Aceratherium

Maxilla of Aceratherium

• Asia
• Europe

Aceratherium is an extinct genus of rhinoceros that lived mainly from Lower to Upper Miocene to the beginning of the millions against 23-7 years in Europe and Asia. It is characterized by slender and rather short limbs, the main feature of which is but a missing or very small -trained horn. The formation of the teeth suggests a specialized herbivore with preference softer vegetable diet.

Features

Aceratherium includes medium to large representatives of the rhinos. Individual members of this genus reached a head -body length of about 230 cm with a shoulder height of 100 to 120 cm. This Aceratherium was more in the size range of modern Sumatran rhino ( Dicerorhinus sumatrensis ), the smallest extant Nashornart. The weight is given for the early members of Aceratherium around 1 t, but later were significantly heavier. The representatives were characterized by a slender and less robust physique.

The skull was about 45 to 58 cm long and was narrow and high. The occiput had a right angle and short form. The nose showed a straight and short course and owned partly a small roughened surface on the tip of the nose as a starting point of a very small horn. In addition, the nasal bone was far above the means jawbone and was not associated with this. This created a very big nose interior with only a short distance from the eye sockets. The front line between the occipital and nasal bone was mostly straightforward in design, but partly they had over the eyes a slight hump on.

The 40 to 49 cm long lower jaw was built narrow but strong and had a well to moderately narrow symphysis, which lasted until the penultimate or last premolar. The body of the mandible reached below the last molar tooth has a height of just over 8 cm. The number of teeth was only slightly reduced, especially in anterior teeth. The dental formula for an adult animal was:. The lower outer incisor (I2 ) had a dagger -like sharp and clear curved shape and was able to more than 3 cm long, with obliquely he stood up, the rest were designed chisel -like. At the rear dentition was a medium-sized diastema. The molars had low crown ( brachyodont ). The premolars were little molarisiert, ie their appearance differed from that of the molars still significantly. However demonstrated by broadening the Kauoberflächen already tendencies to greater Molarisierung. The largest tooth in the dentition was the second molar, which reached summarizes 6 cm in length.

The spinal column was made up of seven cervical, 17 thoracic, four lumbar, five sacral and 21 caudal vertebrae, where the number is seen in the latter as a minimum. The limbs were reduced some, but not as greatly reduced as were the later Chilotherium. The humerus was up to 30 cm long, a cubit to 33 cm. Front legs ending in four toes, wherein the central ray ( metacarpal III) up to 12 cm in length was formed at the most, as in all odd-toed ungulates. The laterally accreting toes were slender and stood off to the side. The occurring at the forefoot fourth toe ( metacarpal V), however, showed a significantly reduced length, which varied but within the genus Aceratherium. The four-toed ( tetradactylen ) front feet point to the position urtümlichere this rhino group compared with the related Chilotherium. The femur could reach a length of 37 cm, tibia of 28 cm. The hind legs ended as in today's rhinos in three toes, too, the average beam ( metatarsus III ) with 10 cm length was most strongly shaped.

Locations

Aceratherium among the most common rhinoceros remains from the Miocene in Eurasia, in this rhino species in East Asia may not occur. Are usually found only some fragments of bone or tooth remnants. Two very well-preserved, nearly complete skeletons are from the volcanic area Höwenegg in southern Baden -Württemberg, which were found in the 1950s. Further finds in Germany are known inter alia from Dorn Durkheim in Hesse and Steinheim an der Murr in Baden- Württemberg. From Austria individual skeletal elements from Atzeldorf were reported during are described from the Czech Republic remains of Tuchořice. Important are especially finds from Spain, which include both individual tooth radicals and more or less complete skeletal remains. Numerous findings are drawn from around Madrid and Guadalajara. Extremely important are also finds from the Dhok Pathan - formation in the Siwaliks of Pakistan. A complete skull with associated mandible could be discovered in Tha Chang in the Thai province of Nakhon Ratchasima, which is also one of the recent finds of Aceratherium.

