Tetrapod origins

Daeschler, Edward B.; Shubin, Neil

doi:10.1017/s0094837300013452

Cited by 12 publications

(7 citation statements)

References 25 publications

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“…lungs were considered to be a feature of both tetrapods and lungfish, the factors that drove the evolution of lungs were linked to the in vasion of the terrestrial environment (Barrell 1916). Although this scenario for tetrapod evolution is no longer generally accepted (re viewed in Coates and Clack 1995;Daeschler and Shubin 1995), the idea that selection for lungs occurred in oxygen-poor water remains the dominant scenario (Johansen 1970(Johansen , 1985Johansen and Burggren 1980;Randall et al 1981;Shelton 1985;Graham 1994;Walker and Liem 1994;Coates and Clack 1995).…”

Section: Hence I P R O P O S E I N This P a P E R That L U N G S I Nmentioning

confidence: 99%

Did lungs and the intracardiac shunt evolve to oxygenate the heart in vertebrates?

Farmer

1997

Paleobiology

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Traditional wisdom of the evolution of lungs in fishes is that lungs arose when gill ventilation was hindered by an aquatic habitat that was low in oxygen. This scenario has been buttressed primarily by a proposed correlation between extant air-breathing fishes and hypoxic habitats, as well as by the fact that early vertebrate fossils were found in sediments believed to indicate a semi-arid environment. There are problems with this scenario, yet it retains a dominant influence on how the evolution of aerial respiration is viewed. This paper presents a new hypothesis for lung evolution that is more consistent with the fossil record and physiology of extant animals than the traditional scenario; I propose that lungs evolved to supply the heart with oxygen. The primitive vertebrate heart was spongy in architecture and devoid of coronary support, obtaining oxygen from luminal blood. By supplying oxygen to this tissue, lungs may have been important in ancient fishes for sustaining activity, regardless of environment. Furthermore, this function for lungs may have influenced cardiovascular adaptations of tetrapods because their divided cardiovascular system isolates the right side of the heart from pulmonary oxygen. I propose that three innovations compensate for this isolation: In extant amphibians oxygen-rich blood from cutaneous and buccal respiration enters the right side of the heart; in chelonians and lepidosaurs the intracardiac shunt washes oxygen-rich blood into the right side of the heart; in mammals, birds, and perhaps in crocodilians, support of the heart by coronary vasculature eliminates this problem.

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Section: Hence I P R O P O S E I N This P a P E R That L U N G S I Nmentioning

confidence: 99%

Did lungs and the intracardiac shunt evolve to oxygenate the heart in vertebrates?

Farmer

1997

Paleobiology

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“…Recent work on Acanthostega and other Devonian tetrapod genera has put forward the alternative hypothesis that limbs with digits evolved first among tetrapods for use in water, and only later were co-opted for terrestrial use (Coates and Clack, 1990;Gould, 1991). Recent ideas on the origin of tetrapods and limbs have recently been reviewed by a number of authors (Thomson, 1991(Thomson, , 1993Ahlberg and Milner, 1994;Daeschler and Shubin, 1995).…”

Section: Introductionmentioning

confidence: 99%

Devonian tetrapod trackways and trackmakers; a review of the fossils and footprints

Clack¹

1997

Palaeogeography, Palaeoclimatology, Palaeoecology

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“…Tulerpeton is known from shallow marine deposits (Lebedev 1984(Lebedev , 1985(Lebedev , 1990, while the apparently terrestrially-adapted Hynerpeton originates from non-marine floodplain sediments (Daeschler et al 1994) rich in faunal and floral remains (Woodrow et al 1995). Concise summaries and discussions of these and further new data concerning questions of tetrapod origin, terrestrialisation, and the changing picture of Upper Devonian terrestrial environments can be found in Shear (1991), Lombard and Sumida (1992), Ahlberg and Milner (1994), Coates and Clack (1995), and Daeschler and Shubin (1995).…”

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confidence: 97%

The Devonian tetrapodAcanthostega gunnariJarvik: postcranial anatomy, basal tetrapod interrelationships and patterns of skeletal evolution

Coates

1996

Transactions of the Royal Society of Edinburgh: Earth Sciences

262

493

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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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Tetrapod origins

Cited by 12 publications

References 25 publications

Did lungs and the intracardiac shunt evolve to oxygenate the heart in vertebrates?

Did lungs and the intracardiac shunt evolve to oxygenate the heart in vertebrates?

Devonian tetrapod trackways and trackmakers; a review of the fossils and footprints

The Devonian tetrapodAcanthostega gunnariJarvik: postcranial anatomy, basal tetrapod interrelationships and patterns of skeletal evolution

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