Eurygeniops Ameghino

Eurygenium Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 655.
Eurygeniops Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 464.

The name first given this genus was found to be preoccupied, and therefore changed. It is a clear cut genus, differing from the others in the family in the expansion of the front of the muzzle, and by the heavy broad character of the skull.

Eurygeniops latirostris Ameghino

E. latirostris Amegh., loc. cited above.

This is the type species and is based on a muzzle which has never been figured, but which I figure, the drawing being made from a photograph taken by Professor Scott and kindly furnished me. The characters of the species are those of the genus, with the following measurements for specific determination, quoted from Ameghino:

Palate, length130 mm.
Palate, width between incisors 341 mm.
Palate, width between premolars 233 mm.
Palate, width between molars 356 mm.
Upper dentition, length from pm. R. to m. 3  82 mm.
Upper premolar 4, length11 mm.
Upper premolar 4, width19 mm.

Eurygeniops normalis Ameghino

E. normalis Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 466.

This second species is described as being much smaller than the preceding, the length from pm. 4 to molar 3 being 65 mm.

CHAPTER VII
Leontinidae

This family was established to include a group of large, heavily built ungulates, not unlike rhinoceroses in form, which have rooted teeth, the molars being similar to those of Rhinchippidae, i. e., composed of a wall and an anterior and posterior lobes, but with the cristae either lacking or little developed; and with the second upper, and the third lower incisors developed into tush-like caniniform teeth. Two genera are especially abundant, Leontinia of the Deseado beds, and Colpodon of the Colpodon beds, the former with the formula

the latter with

In many ways, the family suggests Nesodontidae, and undoubtedly belongs to that series, if not directly ancestral. The lower molars are distinctly of the same type as in all the other toxodonts, but show a tendency to become hyposodont.

The following genera have been assigned by Ameghino to the family. Some of them are based on very scant material and I have ventured to suggest in each case what disposition I have felt to be the proper one.

Leontinia, the type genus, is described in detail on [pages 109-115].

Scaphops is based on a mandibular symphysis, which is wider than usual for Leontinia, and on a second upper incisor which is compressed. The species in the genus Leontinia show a marked degree of variability, and I can see in this only individual variability, so that I place Scaphops under Leontinia and S. grypus, as a synonym of L. gaudryi.

Steniogenium is based on a mandibular symphysis with roots only of the teeth. The incisors are proclivous and inc. 3 small. I consider this also as Leontinia, and the species S. sclerops as a synonym of L. oxyrhynca, which I think is the female of L. gaudryi.

Ancylocoelus is a valid genus, differentiated by its dental formula

the loss of the upper canine and the lower canine and first premolar distinguishing it from either Leontinia or Colpodon.

Rodiotherium is based on a mandibular symphysis which would indicate an animal with the same formula as the foregoing genus, differing only in that lower incisor 3 is large. This, to my mind, does not make a generic character, and at most the species, R. armatum, can only be considered an independent species belonging to the genus Ancylocoelus.

Loxocoelus is a very questionable genus, based simply on an upper molar, which “is similar to that of Homalodontotherium, but more squared.” I feel that in regard to this genus it should stand as unknown until more material is found.

In our collection, over twenty skulls and jaws belonging to this family turned up, but all clearly belong to two types, the typical Leontinia gaudryi, and some others in which the caniniform teeth are not so well developed, which are either L. oxyrhynca or, as I believe, the females of L. gaudryi. It is this uniformity of the material which leads me to doubt the validity of the considerable number of genera which Ameghino has established, for I found on sectioning the teeth that between the little worn crown and the much worn one there was a marked difference in the appearance of the infoldings and in the development of the pits.