs, galeaspids, placoderms and gnathostomes), enables a test of osteostracan polarity and character evolution. A new phylogeny and classification for the Osteostraci is proposed, identifying three main orders – Benneviaspidida, Zenaspidida and Thyestiida. The ‘Ateleaspis-basal’ model is supported along with the homology of paired pectoral fins of Osteostraci and jawed vertebrates.

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O. B. Afanassieva & P. Janvier 1985. Tannuaspis, Tuvaspis and Ilemoraspis, endemic osteostracan genera from the Silurian and Devonian of Tuva and Khakassia (USSR). Geobios 18: 493506.

M. Arsenault & P. Janvier 1995. Combien d'Ostéostracés a Miguasha?. Pp. 1922inH. Lelièvre , S. Wenz , A. R. M. Blieck & R. Cloutier (eds), Premiers Vertébrés et Vertébrés Inférieurs. Géobios, Mémoires Spécial 19. Paris.

A. R. M. Blieck & N. Heintz 1983. The Cyathaspids of the Red Bay Group (Lower Devonian) of Spitsbergen. Polar Research, n.s. 1: 4974.

E. M. Cope 1889. Synopsis of the families of Vertebrata. The American Naturalist 23: 849877.

P. C. J Donoghue & M. A. Purnell 2005. Genome duplication, extinction and vertebrate evolution. Trends in Ecology and Evolution 20: 312319.

P. C. J Donoghue & P. Smith 2001. The anatomy of Turinia pagei (Powrie), and the phylogenetic status of the Thelodonti. Transactions of the Royal Society of Edinburgh: Earth Sciences 92: 1537.

P. C. J Donoghue , P. L. Forey & R. J. Aldridge 2000. Conodont affinity and chordate phylogeny. Biological Reviews 75: 191251.

P. C. J Donoghue , I. J. Sansom & J. P. Downs 2006. Early evolution of vertebrate skeletal tissues and cellular interactions, and the canalization of skeletal development. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution 306B: 278294.

P. M. G. Egerton 1857. Palichthyologic notes. 9. On some fish remains from the neighbourhood of Ludlow. Quarterly Journal of the Geological Society of London 13: 282291.

P. L. Forey 1995. Agnathans recent and fossil, and the origin of jawed vertebrates. Reviews in Fish Biology and Fisheries 5: 267303.

P. L. Forey & P Janvier . 1993. Agnathans and the origin of jawed vertebrates. Nature 361: 129134.

P. L. Forey , R. A. Fortey , P. Kenrick & A. B. Smith 2004. Taxonomy and fossils: a critical appraisal. Philosophical Transactions of the Royal Society of London, series B 359: 639653.

D. Goujet & G. C. Young 1995. Interrelationships of the placoderms revisited. Pp. 8995inH. Lelièvre , S. Wenz , A. R. M. Blieck & R. Cloutier (eds), Premiers Vertébrés et Vertébrés Inférieurs. Géobios, Mémoires Spécial 19. Paris.

P. Janvier 1981 b. The phylogeny of the Craniata, with particular reference to the significance of fossil ‘agnathans’. Journal of Vertebrate Paleontology 1: 121159.

P. Janvier 1984. The relationships of the Osteostraci and the Galeaspida. Journal of Vertebrate Paleontology 4: 344358.

P. Janvier 1985 a. Environmental framework of the diversification of the Osteostraci during the Silurian and Devonian. Philosophical Transactions of the Royal Society of London, series B 309: 259272.

P. Janvier & M. J. Newman 2005. On Cephalaspis magnifica Traquair, 1893, from the Middle Devonian of Scotland, and the relationships of the last osteostracans. Transactions of the Royal Society of Edinburgh: Earth Sciences 95: 511525.

E. Mark-Kurik & P. Janvier 1995. Early Devonian Osteostracans from Severnaya Zemlya, Russia. Journal of Vertebrate Paleontology 15: 449462.

W. Patten 1903 a. On the appendages of Tremataspis. The American Naturalist 37: 223242.

W. Patten 1903 b. On the structure of the Pteraspidae and Cephalaspidae. The American Naturalist 37: 827865.

W. Patten 1931. New ostracoderms from Oesel. Science 73: 671673.

A. Ritchie 1967. Ateleaspis tessellata Traquair, a non-cornuate cephalaspid from the Upper Silurian of Scotland. Journal of the Linnean Society. Zoology 47: 6981.

G. M. Robertson 1939 b. The status of Cephalaspis schrenckii Pander from the Upper Silurian of Oesel. The Journal of Geology 47: 649657.

G. M. Robertson 1940. Witaaspis patteni, a new ostracoderm from the Upper Silurian of Oesel. Transactions of the Kansas Academy of Science 43: 297298.

G. M. Robertson 1945. Cephalaspids from the Upper Silurian of Oesel, with a discussion of cephalaspid genera. American Journal of Science 243: 13191.

I. J. Sansom , P. C. J. Donoghue & G. Albanesi 2005. Histology and affinity of the earliest armoured vertebrate. Biology Letters 1: 446449.

R. Sansom 2008. The origin and early evolution of the Osteostraci (Vertebrata): a phylogeny for the thyestiids. Journal of Systematic Palaeontology 6: 317332.

E. Strong & D. Lipscomb 1999. Character coding and inapplicable data. Cladistics 15: 363371.

A. R. Templeton 1983. Phylogenetic inference from restriction endonuclease cleavage site maps with particular reference to the evolution of humans and the apes. Evolution 37: 221244.

M. Wilkinson , J. L. Thorley & P. Upchurch 2000. A chain is no stronger than its weakest link: double decay analysis of phylogenetic hypotheses. Systematic Biology 49: 754776.

G. C. Young 1986. The relationships of placoderm fishes. Zoological Journal of the Linnean Society 88: 155.

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Journal of Systematic Palaeontology
  • ISSN: 1477-2019
  • EISSN: 1478-0941
  • URL: /core/journals/journal-of-systematic-palaeontology
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