Paleobiology

The slim, but relatively short legs are an adaptation to more open woodlands, however, did not allow a persistent locomotion. The low tooth crowns give indications of a preferred soft plant food like leaves or twigs as a food source. However, this was not incorporated into the soil, since the head was worn significantly horizontally due to its structure and the comparatively to Chilotherium long legs could reach the ground harder. At the mouth a highly mobile top upper lip was formed possibly as in today's leaf-eating rhino, which was probably much more mobile due to the lack or very small horn. The horizontal restraint brought the lower incisors in a frontal position, so that they could optionally be used as a weapon.

System

Earlier rhinos

Molassitherium

Mesaceratherium

Pleuroceros

Protaceratherium

Plesiaceratherium

Alicornops

Aceratherium

Hoploaceratherium

Teleoceratini

The genus belongs to the subfamily within the rhinos of Aceratheriinae, which is a precursor of the modern Rhinocerotinae with today's rhinos and which can be traced back to the Oligocene 32 million years. Characterized they are by the straight running, but weak nasal bone, which typically has no or only poorly developed attachment points for horns, and significantly shortened limbs. Within the Aceratheriinae it belongs to the tribe Aceratheriini, which also includes the closely related Chilotherium is provided. But the latter is much further-developed and has, along with a more reduced set of teeth also significantly shorter limbs with only three toes ( tridactyl ) on the front legs on. The sister taxon of Aceratheriini represent the Teleoceratini. with Teleoceras from the late Miocene of North America and occurring in Eurasia huge Brachypotherium.

There have been described several types of Aceratherium recognized today are two:

• A. incisive Cuvier, 1822
• A. porpani Deng, Hanta & Jintasakul, 2013

. Controversial is the independence of the species A. depereti Borissiak, 1927 Assuming that Alicornops is to be regarded as a subgenus of Aceratherium, as it was called for in 1979 by Claude Guérin and Léonard Ginsburg, the following species have yet to be counted added:

• A. simorrense Lartet & Laurillard, 1848
• A. pauliacense Richard, 1937

This spread in the lower and Middle Miocene representatives show little differences in tooth structure, with the exception of some cases significantly longer lower second incisor. They are also characterized by a largely narrower skull with clear indications on a small Nasalhorn.

The multi- described mainly from the Siwaliks in Pakistan Aceratherium species have been partly evaluated differently. 1910, introduced by Guy E. Pilgrim A. bugtiense has long been recognized as complying with the rhino -like Paraceratherium while A. recently the genus was Pleuroceros blanfordi assigned. Other species such as A. described Brachypotherium perimense are now assigned, while the once East Asian forms (A. zernowi, A. tsaidamense, A. hipparionum ) are now placed to Acerorhinus. The Southeast European form A. has further been incorporated into Chilotherium kiliasi. Originally viewed as a North American representative species A. acutum is identical to Teleoceras fossiger. The African representatives A. acutirostratum is today Turkanatherium.

The genus name Aceratherium in 1832 by Johann Jakob Kaup ( 1803-1873 ) introduced the basis of several findings from the Grand Ducal Museum in Darmstadt. Already a decade earlier Georges Cuvier had described based on some tooth finds the way Rhinoceros incisive, which is valid under the present name A. incisive as type species. The name Aceratherium ( 'not' a) is composed of the Greek words α, κέρας ( keras " horn " ) and θηρίον ( Therion "animal" ) and refers to the absence or very little horn. In a study in the same year Kaup had already described two more skull finds from Eppelsheim in Hesse as to Cuvier's Rhinoceros incisivus belonging, but noted the lack of Hornasatzstellen and wrote this rhino " would therefore be the only rhino that bears his generic name wrong ".

Phylogeny

Aceratherium occurred (including the subgenus Alicornops ) for the first time 23 million years ago in Europe to the earliest sites Paulhiac heard in France. These representatives were still quite small. In Germany, the rhino species is first detected 13 million years ago and was found among others in Steinheim an der Murr. Throughout its history, the tribal Aceratherium_Vertreter grew. The last time she came to nine million years ago. Among the most recent discoveries in Europe that are to be counted from Mont Redon in France, which are about 9 million years old. Slightly younger with 7 million years is the skull find from Tha Chang in Thailand.