Review of the Labyrinthodontia.
About: This article is published in American Midland Naturalist.The article was published on 1950-05-01. It has received 227 citations till now.
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TL;DR: A deep split of early tetrapods between lissamphibian‐ and amniote‐related taxa is detected and is indicated by the results of the original parsimony run ‐ as well as those retrieved from several other treatments of the data set.
Abstract: In an attempt to investigate differences between the most widely discussed hypotheses of early tetrapod relationships,
we assembled a new data matrix including 90 taxa coded for 319 cranial and postcranial characters. We
have incorporated, where possible, original observations of numerous taxa spread throughout the major tetrapod
clades. A stem-based ( total-group) definition of Tetrapoda is preferred over apomorphy- and node-based
(crown-group) definitions. This definition is operational, since it is based on a formal character analysis. A PAUP*
search using a recently implemented version of the parsimony ratchet method yields 64 shortest trees. Differences
between these trees concern: (1) the internal relationships of ai¨stopods, the three selected species of which
form a trichotomy; (2) the internal relationships of embolomeres, with Archeria crassidisca and Pholiderpeton scutigerum
collapsed in a trichotomy with a clade formed by Anthracosaurus russelli and Pholiderpeton attheyi ; (3) the internal
relationships of derived dissorophoids, with four amphibamid species forming an unresolved node with a clade
consisting of micromelerpetontids and branchiosaurids and a clade consisting of albanerpetontids plus basal
crown-group lissamphibians ; (4) the position of albenerpetontids and Eocaecilia micropoda, which form an unresolved
node with a trichotomy subtending Karaurus sharovi, Valdotriton gracilis and Triadobatrachus massinoti ; (5) the
branching pattern of derived diplocaulid nectrideans, with Batrachiderpeton reticulatum and Diceratosaurus brevirostris
collapsed in a trichotomy with a clade formed by Diplocaulus magnicornis and Diploceraspis burkei. The results of the
original parsimony run – as well as those retrieved from several other treatments of the data set ( e.g. exclusion
of postcranial and lower jaw data ; character reweighting ; reverse weighting ) – indicate a deep split of early
tetrapods between lissamphibian- and amniote-related taxa. Colosteids, Crassigyrinus, Whatcheeria and baphetids
are progressively more crownward stem-tetrapods. Caerorhachis, embolomeres, gephyrostegids, Solenodonsaurus
and seymouriamorphs are progressively more crownward stem-amniotes. Eucritta is basal to temnospondyls,
with crown-lissamphibians nested within dissorophoids. Westlothiana is basal to Lepospondyli, but evidence for
the monophyletic status of the latter is weak. Westlothiana and Lepospondyli form the sister group to diadectomorphs
and crown-group amniotes. Tuditanomorph and microbrachomorph microsaurs are successively
more closely related to a clade including proximodistally : (1) lysorophids; (2) Acherontiscus as sister taxon to
adelospondyls; (3) scincosaurids plus diplocaulids ; (4) urocordylids plus ai¨stopods. A data set employing cranial
characters only places microsaurs on the amniote stem, but forces remaining lepospondyls to appear as sister
group to colosteids on the tetrapod stem in several trees. This arrangement is not significantly worse than the tree
topology obtained from the analysis of the complete data set. The pattern of sister group relationships in the
crownward part of the temnospondyl-lissamphibian tree re-emphasizes the important role of dissorophoids in
the lissamphibian origin debate. However, no specific dissorophoid can be identified as the immediate sister taxon
to crown-group lissamphibians. The branching sequence of various stem-group amniotes reveals a coherent set
of internested character-state changes related to the acquisition of progressively more terrestrial habits in several
Permo-Carboniferous forms.
256 citations
Cites background from "Review of the Labyrinthodontia."
...A transverse pelvic ridge appears in some temnospondyls (notablyEryops andDendrerpeton ; Romer, 1947; Holmes et al., 1998)....
[...]
...Eryops appears to be a generalized eryopoid (Holmes, 2000), and is undoubtedly one of the best known Palaeozoic tetrapods (Romer, 1922, 1947; Miner, 1925; Sawin, 1941; Moulton, 1974)....
[...]
...Character 272 shows its derived state in Acanthostega, Crassigyrinus, Baphetes, Eryops, embolomeres, Gephyrostegus, Seymouria and Limnoscelis (White, 1939; Romer, 1946, 1947; Carroll, 1970; Panchen, 1980, 1985; Holmes, 1984, 1989; Smithson, 1985; Milner & Lindsay, 1998)....
[...]
TL;DR: Two species of triconodont (atherian) mammal from the Lower Jurassic are described: M. oehleri from China and M. watsoni from Wales; the systematic position of Morganucodon is discussed.
254 citations
TL;DR: It is suggested that the radiation of the diverse stereospondyl clades, the Capitosauria and Trematosauria, began in the Late Permian of Gondwana, in a «safe haven» that was less severely affected by the LatePermian extinction event.
224 citations
TL;DR: Doleserpeton is unique among nonlissamphibian tetrapods in that it possesses pedicellate, bicuspid teeth together with nearly monospondylous vertebrae in which the main central element is a pleurocentrum.
Abstract: A new genus and family of rhachitomous labyrinthodont amphibian, related to the Upper Paleozoic Dissorophidae and Trematopsidae, may be ancestral to some or all of the modern Amphibia. Doleserpeton occurs in Lower Permian fissure fill deposits in southwestern Oklahoma. It is unique among nonlissamphibian tetrapods in that it possesses pedicellate, bicuspid teeth together with nearly monospondylous vertebrae in which the main central element is a pleurocentrum. Doleserpeton may have been utilizing the food resources of the upland, terrestrial environment in a novel fashion for rhachitomes.
190 citations
01 Jan 1996
180 citations