Stephanorhinus

Skull from the steppe rhinoceros ( Stephanorhinus hemitoechus )

Northern Eurasia

Stephanorhinus is a now extinct genus of the family of rhinos. She was in front of 8 million until about 10,000 years spread mainly from the Upper Miocene to the end of the Pleistocene in northern Eurasia. Related Stephanorhinus with Dicerorhinus whose only living representative is now living in Southeast Asia and highly endangered Sumatran rhinoceros ( Dicerorhinus sumatrensis ). Both genera belong to the Dicerorhinina, rhino with two horns, which were mainly distributed in Eurasia. Chance of the genus also occurred in the northern part of Africa.

Features

The representatives of the genus Stephanorhinus were medium-sized to very large rhinoceros, the different ecological niches occupied and therefore possessed a variable appearance. In general, they had a pretty strong, reminiscent of today's rhinos physique. Forest dwellers were something more graceful with long slender limbs, while residents of the forest edges or open areas and had a powerful physique and rather short and wide limbs. The size of each species varied considerably and be a little representatives such as the Hundsheimer rhinoceros ( Stephanorhinus hundsheimensis ) and the Etruscan rhinoceros ( Stephanorhinus etruscus ) at 700 to 900 kg for the largest forms, such as the steppe rhinoceros ( Stephanorhinus hemitoechus ) and the forest rhinoceros ( Stephanorhinus kirchbergensis ), up to 3 tons live weight achieved. However, some species went through a marked increase in size during development. In the postcranial skeleton Stephanorhinus resembled today's rhinos. The most important feature is the three-pointed hands and feet, which is the rhino species to the modern Rhinocerotini.

The skull varied in its length of 56 to 81 cm, depending on the size of the species, and was very large and massive, with sweeping cheekbones. The occipital bone was extracted as the most rhino back, but had largely a right angle over the Hinterhauptswulst to the joint surfaces where ansetzte the cervical spine. This caused a high to horizontal head posture. The only exception is the steppe rhinoceros, which possessed an acute angle and so had a low or deep head posture. The nose had a significantly rounded shape and pointed to the surface cauliflower-like roughened surfaces as a starting point for the front horn. A similar kind surface structure on the frontal bone, the clear as was usually less marked the second posterior horn. A common feature of all Stephanorhinus species was partially ossified nasal septum, which grew together up to two thirds in the predominant species in the front third, the steppe rhinoceros. A similar feature possessed in modern rhinos only the genus Coelodonta with the woolly rhinoceros ( Coelodonta antiquitatis ), the nasal septum was completely ossified. In contrast to this however, the nasal bone was sitting at Stephanorhinus not directly on the intermediate jaw bone.

The dentition of Stephanorhinus is significantly reduced, so that the front dentition was completely absent in the rule. The dental formula of adult animals was:. The premolars resembled largely the molars, were so molarisiert significantly. As reported in the vast number of early types low tooth crowns ( brachyodont ), later increased this slightly. Only the steppe rhinoceros developed very high crowns ( hypsodont ) with high dental cement content.

Dissemination

Stephanorhinus was particularly common in northern Eurasia and thus partially adapted to cooler climates as Dicerorhinus. It came from the Iberian Peninsula in the west across all of Europe, the Russian steppes to East Asia in the East. However, individual species remained on the western or eastern Eurasia limited, only the forest rhinoceros had a paneurasische distribution, while the steppe rhinoceros is shown nor to Lake Baikal. The southernmost boundary spreading in the western area of ​​distribution is North Africa, but where the species occurred only in the Upper Pleistocene. In East Asia, representatives of Stephanorhinus penetrated to 30 degrees north latitude, southerly areas were inhabited by the genera Rhinoceros and Dicerorhinus.

Paleobiology

The predominant species, especially in the late Miocene, Pliocene and early Pleistocene were with slender limbs adapted to closed forests because of their more delicate physique, later forms, the preferred and more open landscapes developed. But the steppe rhinoceros from the late Middle Pleistocene was the only species that populated also open steppe areas and pointed accordingly stronger and short legs. The mostly niederkronigen teeth and the high head posture in favor of a diet based on soft plant food ( browsing ), which can also be to the of abrasion of the teeth Kauoberflächen prove with trough-like depressions. The Hundsheimer rhino preferred rather mixed diet when forest rhino food residues are in turn handed down in the teeth, originating from birch trees, roses, poplars, oaks, white and Firethorn and water lilies. The steppe rhino hand, has very high crowns and a large dental cement content. Characteristic horizontal grinding pattern on the occlusal surfaces speak for a specialized, hard and siliceous grass diet ( grazing ), which had to be absorbed by the soil. This led to an evolutionary extension of the occiput and to a permanently low head position, as it is still in the white rhinoceros ( Ceratotherium simum ) is the case today.

