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The Devonian tetrapod Acanthostega gunnari Jarvik: postcranial anatomy, basal tetrapod interrelationships and patterns of skeletal evolution

  • M. I. Coates (a1)


The postcranial skeleton of Acanthostega gunnari from the Famennian of East Greenland displays a unique, transitional, mixture of features conventionally associated with fishand tetrapod-like morphologies. The rhachitomous vertebral column has a primitive, barely differentiated atlas-axis complex, encloses an unconstricted notochordal canal, and the weakly ossified neural arches have poorly developed zygapophyses. More derived axial skeletal features include caudal vertebral proliferation and, transiently, neural radials supporting unbranched and unsegmented lepidotrichia. Sacral and post-sacral ribs reiterate uncinate cervical and anterior thoracic rib morphologies: a simple distal flange supplies a broad surface for iliac attachment. The octodactylous forelimb and hindlimb each articulate with an unsutured, foraminate endoskeletal girdle. A broad-bladed femoral shaft with extreme anterior torsion and associated flattened epipodials indicates a paddle-like hindlimb function. Phylogenetic analysis places Acanthostega as the sister-group of Ichthyostega plus all more advanced tetrapods. Tulerpeton appears to be a basal stemamniote plesion, tying the amphibian-amniote split to the uppermost Devonian. Caerorhachis may represent a more derived stem-amniote plesion. Postcranial evolutionary trends spanning the taxa traditionally associated with the fish-tetrapod transition are discussed in detail. Comparison between axial skeletons of primitive tetrapods suggests that plesiomorphic fish-like morphologies were re-patterned in a cranio-caudal direction with the emergence of tetrapod vertebral regionalisation. The evolution of digited limbs lags behind the initial enlargement of endoskeletal girdles, whereas digit evolution precedes the elaboration of complex carpal and tarsal articulations. Pentadactylous limbs appear to have stabilised independently in amniote and amphibian lineages; the colosteid Greererpeton has a pentadactylous manus, indicating that basal amphibian forelimbs may not be restricted to patterns of four digits or less.



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Abel, O. 1911. Grundzüge der Palaeobiologie der Wirbeltiere. Stuttgart: Schweizerbart.
Ahlberg, P. E. 1991. Tetrapod or near-tetrapod fossils from the Upper Devonian of Scotland. NATURE 354, 298301.
Ahlberg, P. E. 1995. Elginerpeton pancheni and the earliest tetrapod clade. NATURE 373, 421–4.
Ahlberg, P. E. (in press). Spare parts for Elginerpeton? The postcranial stem tetrapod remains from Scat Craig, Morayshire, Scotland. ZOOL J LINN SOC.
Ahlberg, P. E. & Milner, A. R. 1994. The origin and early diversification of tetrapods. NATURE 368, 507–14.
Ahlberg, P. E. & Trewin, N. H. 1995. The postcranial skeleton of the Middle Devonian lungfish Dipterus valenciennesi. TRANS R SOC EDINBURGH EARTH SCI 85, 159–75.
Ahlberg, P. E., Luksevics, E. & Lebedev, O. A. 1994. The first tetrapod finds from the Devonian (Upper Famennian) of Latvia. PHILOS TRANS R SOC LONDON B343, 3032847.
Altangerel, P., Norell, M. A., Chiappe, L. M. & Clarke, J. M. 1993. Flightless bird from the Cretaceous of Mongolia. NATURE 362, 623–6; correction 363, 188.
Andrews, S. M. & Carroll, R. L. 1991. The Order Adelospondyli: Carboniferous lepospondyl amphibians. TRANS R SOC EDINBURGH EARTH SCI 82, 239–75.
Andrews, S. M. & Westoll, T. S. 1970a. The postcranial skeleton of Eusthenopteron foordi Whiteaves. TRANS R SOC EDINBURGH 68, 207329.
Andrews, S. M. & Westoll, T. S. 1970b. The postcranial skeleton of rhipidistian fishes excluding Eusthenopteron. TRANS R SOC EDINBURGH 68, 391489.
