. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Temnospondyl Amphibian • Holmes and Carroll 507 Primitive characteristics such as the pres- ence of an intertemporal bone and a mov- able basicranial articulation, as well as the absence of lateral line canal grooves, indi- cate that this animal may be placed within the Superfamily Edopoidea. Furthermore, the general anatomy of the skull roof, palate and pelvic girdle shows that it is closely re- lated to previously described members of the Family Dendrerpetontidae. The ab- scence of a well defined otic notch makes it
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Temnospondyl Amphibian • Holmes and Carroll 507 Primitive characteristics such as the pres- ence of an intertemporal bone and a mov- able basicranial articulation, as well as the absence of lateral line canal grooves, indi- cate that this animal may be placed within the Superfamily Edopoidea. Furthermore, the general anatomy of the skull roof, palate and pelvic girdle shows that it is closely re- lated to previously described members of the Family Dendrerpetontidae. The ab- scence of a well defined otic notch makes it awkward to include Caerorhachis within this family as currently understood, how- ever. The nature of the vertebrae presents a much more serious problem to the classi- fication of Caerorhachis. The vertebrae are well preserved and readily reconstructed. Their structure, however, is entirely differ- ent from that seen in Dendrerpeton and other edopoids, and is of a type totally un- expected in primitive temnospondyl am- phibians. The structure of the vertebrae has been the basis for the major subdivisions of Pale- ozoic amphibians according to all recent authors. The first workable classification of labyrinthodonts was developed by Wat- son (1919, 1926). He considered that the vertebrae of all known labyrinthodonts con- formed to one of three structural stages and he used these differences as a basis for di- viding the Labyrinthodontia into the Orders Embolomeri, Rhachitomi and Stereospon- dyli. In the Embolomeri both the intercen- trum and the pleurocentrum are complete rings, forming a "double" centrum. The Rhachitomi have vertebrae composed of large crescentic intercentra and pleurocen- tra represented by small paired blocks situ- ated dorsally, posterior to the intercentrum. In the Stereospondyli, the pleurocentra have completely disappeared, and the centra are composed of only cylindrical intercentra. At the time Watson wrote, most of the known Permian labyrinth
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