[1] The dental formula was identical to Astrapotherium, but there was some differences in the characteristics of the teeth : the incisors were proportionally narrower and longer, and the lower canines were inserted into the mandible more vertically.

The horizontal branch of the mandible was narrower and higher, without the lateral swelling formed by the base of the canine, typical of the two previous genera.

[2][1] In general, the head of Astrapothericulus was shorter and higher than that of Astrapotherium, and vaguely resembled that of its more ancient relative, Astraponotus.

Astrapothericulus was a member of Astrapotheria, a clade of South American ungulates, vaguely evocating the shape of tapirs or hippopotamus, but not closely related to either of them.

Astrapothericulus is considered a specialized member of the family Astrapotheriidae, comprising the more derived forms of the group, and may have been ancestral to the genus Astrapotherium.