Ashley-Ross, M. A. 1992. The comparative myology of the thigh and crus in the salamanders Ambystoma tigrinum and Dicamptodon tenebrosus. J MORPHOL 211, 147–63.
Bartsch, B. & Gemballa, S. 1992. On the anatomy and development of the vertebral column and pterygiophores in Polypterus senegalus Cuvier, 1829 (‘Pisces’, Polypteriformes). ZOOL JB ANAT 122, 497529.
Beaumont, E. H. 1977. Cranial morphology of the Loxommatidae (Amphibia: Labyrinthodontia). PHILOS TRANS R SOC LONDON B280, 29101.
Bendix-Almgreen, S. E. 1976. Palaeovertebrate faunas of Greenland. In Escher, A. & Watt, W. S. (eds) Geology of Greenland, 536–73. Copenhagen: Geol. Surv. Greenland.
Bendix-Almgreen, S. E., Clack, J. A. & Olsen, H. 1988. Upper Devonian and Permian vertebrates collected in 1987 around Kejser Franz Joseph Fjord, central East Greenland. RAPP GRØNLANDS GEOL UNDERS 140, 95102.
Bendix-Almgreen, S. E., Clack, J. A. & Olsen, H. 1990. Upper Devonian tetrapod palaeoecology in the light of new discoveries in East Greenland. TERRA NOVA 2, 131–7.
Benton, M. J. 1990. Vertebrate Palaeontology. London: Unwin Hyman.
Blanco, M. J. & Alberch, P. 1992. Caenogenesis, developmental variability, and evolution in the carpus and tarsus of the marbled newt Triturus marmoratus. EVOLUTION 46, 677–87.
Bolt, J. R. 1977. Dissorophid relationships and ontogeny, and the origin of the Lissamphibia. J PALEONTOL 51, 235–49.
Bolt, J. R. 1990. Mississippian vertebrates from Iowa. NAT GEOGR RES 6, 339–54.
Bolt, J. R. 1991. Lissamphibian origins. In Schultze, H.-P. & Trueb, L. (eds) Origins of the higher groups of Tetrapods: controversy and consensus, 194222. Ithaca and London: Comstock Publishing Associates.
Brainerd, E. L., Ditelberg, J. S. & Bramble, D. M. 1993. Lung ventilation in salamanders and the evolution of vertebrate air-breathing mechanisms. BIOL J LINN SOC 49, 163–83.
Burke, A. C., Nelson, C. & Tabin, C. J. 1994. Hox genes and vertebrate transposition. J MORPH 220, 331.
Burke, A. C., Nelson, C. & Tabin, C. J. 1995. Hox genes and the evolution of vertebrate axial morphology. DEVELOPMENT 121, 333–46.
Bystrov, A. P. & Efremov, I. A. 1940. Benthosuchus sushkini Efr.—A labyrinthodont from the Eotriassic of Sharjenga River. TRUDY PALEONTOL INST 10, 5152.
Campbell, K. S. W. & Bell, M. W. 1977. A primitive amphibian from the late Devonian of New South Wales. ALCHERINGA 1, 369–81.
Carroll, R. L. 1969. Problems of the origin of reptiles. BIOL REVS 44, 393432.
Carroll, R. L. 1988. Vertebrate paleontology and evolution. New York: W. H. Freeman & Co.
Carroll, R. L. 1995. Problems of the phylogenetic analysis of Paleozoic choanates. In Arsenault, M., Lelièvre, H., & Janvier, P. (eds) Studies on early vertebrates (VIIth International Symposium, Miguasha Pare, Quebec). BULL MUS NATL HIST NAT, PARIS 17, (C) 389445.
Carroll, R. L. & Gaskill, P. 1978. The Order Microsauria. MEM AM PHILOS SOC 126, 1211.
Carroll, R. L., Belt, E., Dineley, D. L., Baird, D. & Mcgregor, D. C. 1972. Excursion A59, Vertebrate paleontology of eastern Canada. 24TH INT GEOL CONGR, MONTREAL, 1972, 1113.
