The vertebral morphology of Gephyrostegus Bohemicus Jaekel 1902, with comments on the atlas-axis complex in primitive tetrapods
Titel:
The vertebral morphology of Gephyrostegus Bohemicus Jaekel 1902, with comments on the atlas-axis complex in primitive tetrapods
Auteur:
Godfrey, Stephen J. Reisz, Robert R.
Verschenen in:
Historical biology
Paginering:
Jaargang 5 (1991) nr. 1 pagina's 27-36
Jaar:
1991-08
Inhoud:
An articulated, partial vertebral column from the Humboldt mine at Nyrany, Czechoslovakia, is assigned to the Silesian (Westphalian D) anthracosaur Gephyrostegus bohemicus Jaekel 1902, on the basis of the posterodorsal enlargement of presacral pleurocentra above the crescentic intercentra. This specimen demonstrates that the intercentra are significantly greater in height than formerly reconstructed and that the length of the neural arches and pleurocentra increases by about 25% in the presacral region whereas the intercentra remain essentially unchanged in their length. Uncinate flanges are present on several pairs of anterior dorsal ribs; they are interpreted here as a tetrapod autapomorphy. The atlas-axis complex of G. bohemicus is reinterpreted. It consists of paired proatlantes, a crescentic atlas intercentrum, possibly a paired atlas pleurocentrum, a paired atlas arch, a crescentic axis intercentrum, a unitary axis pleurocentrum, and a large axis arch. With the exception of the unpaired axis pleurocentrum, the atlax-axis complex in G. bohemicus closely approximates the primitive tetrapod pattern. A pair of posteroventrally directed tubercles are present on at least the atlas and axis intercentra. These tubercles are believed to represent a tetrapod plesiomorphy.
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