Chilotherium

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Chilotherium
Skeletal reconstruction of Chilotherium in the Hong Kong Science Museum

Skeletal reconstruction of Chilotherium in the Hong Kong Science Museum

Temporal occurrence
Upper Miocene to Lower Pliocene
11.2 to 4.7 million years
Locations
  • Asia
  • Southeast Europe
Systematics
Higher mammals (Eutheria)
Laurasiatheria
Unpaired ungulate (Perissodactyla)
Rhinocerotoidea
Rhinoceros (Rhinocerotidae)
Chilotherium
Scientific name
Chilotherium
Ringström , 1924

Chilotherium is an extinct genus of rhinos and lived in the Upper Miocene 11 to almost 5 million years ago. It was common in Asia and Southeast Europe. Characteristic features were the short limbs and the corpulent body. The genus belonged to a group of rhino representatives that did not show any horn formations on the skull. Their anatomy with short legs but also the teeth morphology characterized chilotherium than specialized grazers, who lived in open landscapes. Due to climate changes at the beginning of the Pliocene , the genus died out.

features

Chilotherium comprised medium-sized to large representatives of the rhinos , which had a strong, corpulent, rather cylindrical body with very short but stocky legs. The short legs meant that the body was very low and the stomach was only a little above the ground. Depending on the species, the weight was between 1 and 2.5 t.

Skull of Chilotherium

The skull of Chilotherium was 39 to 54 cm long. The skull was much wider and flatter than the closely related Aceratherium and the occiput was characteristic. This was more rectangular in shape and had an only weakly developed occipital bulge with a slight constriction in the middle. The nasal bone was strikingly straight and wide, the edges bent slightly downwards on the sides. Overall, it was relatively weak and had no surface structures that would suggest the presence of a horn. The forehead line had a noticeable saddle due to the split occiput. Between nose and upper jaw, and the intermaxillary bone is a long nasal cavity was located.

The lower jaw was wedge-shaped and strongly built. It reached a length of 34 to 45 cm. The symphysis had a strong structure and extended to the third premolar . It was also widespread in the front area, so that it had a shovel-like appearance. The bite was significantly reduced and had the following dental formula: . The front set of teeth consisted of only the two lower incisors (I2). These were clearly elongated like a dagger and protruded forward at an angle, swerving to the side. In larger species, the incisors could have a length of up to 12 cm. Some representatives of Chilotherium also had the inner incisors in the lower jaw (I1), but markedly reduced. There was a wide diastema to the subsequent posterior dentition . The premolars and molars were very high crowned ( hypsodontal ), with a high proportion of dental cement and clearly tortuous enamel folds . In addition, the premolars were completely molarized and, like them, had a bilophodontic structure with two transverse enamel ridges.

The postcranial skeleton has survived less often, but the limbs have been completely found several times. These were significantly shortened and very robust and thus differed from those of the closely related genus Aceratherium with its much slimmer long bones. The humerus was up to 33 cm long, as was the triangular cubit in cross-section . The spoke laterally showed significant narrowing and was a maximum of 28 cm long. The longest tubular bone was the thigh bone with 39 cm, which also showed compression on the sides. The tibia and fibula were 28 and 23 cm long, respectively. The limbs each ended in three toes, of which the central ray was the strongest. The metapodia reached 12 cm in length on the forefoot and 10 cm in length on the hind foot. The lateral toe rays stood obliquely, much wider than with Aceratherium , and were also directed somewhat backwards.

Locations

Finds of Chilotherium are relatively common, but mostly isolated skulls, lower jaws or teeth, postcranial skeletal elements or even more complete skeletons are rather rare. The rhinoceros genus appeared very frequently in East Asia , where it was one of the dominant herbivores within the Hipparion fauna in the late Miocene . Extensive finds come from the Linxia Basin in the Chinese province of Gansu , where three species occurred with Ch. Primigenius , Ch. Wimani and Ch. Anderssoni . The most common finds are from Ch. Wimani , of which almost 200 individuals come from a red-tinted layer in the Upper Miocene Liushu Formation . Other outstanding skull finds of the species Ch. Anderssoni are known from the Siziwang banner in Inner Mongolia , also China, as well as finds from Fugu in the Shaanxi province .

