Aceratherium

from Wikipedia, the free encyclopedia
Aceratherium
Upper jaw of Aceratherium

Upper jaw of Aceratherium

Temporal occurrence
Lower to Upper Miocene ( Aquitanium to Tortonium )
23 to 7 million years
Locations
  • Asia
  • Europe
Systematics
Higher mammals (Eutheria)
Laurasiatheria
Unpaired ungulate (Perissodactyla)
Rhinocerotoidea
Rhinoceros (Rhinocerotidae)
Aceratherium
Scientific name
Aceratherium
Kaup , 1832

Aceratherium is an extinct genus of rhinos that lived mainly from the Lower to the beginning of the Upper Miocene 23 to 7 million years ago in Europe and Asia. It is characterized by slim and quite short limbs, but the main feature is a missing or very small horn. The formation of the teeth suggests a specialized herbivore with a preference for a soft vegetable diet.

features

Live reconstruction of Aceratherium by Heinrich Harder 1920

Aceratherium includes medium to large representatives of the rhinos . Individual members of this genus reached a head-trunk length of around 230 cm with a shoulder height of 100 to 120 cm. Thus Aceratherium was more in the size range of today's Sumatran rhinoceros ( Dicerorhinus sumatrensis ), the smallest recent rhinoceros species. The weight of the early members of Aceratherium is given as around 1 t, but later ones were significantly heavier. The representatives were distinguished by a slim and less robust physique.

The skull was about 45 to 58 cm long and narrow and high. The occiput was rectangular and short in shape. The nasal bone was straight and short and in some cases had a small roughened surface at the tip of the nose as the attachment point of a very small horn. In addition, the nasal bone lay well above the median jawbone and was not connected to it. This created a very large nasal cavity with only a short distance to the eye sockets . The forehead line between the occiput and nasal bones was mostly straight, but sometimes it had a slight hump over the eyes.

The 40 to 49 cm long lower jaw was narrow but strongly built and had a likewise to moderately narrow symphysis , which reached to the penultimate or last premolar . The body of the lower jaw reached a height of a good 8 cm below the last molar. The number of teeth was only slightly reduced, especially in the front dentition. The dental formula for an adult animal was: . The lower outer incisor (I2) had a dagger-like, pointed and clearly curved shape and could be up to 3 cm long, protruding upwards at an angle, the remaining ones were shaped like a chisel. The posterior dentition had a medium-sized diastema . The molars had a low crown ( brachyodont ). The premolars were not very molarized, i.e. their appearance differed significantly from that of the molars . However, widening of the chewing surfaces already showed tendencies towards stronger molarization. The largest tooth in the bite was the second molar, which reached a length of 6 cm.

The spine was composed of seven cervical, 17 thoracic, four lumbar, five sacrum and 21 caudal vertebrae, the number of which is considered to be the minimum in the latter. The limbs were partly shortened, but not as reduced as in the later Chilotherium . The humerus was up to 30 cm long, the ulna up to 33 cm. The forelegs ended in four toes, with the central ray ( metacarpus III) being the strongest, up to 12 cm long, as in all unpaired ungulates . The toes set on the sides were slimmer and protruded to the side. The fourth toe (Metacarpus V) on the forefoot, however, had a significantly reduced length, which, however, varied within the genus Aceratherium . The four-toed ( tetradactyl ) forefeet show the more primitive position of this rhinoceros group compared to the related Chilotherium . The thighbone could reach a length of 37 cm, the shin of 28 cm. As with today's rhinos, the hind legs ended in three toes; here, too, the central ray ( metatarsus III) was most strongly formed with a length of 10 cm.

Locations

Lower jaw of Aceratherium

Aceratherium is one of the most common rhinoceros found in the Miocene in Eurasia, although this rhino genus may not occur in East Asia. As a rule, only individual bone fragments or tooth remnants are found. Two very well-preserved, almost complete skeletons come from the Höwenegg volcanic area in southern Baden-Württemberg and were found in the 1950s. Other finds in Germany are known from Dorn-Dürkheim in Hesse and Steinheim an der Murr in Baden-Württemberg , among others . Individual skeletal elements from Atzeldorf have been reported from Austria , while remains of Tuchořice have been described from the Czech Republic . Finds from Spain , which include both individual tooth fragments and more or less complete skeletal remains, are also significant . Numerous finds come from the area around Madrid and Guadalajara . Finds from the Dhok-Pathan formation in the Siwaliks in Pakistan are also extremely important . A complete skull with associated lower jaw was discovered in Tha Chang in the Thai province of Nakhon Ratchasima , which is also one of the most recent discoveries of Aceratherium .

