''Cambaytherium'' is an extinct genus of

placental mammal Placental mammals ( infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguish ...

s in the family

Cambaytheriidae Cambaytheriidae is a family of primitive four or five-toed ungulates native to the Indian subcontinent. They lived during the Early Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years a ...

whose fossils were found in an open pit coal mine located in

Gujarat Gujarat () is a States of India, state along the Western India, western coast of India. Its coastline of about is the longest in the country, most of which lies on the Kathiawar peninsula. Gujarat is the List of states and union territories ...

, India. The mine was a treasure trove full of teeth and bones, over 200 of which were identified as belonging to ''Cambaytherium thewissi.'' The fossils were dated to the Early

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

, 54.5 million years ago, making them slightly younger than the oldest known fossils belonging to the order

Perissodactyla Perissodactyla (, ), or odd-toed ungulates, is an order of ungulates. The order includes about 17 living species divided into three families: Equidae (horses, asses, and zebras), Rhinocerotidae (rhinoceroses), and Tapiridae (tapirs). They t ...

Description

''Cambaytherium'' was a genus of herbivorous four-legged

quadrupeds Quadrupedalism is a form of locomotion in which animals have four legs that are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four legs is said to be a quadruped (fr ...

. The best-known species, ''C. thewissi'', has been estimated to have weighed around , while the smaller ''C. gracilis'' weighed around . The remains of the third species are too fragmentary to allow a consistent estimate of its size, although it appears to have been significantly larger than the others, perhaps weighing or more. The shape and wear patterns of the teeth suggest that it was herbivorous, with a considerable amount of tough vegetation in its diet, such as nuts and abrasive leaves and stems. Many of ''Cambaytherium's'' features, such as the teeth and the number of sacral vertebrae, are intermediate between Perissodactyla and earlier mammals and may be indicative of what the common ancestor of all of Perissodactyla looked like. The limbs have skeletal features suggesting that the animal was capable of running, but would not have been as fast as early perissodactyls. The fore-feet had at least four toes, and the hind-feet had five, one of which was vestigial, whereas even the earliest perissodactyls known had no more than four toes on each foot. The toes were short and stout, with most of the weight placed on digit three, which was slightly enlarged, as seen in living

tapir Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a Suidae, pig, with a short, prehensile nose trunk (proboscis). Tapirs inhabit jungle and forest regions of South America, South and Centr ...

s. The animal was likely at least

digitigrade In terrestrial vertebrates, digitigrade ( ) locomotion is walking or running on the toes (from the Latin ''digitus'', 'finger', and ''gradior'', 'walk'). A digitigrade animal is one that stands or walks with its toes (phalanges) on the ground, and ...

, and perhaps subunguligrade.

Taxonomy

''Cambaytherium'' is considered to be close to the ancestry of

, the odd-toed

ungulate Ungulates ( ) are members of the diverse clade Euungulata ("true ungulates"), which primarily consists of large mammals with Hoof, hooves. Once part of the clade "Ungulata" along with the clade Paenungulata, "Ungulata" has since been determined ...

s. It retains features lost among the perissodactyls, a group which includes

rhinoceroses A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...

, and

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...

s. An analysis published in 2019 placed the Cambaytheriidae as most closely related to the anthracobunids in the order Anthracobunia, a sister group to the true perissodactyls. In addition to ''Cambaytherium'' itself, the family includes ''

Nakusia ''Nakusia'' is an extinct genus of ungulate from the early Eocene epoch, described in 1999 in the Ghazij formation of Baluchistan, Pakistan. It was classified as an anthracobunid in 1999Ginsburg L.; Durrani, K. H.; Kassi, A. M.; Welcomme J.-L., D ...

'' and '' Perissobune'', which are known from more fragmentary remains. The presence of a sister group of perissodactyls in western India near or before the time of its collision with Asia, suggests that Perissodactyla may have originated on the

Indian Plate The Indian plate (or India plate) is or was a minor tectonic plate straddling the equator in the Eastern Hemisphere. Originally a part of the ancient continent of Gondwana, the Indian plate broke away from the other fragments of Gondwana an ...

during its final drift toward Asia.

References

{{Taxonbar, from=Q18575566 Eocene mammals of Asia Panperissodactyla Fossils of India Eocene life Fossil taxa described in 2005