. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. f. cb CM Figure 17. Hyoid elements of Kayentatherium wellesi, MCZ 8812. A) element from the (?) second branchial arch. B) basihyal element. Broken line indicates inferred midline. and Russell, 1974: fig. 13). Rod-like hyoid elements are not uncommon in the gale- saurids Galesaitrns and Thrinaxodon (Hopson, personal communication). Iden- tification of the slightly distorted elements in MCZ 8812 is difficult owing to the lack of extant analogues. They appear to be most similar in shape to the hyoid ele- ments in m
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. f. cb CM Figure 17. Hyoid elements of Kayentatherium wellesi, MCZ 8812. A) element from the (?) second branchial arch. B) basihyal element. Broken line indicates inferred midline. and Russell, 1974: fig. 13). Rod-like hyoid elements are not uncommon in the gale- saurids Galesaitrns and Thrinaxodon (Hopson, personal communication). Iden- tification of the slightly distorted elements in MCZ 8812 is difficult owing to the lack of extant analogues. They appear to be most similar in shape to the hyoid ele- ments in modern turtles (Gaupp, 1905: figs. 38-40). The first type of element, represented by bones from opposite sides, may reason- ably be interpreted as a copula hyoidei. Fusion of the copulae in mammals pro- duces the basihyal. The element (Fig. 17B) bears a prominent posterolateral process with a terminal facet ( 1) and, pos- teromedially, a distinctly off-set second facet ( 2). If it is indeed a copula, these cup-shaped facets presumably were for articulation with elements of the branchi- al arches 1 and 2, respectively, based on the condition in living amniotes (Gaupp, 1905). The dorsal surface of the median plate is thin and transversely concave. The bone forms a short anterolateral process, possibly for contact with a ceratohyal. A second type of hyoidal element is an elongate, curved rod. It bears a cup-shaped facet at one end and is flattened at the other. It almost certainly represents a first ceratobranchial. There is also a shorter, straight bony rod with obliquely inclined facets at either end. A fourth type of hyoidal element is rep- resented by a thin rhomboidal bone. It bears two facets at one end and a smaller terminal one at the other end (Fig. 17A). One of its surfaces is distinctly concave transversely. I have not found any com- parable element in another tetrapod. The bone in question may represent a segment. Please note that these images are extracted from
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