The giant rhino was one of the largest land animals to exist, but its evolutionary history in Asia has been a mystery – except now, scientists have found a new ancient species.
A team of researchers, led by Tao Deng of the Chinese Academy of Sciences, have recovered the remains of a previously undiscovered species and dubbed it Paraceratherium linxiaense, filling in gaps in our understanding.
“Since the 1980s, our team has been searching for mammalian fossils from the Linxia Basin in Gansu Province, in north-western China,” says Deng. “We found very abundant and complete specimens of various late Cenozoic mammalian groups, but only found rare giant rhino fossils in isolated or fragmentary situations.
“Since May 2015, the complete skull and mandible with the associated atlas, and an axis and two thoracic vertebrae of another individual, were discovered from the late Oligocene deposits near the village of Wangjiachuan in Dongxiang County.”
The rhino had a slender skull with a short nose trunk and long neck, and had a deeper nasal cavity than other giant rhinos.
“When the specimens appeared, their huge size and completeness was a great surprise for us,” says Deng. “When I and my team began to think it was a new species, our first reaction was to establish its phylogenetic position in the giant rhino lineage.”
After analysis, the team placed the new rhino species on a phylogenetic tree with other giant rhinos, including the giant rhinos of Pakistan. Potentially, the rhinos travelled through the Tibetan region before it became elevated and hard to traverse, as it is today. After that, they may have continued their journey down to the Indian-Pakistani subcontinent during the Oligocene epoch.
“The giant rhino genus Paraceratherium was widely distributed, but many records comprise only fragmentary specimens,” says Deng. His team’s phylogenetic analysis places P. linxiaense as a derived giant rhino, nested within the monophyletic clade of the Oligocene Asian Paraceratherium.
“The extremely specialised nasal notch is unique to the giant rhino.”
The study was published in Communications Biology.