The name Arsinoitherium (pronounced AR-sin-o-i-THEER-ium) is a combination of a name of a pharoh of Egypt and “therium,” which means "Arsino’s beast." This mammal stood 5’9” (1.75 m) at the shoulder and was 9.8’ (3 m) in length. It was rhinoceros-size (but not a true rhino) and heavily built with stout limbs. Its front legs were really good for pulling backwards (= graviportal limbs) when standing in muds, but this animal was not good at running.
A mature Arsinoitherium zitteli Beadnell, 1902.
Arsinoitherium belonged to the odd-toed (5 toed) ungulates order Embrliothopoda = herbivorous early rooters and browsers. Embrithopods were related to elephants, sirenians, hyraxes, and the extinct desmostylians (see one of my previous posts on desmostylians).
The most distinctive feature of Arsinoitherium is its twin hollow horns, side by side, of massive size and arising from the roof of the skull. Both males and females had these horns. In addition, there were two small knobs high on the skull and behind the large pair of horns. These knobs were probably covered with skin and similar to the ossicones of giraffes.
Arsinoitheres had complete dentition (all 44 teeth present), with no diastema (gap) separating the anterior cropping teeth and the posterior masticatory teeth. Their cheek teeth (premolars and molars) are usually highly crowned, suggesting an ability to eat very tough vegetation.
Arsinoitheres lived during the late Eocene and early Oligocene in northern Africa (Egypt, Tunisia, Lybia, Ethiopia, Angola, Kenya, as well as Saudi Arabia, Oman, Turkey, Romania, and possibly Mongolia). They lived in tropical rainforests and along the edges of mangrove swamps. It is possible that arsinoitheres could have been able to swim rather well.
Sources of information:
Benton, M.J. 1991. The rise of the mammals. Crescent Books, New York, 144 pp.
Savage, R.J.G. and M.R. Long. 1986. Mammal evolution, an illustrated guide. British Museum of Natural History. 259 pp.
en.wikipedia.org (2022)
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