Embolotherium

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Embolotherium
Skull of Embolotherium Andrewsi in the American Museum of Natural History.

Skull of Embolotherium Andrewsi in the American Museum of Natural History .

Temporal occurrence
Upper Eocene
40.5 to 34 million years
Locations
Systematics
Higher mammals (Eutheria)
Laurasiatheria
Unpaired ungulate (Perissodactyla)
Hippomorpha
Brontotheriidae
Embolotherium
Scientific name
Embolotherium
Osborn , 1929

Embolotherium is an extinct mammal from the fossil family of Brontotheria , whichbelongs tothe order of the odd-toed ungulate . It was one of the largest representatives of the Brontotherien, fossils were found in Mongolia and in the Ulan Gochu Formation in Inner Mongolia , whichdateto the late Eocene 40 to 34 million years ago, but mostly only skulls were found. The genus was described by Henry Fairfield Osborn in 1929.

features

Embolotherium was one of the largest representatives of the Brontotheria and reached dimensions comparable to those of its relatives Megacerops and Gnathotitan . All three genera were comparable in their dimensions to today's largest rhinos , at least for Megacerops a weight of around 2 t is given. Probably had embolotherium probably similar to other modern Brontotherien a robust body, but the Brontotherien genus is widely known only skull finds. This reached a length of 78 to 85 cm, measured from the middle jawbone to the joint ends of the occiput , and from the tip of the horn it was even 103 to 105 cm long. The cheekbones had a clearly spreading shape, similar to numerous North American Brontotheria, but partly ran parallel to each other and were also massive. The occiput was typical for Brontotheria strongly drawn back and therefore acute-angled, in addition very broad and angled when viewed from above. As a result, the forehead line was clearly saddled, as with his relatives. The distinctive horn was formed analogously to the other, horn-bearing brontotheria from the extensions or outgrowths of the front part of the frontal bone , which was located above the nasal bone , so did not consist only of the nasal bone itself, as originally assumed. It started above the orbit - this in turn lay above the second molar - and protruded obliquely at an angle of about 45 ° or more steeply upwards. It widened towards the upper end and acted like a ram; in total it reached a length of around 70 cm. The outer edges were usually significantly thickened and consisted of solid bones, but had numerous cavities inside, the top was convex, the bottom concave. In addition, there was a deep constriction on the underside, which represents the nasal canal. At the base of the horn, the very short middle jawbone began, making the rostrum rather short. The interior of the nose was nevertheless very large and extended to the third premolar , and sometimes beyond.

The lower jaw was built relatively gracefully and reached a length of 60 to 69 cm, but the symphysis was wide and reached to the anterior molar . Thus the opposite early mammals not reduced dentition consisted of the complete tooth sequence and had the following dental formula of: . The incisors all had a small, spherical shape and were not closed, the canine was only slightly larger and irregularly shaped. The entire front dentition had a semicircular arrangement, the rear dentition had a large diastema with an extension of up to 7 cm. The premolars were rather small, but increased in size towards the back, and were rectangular in shape. The molars, on the other hand, were massive and large, the rearmost one was additionally elongated and partly over 11 cm long. They had two small enamel cusps on the surface of their chewing, which made them appear bunoselenodont . The upper molars still had a W-shaped enamel course of the ectolpph , a constriction between two clearly protruding enamel loops ( metastylid and parastylid ). The molars were generally low-crowned ( brachyodont ).

Finds of the body skeleton are also available, but they have not yet been examined and described in detail. Above all, the first cervical vertebra ( atlas ), parts of the forelegs such as the ulna , the thigh bone , the kneecap and a large number of hand and foot bones have come down to us. The finds point to a very powerfully built animal that resembled Megacerops from North America in terms of physique .

Paleobiology

Embolotherium andrewsi , artist's impression

Little is known about the way of life. There is a dimorphism between the two sexes in the area of ​​the horn, which in male animals also has small bony elevations on the top of the ram. Different tooth characteristics, especially on the canines, which are typically assessed as gender differences in other Brontotherias, are not known. It is unclear whether the animals lived in herds or in closer social associations. The low-crowned molars suggest a food specialization in soft plant-based food ( browsing ), which, due to the low head posture resulting from the elongated occiput, was probably mainly taken up from the ground. However, based on the extreme body mass, a mixed vegetable diet cannot be ruled out.