Clack, J. A. 1987. Pholiderpeton scutigerum Huxley, an amphibian from the Yorkshire coal measures. PHILOS TRANS R SOC LONDON B318, 1107.
Clack, J. A. 1988. New material of the early tetrapod Acanthostega from the Upper Devonian of East Greenland. PALAEONTOLOGY 31, 699724.
Clack, J. A. 1989. Discovery of the earliest tetrapod stapes. NATURE 342, 425–30.
Clack, J. A. 1992. The stapes of Acanthostega gunnari and the role of the stapes in early tetrapods. In Webster, D., Fay, R. R., & Popper, A. N. (eds) Evolutionary biology of hearing, 405–20. New York: Springer Verlag.
Clack, J. A. 1993. Homologies in the fossil record: the middle ear as a test case. ACTA BIOTHEORETICA 41, 391410.
Clack, J. A. 1994a. Acanthostega gunnari, a Devonian tetrapod from Greenland; the snout, palate and ventral parts of the braincase, with a discussion of their significance. MEDD GRØNLAND GEOSCI 31, 324.
Clack, J. A. 1994b. The earliest known tetrapod braincase and the evolution of the stapes and fenestra ovalis. NATURE 369, 392–4.
Clack, J. A. (in press). The neurocranium of Acanthostega gunnari Jarvik and the evolution of the auditory region in tetrapods. ZOOL J LINN SOC.
Clack, J. A. & Coates, M. I. 1993. Acanthostega gunnari: our present connection. In Hoch, E. & Brantsen, A. K. (eds) Deciphering the natural world and the role of collections and museums, 3942. Copenhagen: Geological Museum.
Clack, J. A. & Coates, M. I. 1995. Acanthostega gunnari, a primitive, aquatic tetrapod? In Arsenault, M., Lelièvre, H., & Janvier, P. (eds) Studies on early vertebrates (VIIth International Symposium, Miguasha Pare, Quebec). BULL MUS NATL HIST NAT, PARIS 17, (C) 359–72.
Cloutier, R. & Ahlberg, P. E. 1995. Sarcopterygian interrelationships: how far are we from a phylogenetic consensus. GEOBIOS 19, 241–8.
Coates, M. I. 1991. New palaeontological contributions to limb ontogeny and phylogeny. In Hinchliffe, J. R., Hurle, J. M. & Summerbell, D. (eds) Developmental patterning of the vertebrate limb, 325–37. New York: Plenum.
Coates, M. I. 1993. Ancestors and homology. The origin of the tetrapod limb. ACTA BIOTHEORETICA 41, 411–24.
Coates, M. I. 1994a. Evolutionary patterns and early tetrapod limbs. J MORPH 220, 334.
Coates, M. I. 1994b. The origin of vertebrate límbs. In Akam, M., Holland, P., Ingham, P. & Wray, G. (eds) The evolution of developmental mechanisms, 169–80. DEVELOPMENT (SUPPL) 1994.
Coates, M. I. 1995. Fish fins or tetrapod limbs—a simple twist of fate? CURR BIOL 5, 844–8.
Coates, M. I. & Clack, J. A. 1990. Polydactyly in the earliest known tetrapod limbs. NATURE 347, 66–9.
Coates, M. I. & Clack, J. A. 1991. Fish-like gills and breathing in the earliest known tetrapod. NATURE 352, 234–6.
Coates, M. I. & Clack, J. A. 1995. Romer's gap: tetrapod origins and terrestriality. In Arsenault, M., Lelièvre, H. & Janvier, P. (eds) Studies on early vertebrates (VIIth International Symposium, Miguasha Pare, Quebec). BULL MUS NATL HIST NAT, PARIS 17, (C) 373–88.
Cook, J. 1990. Proper names for early fingers. NATURE 347, 1415.
Daeschler, E. B., Shubin, N. H., Thomson, K. S. & Amaral, W. W. 1994. A Devonian tetrapod from North America. SCIENCE 265, 639–42.
