Arniso

Extinct Arsinoitherium is an extinct genus of mammals related to elephants, sirenians, and hyraxes. Arsinoitheres were superficially rhinoceros-like herbivores that lived during the Late Eocene and the Early Oligocene, found in North Africa in areas of tropical rainforest and at the margins of mangrove swamps. Arsinoitherium giganteum, described in 2004, lived in Ethiopia about 27 million years ago. It measured 2.5 tons, only slightly smaller than the modern white rhino. Due to the similar features and sizes, Arsinoitherium is commonly thought to be an extinct rhinoceros species, but it is not closely related to rhinos; instead, their closest extant relatives are elephants and manatees. They were massive, slow-moving animals with forelimbs adapted for pulling strongly backward rather than swinging forward, a feature typical of animals that punt themselves through shallow water or walk on soft, sticky ground. Fossils are found in sediments deposited in coastal swamps and warm, humid, heavily-vegetated lowland forests across what is now Africa and Arabia.

Fun Fact: Arsinoitherium had a full complement of 44 teeth, which is the primitive state of placental mammalian dentition. However, the genus had a unique and highly specialized way of chewing, shifting the jaw joint to produce constant pressure along its continuous row of teeth; it has been reconstructed as a highly selective browser.