Paleobiology

The slender, but relatively short legs are an adaptation to the more open forest landscapes, but did not allow sustained locomotion. The low tooth crowns indicate a preferred soft vegetable diet such as leaves or twigs as the basis of nutrition. However, this was not taken up by the ground, as the head was carried clearly horizontally due to its structure and the legs, which were comparatively long to Chilotherium , made it more difficult to reach the ground. As with today's leaf-eating rhinos, a very flexible, pointed upper lip may have been formed on the mouth, which was probably even more mobile due to the missing or only very small horn. The horizontal head position also brought the lower incisors into a frontal position so that they could be used as a weapon if necessary.

Systematics

Internal systematics of the early Eurasian Aceratheriini according to Becker et al. 2013
  Rhinocerotidae  

 previous rhinos 


  Aceratheriinae  

 Mesaceratherium


   

 Pleuroceros


   

 Protaceratherium


   

 Plesiaceratherium


   



 Aceratherium


   

 Hoploaceratherium



   

 Alicornops



   

 Teleoceratini








Template: Klade / Maintenance / Style
Johann Jakob Kaup (1803–1873)

The genus belongs within the rhinoceros to the subfamily of Aceratheriinae , which is a precursor of the more modern Rhinocerotinae with today's rhinos and which can be traced back to the Oligocene 32 million years ago. They are characterized by the straight but weak nasal bone, which typically has no or only slightly developed attachment points for horns, and the clearly shortened limbs. Within the Aceratheriinae it belongs to the tribe Aceratheriini , to which the closely related Chilotherium is placed. The latter, however, is much more developed and, in addition to a more reduced set of teeth, also has significantly shorter limbs with only three toes ( tridactyl ) on the front legs. The sister taxon of the Aceratheriini are the Teleoceratini . with Teleoceras from the late Miocene of North America and the huge Brachypotherium that also occurs in Eurasia .

Several species of Aceratherium have been described, two of which are recognized today:

The independence of the species A. depereti Borissiak , 1927, is controversial. Provided that Alicornops is to be classified as a subgenus of Aceratherium , as was warned in 1979 by Claude Guérin and Léonard Ginsburg, the following species must also be added:

These representatives, which were widespread in the Lower and Middle Miocene, show hardly any differences in the structure of the teeth, with the exception of the sometimes significantly longer lower second incisor. They are also characterized by a largely narrower skull with clear evidence of a small nasal horn.

The Aceratherium species that have been described several times, especially from the Siwaliks in Pakistan , have been assessed differently in some cases. A. bugtiense , introduced by Guy Ellcock Pilgrim in 1910, was recognized early on as conforming to the rhinoceros Paraceratherium , while A. blanfordi was recently assigned to the genus Pleuroceros . Other described species such as A. perimense are now assigned to Brachypotherium , while the former East Asian forms ( A. zernowi , A. tsaidamense , A. hipparionum ) are now assigned to Acerorhinus . The Southeast European form A. kiliasi has also been incorporated into Chilotherium , the Central European form A. kuntneri into Molassitherium . The species A. acutum , originally regarded as a North American representative, is identical to Teleoceras fossiger . The African representative A. acutirostratum belongs to Turkanatherium today .

The genus name Aceratherium was introduced in 1832 by Johann Jakob Kaup (1803–1873) on the basis of several finds from the Grand Ducal Museum in Darmstadt . A decade earlier, Georges Cuvier had already described the species Rhinoceros incisivus , based on some tooth finds , which is considered a type species under the current name A. incisivum . The name Aceratherium is made up of the Greek words α ( a “not”), κέρας ( kéras “horn”) and θηρίον ( thērion “animal”) and refers to the missing or very small horn. In a study in the same year, Kaup had already described two more skull finds from Eppelsheim in Hesse as belonging to Cuvier's Rhinoceros incisivus , but noted the missing horn attachment points and wrote that this rhinoceros "is therefore the only rhinoceros that has its genus name wrongly" .

Tribal history

Aceratherium (including the subgenus Alicornops ) first appeared in Europe 23 million years ago, and Paulhiac in France is one of the oldest sites . These representatives were still quite small. The rhino genus was first recorded in Germany 13 million years ago and was found in Steinheim an der Murr , among other places . In the course of its tribal history , the Aceratherium representatives grew larger and larger. The last time it occurred was nine million years ago. Among the most recent finds in Europe are those from Montredon in France, which are around 9 million years old. The skull find from Tha Chang in Thailand is a little younger, at 7 million years old.