Daeschler, E. B. & Shubin, N. 1995. Tetrapod origins. PALEOBIOLOGY 21, 404–9.
Duboule, D. 1994. How to make a limb? SCIENCE 226, 575–6.
Edwards, J. L. 1989. Two perspectives on the evolution of the-tetrapod limb. AM ZOOL 29, 235–54.
Farris, J. S. 1969. A successive approximation approach to character weighting. SYST ZOOL 18, 374–85.
Forey, P., Gardiner, B. G. & Patterson, C. 1991. The Lungfish, the Coelacanth, and the Cow revisited. In Schultze, H.-P. & Treub, L. (eds) Origins of the higher groups of tetrapods: controversy and consensus, 145–72. New York: Cornell University Press.
Friend, P. F., Alexander-Marrak, P. D., Nicholson, J. & Yeats, A. K. 1976. Devonian sediments of East Greenland II. Sedimentary structures and fossils. MEDD GRØNLAND 206, 99pp.
Francis, E. T. 1934. The anatomy of the salamander. Oxford: Clarendon Press.
Gaffney, E. S. 1979. Tetrapod monophyly: a phylogenetic analysis. BULL CARNEGIE MUS NATL HIST 13, 92105.
Gaunt, S. J. 1994. Conservation in the Hox code during morphological evolution. INT J DEV BIOL 38, 549–52.
Gauthier, J. A., Kluge, A. G. & Rowe, T. 1988. Amniote phylogeny and the importance of fossils. CLADISTICS 4, 105209.
Godfrey, S. J. 1989. The postcranial skeletal anatomy of the Carboniferous tetrapod Greererpeton burkemorani Romer, 1969. PHILOS TRANS R SOC LONDON B323, 75133.
Godfrey, S. J., Fiorillo, A. R. & Carroll, R. L. 1987. A newly discovered skull of the temnospondyl amphibian Dendrerpeton acadianum Owen. CAN J EARTH SCI 24, 796805.
Godfrey, S. J. & Reisz, R. R. 1991. The vertebral morphology of Gephyrostegus bohemicus Jaekel 1902, with comments on the atlas-axis complex in primitive tetrapods. HISTORICAL BIOL 5, 2736.
Goodrich, E. S. 1904. On the dermal fin-rays of fishes, living and extinct. Q J MICROSP SCI 47, 465522.
Goodrich, E. S. 1906. Notes on the development, structure and origin of the median and paired fins of fish. Q J MICROSP SCI 50, 333–76.
Goodrich, E. S. 1916. On the classification of the Reptilia. PROC R SOC LONDON B89, 261–76.
Goodrich, E. S. 1930. Studies on the structure and development of vertebrates. London: Macmillan & Co.
Goulding, M., Leal, Carvalho M. & Ferreira, E. G. 1988. Rio Negro, rich life in poor water. Illinois/Netherlands: SPB Academic Publishing.
Haswell, W. A. 1882. On the structure of the paired fins of Ceratodus, with remarks on the general theory of the vertebrate limb. PROC LINN SOC NEW SOUTH WALES 7, 211.
Holmes, R. 1980. Proterogyrinus scheelei and the early evolution of the labyrinthodont pectoral limb. In Panchen, A. L. (ed.) The terrestrial environment and the origin of land vertebrates, 351–76. London and New York: Academic Press.
Holmes, R. 1984. The Carboniferous amphibian Proterogyrinus scheelei Romer, and the early evolution of tetrapods. PHILOS TRANS R SOC LONDON B306, 431527.
Holmes, R. 1989. The skull and axial skeleton of the Lower Permian anthracosauroid amphibian Archeria crassidica Cope. PALAEONTOGRAPHICA 207, 161206.
Holmes, R. & Carroll, R. L. 1977. A temnospondyl amphibian from the Mississippian of Scotland. BULL MUS COMP ZOOL HARVARD 147, 489511.
