. Bulletin - United States National Museum. Science. 18 UNITED STATES NATIONAL MUSEUM BULLETIN 24 7 Atlas: Except for a portion of the neural spine the atlas (USNM 11976) is well preserved. It is relatively large as compared to those of other Calvert cetotheres. This massive atlas (fig. 9a) measures 176 mm. between the outer margins of the anterior facets for articulation with the occipital condyles of the skull, each facet being deeply concave, broadest ventrally, and inclined obliquely outward; these two facets are separated ventrally by a rather narrow interval (7 mm.). The neural arch (pi.
. Bulletin - United States National Museum. Science. 18 UNITED STATES NATIONAL MUSEUM BULLETIN 24 7 Atlas: Except for a portion of the neural spine the atlas (USNM 11976) is well preserved. It is relatively large as compared to those of other Calvert cetotheres. This massive atlas (fig. 9a) measures 176 mm. between the outer margins of the anterior facets for articulation with the occipital condyles of the skull, each facet being deeply concave, broadest ventrally, and inclined obliquely outward; these two facets are separated ventrally by a rather narrow interval (7 mm.). The neural arch (pi. 4, fig. 6) is rather broad anteroposteriorly. On each side the arch (neura- pophysis) is pierced ventrally near the middle of its length (fig. 9c) by a large vertebra-arterial canal, which opens into a broad ventrally directed groove. The neural spine, judg- ing from the broken basal edges, was rather robust. The transverse process on each side of the atlas is massive and directed more outward than backward, attenuated distally> and terminating in a blunt extremity. The neural canal (pi. 4, fig. 1) is large, but partially obstructed ventially by a pair of osseous excrescences. The two opposite posterior facets (fig. 9b) for articulation with the axis are very broad, but their external margins are not sharply set off from the posterior face of the centrum. The hyapophysial process below the neural canal is low, bluntly pointed and irregularly pitted or roughened. Between the opposite posterior facets and below the neural canal is a broad upwardly sloping surface for articulation with the odontoid process of the axis. All of the Calvert Miocene cetothere atlases available for study have a reduced and unobtrusive hyapophysial process on the posteroventral border of the centrum and but one. a. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfe
Size: 2117px × 1180px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorun, bookcentury1800, bookdecade1870, booksubjectscience
