2021-06-17

Scientists have discovered the largest new genus of land mammals in the history of the earth: “Linxia giant rhinoceros” 26.5 million years ago

By yqqlm yqqlm

China News Service, Beijing, June 17 (Reporter Sun Zifa) As the largest land mammal known to have survived in the history of the earth, the giant rhinoceros was first discovered in Asia. It appeared in the middle of the Eocene 42 million years ago. The research on the evolutionary relationship of extinctions 21 million years ago in the early Pleistocene has attracted much attention.

Scientists have discovered the largest new genus of land mammals in the history of the earth: “Linxia giant rhinoceros” 26.5 million years ago

“Linxia Giant Rhinoceros” ecological restoration map in the late Oligocene (Chen Yu/painted). Photo courtesy of the Institute of Paleospine, Chinese Academy of Sciences

The discovery of a new species of giant rhinoceros “Linxia giant rhinoceros” 26.5 million years ago

Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (Institute of Paleospine, Chinese Academy of Sciences) The Sino-U.S. cooperation team led by researcher Deng Tao has recently completed the analysis of a complete skull with a mandible and annulus, which was collected from the late Oligocene 26.5 million years ago in the Linxia Basin, Gansu, on the northeastern margin of the Qinghai-Tibet Plateau. The study of the fossil found that the fossil was a new species of giant rhinoceros, named “Linxia giant rhinoceros”.

Further research on the “Linxia Giant Rhinoceros” shows that before the extinction, the giant rhinoceros had migrated and spread to South Asia and other places through the Qinghai-Tibet Plateau, which was not a high-altitude area at that time. The major discovery and research progress paper of the Sino-US cooperation team was published online by the international professional academic journal “Communication-Biology” under Springer Nature on the night of June 17th, Beijing time.

Scientists have discovered the largest new genus of land mammals in the history of the earth: “Linxia giant rhinoceros” 26.5 million years ago(1)

Phylogenetic relationship of giant rhinoceros. Photo courtesy of the Institute of Ancient Spine, Chinese Academy of Sciences

Deng Taoke said that the giant rhinoceros can weigh up to 24 tons, which is equivalent to the total weight of the four largest African elephants. The giant rhinoceros has very long legs, 5 meters high at the shoulder when standing, and its head can extend up to 7 meters high. The size of the giant rhinoceros is suitable for living in sparse forests and feeding on the leaves of the canopy like a giraffe. The associated fauna in the strata that lived in the “Linxia Giant Rhinoceros” 26.5 million years ago indicated that there were extensive open and sparse forest areas in Northwest China at that time.

Except for a few giant rhinoceros fossils found in the Balkans, Anatolia and the Caucasus, the giant rhinoceros lives mainly in Asia, especially China, Mongolia, Kazakhstan and Pakistan. Starting with the giant rhinoceros that was 42 million years ago in the mid-Eocene, the giant rhinoceros evolved into 6 different genera, which eventually became extinct 21 million years ago in the early Miocene.

Among them, the rhinoceros is the most widespread rhinoceros, from East Asia to Eastern Europe. The “Bugti rhinoceros” found on the southwestern edge of the Qinghai-Tibet Plateau has a rich fossil record. However, it has been isolated from the unique geographical location of other rhinos in Eurasia, making its origin and evolution long-term obscure.

Scientists have discovered the largest new genus of land mammals in the history of the earth: “Linxia giant rhinoceros” 26.5 million years ago(2)

“Linxia Giant Rhinoceros” skull and mandible orthopedic specimens. Photo courtesy of the Institute of Ancient Spine, Chinese Academy of Sciences

“Linxia rhinoceros” is more advanced than other species of the genus Rhinoceros.

Deng Tao pointed out that fossil studies have found that the “Linxia rhinoceros” is more advanced than the rhinoceros genus. The other species are more advanced, with a larger body, a deeper nasal notch indicating that it has a developed soft nose, and the larger occipital condyle shows strong support for the larger skull above the long neck.