Significant finds also came to light in South Asia , where the species Ch. Persiae and Ch. Intermedium occurred in the Siwaliks in Pakistan and India . In various deposits, such as the Chinji , Nagri and Dhok-Pathan Formations , all of which are to be placed in the Upper Miocene, numerous remains were found, which largely include isolated teeth and fragments of the lower jaw, some of which are in excellent condition.

Four species are known from south-east Europe , where they largely inhabited the Mediterranean region. The species Ch. Samium , Ch. Kiliasi , Ch. Kowalevskii and Ch. Schlosseri have been proven . Significant finds come from Greece , from the island of Samos and from Macedonia , where several individual skulls are present. Other significant finds have been reported from Bulgaria .

Paleobiology

In certain species of the genus Chilotherium , a sexual dimorphism that can be diagnosed more rarely in fossil rhinoceros can be determined based on the features of the skull and teeth . Bulls of the species Ch. Wimani had significantly larger lower jaw incisors , which not only exceeded those of the cows by twice the length, but were also markedly steeper than those of the female representatives. The measured values ​​reached a maximum of 12 in males and 7 cm in females. These values ​​do not overlap between the two sexes. There are also clear differences between the sexes in the robustness of the symphysis.

The high-crowned teeth with a high proportion of dental cement and the curved enamel lines are a characteristic feature of the fact that the representatives of Chilotherium consumed hard, silicic acid-containing grasses ( grazing ). This is also indicated by the grinding pattern on the teeth that were often chewed off, which were more horizontal and not trough-like like those of herbivores specializing in soft vegetable food ( browsing ). The typical structure of the teeth counteracted excessive abrasion of the tooth substance. The specialization in hard vegetable food goes hand in hand with the climate changes and the spread of the steppes in the late Miocene . The short legs represent an adaptation to life in such open landscapes. Often there are traces on the elongated incisors of Chilotherium , which suggest that the Chilotherium , similar to today's Asian rhinos with existing front dentition, for defense in the territorial - or use the fight for dominance. In some cases, pathologies in the dentition in the form of rotated or additionally formed teeth can also be detected.

The analysis of the almost 200 individuals of Chilotherium from the Liushu Formation in the Linxia Basin revealed an astonishingly high proportion of vigorously adult animals between the ages of 14 and 32, which make up over two thirds of all Chilotherium finds, while young and old animals are rare are. Since the animals that originally lived on the shore of a lake all died of natural causes and never fell victim to a catastrophe, it is unclear why so many adult animals are preserved in the fossil record. Little is known about the natural enemies of Chilotherium ; due to the size of the animals, it can be assumed that, like today's rhinos, it was rarely attacked by predators . A skull from the Linxia Basin has scarred structures considered again healed bite wounds and a confrontation with a large predator , possibly with the hyenas here also demonstrated similar and up to 380 kg Dinocrocuta be returned.

Systematics

Internal systematics of the Aceratheriini according to Sun et al. 2018
  Aceratheriini 


 Hoploaceratherium


   

 Aceratherium



   

 Plesiaceratherium


   

 Subchilotherium


   

 Acerorhinus


   

 Shansirhinus


   

 Chilotherium







Template: Klade / Maintenance / Style

Chilotherium is a member of the rhinoceros family (Rhinocerotidae) and belongs to the subfamily Aceratheriinae within the group . Within this he forms part of the tribe Aceratheriini , which the Teleoceratini face. The closest related genera of Chilotherium are Aceratherium and Alicornops . The Aceratheriini are generally characterized by the absence of horns, even if some genera had a very small horn. They are also characterized by short legs and the associated clumsy gait. The shortening of the legs and the resulting low body and head position is probably connected with the conversion of this group of rhinos to grass forage, which enabled the animals to reach the ground to eat. In contrast to the more modern Rhinocerotinae , to which today's rhinos also belong, they did not develop an elongated occiput when specializing in grass forage, which causes a very low head posture as with the white rhinoceros ( Ceratotherium simum ), but instead kept the skull in a more horizontal position.

