Sinotherium
| Sinotherium | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Upper Miocene to Lower Pliocene | ||||||||||||
| 9.5 to 3.6 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Sinotherium | ||||||||||||
| Ringström , 1923 | ||||||||||||
| species | ||||||||||||
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Sinotherium is an extinct representative of the rhinos and lived in the late Miocene and early Pliocene . It has been found in fossils primarily in East and Central Asia and was one of the largest known rhinos. Its closest relative is Elasmotherium , with whom it forms the end link in the line of Elasmotheria ( Elasmotheriini ), a group ofrhinosthat was oncewidespreadin Eurasia and Africa . Only a few fossil finds are known to date. A relatively complete skull shows that Sinotherium had two horns , a hitherto undocumented feature of Elasmotheria. In addition, both horns sat on the forehead, which is so far unique among all known rhino representatives.
features
Sinotherium was a massive rhinoceros that almost reached the size of its closest relative Elasmotherium , which with a weight of 5 to 7 tons was one of the largest known rhinos ever. However, Sinotherium is only known from individual fossil remains. A complete skull has not survived, but a skull from the Linxia basin that is more than 80 cm long is only missing the front snout area, which is known in part from other finds. Overall, the skull was large and robust and wedge-shaped in outline. The occipital bone was like Elasmotherium pulled back, but is not completely preserved. However, the lengthening caused the head to be tilted. The joint surfaces at the beginning of the cervical spine were very massive and measured over the occipital opening had a total extension of up to 24 cm, the joint surfaces themselves reached a width of 6.8 cm. The nasal bone is also not fully known, but the paired bones were completely fused. In addition, Sinotherium had an ossification of the nasal septum , which was up to 6.5 mm thick in the traditional posterior area of the interior of the nose. Noteworthy were two dome-like bulges of the skull, which were separated by a shallow and transverse depression. The back was on the frontal bone and measured 16.1 by 12.1 cm. The anterior rose above the anterior end of the frontal bone and the posterior end of the nasal bone, reaching 18.6 cm in length by 12.8 cm in width. Due to the front dome-like bulge, the lateral surfaces of the nasal bone were almost vertical. The surfaces of the elevations had clear roughening, which indicated the respective position of the horn. Sinotherium thus had an anterior nasofrontal horn, which was significantly larger than the directly adjoining frontal horn. The close tandem position of the two horns to each other and the position of the front horn on the transition from the nasal to the frontal bone is so far unique among the rhinos; in other representatives of this group of mammals, the nasal horn usually rises directly on the tip of the nose. In addition, such dome-like bulges as the base of the horns are only known from Elasmotherium . Sinotherium is the only known representative with two horns within the Elasmotheria .
A completely traditional lower jaw reached 72 cm in length and was very massive with a body almost 18 cm high and towering joint ends. The symphysis extended 16 cm before the beginning of the posterior teeth. The dentition was, characteristic of Elasmotheria, greatly reduced. In the lower jaw there were only two premolars (front molars ) and three molars (rear molars) per jaw branch. It is unclear whether an anterior third premolar was also formed in the upper jaw, but this is suspected in individual publications. A front set of incisors and canines did not exist with Sinotherium . The molars were extremely high crowned (hypsodont) and had a lot of dental cement . In addition, the tooth enamel on the chewing surfaces was markedly folded and had additional internal sinus-shaped angulations, but these were not as pronounced as later with Elasmotherium . The largest tooth was the second molar, which was sometimes up to 16 cm high and 9 cm long.
The trunk skeleton and the limbs are hardly known to have been found in fossils. A single radius was 52 cm in length and the ulna was 58 cm in length. These are bones that are homologous (correspondingly) to the forearm bones in the human skeleton . In addition, individual elements of the hind foot are known, such as the metatarsal bones II to IV and some tarsal bones .
Fossil finds
Finds of Sinotherium are rather rare and often only fragmentary. The first fossils, which also led to the description of the rhino genus, came to light at the beginning of the 20th century and were discovered by JG Andersson in the Baode district in the Chinese province of Shanxi in deposits from the Upper Miocene . These mainly comprised isolated teeth, but also an upper jaw fragment with the preserved row of teeth from the second premolar to the penultimate molar and a lower jaw fragment. From northwestern Mongolia near Chono-Khariakh a 72 cm long, quite well preserved lower jaw was published , which dates to the lower Pliocene . Further individual finds are known from Kazakhstan , including a rear part of the skull with part of the teeth and several skeletal elements of the body. The most complete skull to date was found in the upper area of the Liushu Formation near Houaigou in the Guanghe District of Gansu Province . The Liushu formation is around 100 m thick and open over large areas of the Linxia basin . This section is dated to about 7 to 6.4 million years and thus belongs to the end of the Miocene. The geological deposits of the Linxia Basin have already produced numerous well-preserved fossil rhinoceros remains, including numerous representatives of the Elasmotheria. The skull is only missing the part of the snout and it provided evidence of the location of the horns in Sinotherium .