Originally, the head of Embolotherium was reconstructed analogous to today's rhinos with an ascending and free-standing horn, whereby the nostrils were relatively low and just above the median jawbone based on what was then assumed to be the thin skin covering of the horn. Recent studies have shown that the expansion of the nasal bone and the course of the nasal canal to the end of the horn suggest that the nasal cavity was much more extensive and that the entire anterior skull including the horn was covered by thick soft tissue . The upper lip of Embolotherium must have had an extent not known in modern mammals and it occupied the frontal area of ​​the face. According to this reconstruction, the nostrils were probably significantly higher - how high, however, is unknown - and, due to the soft tissue cover, they were clearly in front of the median jawbone. In Embolotherium, as in the other Brontotheria, the horn consisted of the nasal bone interspersed with individual bone cavities and consisting of cancellous bone substance and was covered by anterior outgrowths of the frontal bone; it was much better protected by being embedded in dense soft tissue, since bony horns are more unstable than those of today's mammals from horny substance or fused keratin . What the horn was used for is unknown; it is sometimes assumed that it was mainly used in males for showing off and only rarely in fights. These, if they did take place, then possibly consisted of pressure or sliding competitions rather than battles of poking and ramming.

Fossil finds

Finds of Embolotherium are only known from northern East Asia and are largely from the Chinese autonomous region of Inner Mongolia and Mongolia . The Ulan Gochu formation in the Shara Murun region in Inner Mongolia is outstanding . The first finds were discovered here in 1928, which include the remains of 14 individuals in the form of several complete or fragmented skulls, including the holotype of the genus (specimen number AMNH 26001). Even later, further fossils were recovered from this rich geological layer. Additional find material comes from the Baron-Sog formation with skull parts and lower jaw fragments , while in the Shara-Murun formation only individual remains of the lower jaw came to light. Both are in the same region, but stratigraphically a little younger than the Ulan Gochu Formation. In addition, previously undescribed postcranial skeletal material was recovered from both formations . A single, 74 cm long skull came to light in red-clay deposits near Alxa Zuoqi in the Ningxia region . Again very numerous are fossils from the Ergilin-Dzo formation in the eastern Gobi in Mongolia. These include skulls of various ages, but also individual molars.

Systematics

Internal systematics of the Embolotheriita according to Averianov et al. 2018
  Embolotheriita  


 Aktautitan


   

 Pollyosbornia


   

 Gnathotitan




   


 Brachydiastematherium


   

 Metatitanium



   

 Pygmy Titan


   

 Maobron tops


   

 Nasamplus


   

 Protembolotherium


   

 Embolotherium








Template: Klade / Maintenance / Style

Embolotherium belongs to the family of Brontotheriidae (originally Titanotheriidae), an extinct group of mammals, which also includes Megacerops . The family is viewed as distant relatives of today's horses because of the dental structure . Within the Brontotheriidae, Embolotherium belongs to the subfamily of the Brontotheriinae and to the intermediate tribus of the Embolotheriita. This was originally introduced by Henry Fairfield Osborn in 1929 as a subfamily of the Embolotheriinae only for Embolotherium because of the supposedly different structure of the horn from other Brontotheri forms. In 2008, however, Matthew C. Mihlbachler moved this to the level of the intermediate tribus. Today the Embolotheriita with Aktautitan , Metatitan and Protembolotherium include further genera, which however had less massive horns. Opposite the Embolotheriita are the Brontotheriita, which mostly include North American representatives such as Megacerops . These are characterized by a pair of horns.