In total, more than 30 different types of Chilotherium have been described over the years , twelve of which are recognized today. There are also several sub-genera which include Chilotherium , Eochilotherium and Subchilotherium .

  • Ch. anderssoni Ringström , 1924
  • Ch.haberi ( locksmith , 1903)
  • Ch. Intermedium ( Lydekker , 1884)
  • Ch. Kiliasi ( Geraads & Koufos , 1990)
  • Ch.kowalevskii ( Pavlov , 1913)
  • Ch.licenti Sun , Li & Deng , 2018
  • Ch.persiae ( Pohlig , 1885)
  • Ch.primigenius Deng , 2006
  • Ch. Pygmaeum Ringström , 1927
  • Ch. Samium ( Weber , 1905)
  • Ch. Schlosseri ( Weber , 1905)
  • Ch.Wimani Ringström , 1924
  • Ch.xizangensis Ji , Xu & Huang , 1980

The genus Chilotherium was first described by Torsten Ringström in 1924 using finds from northern China . Several representatives of Chilotherium had previously been presented, but most of them had been classified in the related genus Aceratherium or in the modern genus Rhinoceros . A last major revision of Chilotherium was made in 2006. The form Ch. Orlovi from Kazakhstan , which is closely related to the species Ch. Schlosseri , was not taken into account, while Chilotherium finds described from Africa must be assigned to a different genus of rhinoceros due to different skull characteristics.

Tribal history

Chilotherium appeared for the first time at the beginning of the Upper Miocene around 11 million years ago in East Asia, the oldest representative is the relatively small and primitive Ch. Primigenius from the Liushu formation in the Linxia Basin. The genus may have appeared 15 million years ago, but these individual finds from the northern Chinese regions of Xinjiang and Hebei cannot be assigned with certainty. Subsequently, the rhinoceros representative spread over large parts of Asia and also increased significantly in body size. It first appeared in south-eastern Europe 9 million years ago. The species occurring here are usually very large, with the youngest representative, Ch. Schlosseri, not only being the largest species, but also having the highest tooth crowns. About 5 million years ago, in the beginning of the Pliocene , Chilotherium died out as a result of climate changes leading to cooler climatic conditions.