In the past, the phylogenetic relationship of the rhinoceros was only partially resolved at the genus level. The branch sequence analysis failed to reveal the evolutionary pedigree of the different species of the rhinoceros. Through the discovery and research of the “Linxia Giant Rhinoceros” this time, the Sino-US cooperation team carried out a new phylogenetic analysis based on the addition of a large number of skulls, teeth and back bone traits, thereby solving the different giants separated from the north and south of the Qinghai-Tibet Plateau. The origin and evolution of rhinoceros.

In the rhinoceros branch, the new phylogenetic analysis indicated that from the “German rhinoceros” in the Mongolian Plateau through the “Yellow River rhinoceros” in the Lanzhou Basin and the “Asian rhinoceros” in Kazakhstan The gradual evolutionary sequence of the “Bugatti giant rhinoceros” in Pakistan, and finally the “beautiful giant rhinoceros” in Xinjiang and the “Linxia giant rhinoceros” in Gansu.

Scientists have discovered the largest new genus of land mammals in the history of the earth: “Linxia giant rhinoceros” 26.5 million years ago(3)

Cenozoic strata in Linxia Basin, Gansu. Photo courtesy of the Institute of Ancient Spine, Chinese Academy of Sciences

“Linxia Giant Rhinoceros” shows a high level of specialization similar to “Beautiful Giant Rhinoceros”, and both of these two species have a larger body shape than the “Bugti “Giant rhinoceros” is a fifth larger, and these three species originated from a common ancestor. The adaptation of the ring vertebrae and axis of the giant rhinoceros to the large size and slender neck has been completed in the “German rhinoceros” and “Burgerty giant rhinoceros” stages, and further developed in the “Linxia giant rhinoceros”. Its ring vertebra The morphological characteristics and joint structure of the axis make the neck more flexible.

Deng Tao said that according to the system relationship and the context of the times, the “Bugatti rhinoceros” evolved from the “Yellow River rhinoceros” through the “Asian rhinoceros” in the early Oligocene, and is gradually emerging In the late 2000s, as a sister group of the “Bugti Giant Rhinoceros”, the “Beautiful Giant Rhinoceros” was discovered in Ningxia, Xinjiang and Kazakhstan, and the “Linxia Giant Rhinoceros” was discovered in Gansu.

Scientists have discovered the largest new genus of land mammals in the history of the earth: “Linxia giant rhinoceros” 26.5 million years ago(4)

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p >The distribution and spread of rhinoceros in the Oligocene. Photo courtesy of the Institute of Ancient Spine, Chinese Academy of Sciences

How the rhinoceros migrated and spread across the Qinghai-Tibet Plateau

In the Eocene, Asia and Europe were separated because the Middle East and western Siberia were still occupied by sea water , Turgai Strait is still underwater, but in the Oligocene transitional sediments have developed between land and sea.

Deng Tao said that the southwest sag of the Tarim Basin extends eastward to the Altun Mountains. It is distributed with marine deposits from the Eocene to the early Miocene. It is rich in marine foraminifera, Ostracods and bivalves fossils. The marine fish fossils are very similar to cartilaginous fishes in the Paris Basin, indicating that there was an east-west extending sea area in this area in ancient times. Therefore, South Asia and Kazakhstan are separated by the sea, which also prevents the giant rhinos from communicating directly in this direction.

Studies have shown that in the Oligocene, the proliferation of giant rhinoceros from the Mongolian Plateau to South Asia will proceed along the eastern bank of the Tethys Ocean through some low-elevation valleys in the hinterland of Tibet. This route is supported by other evidence. The fish and plant fossils found in the Oligocene strata in the central Qinghai-Tibet Plateau all show tropical characteristics, indicating that the altitude of the Qinghai-Tibet Plateau did not exceed 2000 meters at that time.

“The giant rhinoceros spread from the Mongolian plateau on the northern side of the Qinghai-Tibet Plateau to South Asia via northwestern China in the early Oligocene. The descendants of the Pakistan rhinoceros returned to Gansu and Xinjiang in the late Oligocene. It proves that the Qinghai-Tibet region has not yet risen to the plateau it is today, and there is not enough height to hinder the spread of large mammals like giant rhinoceros.” Deng Tao said. (End)