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18.12.2015 18:09 - Encyclopedia Largest prehistoric animals Vol.1 Vertebrates part1 Mammals ch.18 Astrapotherians,Arsinoitheres and Pyrotherium
Автор: valentint Категория: Забавление   
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Astrapotherians (Astrapotheria)
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Astrapotheria is an extinct order of South American and Antarctic hoofed mammals that existed from the Late Paleocene to the Middle Miocene, 59 to 12 million years ago.Astrapotheres were large and rhinoceros-like animals and are certainly one of the most bizarre orders of mammals with an enigmatic evolutionary history.
This taxonomy of this order is not clear, but it may belong to Meridiungulata (along with Notoungulata, Litopterna, Pyrotheria and Xenungulata).In turn, Meridungulata is believed to belong to the extant superorder Laurasiatheria. Some scientists have regarded the astrapotheres (and sometimes the Meridiungulata all together) as members of the clade Atlantogenata. However, recent collogen and mitonchodrial DNA sequence data places at least the notoungulates and litopterns firmly within Laurasiatheria, as a sister group to the perissodactyls.

The largest astrapotherians weight about 3-4 metric tonnes, including the genus Granastrapotherium and some species of Parastrapotherium (P. martiale).


The largest astrapotherian was Hilarcotherium
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Hilarcotherium is an extinct genus of astrapotheriid mammals that lived in South America during the Middle Miocene. The type species is H. castanedaii, found in sediments of the La Victoria Formation, part of the Honda Group in the department of Tolima in Colombia.In 2018, Carrillo et al. described a partial skull and mandible of a second species H. miyou from the Castilletes Formation in the Cocinetas Basin of northern Colombia and estimated the body weight of the animal at 6,465 kilograms (14,253 lb).
The holotype specimen of Hilarcotherium castanedaii is named IGM p881231. This consists of fragments of skull, a partial jaw, the vertebral ramus of a dorsal rib, a complete left humerus and an incisor tooth associated. The skull includes the rostrum area, the palate with the fourth premolar (P4) and the three upper molars (M1-M2-M3) plus part of the zygomatic arch and the braincase, but lacks the upper canines and the top portion of the skull. The premaxilla shows no sign of having teeth, as in other astrapotheres. The jaw missing the incisors, the crown of the fourth premolar and the left mandibular ramus, but has the roots of the teeth of the right side and a broken canine with an oval cross section. It has however the sockets for three incisors on each side of the jaw, which is a plesiomorphic feature, as his other relatives as Xenastrapotherium had two.
Hilarcotherium belongs to the family Astrapotheriidae, the family of advanced astrapotheres characterized by its developed tusks, separated by a diastema of the other teeth, the retracted nasal bones that indicate the presence of a trunk in his snout and the flattened astragalus.Within this group, Hilarcotherium shares with Xenastrapotherium, Uruguaytherium and Granastrapotherium the lower canines that are horizontally inserted into the jaw, in addition to the characteristics of the molars (without labial cingulum, an inner protuberance of the molars), indicating that Hilarcotherium and the others genera already mentioned belongs to the subfamily Uruguaytheriinae, a group that colonized the equatorial region of South America during the Miocene until their extinction in the middle of such period, in contrast with other astrapotheres only known in the south of the continent.



Granastrapotherium
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Granastrapotherium is an extinct genus of ungulate mammals, described from remains found in rocks of the Honda Group in the Tatacoa Desert,in the Colombian departments of Huila and Tolima, at the Miocene fossil site La Venta.
This astrapothere differs from its coeval, the uruguaytheriine astrapotheriid Xenastrapotherium by their larger size, between 2.5 and 3.5 tonnes, with tusks about one meter long, making it one of the largest representatives of Astrapotheria, only surpassed by some species of Parastrapotherium.Other differences include the presence of only one premolar, the lack of incisors in both jaws and the disposition of the canine tooth, which are very large and horizontal, which reminds much less of those of hippos and more of the tusks of some ancient relatives of elephants (such as Palaeomastodon), although the defences in elephants and their relatives are not formed by the canines but the incisors. Similarly, the large nostrils appear extremely withdrawn on the skull, so this creature had to have a larger trunk than other astrapotheres. Most likely, like elephants, this animal used its muscular proboscis together with its tusks to cut leaves off trees and shrubs.