Individual evidence

  1. ↑ a b c d e Denis Geraads and Nikolai Spassov: Rhinocerotidae (Mammalia) from the Late Miocene of Bulgaria. Palaeontographica A, 287, 2009, pp. 99-122
  2. ↑ Esperanza Cerdeño: Diversity and evolutionary trends of the the family Rhinocerotidae (Perissodactyla). Palaeo 141, 1998, pp. 13-34
  3. ↑ a b c Deng Tao: New material of Chilotherium wimani (Perissodactyla, Rhinocerotidae) from the Late Miocene of Fugu, Shaanxi. Vertebrata Palasiatica 39 (2), 2001, pp. 129-138
  4. ↑ a b c d 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
  5. ↑ 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
  6. ↑ a b Chen Shaokun, Deng Tao, Hou Sukuan, Shi Qinqin and Pang Libo: Sexual dimorphism in perissodactyl rhinocerotid Chilotherium wimani from the late Miocene of the Linxia Basin (Gansu, China). Acta Palaeontologica Polonica 55 (4), 2010, pp. 587-597
  7. ↑ a b Abdul Majid Khan, Muhammad Akbar Khan, Umar Farooq, Muhammad Akhtar and Ajesha Abdul Majeed: New remains of Chilotherium intermedium from the Chinji Formation of the Siwaliks. Punjab University Journal of Zoology 21 (1-2), 2006, pp. 59-65
  8. ↑ Deng Tao: Limb bones of Chilotherium wimani (Perissodactyla, Rhinocerotidae) from the Late Miocene of the Linxia Basin in Gansu, China. Vertebrata Palasiatica 40 (4), 2002, pp. 305-316
  9. ↑ a b Liang Zhong and Deng Tao: Age structure and habitat of the Rhinoceros Chilotherium during the Late Miocene in the Linxia Basin, Gansu, China. Vertebrata Palasiatica 43 (3), 2005, pp. 319-230
  10. ↑ Deng Tao, Liang Zhong, Wang Shi-Qi, Hou Su-Kuan and Li Qiang: Discovery of a Late Miocene mammalian fauna from Siziwang Banner, Inner Mongolia, and its paleozoogeographical significance. Chinese Science Bulletin 56 (6), 2011, pp. 526-534
  11. ↑ Mohammad Akbar Khan, M. Iqbal, Muhammad Akhtar, Abdul Majid Khan and Ajesha Abdul Majeed: Some new fossil remains of Chilotherium sp. from the Dhok Pathan Formation of the Siwaliks. Journal of Animal & Plant Sciences 18 (4), 2008, pp. 155-157
  12. ↑ a b Abdul Majid Khan, Esperanza Cerdeño, Muhammad Akbar Khan, Muhammad Akhtar and Muhammad Ali: Chilotherium intermedium (Rhinocerotidae: Mammalia) From the Siwaliks of Pakistan: Systematic Implications. Pakistan Journal of Zoology 43 (4), 2011, pp. 651-663.
  13. ^ Max Wilhelm Carl Weber: About tertiary rhinocerotids from the island of Samos. II. Bulletin de la Societe Imperiale Naturalistes de Moscou NS 18, 1905, pp. 344-363
  14. ↑ Denis Geraads and George Koufos: Upper Miocene Rhinocerotidae (Mammalia) from Pentalophos-1, Macedonia, Greece. Palaeontographica A 210 (4/6), 1990, pp 151-168
  15. ↑ Vlad A. Codrea, Laurenţiu Ursachi, Daniel Bejan and Cristina Fǎrkaș: Early Late Miocene Chilotherium (Perissodactyla, Mammalia) from Pogana (Scythian Platform). Northwestern Journal of Zoology 7 (2), 2011, pp. 184-188
  16. ↑ Chen Shao-Kun, Deng Tao, He Wen and Chen Shan-Qin: A dental pathological deformity of Chilotherium wimami from the Linxia Basin of Gansu, China. Vertebrata Palasiatica 49 (2), 2011, pp. 223-228
  17. ↑ a b c Deng Tao and Tseng Zhijie J: Osteological evidence for predatory behavior of the giant percrocutid (Dinocrocuta gigantea) as an active hunter. Chinese Science Bulletin 55 (17), 2010, pp. 1790-1794
  18. ↑ a b Sun Dan-Hui, Li Yu and Deng Tao: A new species of Chilotherium (Perissodactyla, Rhinocerotidae) from the Late Miocene of Qingyang, Gansu, China. Vertebrata Palasiatica, 2018 doi: 10.19615 / j.cnki.1000-3118.180109
  19. ↑ 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.
  20. ↑ Qiu Zhanxiang and Yan Defa: A horned Chilotherium skull from Yushe, Shansi. Vertebrata Palasiatica 20 (2), 1982, pp. 123-132
  21. ↑ Болат У. Байшашов: Новый вид носорога рода Chilotherium из Павлодара. In: Фауна позвоночных и флора Мезозоя и Кайнозоя северо-востока и юго Казахстана. Alma-Ata, 1982, pp. 72-83
  22. ↑ Denis Geraads: Rhinocerotidae. In: L. Werdelin and DJ Sanders (eds.): Cenozoic Mammals of Africa. Berkeley, 2010, pp. 669-683
  23. ↑ Deng Tao: Evolution of Chinese Neogene Rhinocerotidae and Its Response to Climatic Variations. Acta Geologica Sinica 76 (2), 2002, pp. 139-145