On Neusticosaurus pusillus (Fraas), an amphibious reptile having affinities with the terrestrial Nothosauria and with the marine Plesiosauria / by H.G. Seeley.

  • Harry Govier Seeley
Date:
1882
Catalogue details

Licence: Public Domain Mark

Credit: On Neusticosaurus pusillus (Fraas), an amphibious reptile having affinities with the terrestrial Nothosauria and with the marine Plesiosauria / 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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    The superior aspect of the skull is remarkable for the large size of the temporal fosste, orbits, and nostrils, the latter having a very forward position. The palate, on the other hand, is remarkable for its extensive ossification (pi. 17); and, as Professor Owen has observed, the ptery- goids form a broad, expanded, unbroken, flat, imperforate expanse of bone, united by a median suture, and underlapping the sphenoid. The only large perforations on the palate are those beneath the anterior nares and those external to the pterygoids. If we now turn to the skull of the little animal figured by Dr. Fraas, the exposed surface, which he identifies as the palate, sliows exactly that arrangement of vacuities which von Meyer figures (pi. 18) as distinctive of the superior surface of the head. There is, however, no reason to question the accuracy of Dr. Fraas’s topographical iden- tification, since the exposed suii'ace is concave, as only the palate could be, shows alveoli, and has no trace of a parietal foramen, though the bones are too perfectly ossified and blended to permit of their individual definition in detail. But such a palate as the specimen exhibits makes reference of the species to Simosaunis impossible. Equally impossible is it to refer the type to any other genus hitherto instituted. The difference, indeed, is of a subordinal rather than a generic quality; for since all the allied Triassic genera hitherto known have the palate closed, in harmony with the Plesio- saurian plan (and it maybe in relation to aquatic conditions of life), here we may have an indication of the kind of skull from which the Plesiosaurian type was originally derived. It has therefore appeared desirable to offer to the Society some further details of the anatomical structui'e of this animal, which I was enabled to study by the courtesy of Mr. Iloser, before the skeletons became finally deposited in the national collection at South Kensington. The larger specimen (PI. XIII. fig. 1) lies on the back in a slight sigmoid curve, and exposes the abdominal aspect of the skeleton, all the bones of which are in situ except some elements of the pectoral girdle, the abdominal ribs, and parts of the limbs, which are lost. The extreme length of this skeleton as it lies hardly exceeds 270 mm., though Mr. Iloser measuring the separate regions makes it 285 mm. The second and somewhat smaller individual (PI. XIII. fig. 3) ex- poses the dorsal aspect of the bones, but has lost the head and anterior part of the neck, the extremity of the tail, some of the smaller limb- bones, and the right hind limb. But though the conformation of the bones is slightly different in this animal, the differences are no more than may perhaps be attributed to sex or age. The Head. The head (PL XIII. fig. 2) is nearly 3 cm. long, and is 14 mm. wide in the posterior or quadrate region, where it is widest: the sides are at first nearly parallel, and then taper forward in a lanceolate shape. It lies flat, and has been carefully excavated so as to display the several regions of the palate. In front, resting close upon the maxillary bones, there appears to be a small fragment of the lower
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