Gobiconodon

Gobiconodon is an extinct genus of carnivorous mammals (or possibly non-mammalian mammaliaforms) belonging to the family Gobiconodontidae.

Undisputed records of Gobiconodon are restricted to the Early Cretaceous of Asia and North America, but isolated teeth attributed to the genus have also been described from formations in England and Morocco dating as far back as the Middle Jurassic.

Like other gobiconodontids, it possessed several speciations towards carnivory, such as shearing molariform teeth, large canine-like incisors and powerful jaw and forelimb musculature, indicating that it probably fed on vertebrate prey.

A. Trofimov, based on remains from the Khoboor beds (Dzunbain Formation) of the Mongolian Gobi Desert, which date to the Aptian to Albian ages of the Early Cretaceous.

[3] Gobiconodon ostromi, from the Aptian–Albian Cloverly Formation of the US state of Montana, was described in 1988 by Farish A. Jenkins and Charles R. Schaff.

The referred specimen MCZ 19860 contains both sides of the dentary and parts of the upper jaw, cranium, vertebrae, ribs, shoulders, pelvis and limbs.

[2] Gobiconodon hopsoni, from the Early Cretaceous (Berriasian–Barremian) Öösh Formation of Mongolia, was described in 2001 by Guillermo W. Rougier, Michael J. Novacek, Malcolm McKenna and John R. Wible.

[3] The referred specimen PSS-MAE 139 consists of a part of the right dentary bone preserving an unerupted molariform and sockets for two other teeth.

[4] Gobiconodon palaios, from the Early Cretaceous (possibly Berriasian) of Morocco, was described in 2003 by Denise Sigogneau-Russell.

[3] Gobiconodon zofiae was described in 2003 by Li Chuankui, Wang Yuanqing, Hu Yaoming and Meng Jin.

The holotype, IVPP V12585, is based on a single skull and lower jaw found near the village of Lujiatun in the province of Liaoning in Northeast China.

[5] The rocks in which the species was found belong to the basal member of the Yixian Formation, and have been dated to the Barremian age of the Early Cretaceous.

[5] According to Lopatin & Averianov (2015), G. zofiae possesses no features clearly distinguishing it from G. hopsoni of Mongolia, but they provisionally retained it as a valid taxon until more material of the two species is discovered.

[3] Gobiconodon luoianus was described in 2009 by Yuan Chongxi, Xu Li, Zhang Xingliao, Xi Yunhong, Wu Yanhua and Ji Qiang based on material found near Lujiatun, in the same member of the Yixian Formation that yielded G. zofiae.

[6] Lopatin (2017) commented that G. haizhouensis has no valid characteristics distinguishing it from the Mongolian species G. hoburensis, but did not formally synonymise the two.

[6] Gobiconodon bathoniensis was described in 2016 by Percy M. Butler and Denise Sigogneau-Russell based on materials found in the Forest Marble Formation of England, which is dated to the Bathonian age of the Late Jurassic.

[9] In 2005, two new species of Gobiconodon were described based on material from the Bol'shoi Kemchug 3 locality in the Krasnoyarsk Krai of Russia, which belongs to the Early Cretaceous Ilek Formation.

Both species are based on isolated teeth and/or jaw fragments, and were described in open nomenclature as Gobiconodon sp.

[11] In 2006, an isolated premolariform tooth from Barremian-aged strata of the Wessex Formation of England was described as possibly belonging to Gobiconodon.

[2][13] Size may not be a reliable way of distinguishing between species of Gobiconodon, as the animal is thought to have had a long, protracted growth period compared to extant mammals.

[14] Unusually, part of the lower border of the eye socket appears to have been formed by the maxilla, as there was seemingly no connection between the lacrimal and jugal bones in this region.

[3] On the braincase, the anterior lamina of the petrosal bone bore a large foramen (hole), which may have served as a common exit for the maxillary (V2) and mandibular (V3) branches of the trigeminal nerve.

Unlike in modern therians and monotremes, there was however still an indirect connection between the middle ear and the jaw, formed by an ossified (bony) Meckel's cartilage.

The lower molariforms had a typical "triconodont" shape quite similar to that of the "amphilestids", with three large main cusps arranged in a straight line.

[3] Before their formal description, the remains of the type species Gobiconodon borissiaki were interpreted as belonging to the family Triconodontidae, but they were assigned to Amphilestidae in the describing paper.

[2] In later decades, multiple new genera have been assigned to Gobiconodontidae, including Fuxinoconodon, Hangjinia, Meemannodon and Repenomamus from China,[3][9] and Spinolestes from Spain.

[17] Huasteconodon, from the Early Jurassic of Mexico, was also assigned to Gobiconodontidae when first described, but its inclusion within the family has been disputed.

G. ostromi cast, at the AMNH .
Jaw bones and teeth of G. borissiaki
Lower molariform of G. hoburensis