A dozen species of Embolotherium were originally described, two of which are now recognized:

  • E. andrewsi Osborn , 1929
  • E. grangeri Osborn , 1929

In his first description of Embolotherium in 1929, Osborn differentiated an additional third species, E. loucksii , but this is identical to E. grangeri , as is E. ultimatum introduced by Walter W. Granger , which is a synonym of E. andrewsi . The genus Titanodectes named by Granger is also invalid, as the determination in relation to young animals of Embolotherium was made with incomplete dentition. The first fossils of this genus of Brontotheria were discovered in 1928 during the Fifth Central Asiatic Expedition of the American Museum of Natural History , led by Roy Chapman Andrews and Walter W. Granger . The embolotherium is of Greek origin and consists of the words εμβωλή ( embolê "battering ram") and θήριον ( thêrion "animal") and refers to the particularly large formation of the bony horns.

literature

  • Henry Fairfield Osborn: Embolotherium, called nov., Of the Ulan Gochu, Mongolia. In: American Museum Novitates 353, 1929, pp. 1–20 ( [2] )
  • Donald R. Prothero and Robert M. Schoch: Horns, tusks, and flippers. The evolution of hoofed mammals. Johns Hopkins University Press, Baltimore, 2003, ISBN 0-8018-7135-2 (pp. 229-239)

Individual evidence

  1. ↑ Alessandro Zanazzi and Matthew J. Kohn: Ecology and physiology of White River mammals based on stable isotope ratios of teeth. In: Palaeogeography, Palaeoclimatology, Palaeoecology 257, 2008, pp. 22-37
  2. ↑ a b c d Henry Fairfield Osborn: Embolotherium, gen. Nov., Of the Ulan Gochu, Mongolia. In: American Museum Novitates 353, 1929, pp. 1–20 ( [1] )
  3. ^ A b Matthew C. Mihlbachler and Nikos Solounias Niko: Anatomy and Evolution of the Bizarre “Battering Ram” of the Brontothere, Embolotherium (Mammalia, Perissodactyla). In: Journal of Morphology Special Issue : Seventh International Congress of Vertebrate Morphology, Boca Raton, Florida, July 27 to August 1, 2004. 260 (3), 2004, pp. 274–342 (313)
  4. ↑ a b c d e f g Matthew C. Mihlbachler: Species taxonomy, phylogeny, and biogeography of the Brontotheriidae (Mammalia: Perissodactyla). In: Bulletin of the American Museum of Natural History 311, 2008, ISSN  0003-0090 , pp. 1-475
  5. ↑ a b c Wang Ban Yue: A Skull of Embolotherium (Perissodactyla, Mammalia) from Erden Obo, Nei Mongol, China. In: Vertebrata Palasiatica 38 (3), 2000, pp. 237-240
  6. ^ A b Granger, Walter: A revision of the Mongolian titanotheres. In: Bulletin of the American Museum of Natural History 80, 1943, pp. 349-389
  7. ↑ a b Benjamin McLaughin, Matthew C. Mihlbachler and Mick Ellison: The postcranial skeleton of embolotherium (brontotheriidae) from the Middle and Late Eocne of Central Asia. In: Journal of Vertebrate Paleontology 30 (suppl.), 2010, pp. 132A-133A.
  8. ^ Matthew C. Mihlbachler: A New Uintan Horned Brontothere from Wyoming and the Evolution of Canine Size and Sexual Dimorphism in the Brontotheriidae (Perissodactyla: Mammalia). In: Journal of Vertebrate Paleontology 31 (1), 2011, pp. 202-214
  9. ↑ Donald R. Prothero and Robert M. Schoch: Horns, tusks, and flippers. The evolution of hoofed mammals. Johns Hopkins University Press, Baltimore, 2003, ISBN 0-8018-7135-2 (pp. 229-239)
  10. ^ Qi Tao: An Early Oligocene Mammalian fauna of Ningxia. In: Vertebrata Palasiatica 13 (4), 1975, pp. 217-224
  11. ↑ Demberelyin Dashzeveg: A new Hyracodontid (Perissodactyla, Rhinocerotoidea) from the Ergilin Dzo formation (Oligocene Quarry 1) in Dzamyn Ude, Eastern Gobi Desert, Mongolia. In: American Museum Novitates 3178, 1996, pp. 1-12
  12. ↑ Alexander Averianov, Igor Danilov, Wen Chen and Jianhua Jin: A new brontothere from the Eocene of South China. In: Acta Palaeontologica Polonica 63. 2018 doi: 10.4202 / app.00431.2017

Web links

Commons : Embolotherium  - collection of images, videos and audio files