. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Skull of American Tritylodontidae • Sues 231. I CM Figure 9. Maxillary sinuses and infraorbital canal system in the snout of Kayentatherium wellesi, MCZ 8812, in dorsal view. bone whereas the dorsal edge turns me- dially. The anterior root of the zygoma is trihedral in transverse section. Its ventral aspect bears a distinct ridge (, Fig. 6), probably for the insertion of the pars su- perficialis of M. masseter and homologous to the suborbital process in the tritylodon- toids Exaeretodon (Bonaparte, 1962: fig. 4) a
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Skull of American Tritylodontidae • Sues 231. I CM Figure 9. Maxillary sinuses and infraorbital canal system in the snout of Kayentatherium wellesi, MCZ 8812, in dorsal view. bone whereas the dorsal edge turns me- dially. The anterior root of the zygoma is trihedral in transverse section. Its ventral aspect bears a distinct ridge (, Fig. 6), probably for the insertion of the pars su- perficialis of M. masseter and homologous to the suborbital process in the tritylodon- toids Exaeretodon (Bonaparte, 1962: fig. 4) and Trirachodon (Crompton, 1963: fig. 10). Squamosal (Sq). The cranial and zygo- matic portions of the squamosal (Fig. 2) are separated by a depression that extends from the V-shaped notch in the postero- lateral corner of the zygomatic arch to the region above the prominent crista paroti- ca. The dorsal edge of the cranial process, corresponding to the mammalian crista lambdoidea, extends obliquely postero- ventrally to the V-shaped notch and over- hangs the occipital plate. The cranial part forms the dorsolateral margin of the post- temporal fenestra anteriorly. Cranial and zygomatic process join along a broad con- tact (Fig. 2). The zygomatic portion is quite deep (Fig. 1). The rounded posterodorsal margin of the zygomatic process overhangs a distinct but rather narrow sulcus that extends along the posterolateral aspect of the squamosal ( Figs. 1, 22). This groove expands posteroventrally, resulting in a hollow on the ventral aspect of the posterior zygo- matic root. This depression is delimited by the posterolateral portion of the squamo- sal behind, by the crista parotica (anterior paroccipital process) anteromedially, and a low ridge, which separates it from a large pocket for the proximal end of the qua- dratojugal, anteriorly. One (MCZ 8842) or two (MCZ 8812, right side) foramina are developed near the posterior margin of the hollow ( Fig. 3). The squamosal
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Keywords: ., bookauthorharvarduniversity, bookcentury1900, booksubjectzoology