Stephanorhinus typically had two horns, of which the forward ( nasal or nasal horn) ansetzte on the nose and the rear ( frontal or frontal lobe ) on the frontal bone, as can be seen on the roughened bone surfaces, is composed of keratin horn itself but fossil not delivered. Such so-called tandem horns are still evident in the Sumatran rhino and the more distantly related African rhinos. The expansion of the roughened surfaces suggests the size of the former horn, generally the Nasalhörener here were larger than the frontal horns. Early Stephanorhinus representatives tended to be rather small horns, whereas subsequent larger. Originally, the deformed nasal septum was associated with the increase in size of the horns, the contemporary African rhinos have some very long horns, but have no ossification of the nasal septum on. In addition to the Stephanorhinus - Coelodonta line is the fossil urtümlichere and not related to the modern rhinoceros Elasmotherium known, which also had such ossification. However, this had no nose horn, but only one may be up to two meters long front horn.

System

In today's classification of rhinos Stephanorhinus is provided subtribes Dicerorhinina, which in turn provided the Rhinocerotini tribe, to which all extant rhinos. Closely related genera are Coelodonta with the woolly rhinoceros, but also the phylogenetically older forms Dihoplus and Lartetotherium. The next still living representative is the Sumatran rhinoceros ( Dicerorhinus sumatrensis ), whose generic name is also the name of the subtribes derived. His direct phylogenetic ancestor is unknown. Due to the preservation of the anterior dentition represents the Sumatran rhino but a phylogenetically more primordial Member dar. Dicerorhinus split 26 million years ago from the line of Asian rhinos from, Coelodonta then parted before 21 million years of the Dicerorhinus line.

Numerous species of the genus Stephanorhinus have been assigned. The following are recognized today:

• Stephanorhinus etruscus ( Etruscan rhinoceros) Falconer, 1868
• Stephanorhinus hemitoechus ( steppe rhinoceros) Falconer, 1868
• Stephanorhinus hundsheimensis ( Hundsheimer rhinoceros) Toula, 1902
• Stephanorhinus jeanvireti Guérin, 1972
• Stephanorhinus lantianensis Hu & Qi, 1978
• Stephanorhinus megarhinus De Christol, 1834
• Stephanorhinus miguelcrusafonti Guérin & Santafe - Llopis, 1978
• Stephanorhinus pikermiensis Toula, 1906
• Stephanorhinus yunchuchensis Chow, 1963

The name Stephanorhinus was introduced in 1942 by the Hungarian Miklós Kretzoi paleontologists. The name consists of the name " Stefan" and the Greek word ῥίς ( rhis 'nose', genitive rhinos ) together. " Stephan " represents a tribute to the first King of Hungary and today's national saint of the country, Stephen I. ( István ) dar. However Kretzoi then joined the steppe rhinoceros ( Stephanorhinus hemitoechus ) due to the different built skull with not one, but referred this to the of him independently created species Procerorhinus. The name Stephanorhinus sat down initially by little. The French researcher Claude Guérin did not recognize the name, instead he created in 1980 with Brandtorhinus own, in which he included all European Plio - Pleistocene and Dicerorhinina - forms ( with the exception of Coelodonta ); However summarized Guérin Brandtorhinus only as a subgenus of Dicerorhinus. In 1993 Mikael Fortelius published an extensive review of the western Eurasian Stephanorhinus representatives and so helped the names for approval. Today, the name Stephanorhinus is widely accepted, however, partially came the demand on to unite the genus due to a number of similar features with Coelodonta, but this was far refused. In 2012 there was a revision of the osteurasischen species.

Phylogeny

The genus Stephanorhinus first appeared in the Upper Miocene epoch, about 8 million years, the oldest type is Stephanorhinus pikermiensis. Earlier findings come mainly from Greece, as of Pikermi and the island of Samos. Especially in the Pliocene and Pleistocene created numerous ways. Basically can be traced two lines of development in western Eurasia: A ran over Stephanorhinus megarhinus to Stephanorhinus kirchbergensis. The other comprised Stephanorhinus etruscus from which Stephanorhinus jeanvireti, Stephanorinus hundsheimensis and finally Stephanorhinus hemitoechus descended, but the process has not yet been clarified in detail. Especially in Central and Upper Pleistocene, with its highly fluctuating climatic phases developed two highly specialized species, on the one hand the forest rhino, on the other hand, the steppe rhinoceros. While most species had already disappeared into the early Middle Pleistocene, survived the forest rhino until the beginning of the late Pleistocene, while the steppe rhino may die out until the beginning of the Holocene. A very late evidence comes here from La Ventana in Spain.