Sinotherium
- East Asia
- Central Asia
- Sinotherium lagrelii Ringström, 1923
Sinotherium is an extinct representative of the rhinos and lived in the late Miocene and early Pliocene. It has been proven fossil, especially in East and Central Asia and one of the largest known rhinos. Its closest relative is Elasmotherium, with which it forms together the final link in the line of Elasmotherien ( Elasmotheriini ), a once widespread in Eurasia and Africa rhino group. So far, only few fossils are known. A relatively complete skull shows that Sinotherium had two horns, a hitherto undocumented feature in Elasmotherien. In addition, both horns were sitting on the forehead, which is unique among all known rhino representatives.
Features
Sinotherium was a massive rhino that almost the size of its closest relatives Elasmotherium reached, which belonged at all with a weight of 5 to 7 tons to the largest known rhinos. However Sinotherium is only known from fossil remains single. A complete skull is not known, but a more than 80 cm long skull from the Linxia Basin missing only the front snout area, but which is partially known by other finds. Overall, the skull was large and robust, and wedge-shaped in outline. The occiput was pulled as Elasmotherium backwards, but is not completely preserved. However, the extension resulted in a tilted head posture. Very solid were the joint surfaces to approach the cervical spine, which measured a total extension of up to 24 cm had about the foramen magnum, the joint surfaces even reached a length of 6.8 cm. The nasal bone is also not fully known, the paired bones, however, were completely overgrown. In addition Sinotherium had a ossification of the nasal septum, which had up to 6.5 mm thickness at the traditional rear of the nasal cavity. Noteworthy were two dome-like swellings of the skull, which were separated by a shallow and transverse depression. The rear was on the frontal bone, and measured 16.1 times 12.1 cm. The front rose above the front end of the frontal bone and the posterior end of the nasal bone, reaching 18.6 cm in length and 12.8 cm width. Through the front dome-like bulge lateral surfaces of the nasal bone were almost vertical. The surfaces of the surveys had significant roughening, which indicated the respective position of the horn. Thus Sinotherium had a front nasofrontales horn, which was significantly larger than the directly subsequent frontal horn. The close tandem position of the two horns to each other and the position of the anterior horn on the transition from the nose to the frontal bone is unique among the rhinos, with other representatives of this group of mammals, the Nasalhorn will normally impose directly on the tip of the nose. In addition, such dome-shaped bulges are as base of the horns so far only in Elasmotherium known. Within the Elasmotherien Sinotherium is the only known representative with two horns.
A full of traditional mandibular reached 72 cm in length and was very massive, with a nearly 18 cm high body and towering joint ends. The symphysis extended over 16 cm until the beginning of the posterior dentition. The dentition was reduced characteristic of Elasmotherien, strong. In the lower jaw only two premolars ( Vorbackenzähne ) and three molars (back molars ) were formed depending pine bough. Whether additionally a leading third premolar was formed in the upper jaw, it is unclear in some publications this is suspected. A front teeth from incisors and canines so did not exist at Sinotherium. The molars were extremely hochkronig ( hypsodont ) and had a lot of dental cement. In addition, the enamel was folded sharply to the Kauoberflächen and possessed plus an additional internal sine -shaped Verwinklungen, but they were not as sharp as later in Elasmotherium. The largest tooth was the second molar, which partly to over 16 cm was high, with a length of 9 cm.
The fuselage skeleton and the limbs are hardly in the fossil record. A single radius had a length of 52 cm, still reached the ulna 58 cm in length. It is bone, the forearm bones are in the human skeleton homologous (corresponding ). In addition, individual elements of the rear foot are known as the metatarsal II to IV and some tarsal bones.
Fossil finds
Finds of Sinotherium are rare and often only fragmentary. The first fossils that also led to the description of the rhino species, came to light early 20th century and were discovered by JG Andersson in the district Baode in the Chinese province of Shanxi in the upper Miocene deposits. These included mainly isolated teeth, but also a maxillary fragment with the resulting row of teeth from the second premolar to the penultimate molar and a mandibular fragment. From the northwest near Mongolia Chono - Khariakh a 72 cm long, fairly well-preserved lower jaw was published, which dated to the lower Pliocene. Other individual finds are known from Kazakhstan, here under a rear skull part with a portion of dentition and multiple skeletal elements of the body. However, so far the most complete skull rendered the upper portion of Liushu - formation near Houaigou in the district Guanghe of Gansu Province. The Liushu Formation is approximately 100 m thick and disrupted 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 already provided numerous well-preserved fossil remains of rhinoceros, including many representatives of Elasmotherien. The skull missing only part of the snout and he provided evidence for the location of the horns at Sinotherium.
Paleobiology
The proliferation of Sinotherium in East Asia largely coincides with that of today also extinct three-toed horse Hipparion. In the Linxia Basin both mammalian forms have been found associated. Hipparion inhabited largely open, steppe-like landscapes. Certain anatomical features of Sinotherium, such as the low-hanging by the long occipital skull, which greatly hochkronigen and filled with a lot of cementum cheek teeth as well as their considerably curved enamel folds on the Kauoberflächen leave a predominantly recognize hard plant foods such as grasses adapted animal ( grazer ). Through pollen analysis, such a landscape could also be determined for the Linxia Basin.
System
Menoceratini
Kenyatherium
Caementodon
Procoelodonta
Huaqingtherium
Ningxiatherium
Parelasmotherium
Sinotherium
Elasmotherium
Rhinocerotini
Sinotherium is a genus of the family of rhinos and belongs within this subfamily of Rhinocerotinae and the tribe of Elasmotheriini. This tribe includes rhinos with a generally large to very large physique and extremely high tooth crowns, partly due to this feature make it at least in its late stage, the most specialized rhino representatives; they are also the sister taxon of Rhinocerotini, which in turn the extant rhino species belong. Within the Elasmotheriini Sinotherium is a member of the subtribes Elasmotheriina, whose members also heard Elasmotherium. These subtribes is characterized by the formation of horn on its forehead. The Elasmotherrina facing the Iranotheriina, phylogenetically older Elasmotherien with a Nasalhorn, which also generally not quite as having hochkronige molars and a less folded enamel. This subtribes be assigned, in addition to the eponymous Iranotherium among other Ningxiatherium, Parelasmotherium or Hispanotherium. The distinction between Elasmotheriina and Iranotheriina was the first time by the Hungarian Miklós paleontologists Kretzoi (1907-2005) in 1943.
Sinotherium described in 1923 by Torsten Ringström based on a very large molar from Shanxi scientifically for the first time, a year later there was a much more extensive discussion of the genus with respect to more archaeological material. Ringström established the hitherto only recognized species: S. lagrelii. With S. Bolat zaisanensis Bayshahsov described in 1986 another kind of Kazakhstan, but this shows very little difference to the species S. lagrelii. 1958 led Chow Minna the species S. simplum one whose description was based on a tooth, which was discovered in a pharmacy in the Chinese province of Harbin ( " dragon bones "), but was originally supposed to come from Shanxi. Today the species is, however, too Parelasmotherium. The term Sinotherium derives from the Latin word sina for " China" and the Greek word θήριον ( therion "beast" ). A direct etymological origin of the name gave Ringström in his first description not to, but the award was made, according to his statements as a result of the discovery area in China.