. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 100 bulletin: museum of comparative zoology tion of the orbits in combination with numerous cranial features which appear to be primitive. The skull pattern of (for example) Loxomma is, barring the orbital shape, in many ways that which would be expected in an ancestral tetrapod. It differs in two respects from the typical embolomere: (1) close union of cheek and table; (2) small tabular. In both respects the loxommids agree with ichthyoste- gals and typical Rhachitomi; the temporal pattern, however, clearly distingui
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 100 bulletin: museum of comparative zoology tion of the orbits in combination with numerous cranial features which appear to be primitive. The skull pattern of (for example) Loxomma is, barring the orbital shape, in many ways that which would be expected in an ancestral tetrapod. It differs in two respects from the typical embolomere: (1) close union of cheek and table; (2) small tabular. In both respects the loxommids agree with ichthyoste- gals and typical Rhachitomi; the temporal pattern, however, clearly distinguishes them from the former, for an intertemporal was primi- tively present and a frontal contact is preserved by that element (or, in its absence, by the supratemporal); further, the post-orbital region is relatively short. The palatal structure is of a diagrammatically simple pattern. The closed palate and movable basipterygoid processes are primitive features seen also in early ichthyostegals and in embolomeres and. Fig. IS. The skull roof of Loxomma, modified by reduction of the orbit to normal proportions, for comparison with edopsoid rhachitomes. presumably a direct fish heritage. The presence of broad vomers widely separating the nostrils is in agreement Avith ichthyostegids, rhachitomes and stereospondyls, and in contrast with typical em- bolomeres. The restriction of the larger palatal teeth to a pair on each of tlie three lateral palatal elements is exactly repeated in primi- tive rhachitomes and may well be primitive; in anthracosauroids the vomerine tusks are reduced. The jaw structure is presumably primitive. It must be emphasized that there is absolutely no positive evidence regarding the postcranial structure of any loxommid. In sum, apart from the orbits, the loxommids are extremely primi- tive amphil)ians. An ancestor of the loxommids with normal orbits. Please note that these images are extracted from scanned page images that may have been digitally enhanced for
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