Dentition of the palate in Cynognathus / by H.G. Seeley.

  • Harry Govier Seeley
Date:
1908
Catalogue details

Licence: In copyright

Credit: Dentition of the palate in Cynognathus / by H.G. Seeley. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    from the flat maxillary bones of the palate by vertical sutures. It appears to afford evidence that the premaxillary bones enter into the fi-ont of the hard palate, and are free from palatal teeth. The skull of C. platyceps (op. cit., flg. 30, p. 139) adds nothing to our knowledge of the anterior part of the palate. Only the posterior part of the median suture is exposed, dividing the concave channel of the hard palate. There are no indications of palatal teeth; but this is no evidence that such teeth did not exist, for such structures are not likely to be found unless there is reason to look for them, and they would be easily removed by the chisel without detection. I am indebted to the generous co-operation and enthusiasm of Dr. D. R. Kannemeyer for a fragment of a right maxillary hone from Wonderboom, which has almost exactly the size, form, and aspect of the corresponding region of the jaw of Cynognathus crateronotus. I have removed the matrix in the Geological Laboratory of King’s College, London ; and the bone (Plate XXIV) shows both externally (Fig. 2) and on the palate (Fig. 1) characteristics seen in no other figured example, but confirmed by other evidence in my hands. The maxillary bone is separated by sutures of a squamose type from the nasal bones above and the premaxillaiy bones in front. The vertical premaxillary sutural surface is 1-A-inch deep, flattened, i^inch wide, and is limited posteriorly by the large cavity for the mandibular canine, which is excavated in the skull for 11 inch, and made partly by the maxillary, partly by the premaxillary bone. Above the premaxillary suture in front is a small, smooth, rounded notch, which appears to be the hinder angle of the anterior narine, between the premaxillary and nasal hones. i The maxillary bone is limited at the upper border by the strong, j vertical, squamous suture with the nasal bone. This sutural surface seen on the inner aspect of the specimen is half an inch deep in front, with the depth increasing as it extends backward. The curved contour- line of junction is indicated by the maxillary bone being 2 inches deep in front and about 3^ inches in depth at the vertical fracture behind. Externally (PI. XXIV, Fig. 2) the anterior and larger part of the bone is convex, both from front to back and from above downward. This convexity is only modified by a slight, shallow, wide, longitudinal I concavity, extending backward from below the nasal suture towards I the direction of the prefrontal bone. But interiorly the bone contracts I in width behind the canine tooth, defining the bulbous snout, so that I the lower and hinder external surface is concave. I The alveolar border behind the canine tooth, seen from the side, I is straight or concave in length, while in front it recedes laterally j upward towards the premaxillary suture, being convex above the .< maxillary canine and concave in front of the mandibular canine. The posterior fracture passes through a conspicuous, circular, pre- orbital pit in the middle depth of the bone, situated above the fourth or fifth molar tooth. It corresponds in position exactly with ’ the sub-orbital or middle foramen seen in the maxillaiy bone of the type-specimen of Cynognathus crateronotus (op. cit., p. 72, fig. 5). Now that the matrix is removed (PL XXIV, Fig. 2), the fossil shows externally at -ft- inch above the alveolar border a linear succession J
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