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The Deseado Formation of Patagonia

Chapter 22: Proadianthus Ameghino
By Frederic Brewster Loomis
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Archaeology & AnthropologyScience - Biology

About This Book

A detailed report of an early Tertiary paleontological expedition that documents the geology and stratigraphy of a Patagonian formation, the expedition’s fieldwork and localities, and a complete systematic treatment of the vertebrate fossils recovered. It examines fauna composition, feeding adaptations, and habitat, compares the new material with earlier fragmentary finds, and provides careful descriptions and taxonomic revisions across many groups of mammals and a few birds, supplying measurements, illustrations, and arguments about relationships and the origins of the constituent taxa.

Fig. 22. Lower right pm. 3-m.
1—natural size,
after Ameghino.

The species is the only one known of the genus, and its features are those of the genus. The following measurements indicate the size, lower pm. 3 to m. 1, 25 mm.; height of the mandible under molar 1 is 12 mm.

Proadianthus Ameghino

Proadianthus Amegh., 1897, Bol. Inst. Geog. Argen., t. 18, p. 455.

This genus is known only by the last two premolars of the lower jaw, which are compressed and moderately high. The two crescents are markedly separated by a cleft from the external side of the tooth, opposite to which is a high denticle, made by the fusion of the two ends of the crescents where they come together.

Proadianthus excavatus Ameghino

Fig. 23. Lower right
pm. 3 and 4—
natural size,
after Ameghino.

P. excavatus Amegh., loc. cit. above.

The species is based on the two lower premolars described above. I reproduce the figure given by Ameghino. The measurements are: length of pm. 3 and 4, 10 mm.; height of mandible under pm. 4, 8 mm.