Maobron tops
| Maobron tops | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Upper jaw of Maobrontops (holotype) |
||||||||||||
| Temporal occurrence | ||||||||||||
| Upper Eocene | ||||||||||||
| 38 to 33.9 million years | ||||||||||||
| Locations | ||||||||||||
|
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Maobron tops | ||||||||||||
| Averianov , Danilov , Chen & Jin , 2018 | ||||||||||||
Maobrontops is an extinct genus of Brontotherien , a non-existent group of odd- toed ungulates that may becloser tothe Equidae . So far, only a fragmented upper jaw has been found thatcomesfrom southern China and dates to the Upper Eocene around 38 to 33 million years ago. The find refers to a larger representative of the Brontotherien. It is the group's southernmost find in China to date. The genus was introduced in 2018.
features
Maobrontops is a large representative of the Brontotherien, but so far only a fragment of the upper jaw with the preserved rearmost two premolars and the first two molars is available. Based on the tooth sizes, a weight of around 790 kg is concluded, which is significantly less than the known maximum weight of Embolotherium . The upper jaw itself is poorly recorded and does not contain any differential diagnostic features, and the penultimate premolar has only survived in fragments. The last premolar was rectangular and short. On the cheek side there was a thick enamel band that included two prominent humps, the metaconus and the paraconus. There were distinctive ripples on the back of both humps. The tongue side of the tooth, on the other hand, was dominated by the protoconus, which was as high as the other two cusps. The hypoconus, which occurs on the premolars in some other developed Asian Brontotheria, was absent in Maobrontops . Around the tooth, on the tongue side, ran a cingulum, a bulge-like protrusion made of tooth enamel , on which individual smaller bumps were formed. The molars were rectangular to trapezoidal in shape. They had the W-shaped, cheek-side enamel folds that were typical of Brontotheria and connected the meta with the paraconus, whereby the tooth enamel was up to 3 mm thick. The protoconus and the hypoconus protruded on the opposite side of the tongue, but were significantly lower than the other two humps. The former had a conical , the latter a more ripple-like appearance. At the anterior, tongue-side end of the molars there was an additional cusp which, unlike many other Brontotheria, with the exception of some late Asian forms, was relatively large. A cingulum only appeared on the anterior molar on the tongue side. The first molar was 5.6 cm long and 5.7 cm wide, the second was significantly larger at 7.3 cm long and 7.0 cm wide.
Fossil finds
The so far unique find of Maobrontops was discovered in southern China in the Maoming Basin near Maoming in Guangdong Province . Sediments of the Youganwo Formation are exposed there . These consist of individual layers of coal , covered by clay and silt stones , on which a massive package of dark brown deposits containing oil shale follows. The sediment sequence can be interpreted as the remains of a former lake. The age of the deposits was determined magnetostratigraphically and palynologically for a period from the transition of the Middle to the Upper Eocene to the end of the Upper Eocene with absolute ages of about 38 to 33 million years. Most of the fossil record, especially that of vertebrate animals , is stored in the upper reaches of the oil shale. So far, the finds consisted of carp-like fish, various Halsberger turtles , gavials and alligators as well as mammals . The mammals are only documented about a few finds, including, in addition to the evidence of Maobrontops, a skull of a representative of the Amynodontidae (extinct unpaired ungulates in the family of the rhinos ) and a skull of a member of the Nimravidae (extinct saber-toothed predators with closer ties to cats ). The upper jaw of Maobrontops is the southernmost remnant of the Brontotheria found in China.
