These figures would indicate a form about 15% larger than R. pumulis, and 35% smaller than R. equinus.

Morphippus Ameghino

Morphippus, Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 459.

This genus is very similar to Rhynchippus, with the same dental formula, the same grooves in the upper incisors, and the same pattern of the premolars and molars. It differs, however, in the lower incisors having no cingulum at their base, in the upper molars having a shallower basin, and in bays 3 and 4 being absent from the lower molars. These features simply indicate a slightly less advanced specialization, less hypsodont teeth. I do not think that the bays are any of them lacking in unworn teeth, but in a less hypsodont tooth, with the pits extending a less distance into the crown, all indication of the bays disappears early.

M. imbricatus is described as the type species, and four others have been described, all equal in size to M. imbricatus, and distinguished by the teeth being slightly more compressed, by the external cleft of the lower molars being deeper, or by variations in the pits. All these features I consider to be either age characters or individual variations, so that all five species of this genus are lumped under M. imbricatus.

Morphippus imbricatus Ameghino

M. imbricatus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 459.
M. hypsolodus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 461.
M. complicatus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 461.
M. fraternus Amegh., 1901, Bol. Acad. Nac. Cienc. Cordoba, t. 16, p. 374.
M. quadrilobus Amegh., 1901, Bol. Acad. Nac. Cienc. Cordoba, t. 16, p. 374.

The general characters of this species are given under the generic description and I will here give only Ameghino’s measurements which go with the figure:

Skull, length over210 mm.
Skull, length of the palate120 mm.
Upper dentition, length the inc. 1 to m. 3  120 mm.
Diameter of the palate opposite inc. 337 mm.
Diameter of the palate opposite m. 375 mm.
Height of mandible under m. 133 mm.