Gaudry outlines a short, heavy, rugose calcaneum which has but a short tuber; a flat navicular; a small cuboid; and an astragulus with only a slight convexity of the trochlea, and with the navicular facet directed obliquely forward, making an angle of 127° with the plane of the trochlea, which, as he says, would indicate a semidigitigrade position of the pes.

The following species are distinguished by Ameghino as coming from the Deseado beds: P. holmbergi, P. troussarti, P. lemoinei, P. ephebicum, P. martiale, P. superabile, P. insuperabile. The various species are known from the same parts in but a few cases. Their relative sizes are indicated from the following compilation of the measurements given by Ameghino:

UpperLower Lower Lower
pm. 4m. 1m. 2m. 3pm. 4m. 1m. 2m. 3inc. 1
-m. 3		pm. 4
-m. 3
P. holmbergi 56-56
P. troussarti 24-40-57-60- 180
P. lemoinei 34-34
P. ephebicum 31-1642-21
P. martiale30-42 82-83 550
P. superabile30-43
P. insuperabile37-48 100-80 34-23
P. (Liarthrus) copei29-46
P. (Traspoatherium)
 convexidens
Amherst specimen 28-26 43-28 58-32 70-36 455200

P. holmbergi is the type species, and of considerable size, and to it I have assigned my material. In such a large animal, variations in size are to be expected. P. troussarti, as described, is a tenth smaller than P. holmbergi, the only structural character differentiating it being the isolation of the pillar in the lower molars, which is a character due to youth; so I have considered it a synonym of P. holmbergi. P. ephebicum is a much smaller and distinct species, with which I should associate the single upper molar to which the name P. lemoinei has been given. P. martiale is a large species, distinguished by the strong development of the cingulum on the internal side of the upper molars, and on the inner side of the lower molars; and by lower premolar 3 being well developed with two roots. P. superabile is of the same size as the foregoing, but has the cingulum on upper premolar 4 (the only tooth known) less developed. I should therefore consider it a synonym of P. martiale. P. insuperabile is the largest species, and is distinguished by the excessive development of the cingulum. Liarthrus is founded on an upper pm. 4 with a part of pm. 3, but, as far as I can see, does not differ in character or size from P. holmbergi. Traspoatherium is based on upper premolars which are distinguished by the roots being fused from side to side. I think it is an age character and for the present would consider it the same as P. holmbergi, probably the tooth being pm. 3.

Parastrapotherium holmbergi Ameghino

To this, the type species, I have assigned all the material we found on the Chico del Chubut, west of Puerto Visser, as enumerated under the generic description. The lower jaws belonged to an old individual. The humerus and scapulae were found associated, the femur isolated.

Of the upper dentition, the only available measurements are those of Ameghino for the first molar, and the canine.

Upper dentition,canine,length 256 mm.
Upper dentition,molar 1,length 57 mm.,width57 mm.