Proschismotherium

Proschismotherium is an extinct genus of ground sloth of the family Megalonychidae, endemic to Argentina during the Early Miocene. It lived from 17.5 mya — 16.3 mya, existing (as a genus) for approximately 1.2 million years.^[1] The type, and only, species, P. oppositum, was named in 1902 by Florentino Ameghino based on a single specimen found in the Santacrucian-aged Colpodon Beds of Argentina.^[2] Ameghino in 1902 placed Proschismotherium in the Megatheriidae,^[2] alongside Hapaloides, which was its sister taxon.^[1][3][4][5]

Proschismotherium Temporal range: Early Miocene, 17.5–16.3 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓ Santacrucian
Holotype jaw
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Pilosa
Family:	†Megalonychidae
Genus:	†Proschismotherium Ameghino, 1902
Species:	†P. oppositum
Binomial name
†Proschismotherium oppositum Ameghino, 1902

The holotype jaw was compared to that of Schismotherium fractum and was found to be roughly the same size,^[2] indicating that Proschismotherium weighed roughly 45 kilograms (99 lb) and grew up to 1 metre (3.3 ft);^[6] the size estimate was loosely based on Hapalops and also Schismotherium.^[7]

References

1. R. L. Carroll. (1988). Vertebrate Paleontology and Evolution 1-698
2. F. Ameghino. (1902). Première contribution à la connaissance de la fauna mammalogique des couches à Colpodon [First contribution to the knowledge of the mammalian fauna of the Colpodon Beds]. Boletin de la Academia Nacional de Ciencias de Córdoba 17:71-141
3. McKenna & Bell (1997) Classification of Mammals Above the Species Level
4. "Hapaloides". Fossilworks. Retrieved 11 August 2022.^{[permanent dead link]}
5. "Proschismotherium". Fossilworks. Archived from the original on 26 September 2021. Retrieved 11 August 2022.
6. Toledo, Néstor (2012-09-07). "Mass estimation of Santacrucian sloths from the Early Miocene Santa Cruz Formation of Patagonia, Argentina". Acta Palaeontologica Polonica. doi:10.4202/app.2012.0009. hdl:11336/20506.
7. Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 207. ISBN 978-1-84028-152-1.