Hook, R. W. 1983. Colosteus scutellus (Newberry), a primitive temnospondyl amphibian from the Middle Pennsylvanian of Linton, Ohio. AM MUS NOVIT 2770, 141.
Jarvik, E. 1942. On the structure of the snout of crossopterygians and lower gnathostomes in general. ZOOL BIDR UPPS 21, 235675.
Jarvik, E. 1952. On the fish-like tail in the ichthyostegid stegocephalians with descriptions of a new stegocephalian and a new crossopterygian from the Upper Devonian of East Greenland. MEDDR GRØNLAND 114, 190.
Jarvik, E. 1955. The oldest tetrapods and their forerunners. SCI MONTHLY 80, 141–54.
Jarvik, E. 1980. Basic structure and evolution of vertebrates 1, 1591. London and New York: Academic Press.
Jarvik, E. 1996. The Devonian tetrapod Ichthyostega. FOSSILS & STRATA 40, 1206.
Klembara, J. 1995. The external gills and ornamentation of skull roof bones of the Lower Permian tetrapod Discosauriscus Kuhn 1933) with remarks to its ontogeny. PALÄONT Z 69, 265–81.
Kodera, H. 1994. Jurassic fishes. New Jersey: TFH Publications.
Laurin, M. (1996). Redescription of the cranial anatomy of Seymouria baylorensis, the best known seymouriamorph (Vertebrata: Seymouriamorpha). PALEOBIOS, 17, 116.
Laurin, M. & Reisz, R. R. 1995. A reevaluation of early amniote phylogeny. ZOOL J LINN SOC 113, 165223.
Lebedev, O. A. 1984. The first find of a Devonian tetrapod in USSR. DOKLADY AKAD NAUK SSSR 278, 1407–73 [In Russian].
Lebedev, O. A. 1985. The first tetrapods: searches and findings. PRIRODA 1985 11, 2636. [In Russian].
Lebedev, O. A. 1990. Tulerpeton, l'animal à six doigts. LA RECHERCHE 225, 1274–75.
Lebedev, O. A. 1992. The latest Devonian, Khovanian vertebrate assemblage of Andreyevka-2 locality, Tula Region, Russia. In Mark-Kurik, E. (ed.) Fossil fishes as living animals, 265–72. Proceedings of the IInd International Colloquium on the study of Palaeozoic Fishes, Tallin, 1989. ACADEMIA 1. Tallin: Academy of Sciences of Estonia.
Lebedev, O. A. & Clack, J. A. 1993. Upper Devonian tetrapods from Andreyevka, Tula Region, Russia. PALAEONTOLOGY 36, 721–34.
Lebedev, O. A. & Coates, M. I. 1995. The postcranial skeleton of the Devonian tetrapod Tulerpeton curtum Lebedev. ZOOL J LINN SOC 113, 307–48.
Leonardi, G. 1983. Notopus petri nov. gen., nov. sp.: Une empreinte d'amphibien de Devonian au Parana (Brésil). GEOBIOS 16, 233–9.
Lewis, J. & Martin, P. 1989. Limbs: a pattern emerges. NATURE 342, 734–5.
Linnaeus, C. 1758. Systema naturae (10th edn). Stockholm: Laurentii Salvii.
Lombard, R. E. & Bolt, J. R. 1995. A new primitive tetrapod Whatcheeria deltae from the Lower Carboniferous of Iowa. PALAEONTOLOGY 38, 471–94.
Lombard, R. E. & Sumida, S. S. 1992. Recent progress in understanding early tetrapods. AM ZOOL 32, 609–22.
Long, J. A. 1989. A new rhizodontiform fish from the early Carboniferous of Victoria, Australia, with remarks on the phylogenetic position of the group. J VERT PALEONTOL 9, 117.
Long, J. A. 1990. Heterochrony and the origin of tetrapods. LETHAIA 23, 157–66.
McNamara, K. J. 1986. A guide to the nomenclature of heterochrony. J PALEONTOL 60, 413.
