Temporal range: Oligocene
Buzdartherium is an extinct genus of hornless rhinoceros from Oligocene Pakistan. The monotypic species is Buzdartherium gulkirao. Its remains have been found only in the Sulaiman Basin, which preserves rocks dating from as early as the Cretaceous. It is classified as a member of the hyracodont subfamily Indricotheriinae. Buzdartherium means "Buzdar beast", in reference to Buzdar, where the holotype was discovered. Buzdartherium would have been around 5 meters long when fully grown.
The genus is based on a single tusk like incisor tooth, a premolar tooth, a cross-sectioned tooth, vertebrae, ribs, a spine, proximal humerus, ulna, proximal pubis, a cross-sectioned pubis, proximal ischium, ischium cross section, femur, carpal/astragalous/tarsal, metacarpal/metatarsal, phalanges, and ungual/toe It is not known when it was found but it was found in Buzdar, Pakistan in Oligocene strata. The genus was described by Malkhani in 2016. The animal came from the Chitarwata Formation.
Buzdartherium shows Eurasian affinity and migrated from Eurasia to the Indo-Pak subcontinent or vice versa via the Western and Northern Indus Sutures, after the collision of the Indo-Pak subcontinent with Asia, which occurred at the turn of the Cretaceous.
The superfamily Rhinocerotoidea, which includes modern rhinoceroses, can be traced back to the early Eocene - about 50 million years ago - with early precursors such as Hyrachyus. Rhinocerotoidea contains three families; Amynodontidae, Rhinocerotidae ("true rhinoceroses"), and Hyracodontidae. The diversity within the rhinoceros group was much larger in prehistoric times; they ranged from dog-sized to the size of Paraceratherium. There were long-legged, cursorial forms adapted for running and squat, semi aquatic forms. Most species did not have horns. Rhinoceros fossils are identified as such mainly by characteristics of their teeth, which is the part of the animals most likely to be preserved. The upper molars of most rhinoceroses have a pi-shaped (π) pattern on the crown, and each lower molar has paired L-shapes. Various skull features are also used for identification of fossil rhinoceroses.
The subfamily Indricotheriinae, to which Buzdartherium belongs, was first classified as part of the family Hyracodontidae by the American palaeontologist Leonard B. Radinsky in 1966. Previously, they had been regarded as a subfamily within Rhinocerotidea, or even a full family, Indricotheriidae. In a 1999 cladistic study of tapiromorphs, the American palaeontologist Luke Holbrook found indricotheres to be outside the hyracodontid clade, and wrote that they may not be a monophyletic (natural) grouping. Radinsky's scheme is the prevalent hypothesis today. The hyracodont family contains long-legged members adapted to running, such as Hyracodon, and were distinguished by incisor characteristics. Indricotheres are distinguished from other hyracodonts by their larger size and the derived structure of their snouts, incisors and canines. The earliest known indricothere is the dog-sized Forstercooperia from the middle and late Eocene of western North America and Asia. The cow-sized Juxia is known from the middle Eocene; by the late Eocene the genus Urtinotherium of Asia had almost reached the sizes of Buzdartherium Paraceratherium. Buzdartherium itself lived in Eurasia (Pakistan) during the Oligocene period, 23 to 34 million years ago. The genus is distinguished from other indricotheres by its large size, nasal incision that would have supported a muscular snout, and its down-turned premaxillae. It had also lost the second and third lower incisors, lower canines, and lower first premolars. The cladogram below follows the 1989 analysis of Indricotheriinae by Lucas and Sobus, and shows the closest relatives of Paraceratherium (Buzdartherium has been added later):
Lucas and colleagues had reached similar conclusions in a previous 1981 analysis of Forstercooperia, wherein they still retained Paraceratherium and Indricotherium as separate genera. In 2016, the Chinese researchers Haibing Wang and colleagues used the name Paraceratheriidae for the family and paraceratheriine for the subfamily, and placed them outside of Hyracodontidae.
Buzdartherium would have been a large mammal with long bulky legs and a long neck, used to forage for plants that would have made up its diet.
Bazdartherium would have had a long forehead, which was smooth and lacked the roughened area that serves as attachment point for the horns of other rhinoceroses. The back of the skull was low and narrow, without the large lambdoid crests at the top and along the sagittal crest, which are otherwise found in horned and tusked animals that need strong muscles to push and fight. It also had a deep pit for the attachment of nuchal ligaments, which hold up the skull automatically. Buzdartherium would have had large, strong neck muscles, which allowed it to sweep its head strongly downwards while foraging from branches.
Unlike those of most primitive rhinoceroses, the front teeth of Bazdartherium were reduced to a single pair of incisors in either jaw, which were large and conical, and have been described as tusks. Only two teeth are known: a premolar and a tusk like incisor.
The postcranial skeleton is mostly identical to that of other indricotheres (see ).
The site where Buzdartherium was found was also home to its relatives, Paraceratherium and Pakitherium. It also shared its environment with the basilosaur Sulaimanitherium, the proboscidean Gomphotherium buzdari, the eucrocodile Asifcroco and the bear dog Bolanycion.
- Prothero, 2013. pp. 53–66
- (1966) "The families of the Rhinocerotoidea (Mammalia, Perissodactyla)". Journal of Mammalogy 47 (4): 631–639. DOI:10.2307/1377893.
- (1999) "The phylogeny and classification of tapiromorph perissodactyls (Mammalia)". Cladistics 15 (3): 331–350. DOI:10.1006/clad.1999.0107.
- Lucas, S. G. (1981). "The systematics of Forstercooperia, a Middle to Late Eocene hyracodontid (Perissodactyla: Rhinocerotoidea) from Asia and Western North America". Journal of Paleontology 55 (4): 826–841.
- (2016) "Earliest known unequivocal rhinocerotoid sheds new light on the origin of Giant Rhinos and phylogeny of early rhinocerotoids". Scientific Reports 6 (1). DOI:10.1038/srep39607. PMID 28000789.