Individual evidence

  1. ↑ a b c d e Esperanza Cerdeño and Begoña Sánchez: Intraspecific variation and evolutionary trends of Alicornops simorrense (Rhinocerotidae) in Spain. The Norwegian Academy of Science and Letters Zoologica Scripta 29 (Oct. 4), 2000, pp. 275-305
  2. ↑ a b c d Kurt Heissig: The early Vallesian vertebrates of Atzelsdorf (Late Miocene, Austria) 11. Rhinocerotidae and Chalicotheriidae (Perissodactyla). Annals of the Natural History Museum in Vienna 111 A, 2009, pp. 619–634
  3. ↑ a b c d e f g Karl Alban Hünermann : Reconstruction of the Aceratherium (Mammalia, Perissodactyla, Rhinocerotidae) from the Young Tertiary from Höwenegg / Hegau (Baden-Württemberg). Journal of Geological Sciences 10 (7), 1982, pp. 929-942
  4. ↑ a b c d e Kurt Heissig: Family Rhinocerotidae. In: Gertrud E. Rössner and Kurt Heissig: The Miocene land mammals of Europe. Munich, 1999, pp. 175-188
  5. ↑ a b c David García Fernández and Esperanza Cerdeño: Nuevos datos sobre Aceratherium incisivum (Rhinocerotidae) del Turoliense de Piera (Barcelona y Concud (Teruel). Butlleti del Center d'Estudis de la Natura del Barcelonas-Nord 4 (3), 1999 , Pp. 279-289
  6. ↑ a b c Kurt Heissig and Oldřich Fejfar: The fossil rhinos (Mammalia, Rhinocerotidae) from the Lower Miocene of Tuchorice in northwestern Bohemia. Sborník Národního Muzea v Praze (Acta Musei Nationalis Pragae series B, Natural History) 63 (1), 2007, pp. 19-64
  7. ↑ a b c d Tao Deng, Rattanaphorn Hanta and Pratueng Jintasakul: A new species of Aceratherium (Rhinocerotidae, Perissodactyla) from the late Miocene of Nakhon Ratchasima, northeastern Thailand. Journal of Vertebrate Paleontology 33 (4), 2013, pp. 977-985
  8. ^ MA Khan, AM Khan, U. Farooq, M. Iqbal and M. Akhtar: Aceratherium from the Dhok Pathan Formation of the Middle Siwaliks, Pakistan. The Journal of Animal & Plant Sciences 19 (1), 2009, pp. 50-53
  9. ↑ a b c Damien Becker, Pierre-Olivier Antoine and Olivier Maridet: A new genus of Rhinocerotidae (Mammalia, Perissodactyla) from the Oligocene of Europe. Journal of Systematic Palaeontology, 2013 doi : 10.1080 / 14772019.2012.699007
  10. ^ A b Donald R. Prothero: The evolution of North American rhinoceroses. Cambridge University Press, 2005
  11. ^ Leonard Ginsburg and Claude Guérin: Sur l'origine et l'extension stratigraphique du petit rhinocerotide miocene Aceratherium (Alicornops) simorrense (Lartet, 1851), nov. subgen. Compte Rendu Sommaire des Seances de la Societe de Geologie de France 3, 1979, pp. 114-116.
  12. ↑ Clive Forster-Cooper: Paraceratherium bugtiense, a new genus of Rhinocerotidae from the Bugti Hills of Baluchistan - preliminary notice. The Annals and Magazine of Natural History 8, 1911, pp. 711-716
  13. ↑ Pierre-Olivier Antoine, Kevin F. Downing, Jean Yves Crochet, Francis Duranthon, Lawrence J. Flynn, Laurent Marivaux, Gregoire Métais, Abdul Rahim Rajpar and Ghazala Roohi: A revision of Aceratherium blanfordi Lydekker, 1884 (Mammalia: Rhinocerotidae) from the Early Miocene of Pakistan: postcranials as a key. Zoological Journal of the Linnean Society, 160, 2010, pp. 139-194
  14. ↑ Zin-Maung-Maung-Thein, Masanaru Takai, Takehisa Tsubamoto, Naoko Egi, Thaung-Htike, Takeshi Nishimura, Maung-Maung and Zaw-Win: A review of fossil rhinoceroses from the Neogene of Myanmar with description of new specimens from the Irrawaddy sediments. Journal of Asian Earth Sciences 37, 2010, pp. 154-165
  15. ↑ Deng Tao: A primitive species of Chilotherium (Perissodactyla, Rhinocerotidae) from the Late Miocene of the Linxia Basin (Gansu, China). Cainozoic Research, 5 (1-2), 2006, pp. 93-102
  16. ↑ Denis Geraads: Rhinocerotidae. In: L. Werdelin and DJ Sanders (eds.): Cenozoic Mammals of Africa. Berkeley, 2010, pp. 669-683
  17. ^ Johann Jakob Kaup: About Rhinoceros incisivus Cuv., And a new kind, Rhinoceros Schleiermacheri. Isis von Oken 25, 1832, pp. 898-904 (900).