Meyer, A. 1995. Molecular evidence on the origin of tetrapods and the relationships of the coelacanth. TREE 10, 111–16.
Milner, A. R. 1980. The temnospondyl amphibian Dendrerpeton from the Upper Carboniferous of Ireland. PALAEONTOLOGY 23, 125–41.
Milner, A. R. 1988. The relationships and origin of living amphibia. In Benton, M. J. (ed.) The phylogeny and classification of the tetrapods, 1, 59102. Oxford: Clarendon Press.
Milner, A. R. 1990. The radiations of temnospondyl amphibians. In Taylor, P. D. & Larwood, G. P. (eds) Major evolutionary radiations, 321–49. Oxford: Clarendon Press.
Milner, A. R. & Sequeira, S. E. K. 1994. The temnospondyl amphibians from East Kirkton, West Lothian, Scotland. TRANS R SOC EDINBURGH EARTH SCI 84, 331–61.
Milner, A. R., Smithson, T. R., Milner, A. C., Coates, M. I., & Rolfe, W. D. I. 1986. The search for early tetrapods. MOD GEOL 10, 128.
Molven, A., Wright, C. V., Bremiller, R., DeRobertis, E. M. & Kimmel, C. B. 1990. Expression of a homeobox gene product in normal and mutant zebrafish embryos: evolution of the tetrapod body plan. DEVELOPMENT 109, 279–88.
Moulton, J. M. 1974. A description of the vertebral-column of Eryops based on the notes and drawings of A. S. Romer. BREVIORA 428, 144.
Nelson, C. E., Morgan, B. A., Burke, A. C., Laufer, E., DiMambro, E., Murtaugh, L. C., Gonzales, E., Tessarollo, L., Parada, L. F. & Tabin, C. 1996. Analysis of Hox gene expression in the chick limb bud. DEVELOPMENT 122, 1449–66.
Nicholson, J. & Friend, P. F. 1976. Devonian sediments of East Greenland V. The central sequence, Kap Graah Group and Mount Celsius Supergroup. MEDDR GRØNLAND 206, 1117.
Olsen, E. C. 1936. The ilio-sacral attachment of Eryops. J PALEONTOL 10, 648–51.
Panchen, A. L. 1966. The axial skeleton of the labyrinthodont Eogyrinus attheyi. J ZOOL LONDON 150, 199220.
Panchen, A. L. 1985. On the amphibian Crassigyrinus scoticus Watson from the Carboniferous of Scotland. PHILOS TRANS R SOC LONDON B309, 505–68.
Panchen, A. L. 1988. In search of earliest tetrapods. NATURE 333, 704.
Panchen, A. L. 1992. Classification, evolution, and the nature of biology. New York: Cambridge University Press.
Panchen, A. L. & Smithson, T. R. 1988. The relationships of early tetrapods. In Benton, M. J. (ed.) The phylogeny and classification of the tetrapods, 1, 132. Oxford: Clarendon Press.
Panchen, A. L. & Smithson, T. R. 1990. The pelvic girdle and hind limb of Crassigyrinus scoticus (Lydekker) from the Scottish Carboniferous and the origin of the tetrapod pelvic skeleton. TRANS R SOC EDINBURGH EARTH SCI 81, 3144.
Patterson, C. 1975. The braincase of pholidophorid and leptolepid fishes, with a review of the actinopterygian braincase. PHILOS TRANS R SOC LONDON B269, 275579.
Patterson, C. 1993a. Bird or dinosaur? NATURE 365, 21–2.
Patterson, C. 1993b. Naming names. NATURE 366, 518.
Patterson, C. & Rosen, D. E. 1977. Review of ichthyodectiform and other Mesozoic teleost fishes and the theory and practice of classifying fossils. BULL AM MUS NAT HIST 158, 81172.
Pendleton, J. W., Nagai, B. K., Murtha, M. T. & Ruddle, F. H. 1993. Expansion of the Hox gene family and the evolution of chordates. P N A S 90, 6300–4.
