Shansirhinus
| Shansirhinus | ||||||||||||
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Shansirhinus skull part |
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| Temporal occurrence | ||||||||||||
| Upper Miocene to Lower Pliocene ( Turolium to Ruscinium ) | ||||||||||||
| 8.2 to 3.4 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Shansirhinus | ||||||||||||
| Kretzoi , 1942 | ||||||||||||
Shansirhinus is an extinct genus of rhinos and livedin East Asia in the late Miocene and Pliocene 8 to 3.5 million years ago. So far it is only known from individual skulls and a few lower jaws and was a specialized herbivore due to the structure of the teeth.
features
Shansirhinus comprised large rhinos, but so far only known from remains of the skull, the weight is calculated at about 2.6 t. The skull was relatively short and was up to 52 cm long, when viewed from above it had a wedge-like shape with protruding cheekbones . The occiput was short and rectangular in shape and had a strong bulge as a muscle attachment point. The entire rostrum is shortened. The nasal bone was short and ran slightly upwards, the long edges were clearly curved downwards. There was a small roughened surface on the foremost tip that indicates the location of the horn. The interior of the nose between the nasal bone and the intermaxillary bone was extensive and reached to the last premolar . The forehead line was straight.
The lower jaw was massive and also wedge-shaped and was 46 cm long. The body reached a height of 8.3 cm, this was near the last molar and just before the ascent of the articular branches. The symphysis was also strong and extensive, it ended at the posterior margin of the second premolar. In the anterior area, the symphysis was significantly widened. The dentition is significantly reduced, but it is not known whether incisors were formed in the upper jaw . In the lower jaw is a pair, I2, which, with its conical shape, resembled a small tusk. He was 5.9 cm long and was clearly erect. One of the canines was not formed, and there was a 6.2 cm diastema to the posterior teeth . The rear teeth consisted of three premolars and three molars per half of the jaw. These were relatively high crowned ( hypsodont ) with a height of up to 6 cm. The premolars were similar to the molars, i.e. they were clearly molarized, the chewing surfaces had clearly folded enamel , but not as much as in the closely related Chilotherium . The second molar was the largest tooth in the dentition.
Fossil finds
Finds of Shansirhinus come exclusively from East Asia , often from northern China , but mostly only skulls and teeth have survived. The front part of a skull with complete rear teeth comes from Haobei in the Yushe Basin in Shanxi Province and came to light in the late Miocene Mahui Formation . Another upper jaw fragment, which was the basis for the first description, was discovered in Huangshigou in the same basin and comes from the Goazhuang Formation of the Lower Pliocene . Today it is considered the lectotype of the genus. A complete skull with associated lower jaw from Yinchuan in very fossiliferous Linxia Basin of the province of Gansu known. These lay in red-clay deposits of the Hewengjia Formation , which can also be found in the late Miocene.
Paleobiology
The high-crowned teeth suggest a food specialization in hard, silicic acid-rich grasses ( grazing ), possibly even more so than in the case of Chilotherium , although some researchers do not rule out a certain proportion of softer or hard-fiber plant food. The specialization in grass goes hand in hand with a greater expansion of open landscapes and a cooler climate in the transition from the Miocene to the Pliocene . May be possessed shansirhinus a very mobile upper lip, as the attachment points of the levator nasolabialis the infraorbital foramen show by two longitudinal bone back. This was probably necessary to push the grass past the two protruding incisors. The roughened surfaces of the nasal bone suggest the presence of a small horn. The position of these surface structures at the foremost tip of the nasal bone suggest that it was not upright as in today's rhinos, but pointed forward. The frequent socialization with representatives of the Hipparion fauna suggests life in open landscapes.
Systematics
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Internal systematics of the Aceratheriini according to Sun et al. 2018
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Shansirhinus is an extinct genus of the family of Aceratheriinae whose representatives part of unspecified related precursors of today's rhinos and were characterized by the virtual absence of a horn formation. Within the Aceratheriinae, the genus of the tribe Aceratheriini belongs to and is closely related to Chilotherium , differences are mainly in the structure of the molars, which in Shansirhinus are partially characterized by hardly any additional secondary folds of the tooth enamel in the upper jaw teeth. Both form the sister group to Aceratherium .
The following types are recognized today:
- S. brancoi ( locksmith , 1903)
- S. ringstromi (originally referred to as S. ringströmi ) Kretzoi , 1942
Here, p ringstromi the original species. Other species have been associated with the close related genus chilotherium described as C. cornutum and C. yunnanensis and C. tianzhuensis , but are synonymous with the accepted types of shansirhinus . Miklós Kretzoi introduced the name Shansirhinus in 1942, referring to an upper jaw fragment from the Chinese province of Shanxi , which Torsten Ringström had assigned to Rhinoceros brancoi in 1927 . This in turn received its first description from Max Schlosser in 1903 . Schlosser found the bones and teeth on which the description was based in pharmacies in Shanghai , where they were sold as "dragon bones" within traditional Chinese medicine . The name Shansirhinus refers on the one hand to the place of discovery of the first find, Shanxi, on the other hand the Greek word ῥίς ( rhīs "nose"; genitive rhinos ) refers to the relationship with the rhinos.
Shansirhinus developed in the late Miocene and possibly goes back to Chilotherium . Its earliest occurrence was recorded more than 8 million years ago. However, it died out again around 3.5 million years ago in the middle Pliocene .
Individual evidence
- ↑ Tao Deng: Late Cenozoic environmental changes in the Linxia basin (Gansu, China) as indicated by cenograms of fossil Mammals. Vertebrata Palasiatica 47 (4), 2009, pp. 282-298
- ↑ a b c d e f Tao Deng: New cranial material of Shansirhinus (Rhinocerotidae, Perissodactyla) from the Lower Pliocene of the Linxia Basin in Gansu, China. Geobios 38, 2005, pp. 301-313
- ↑ a b c d Qiu Zhanxiang and Yan Defa: A horned Chilotherium skull from Yushe, Shansi. Vertebrata Palasiatica 20 (2), 1982, pp. 122-132
- ↑ a b c Torsten Ringström: About Quaternary and Young Tertiary Rhinocerotids from China and Mongolia. Palaeontologia Sinica (C) 4 (3), 1927, pp. 1-23
- ^ Sun Dan-Hui, Li Yu and Deng Tao: A new species of Chilotherium (Perissodactyla, Rhinocerotidae) from the Late Miocene of Qingyang, Gansu, China. Vertebrata Palasiatica, 2018 doi: 10.19615 / j.cnki.1000-3118.180109
- ↑ a b Miklós Kretzoi: Comments on the system of the post-Miocene rhinoceros genera. Földtani Közlöni, Budapest 72 (4-12), 1942, pp. 309-318
- ↑ Deng Tao: A primitive species of Chilotherium (Perissodactyla, Rhinocerotidae) from the Late Miocene of the Linxia Basin (Gansu, China). Cainozoic Research, 5 (1-2), 2006, pp. 93-102