Systematics
|
Internal systematics of the Embolotheriita according to Averianov et al. 2018
|
Maobrontops is a genus within the extinct family of Brontotheriidae (originally Titanotheriidae) and the order of the odd ungulate . The family is partly classified as a distant kinship group of today's horses due to the dental structure . The Brontotherien were very varied and occurred mainly in the Eocene in North America and Eurasia . Especially late forms such as Megacerops , the gigantic character form of the Brontotherien, reached enormous sizes and are characterized by their bony horns on the nose. Within the Brontotheri, Maobrontops belongs to the subfamily Brontotheriinae and to the tribe of the Brontotheriini. Here it is referred to a group of mainly Asiatic forms, which are distinguished by a distinctive, ram-like horn formation and stand on the level of an intermediate tribus with the designation Embolotheriita, named after the huge type form Embolotherium . The intermediate tribus was originally introduced by Henry Fairfield Osborn in 1929 as a subfamily (Embolotheriinae) only for Embolotherium because of the supposedly different structure of the horn from other Brontotheria forms. In 2008, however, Matthew C. Mihlbachler moved this to the level of the intermediate tribus and assigned it to other forms. Closely related to Maobron tops include Pygmaetitan and Nasamplus .
The first scientific description of Maobrontops was carried out by Alexander Averianov and research colleagues in 2018. The holotype of the genus (specimen number SYSU -M-4) consists of the left upper jaw remnant with the completely preserved row of teeth from the last pre-grinding to the second molar from the Maoming basin in southern China. The name Maobrontops refers on the one hand to the city of Maoming near the place of discovery, on the other hand to the genus Brontops , a synonym for Megacerops . The name Brontops is occasionally used as an addition to the name of Asian Brontotherien. As the only recognized species, Averianov and colleagues established Maobrontops paganus . The specific epithet is derived from the Latin word for "rustic" or "peasant" and alludes to the local people's collection of numerous fossils in the Maoming basin.
With the discovery of Maobrontops , the taxonomic diversity of the Brontotheria in Asia increases. The Embolotheriita as a terminal group of the Asian Brontotheria show a lower number of species in today's southern China than in comparison to northern China, especially Inner Mongolia , it is nevertheless assumed that the group developed and developed there due to the high diversity of the detected forms later spread further. With Pollyosbornia , a representative also reached North American soil.
literature
- Alexander Averianov, Igor Danilov, Wen Chen and Jianhua Jin: A new brontothere from the Eocene of South China. Acta Palaeontologica Polonica 63 (1), 2018; Pp. 189–196 doi: 10.4202 / app.00431.2017
Individual evidence
- ↑ a b c d e f Alexander Averianov, Igor Danilov, Wen Chen and Jianhua Jin: A new brontothere from the Eocene of South China. Acta Palaeontologica Polonica 63 (1), 2018; Pp. 189–196 doi: 10.4202 / app.00431.2017
- ↑ GN Aleksandrova, TM Kodrul and JH Jin: Palynological and Paleobotanical Investigations of Paleogene Sections in the Maoming Basin, South China. Stratigraphy and Geological Correlation 23 (3), 2015, pp. 300-325
- ↑ YX Li, WJ Jiao, ZH Liu, JH Jin, DH Wang, YX He and C. Quan: Terrestrial responses of low-latitude Asia to the Eocene – Oligocene climate transition revealed by integrated chronostratigraphy. Climate of the Past 12, 2016, pp. 255-272
- ↑ Alexander Averianov, Ekaterina Obraztsova, Igor Danilov, Pavel Skutschas and Jianhua Jin: First nimravid skull from Asia. Scientific Reports 6, 2016, p. 25812 doi: 10.1038 / srep25812
- ↑ Alexander Averianov, Igor Danilov, Jianhua Jin and Yingyong Wang: A new amynodontid from the Eocene of South China and phylogeny of Amynodontidae (Perissodactyla: Rhinocerotoidea). Journal of Systematic Palaeontology 15, 2017, pp. 927-945
- ^ Henry Fairfield Osborn: Embolotherium, gen. Nov., Of the Ulan Gochu, Mongolia. American Museum Novitates 353, 1929, pp. 1–20 ( [1] )
- ^ Matthew C. Mihlbachler: Species taxonomy, phylogeny, and biogeography of the Brontotheriidae (Mammalia: Perissodactyla). Bulletin of the American Museum of Natural History 311, 2008, ISSN 0003-0090, pp. 1-475