Pridmore, P. A. 1995. Submerged walking in the epaulette shark Hemiscyllium ocellatum (Hemiscyllidae) and its implications for locomotion in rhipidistian fishes and early tetrapods. ZACS ZOOL 98, 278–97.
de Quieroz, K. & Gauthier, J. 1992. Phylogenetic taxonomy. ANN REV ECOL SYST 23, 449–80.
Rackoff, J. S. 1980. The origin of the tetrapod limb and the ancestry of tetrapods. In Panchen, A. L. (ed.) The terrestrial environment and the origin of land vertebrates, 255–92. SYSTEMAT1CS ASSOC SPEC VOL 15. London: Academic Press.
Reilly, S. M. & Lauder, G. V. 1990. The evolution of tetrapod feeding behaviour: kinematic homologies in prey transport. EVOLUTION 44, 1542–57.
Rogers, D. 1990. Probable tetrapod tracks rediscovered in the Devonian of North Scotland. J GEOL SOC LONDON 147, 746–8.
Romer, A. S. 1922. The locomotor apparatus of certain primitive and mammal-like reptiles. BULL AM MUS NAT HIST 46, 517606.
Romer, A. S. 1956. Osteology of the reptiles. Chicago: University of Chicago Press.
Romer, A. S. 1957. The appendicular skeleton of the Permian embolomerous amphibian Archeria. CONTRIB MUS GEOL UNIV MICHIGAN 13, 103–59.
Romer, A. S. & Parsons, T. S. 1977. The vertebrate-body (5th edn). Philadelphia: W. B. Saunders Company.
Romer, A. S. & Price, L. I. 1940. Review of the Pelycosauria. SPEC PAP GEOL SOC AM 28, 1538.
Ruddle, F. H., Bartels, J. L., Bentley, K. L., Kappen, C., Murtha, M. T. & Pendleton, J. W. 1994. Evolution of Hox genes. ANN REV GEN 28, 423–42.
Säve-Söderbergh, G. 1932. Preliminary note on Devonian stegocephalians from East Greenland. MEDDR GRØNLAND 94, 1107.
Säve-Söderbergh, G. 1934. Some points of view concerning the evolution of vertebrates and the classification of this group. ARK ZOOL 26A, 120.
Sayer, M. D. J. & Davenport, J. 1991. Amphibious fish: why do they leave the water? REV FISH BIOL FISHERIES 1, 159–81.
Schultze, H.-P. 1994. Comparison of hypotheses on the relationships of sarcopterygians. SYST BIOL 43, 155–73.
Schultze, H.-P. & Arsenault, M. 1985. The panderichthyid fish Elpistostege: a close relative of tetrapods? PALAEONTOLOGY 28, 293310.
Shear, W. A. 1991. The early development of terrestrial ecosystems. NATURE 351, 283–9.
Shubin, N. H. 1995. The evolution of paired fins and the origin of tetrapod limbs. Phylogenetic and transformational approaches. EVOL BIOL 28, 3986.
Shubin, N. H. & Alberch, P. 1986. A morphogenetic approach to the origin and basic organisation of the tetrapod limb. EVOL BIOL 20, 319–87.
Smith, A. B. 1994. Systematics and the fossil record: documenting evolutionary patterns. London: Blackwell Scientific Publications.
Smithson, T. R. 1982. The cranial morphology and relationships of Greererpeton burkemorani Romer (Amphibia: Temnospondyli). ZOOL J LINN SOC 76, 2990.
Smithson, T. R. 1985. The morphology and relationships of the Carboniferous amphibian Eoherpeton watsoni Panchen. ZOOL J LINN SOC 85, 317410.
Smithson, T. R. 1986. A new anthracosaur amphibian from the Carboniferous of Scotland. PALAEONTOLOGY 29, 603–28.
Smithson, T. R. 1994. Eldeceeon rolfei, a new reptiliomorph from the Visean of East Kirkton, West Lothian, Scotland. TRANS R SOC EDINBURGH EARTH SCI 84, 377–82.
