Nanotitanops

Nanotitanops
Temporal occurrence
	Middle Eocene
	47.8 to 38 million years
Locations
	East Asia (China);
Systematics
	Higher mammals (Eutheria)
	Laurasiatheria
	Unpaired ungulate (Perissodactyla)
	Hippomorpha
	Brontotheriidae
	Nanotitanops
Scientific name
	Nanotitanops
	Qi & Beard , 1998

Nanotitanops is an extinct representative of the Brontotherien that lived about 40 million years ago in the Middle Eocene in East Asia . The genus is only known for about a dozen tooth finds from a site west of Shanghai , but the fossils represent the smallest representative of the Brontotherien so far. The Brontotherien belong to the unpaired ungulates and produced several gigantic forms, especially in the late Eocene.

features

Nanotitanops is the smallest member of the Brontotheriidae family to date , but it is only known about a dozen isolated teeth of the upper and lower jaw. These include the full number of premolars (P1 to P4) and anterior molars (M1 and M2). Two of these teeth also represent deciduous molars, all others are permanent teeth. The front molars were square or rectangular in shape, except for the first, which was more rounded in shape. This also had a simpler chewing surface design with a single, larger tooth enamel cusp . All other premolars were more clearly molarized and resembled the posterior molars. These had a bilophodontic tooth structure formed by two enamel strips and typical for Brontotherien, the enamel strips were clearly curved. The molars continued to stretch laterally and were therefore significantly larger than the premolars. The length of the first two molars varied from 1.2 to 1.36 cm. Compared to the 5 and 9 cm long front molars of the giant form Embolotherium , one of the largest known members of the Brontotherium, these were extremely small. Even with the Eotitanops, which are very original in phylogeny, they were 1.4 to 2.1 cm in length and larger.

References

The genus Nanotitanops is only known from a single site. It is a sediment- filled karst fissure in a quarry for the extraction of limestone near the village of Shanghuang in the city of Liyang in the south of the Chinese province of Jiangsu, west of Shanghai . In the same karst fissure , remains of Microtitan were also discovered, another very small representative of the Brontotherien. The deposits are generally assigned to the Middle Eocene and, in terms of local stratigraphy, should belong to the Irdinmanhum or the lowest Sharamurunian , i.e. around 40 million years old.

Systematics

The genus Nanotitanops belongs to the family of Brontotheriidae (originally Titanotheriidae), which represent an extinct group of mammals from the order of the odd ungulate . Due to the structure of the rear teeth, the Brontotherien are to be placed in the vicinity of today's horses . Within this mammal family, Nanotitanops of the subfamily of the Brontotheriinae and the tribe of the Brontotheriini are referred to, but here with the addition incertae sedis , since the only sparse fossil material does not allow further or more precise classification. With Nanotitanops the smallest known representative of Brontotherien has been proven. Within the Brontotherien there were several dwarves , as shown by Microtitan or Pygmaetitan . Remarkably, these small forms are found more frequently in Asia , from North America such are so far only known with xylotitanium . Nanotitanops is also smaller than its earliest ancestors, such as Eotitanops and Palaeosyops . The elongated molars and the further developed structure of the chewing surfaces due to their more complex enamel folds suggest, however, that Nanotitanops was not a primitive, but rather a younger member of the Brontotheria family, so the dwarfing must be based on other causes that are not yet known. Possibly the dwarf Brontotherien form their own line within this odd ungulate group.

The first description of Nanotitanops was in 1996 by Qi Tao and K. Christopher Beard on the basis of the tooth finds from Shanghuang. In this first publication, 13 teeth were presented, but a further review showed that a milk premolar should be referred to another odd-toed ungulate. The holotype (copy number IVPP V11032) was referred to as the fourth premolar, but probably represents the first or second molar. The original name was nanotitan , but since the name is already preoccupied by a genus of locusts from the Triassic of Kyrgyzstan , the name was given in 1998 in Nanotitanops changed so that this publication represents the first valid description of the genus. The only recognized species is Nanotitanops shanghuangensis . The generic name Nanotitanops is made up of the Greek words νανος ( nanos "dwarf"), τιτάν ( titan "titanium" or "giant") and ὤψ ( ōps "face" or "countenance"), the species name shanghuangensis is a reference to that Find area.

literature

Qi Tao and K. Christopher Beard: Nanotitan shanghuangensis, gen. Et sp. nov .: the smallest known brontothere. Journal of Vertebrate Paleontology 16, 1996, pp. 578-581; in addition: Qi Tao and K. Christopher Beard: Nanotitanops, a new name for Nanotitan Qi and Beard, 1996 not Nanotitan Sharov, 1968. Journal of Vertebrate Paleontology 18, 1998, p. 812

Individual evidence

↑ ^a ^b ^c ^d Qi Tao and K. Christopher Beard: Nanotitan shanghuangensis, gen. Et sp. nov .: the smallest known brontothere. Journal of Vertebrate Paleontology 16, 1996, pp. 578-581
↑ ^a ^b ^c ^d 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
^ Bryn R. Mader, A species-level revision of the North American brontotheres Eotitanops and Palaeosyops (Mammalia, Perissodactyla). Zootaxa 2339, 2010, pp. 1-43
^ Matthew C. Mihlbachler and Joshua X. Samuels: A small-bodied species of Brontotheriidae from the middle Eocene Nut Beds of the Clarno Formation, John Day Basin, Oregon. In: Journal of Paleontology 90 (6), 2016, pp. 1233-1244 doi: 10.1017 / jpa.2016.61 .
^ Qi Tao and K. Christopher Beard: Nanotitanops, a new name for Nanotitan Qi and Beard, 1996 not Nanotitan Sharov, 1968. Journal of Vertebrate Paleontology 18, 1998, p. 812

[Qi_et_al._1996-1] Qi Tao and K. Christopher Beard: Nanotitan shanghuangensis, gen. Et sp. nov .: the smallest known brontothere. Journal of Vertebrate Paleontology 16, 1996, pp. 578-581

[Mihlbachler_2008-2] 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

[Mader_2010-3] Bryn R. Mader, A species-level revision of the North American brontotheres Eotitanops and Palaeosyops (Mammalia, Perissodactyla). Zootaxa 2339, 2010, pp. 1-43

[Mihlbachler_et_al._2016-4] Matthew C. Mihlbachler and Joshua X. Samuels: A small-bodied species of Brontotheriidae from the middle Eocene Nut Beds of the Clarno Formation, John Day Basin, Oregon. In: Journal of Paleontology 90 (6), 2016, pp. 1233-1244 doi: 10.1017 / jpa.2016.61 .

[Qi_et_al._1998-5] Qi Tao and K. Christopher Beard: Nanotitanops, a new name for Nanotitan Qi and Beard, 1996 not Nanotitan Sharov, 1968. Journal of Vertebrate Paleontology 18, 1998, p. 812