Trimerostephanos Ameghino
Trimerostephanos Amegh., 1895, Bol. Inst. Geog. Argen., t. 15, p. 646.
Trimerostephanos Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 483.
This genus is based on upper and lower teeth, and distinguished by the premolars and molars having a weak style on the anterior corner, and by the anterior lobe being considerably larger than the posterior. Four species have been described.
T. scabrus Amegh., loc. cit. for genus.
This is the type species, originally based on the third lower molar, to which was later added, upper premolar 4 and the molars, and lower molar 2. The following measurements are given:
| Measurements | |||
|---|---|---|---|
| Upper premolar 4, | length | 15 mm., | width 21 mm. |
| Upper molar 2, | length | 31 mm. | |
| Upper molar 3, | length | 35 mm. | |
| Lower molar 2, | length | 20 mm. | |
| Lower molar 3, | length | 29 mm. | |
Fig. 87. T. scabrus—natural size;
A, upper premolar 4;
B, lower molars 1 and 2.
T. scalaris Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 483, is based on lower pm. 2 to m. 2, a somewhat smaller species than the preceding, the series as given measuring 53 mm.
Fig. 88. T. scalaris, premolar 2 to molar 2—
natural size.
T. angustus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 484.
This species is described without a figure, as smaller than T. scalaris, pm. 2 to m. 2 being 59 mm. The mandible is also slenderer.
T. biconus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18. p. 484.
This species is based on two lower premolars, said to be the same size as T. angustus, but with the pillar larger.