Smithson, T. R., Carroll, R. L., Panchen, A. L. & Andrews, S. M. 1994. Westlothiana lizziae from the Visean of East Kirkton, West Lothian, Scotland and the amniote stem. TRANS R SOC EDINBURGH EARTH SCI 84, 377–82.
Smithson, T. R. & Thomson, K. S. W. 1982. The hyomandibular of Eusthenopteron foordi Whiteaves (Pisces: Crossopterygii) and the early evolution of the tetrapod stapes. ZOOL J LINN SOC 74, 93103.
Sordino, P. & Duboule, D. 1996. A molecular approach to the evolution of vertebrate paired appendages. TREE 11, 114–19.
Sordino, P., van der Hoeven, F. & Duboule, D. 1995. Hox gene expression in teleost fins and the origin of vertebrate digits. NATURE 375, 678–81.
Stossel, I. 1995. The discovery of a new Devonian tetrapod trackway in SW Ireland. J GEOL SOC LONDON 152, 407–13.
Swofford, D. L. 1990. PAUP, Phylogenetic Analysis Using Parsimony, Version 3.1 (Computer program: Apple Macintosh version). Illinois Natural History Survey.
Symmons, S. 1979. Notochordal and elastic components of the axial skeleton of fishes and their functions in locomotion. J ZOOL LONDON 189, 157206.
Tabin, C. J. 1992. Why we have (only) five fingers per hand: Hox genes and the evolution of paired limbs. DEVELOPMENT 116, 289296.
Thorogood, P. 1991. The development of the Teleost fin and implications for our understanding of tetrapod limb evolution. In Hinchliffe, J. R., Hurle, J. M. & Summerbell, D. (eds) Developmental patterning of the vertebrate limb, 347–54. New York: Plenum.
Tickle, C. 1995. Vertebrate limb development. CURR OPIN GEN DEV 5, 478–84.
Tickle, C. & Eichele, G. 1994. Vertebrate limb development. ANN REV CELL BIOL 10, 121–52.
Vorobyeva, E. 1992. The problem of the terrestrial vertebrate origin. Moscow: Nauka.
Vorobyeva, E. & Schultze, H.-P. 1991. Description and systematics of panderichthyid fishes with comments on their relationship to tetrapods. In Schultze, H.-P. & Treub, L. (eds) Origins of the higher groups of tetrapods, 68109. Ithaca: Comstock, Cornell University Press.
Wagner, G. P. 1989. The origin of morphological characters and the biological basis of homology. EVOLUTION 43, 1157–71.
Warren, A. A., Jupp, R. & Bolton, B. R. 1986. Earliest tetrapod trackway. ALCHERINGA 10, 183–6.
Warren, J. W. & Wakefield, N. A. 1972. Trackways of tetrapod vertebrates from the Upper Devonian of Victoria, Australia. NATURE 238, 469–70.
Watson, D. M. S. 1914. On a femur of reptilian type from the Lower Carboniferous of Scotland. GEOL MAG (6) 1, 347–8.
Wellstead, C. F. 1982. A Lower Carboniferous aïstopod amphibian from Scotland. PALAEONTOLOGY 25, 193208.
Wettstein, O. 1931. Ordnung der Klasse Reptilia: Rhynchocephalia. In Kükenthal, W. & Krumbach, T. (eds) Handbuch Der Zoologie VII, 1128. Berlin & Leipzig: Walter Der Gruyter & Co.
White, T. E. 1939. Osteology of Seymouria baylorensis Broili. BULL MUS COMP ZOOL 85, 325409.
Woodrow, D. L., Robinson, R. A. J., Prave, A. R., Traverse, A., Deaschler, E. B., Rowe, N. D. & DeLaney, M. A. 1995. Stratigraphic, sedimentologic, and temporal framework of Red Hill (Upper Devonian Catskill Formation) near Hyner, Clinton County, Pennsylvania: Site of the oldest amphibian known from North America. 60th Annual Field Conference of Pennsylvania Geologists.



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