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On Acanthostoma vorax Credner.
Author(s) -
Steen Margaret C.,
Brough Mrs. James
Publication year - 1937
Publication title -
proceedings of the zoological society of london
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0370-2774
DOI - 10.1111/j.1469-7998.1937.tb00020.x
Subject(s) - anatomy , vertebral column , vertebra , dorsum , ossification , vomer , arch , biology , geography , archaeology
Summary. The vertebral column and “part of the limbs” in Acanihostoma vorax were known to Credner in a single specimen, in which he states the vertebras occur as a weak impression. On this statement, and Geinitz and Deichmuller's figures (1882. pi. vii. fig. 9), Acanthostoma vorax has been regarded as a Phvllo‐spondvl (Jaekel, 1009, p. 254; Romer, 1930, pp. 117–118; Steen, 1931, p. 889). The vertebra! are, however, Labyrinthodont in type, although unique in the structure of the centra (both pleura‐ and intercentra being ossified as right and left hemicyclinders unfused in the mid‐dorsal or mid‐ventral line). In the development of the Acanthostoma vertebra, as in those of the Labyrinthodont Archegosaurus, ossification of the neural arch precedes that of the centra, the neural arches passing through a stage which is very similar to the neural arches of an adult Phyllospondyl. It is also important to point out that short straight ribs expanded at both ends, as well as occurring in the Phyllo‐spondyli, also occur as a stage in the development of the rib in Acanthostoma and Archegosaurus. Such resemblances suggest that the Phyllospondyli are more closely related to the Labyrmthodonta than to the other amphibian orders.