Pyrotherium
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Size: 3,5 m in length, 150 cm in height, 2500 - 3000 kg of weight
Pyrotherium - extinct South American mammals of the superorder hoofed animals that lived in the Eocene and Oligocene. Pyrotherium have convergent similarity with the primitive Proboscidea, which was caused by the similarity of their ecological niches occupied.
Pyrotherium differed massive physique, columnar legs with short and wide toes, as well as a large head with a small trunk. The four upper and two lower incisor teeth, resembling tusks, were issued in advance. These animals reach 3 m in length and 1.5 m tall at the shoulders.
The name, which in Greek means «the fiery beast», was given because of the fact that the first fossils of Pyrotherium were found in sedimentary rocks of volcanic ash.
In comparison with other orders of the South American ungulates, Pyrotheriums were relatively not varied order. Period of their existence is also not particularly long. Pyrotherium kinship with other South American ungulates (Meridiungulata) is currently not clear. The structure of the tarsus does not indicate any obvious relationship with them. Most Pyrotherium’s tarsus is similar to Arsinoitherium’s tarsus, but it is unclear about evidence of relationship of these animals (who are representatives of different orders), or this similarity is dictated by a similar method of movement (it means - convergence).


Arsinoitheres (Arsinoitheriidae)
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Arsinoitheriidae is a family of hoofed mammals belonging to the extinct order Embrithopoda. Remains have been found in the Middle East, Africa, Asia and Romania. When alive, they would have borne a strong but superficial resemblance to modern rhinoceroses; however, they were not closely related to them (or any other perissodactyl), instead being more closely related to hyraxes, elephants, sirenians, and possibly desmostylians (as part of the superorder afrotheria).


The largest arsinoithere was Arsinoitherium giganteum
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When alive, it would have been 1.8 m (5.9 ft) tall at the shoulders, and 3 m (9.8 ft) long. Arsinoitherium is an extinct genus of paenungulate mammal belonging to the extinct order Embrithopoda. It is related to elephants, sirenians, hyraxes and the extinct desmostylians. Arsinoitheres were elephant-like herbivores that lived during the late Eocene and the early Oligocene of northern Africa from 36 to 30 million years ago, in areas of tropical rainforest and at the margin of mangrove swamps. A newly discovered species, Arsinoitherium giganteum, lived in Ethiopia ~27 million years ago.

The generic name Arsinoitherium comes from Queen Arsinoe after whom the Fayum, the region in which the fossils were found, was called during Ptolemaic times, and the Greek: θηρίον (therion), "beast". The species epithet of the type species, A. zitteli, was given to it in honor of the eminent German paleontologist Karl Alfred von Zittel, regarded by some as the pioneer of paleontology in Egypt.
While the Fayum Oasis is the only site where complete skeletons of Arsinoitherium fossils were recovered, remnants of earlier relatives have been found in south-eastern Europe and Mongolia, in the form of jaw fragments. These earlier arsinoitheres have yet to be formally described. The best known (and first described) species is A. zitteli. Another species, A. giganteum, was discovered in the Ethiopian highlands of Chilga in 2003. The fossil teeth, far larger than those of A. zitteli, date back to around 28-27 million years ago The Mongolian material has been named Radinskya yupingae, while the European material has been given the nomen dubium of Crivadiatherium iliescui, and the Turkish material has been named Palaeoamasia kansui (also nomen dubium).
When alive, they would have superficially resembled a rhinoceros. Adults of the species A. zitteli stood around 1.75 m (5 ft 9 in) tall at the shoulders and 3 m (9 ft 10 in) in length. The most noticeable features of Arsinoitherium were a pair of enormous horns above the nose and a second pair of tiny knob-like horns over the eyes. The skeleton is robust and the limbs were columnar, similar to those of elephants; the hips were also elephant-like.
Arsinoitherium had a full complement of 44 teeth, which is the primitive state of placental mammalian dentition, with characteristics suggesting that it was a selective browser.















 

 




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