Paleobiology
The distribution of Sinotherium in East Asia largely coincides with that of the three-toed horse Hipparion, which is also extinct today . Both mammalian forms have been found together in the Linxia Basin. Hipparion lived in largely open, steppe-like landscapes. Certain anatomical features of Sinotherium , such as the skull hanging low due to the long occiput, the high-crowned molars filled with a lot of dental cement, and their clearly curved enamel folds on the chewing surfaces, indicate an animal that has mainly adapted to hard plant foods such as grasses ( grazer ). Such a landscape could also be determined for the Linxia basin through pollen analyzes .
Systematics
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Internal systematics of the Elasmotheriini according to Sanisidro et al. 2012 and Deng 2008
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Sinotherium is a genus from the family of the rhino , is within this to the subfamily of Rhinocerotinae and tribes of Elasmotheriini. This tribe includes rhinos with a generally large to very large body and extremely high tooth crowns, due to this feature, among other things, they represent the most specialized rhinoceros representatives, at least in their late development phase. They are also the sister taxon of the rhinocerotini, which in turn are the rhinoceros species living today belong. Within the Elasmotheriini, Sinotherium is a member of the sub-tribus Elasmotheriina, to which Elasmotherium also belongs. This sub-tribus is characterized by the horn formation on the forehead. Opposite the Elasmotherrina are the Iranotheriina, ancestral Elasmotheriina with a nasal horn, which also generally have not quite as high-crowned molars and less folded tooth enamel. This sub-tribus is assigned to the eponymous Iranotherium, among others, Ningxiatherium , Parelasmotherium or Hispanotherium . The distinction between Elasmotheriina and Iranotheriina was first made by the Hungarian paleontologist Miklós Kretzoi (1907-2005) in 1943.
Sinotherium was scientifically described for the first time in 1923 by Torsten Ringström on the basis of a very large molar tooth from Shanxi , and the following year there was a much more extensive treatise on the genus with reference to more finds. Ringström also established the only recognized species to date: S. lagrelii . With S. zaisanensis , Bolat Bayshahsov described another species from Kazakhstan in 1986, but this hardly differs from the species S. lagrelii . In 1958, Chow Minchen introduced the species S. simplum , the description of which was based on a tooth that was discovered in a pharmacy in the Chinese province of Harbin (" dragon bone "), but was originally supposed to come from Shanxi. Today, however, the species is put to Parelasmotherium . The term Sinotherium is derived from the Latin word sina for "China" and the Greek word θήριον ( thêrion "animal"). Ringström did not give a direct etymological origin of the name in his first description, but according to him, the assignment was based on the discovery area in China.
Individual evidence
- ↑ a b c Tao Deng, ShiQi Wang and SuKuan Hou: A bizarre tandem-horned elasmothere rhino from the Late Miocene of northwestern China and origin of the true elasmothere. Chinese Science Bulletin 2012, pp. 1-7
- ↑ a b c Torsten Ringström: Rhinos of the Hipparion fauna of northern China. Palaeontologia Sinica (C) 1 (4), 1924, pp. 1-156
- ↑ a b c П. Е. Кондрашов: Sinotherium (Mammalia, Rhinocerotidae) из раннего плиоцена Монголии. Палеонтологический Журнал 6, 2000, pp. 71-79
- ↑ a b c Болат У. Байшашов: Новыи вид синотерия из плиоцена Казахстана. Палеонтологический Журнал 4, 1986, pp. 83-88
- ↑ a b c Torsten Ringström: Sinotherium lagrelii Ringström, a new fossil rhinocerotid from Shansi, China. Bulletin of the Geological Survey of China 1923, pp. 91-93
- ↑ Oscar Sanisidro, María Teresa Alberdi and Jorge Morales: The First Complete Skull of Hispanotherium matritense (Prado, 1864) (Perissodactyla, Rhinocerotidae) from the Middle Miocene of the Iberian Peninsula. Journal of Vertebrate Paleontology, 32 (2), 2012, pp. 446-455
- ↑ a b Tao Deng: A new elasmothere (Perissodactyla, Rhinocerotidae) from the late Miocene of the Linxia Basin in Gansu, China. Geobios 41, 2008, pp. 719-728
- Jump up ↑ EA Vangengeym, IA Vislobokova, AYA Godina, EL Dmitrieva, VI Zhegallo, MV Sotnikova and PA Tleuberdina: On the age of mammalian fauna from the Karabulak Formation of the Kalmakpai River (Zaysan Depression, Eastern Kazakhstan). Stratigrafya i Geologicheskaya Korrelyazya Moscow 1 (2), 1993, pp. 165-171
- ↑ Chow Minchen: New elasmotherine rhinoceroses from Shansi. Vertebrata Palasiatica 2, 1958, pp. 131-142
- ↑ Deng, Tao: Skull of Parelasmotherium (Perissodactyla, Rhinocerotidae) from the Upper Miocene in the Linxia Basin (Gansu, China). Journal of Vertebrate Paleontology 27 (2), 2007, pp. 467-47
