. Bulletin - United States National Museum. Science. NEW iSPECIBS OF EXTTNCT MIOCENE SIRENIA 73 At the posterior end of the mesorostral fossa of Cari- bosiren, Hesperosiren, Metaxytherium, Thattatosiren and Felsino- therium, the nasal bones are separated by the forward pro- jecting wedge of the frontals above the nzisal chamber. As a possible indication of some variability, it should be noted that the nasals are almost in contact medially on one skull of Felsinotherium serresii (Gervais, 1859, pi. 6, fig. 3). This relationship of the nasals and frontals was employed by Kretzoi (1941) to suppor
. Bulletin - United States National Museum. Science. NEW iSPECIBS OF EXTTNCT MIOCENE SIRENIA 73 At the posterior end of the mesorostral fossa of Cari- bosiren, Hesperosiren, Metaxytherium, Thattatosiren and Felsino- therium, the nasal bones are separated by the forward pro- jecting wedge of the frontals above the nzisal chamber. As a possible indication of some variability, it should be noted that the nasals are almost in contact medially on one skull of Felsinotherium serresii (Gervais, 1859, pi. 6, fig. 3). This relationship of the nasals and frontals was employed by Kretzoi (1941) to support his conception of phyletic rela- tionship of genera. Kaltenmark asserts that on the cranium firom Chaze-Henry, a photograph of which was published by Deperet and Roman (1920, pi. 7, fig. 3), the nasals meet on the midline, but Reinhart (1959, p. 61) questions this interpretation and believes that the right nasal is labeled as the premaxillary (Kaltenmark, 1942, vol. 6, p. 107, fig. 2). As with all known sirenians, the slender premaxillaries are well developed and contribute the external borders of the mesorostral fossa. The left premaxillary is complete, but the right premaxillary has at least 20 mm. of the extrem- ity broken ofT. At the anterior end of the mesorostral fossa, the premaxUlaries are bent strongly downward and are closely approximated, forming a symphysis of about 84 mm. in length. No vestige of an alveolus even for a small incisor tusk is present in the extremity of the left premaxillary, but the internal surfaces of both premaxillaries are incom- plete. This apparent absence of a tusk may indicate the female sex. Although the extremity of the rostrum pro- jected obliquely downward and forward, the extent of its prolongation resembles Metaxytherium cuvierii (Cottreau, 1928, pi. 1, fig. 2c) more closely than Felsinotherium serresii (Deperet and Roman, 1920, pi. 2, fig. la). In front of the supraorbital process of the frontal the external face of the premaxillary
Size: 2063px × 1212px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorun, bookcentury1800, bookdecade1870, booksubjectscience
