Shansirhinus
Shansirhinus is an extinct genus of rhinoceros and lived in the late Miocene and the Pliocene before 8 to 3.5 million years ago in East Asia. It is only known from individual skeletal remains and some mandibles and was due to the structure of the teeth a specialized grazers.
Features
Shansirhinus included large rhinos that were previously known only skull fragments, however, the weight is about 2.6 tons calculated. The skull was relatively short and was long up to 52 cm, in the plan he had a wedge-like shape with sweeping cheekbones. The occiput had a short and rectangular shape and had a strong bead as a muscle attachment point on. The entire rostrum is shortened. The nose was short and was slightly upward, the longitudinal edges were distinctly curved downward. There was a small roughened surface, which indicates the location of the horn on the front top. The nasal interior space between the nasal bone and premaxilla was spread out and handed to the last premolar. The front line had a straight course.
The lower jaw was massive and also wedge-shaped and was 46 inches long. The body reached a height of 8.3 cm, this was near the last molar and just before the rise of joint branches. The symphysis was strong and extended, it ended at the rear edge of the second premolars. At the front of the symphysis was significantly broadened. The dentition is greatly reduced, but it is not known whether were formed in the maxillary incisors. In the lower jaw there is a pair, I2, which resembled the with its conical form a small tusk. He was a total of 5.9 cm and was significantly raised. A canine was not designed for rear dentition was a diastema of 6.2 cm in length. The back teeth consisted of three premolars and three molars each half of the jaw. These were relatively hochkronig ( hypsodont ) with up to 6 cm in height. The premolars resembled the molar teeth were so molarisiert clear the chewing surfaces not reported significantly folded enamel, but as strong as the closely related Chilotherium. The largest tooth in the dentition was the second molar.
Fossil finds
Finds of Shansirhinus come exclusively from East Asia, often there from northern China, there are, however, largely survives only finds skull and teeth. The front part of a skull with complete dentition rear comes from Haobei in Yushe Basin in Shanxi Province, and came into the spätmiozänen Mahui lineup for days. Another maxilla fragment, which was the basis for the first description, has been discovered in Huangshigou in the same basin and comes from the formation of the Lower Pliocene Goazhuang. He is now regarded as lectotype of the species. A complete skull with associated mandible is known from Yinchuan in very fossiliferous Linxia Basin in Gansu Province. These were in rottonigen deposits of Hewengjia formation, which is also to provide the late Miocene.
Paleobiology
The hochkronigen teeth suggest a diet specialization on hard, silica- rich grasses ( grazing ), possibly even more so than in Chilotherium, but not close some researchers also a certain amount of softer or hartfasriger plant food from. The specialization on grasses associated with a greater spread of open landscapes and cooler climate in the transition from the Miocene to Pliocene. Maybe Shansirhinus had a very mobile upper lip as the infraorbital foramen, the points of attachment of the musculus leviator nasolabialis show by two longitudinal bone back. This was probably necessary to push the grass over food at the two protruding incisors. The roughened surface of the nasal bone to speak of the presence of a small horn. Evidence gathered at the cutting tip of the nasal bone, the location of these surface structures, that this was not raised as in today's rhinos, but pointed ahead. The frequent association with representatives of the Hipparion fauna suggests a life in open landscapes.
System
Shansirhinus is an extinct genus of the family of Aceratheriinae whose representatives belongs to not more closely 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 lie mainly in the construction of the molars that are partially characterized by Shansirhinus at little additional secondary folds of enamel in the maxillary teeth. Both form the sister group to Aceratherium.
The following subspecies are recognized today:
- S. ringstromi (originally referred to as S. ringströmi ) Kretzoi, 1942
Here, p ringstromi the original art Other types have been described in connection with the related genus near Chilotherium, C. cornutum and about yunnanensis C. and C. tianzhuensis but are synonymous to the accepted types of Shansirhinus. The name Shansirhinus led Miklós Kretzoi 1942, citing an upper jaw fragment from the Chinese province of Shanxi, which Torsten Ringström had assigned 1927 Rhinoceros brancoi. This, in turn, received its first description in 1903 by Max Schlosser. This locksmith had found the bones and teeth lying in the description of reason in pharmacies in Shanghai, where they were sold within the Traditional Chinese Medicine as " dragon bones ". The term Shansirhinus refers on the one hand on the place where the Erstfundes, Shanxi, on the other hand refers the Greek word ῥίς ( rhis 'nose', genitive rhinos ) on the relationship with the rhinos.
Shansirhinus developed in the late Miocene and possibly goes back to Chilotherium. His earliest occurrence is recorded more than 8 million years ago. However, it died of some 3.5 million years ago in the Middle Pliocene again.