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19301
Romer, The Pennsylvanian Tetrapods of Linton, Ohio
139
specimen is a poorly preserved ccelacanth, the fin supports of which are
the apparent limbs. The only evidence to the contrary is the fact that
there are distinct, although rather faint, impressions of vertebral structures
in the central region of the specimen, whereas there is normally
little or no ossification of the centra in later members, at least, of the
ccelacanth group.
DISCUSSION
In the descriptive portion of this paper, I have attempted to clarify
the confused mass of taxonomic terms that obscures the true nature of
the Linton tetrapods, and to gain some understanding of the structure
and appearance of the forms which inhabited this pool. As suggested
in the preface, these have proved to be comparatively few in number.
Instead of about sixty forms of tetrapods, there are less than twenty of
whose presence we can be certain. There are a number of cases (the
"Molgophis" group, for example) in which tentative associations of
postcranial material may prove incorrect, and in the writer's effort to
simplify the picture he may have been over hasty in relegating a few
forms founded on poorly preserved or fragmentary material to the
synonymy. However, the story is, surely, much clearer than it has been
in the past.
SUMMARY OF THE FAUNA
The Linton forms, as I understand them, include the following:
Cocytinus, a small elongate form, probably with tiny limbs and a peculiar skull,
obviously a perennibranchiate type, related to Lysorophus of the Permian.
Two aistopods, Ophiderpeton and Phlegethontia, slim, elongate, limbless amphibians,
with elongate skulls of peculiar structure.
Two small long-tailed members of the nectridian genus Sauropleura, probably
somewhat similar to the last in superficial appearance, although possessing small
limbs and differing radically in morphology and relationships; and Ctenerpeton, a
larger relative, with somewhat better-developed limbs.
A small "horned" nectridian, Diceratosaurus, with a depressed body, rather
small limbs and a very long tail.
Two primitive branchiosaurs, one (Pelion lyeUi) large, a second (Branchiosauravus
tabulatus) considerably smaller, both tending towards the short skull type of
the group.
Colosteus, one of the larger forms, with a maximum length of the comparatively
elongate skull of about eight inches, the eyes placed somewhat anteriorly; resembling
the labyrinthodonts in many respects, but apparently an aberrant offshoot of the
branchiosaur stock.
Erpetosaurus, a much smaller relative, with larger orbits.
Stegops, a branchiosaur with an extremely peculiar "spinescent" type of skull,
already highly specialized but close to the ancestry of certain larger Permian amphi-