Identifier: deseadoformation00loom (find matches)
Title: The Deseado formation of Patagonia
Year: 1914 (1910s)
Authors: Loomis, Frederic Brewster, b. 1873 Amherst College
Subjects: Paleontology
Publisher: (Concord, N.H., The Rumford press)
Contributing Library: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library
Digitizing Sponsor: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library

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ter of the shaft 10 mm. The calcaneum is of moderate length, and very stout,resembling that of Adinotherium, except that it is longer. Calcaneum, length 64 mm. Calcaneum, width 28 mm. Of the hind foot there is preserved only the distal por-tions of two metatarsals, which are about the same sizeand character as those of the front foot, and a phalanx ofthe first row, also similar to the same one of the front foot. Figure 65 gives a restoration of the animal based on thebones described in the foregoing pages. The animal in allfeatures turns out a typical toxodont, adapted, by thecropping teeth, and the broad-faced premolars and molars,for a grazing animal, but its advancement in adaptingitself to feeding on grass has not proceeded very far, as isindicated by the shortness of the molars. The legs arelonger than in the other families of the toxodonts whichwould signify that it had developed some speed, but thefeet have progressed toward the modification of the hoofs RHYNCHIPPUS EQUINUS 103
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104 THE. DESEADO FORMATION OF PATAGONIA into claws, indicating a foot more like that of a dog, inwhich the weight is not carried on the ungual phalanges, butrather on the ball of the foot, or bases of the metapodials.I should not feel that this group was the ancestral one tolater groups of toxodonts, but it seems rather to representa line which terminates in the Deseado or very little later,not having run up into the Santa Cruz. The line of an-cestry for the toxodonts is rather through Leontinidae. Rhynchippus pumulis Ameghino R. pumulis Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 464. We found no speci-mens of this species, butAmeghino has describeda complete skull, a fig-ure of which is repro-duced here. It indicatesa smaller lighter builtanimal, differing from R.equmus not only in smallsize, but also in having arelatively longer and nar-rower head. The indi-vidual is a rather oldone, so that the pits ininc. I and 2 have divSap-peared, as is also thecase with the cingulumon the

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