OCR Text |
Show 1870.] DR. J. MURIE ON SAIGA TARTARICA. 469 ridges bound the groove; and in front and behind a pair of large prominences or tubercles are developed. In the true Ovine, Cervine, and Caprine Antelopes these parts present varied grades of development. The genus Oreotragus alone has a tendency to flattening, and Nemorheedus evinces relative broadening of the bone. In the Sheep and the Goats the basilar bone assumes a totally different form ; it is as broad as it is long, widest in front, flat or slightly concave, the posterior tubercles small, and the anterior ones extended onwards rather than highly raised. The same bone in the Saiga, as previously described, essentially resembles these. The Rocky-Mountain Sheep, Ovis montana, offers analogy to the Saiga in having an outer mastoidal depression at the root of the paramastoid. This, partially, is the condition met with in some Oxen ; but in Goats there is a great mastoidal eminence: in the Antelopes and Deer it is also convex, but less elevated. The Saiga, in the backward extension of its horizontal palatines, width of postero-nares, and long, vertically high spheno-pterygoid plates, is interesting, as this is not witnessed to the same extent in living Ruminantia. The short and higher rounding of its skull is also met with in the Chamois, AEpyceros and Damalis. There is something peculiar in the dentition; absence of supplemental lobes separate it from the Cervine Antelopes and all Deer; but the teeth might belong to the Gazelle group, though as closely Ovine in character. In its subequal incisors, however, it is unlike the antilopine section that have the median ones extra large and expanded at the summit. Altogether, the cranial anatomy of Saiga tartarica has for its groundwork a basioccipital derivatively modelled from Sheep-structure ; to this are added mastoid, auditory, and tympanic elements modified between those of Antilope and Ovis. The rest of the broad basis cranii, palatal region, and the foramina are built typical of Sheep, but correlated with change of cranial form. The upward set of the basisphenoid and the postcranial contour incline to those of Goats, though the glenoid articulation and posterior border of the maxilla are truly Antilopine. The horns and interfrontals pertain to the latter group in shape; but the diaphanous corneous texture, as the older naturalists did not fail to observe, are restrictedly Bovine. Forasmuch as stout abbreviated nasals and praemaxillae indicate family connexion, the Elk and Oxen show a tendency to agreement with Saiga; but the facial region, notwithstanding, by no means approximates close, and rather, in the latter, denotes ancient Sivathere parentage. In fine, the extraordinary- looking soft structures of the nares and the coordinate adaptation of these with deficiency of osseous framework, as in the Tapirs and other Pachyderms, point to physiological function of the nasal region of a kind different in the extreme from the ordinary living Ruminant type. That in by-goue ages kindred proboscidian Ruminants were more numerous, and varied concomitantly in cranial characteristics, the fossil remains attest. |