Adinotherium

Adinotherium [1] Temporal range: Mid-Late Miocene (Santacrucian-Huayquerian) ~17.5–6.8  Ma PreꞒ Ꞓ O S D C P T J K Pg N
A. ferum skull at the Museum für Naturkunde, Berlin
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	† Notoungulata
Family:	† Toxodontidae
Subfamily:	† Nesodontinae
Genus:	† Adinotherium Ameghino 1887
Type species
†Adinotherium ovinum
Species
A. corriguenenseAmeghino 1907 A. ferumAmeghino 1887 A. haplodontoidesAmeghino 1891 A. karaikense A. nitidumAmeghino 1887 A. ovinum(Owen 1846) A. robustumAmeghino 1891 A. splendidum
Synonyms
Phobereotherium Ameghino 1887 Noadinotherium Ameghino 1907

Adinotherium (meaning "not terrible beast") ^[2] is an extinct genus of toxodontid, large bodied hoofed ungulates which inhabited South America during the Middle to Late Miocene, from 17.5 to 6.8 Ma and existed for approximately 10.7 million years, Santacrucian to Huayquerian in the South American land mammal ages (SALMA). Fossils of Adinotherium have been found in the Santa Cruz and Ituzaingó Formations of Argentina and the Chucal and Río Frías Formations of Chile. ^[3]

Description

A. ovinum skull, right lateral and dorsal view

The approximately 1.5 metres (4.9 ft) long animal, with an estimated 120 kilograms (260 lb) body mass, looked like a smaller version of its rhinoceros-like relative Toxodon . ^[4] Its front legs were somewhat longer than those of its relatives, making its hip and shoulder height about equal. A small horn atop Adinotherium's skull may have played a role in the mating season. ^[5]

Palaeobiology

Life cycle

The fractal complexity of the enamel crests and the occlusal surface tooth area of A. ovinum teeth from the second premolar to the third molar both varied with age, making both of them useful tools for age estimation in this species and other toxodontids. Enamel crest complexity decreased as the animal matured due to wear, while the area of the tooth's occlusal surface was greater in adults than juveniles due to a combination of both wear and increase in overall size of the teeth of adults. ^[6]

Palaeoecology

Adinotherium had highly hypsodont dentition, which may have been an adaptation for grazing on grasses, habitats heavily featuring which were spreading throughout South America at the time Adinotherium was extant. ^[7]

1813 A. ovinum illustration.

References

1. range and species from Croft et al. (2004), p. 8; synonyms from McKenna and Bell (1997), p. 459.
2. Palmer (1904) p. 80.
3. Adinotherium at Fossilworks.org
4. "Adinotherium ferum - Бестиарий - Доисторические животные - Prehistoric Fauna". prehistoric-fauna.com. Archived from the original on 14 July 2012. Retrieved 26 January 2022.
5. Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 253. ISBN   1-84028-152-9.
6. Costamagna, Donato; Cassini, Guillermo; Cabral, Vanina; Schmidt, Gabriela I.; Ferrero, Brenda S. (16 July 2025). "Fractal Dimension of Dental Crowns: An Innovative Method for Age Estimation in Toxodonts". Journal of Experimental Zoology Part B: Molecular and Developmental Evolution . doi:10.1002/jez.b.23319. ISSN   1552-5007 . Retrieved 27 September 2025– via Wiley Online Library.
7. Cassini, Guillermo H.; Hernández Del Pino, Santiago; Muñoz, Nahuel A.; Acosta, M. V. Walter G.; Fernández, Mercedes; Bargo, M. Susana; Vizcaíno, Sergio F. (December 2015). "Teeth complexity, hypsodonty and body mass in Santacrucian (Early Miocene) notoungulates (Mammalia)". Earth and Environmental Science Transactions of the Royal Society of Edinburgh . 106 (4): 303–313. doi:10.1017/S1755691016000153. ISSN   1755-6910 . Retrieved 21 September 2025– via Cambridge Core.

Bibliography

• Croft, D.A., Flynn, J.J. and Wyss, A.R. 2004. Notoungulata and Litopterna of the Early Miocene Chucal Fauna, Northern Chile. Fieldiana Geology 50(1):1-52.
• McKenna, Malcolm C., and Bell, Susan K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp. ISBN   0-231-11013-8
• Palmer, T.S. 1904. Index Generum Mammalium: a List of the Genera and Families of Mammals. North American Fauna 23:1-984.

External links

• Media related to Adinotherium at Wikimedia Commons