Gobiconodon
Gobiconodon Temporal range: Possible Bathonian record
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Skeletal reconstruction of Gobiconodon ostromi | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | †Eutriconodonta (?) |
Family: | †Gobiconodontidae |
Genus: | †Gobiconodon Trofimov, 1978 |
Species | |
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Synonyms | |
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Gobiconodon is an extinct genus of carnivorous
Discovery and naming
In 1978, the species Gobiconodon borissiaki and Guchinodon hoburensis were described by the Soviet palaeontologist B. A. Trofimov, based on remains from the
- G. ostromi
Gobiconodon ostromi, from the Aptian–Albian
- G. hopsoni
Gobiconodon hopsoni, from the Early Cretaceous (
- G. palaios
Gobiconodon palaios, from the Early Cretaceous (possibly Berriasian) of Morocco, was described in 2003 by
- G. zofiae
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.[3] The species is named after the Polish palaeontologist Zofia Kielan-Jaworowska.[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]
- G. luoianus
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. It is known from a single specimen, 41H III-0320, consisting of a nearly complete skull with well-preserved upper and lower teeth. The species is named after the Chinese palaeontologist
- G. haizhouensis and G. tomidai
Gobiconodon haizhouensis and Gobiconodon tomidai were described in 2015 by Nao Kusuhashi, Wang Yuanqing, Li Chuankui and Jin Xun. Both species are from the Early Cretaceous (Aptian to Albian) of the Liaoning province of China. G. haizhouensis is known from a single specimen (IVPP V14509) from the Fuxin Formation, consisting of a nearly complete right dentary. The species is named after Haizhou, an old name for the town of Fuxin where the type specimen was found.[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.[7]
G. tomidai is known from one specimen (IVPP V14510) from the Shahai Formation, consisting of an incomplete right dentary. The species is named after the Japanese palaeontologist Yukimitsu Tomida.[6]
- G. bathoniensis
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. The holotype (M46527) consists of an upper right molariform from the Old Cement Works Quarry of Kirtlington, Oxfordshire. Other specimens include two upper left molariforms from Kirtlington and a possible upper right molariform from Swyre, Dorset. As with G. palaios, the attribution of G. bathoniensis to the genus Gobiconodon is based mainly on the triangulated cusps of the teeth.[8] A 2020 paper by Kusuhashi et al. therefore recommended that its attribution to Gobiconodon should be reexamined.[9]
- Other material assigned to Gobiconodon
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. A and B.[10] Two indeterminate species of the genus of distinct size have also been reported from the Early Cretaceous Batylykh Formation in Yakutia, Russia, which represents the northernmost record of the genus.[11]
In 2006, an isolated premolariform tooth from Barremian-aged strata of the Wessex Formation of England was described as possibly belonging to Gobiconodon. The tooth has a mostly symmetrical crown with three cusps, and a single, strongly curved root.[12] Lopatin & Averianov (2015) disputed the assignment of this tooth to Gobiconodon, as it differs markedly from typical Gobiconodon premolariforms.[3] Teeth from the Early Cretaceous Angeac-Charente bonebed in France have also been referred to the genus, though like the British specimens, their placement in the genus has been questioned because they lack tricuspid premolars.[11]
Description
Different species of Gobiconodon ranged from small to medium-sized.[4] G. ostromi, one of the largest and most well-preserved species of Gobiconodon, had a skull length of around 10 centimetres (3.9 in) and an estimated presacral body length of around 35 centimetres (14 in), making it comparable to a modern Virginia opossum.[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.[3]
Skull
Most Gobiconodon species are known from highly incomplete skull material, usually only preserving parts of the jaws. The species G. zofiae and its possible synonym G. luoianus are known from more complete skulls.
The lower jaw was formed mostly by the dentary bone. The
Dentition
Gobiconodon and other gobiconodontids can be distinguished from their relatives by their specialised anterior (front) dentition. The
As most Gobiconodon specimens consist of dentary fragments, the lower dentition is better known than the upper. The incisors and canine were all single-rooted. The first lower incisor (i1) was large and strongly procumbent (forwards-pointing). The second incisor (i2) was also procumbent, but was smaller than the first one. The third incisor (i3) and canine (c) were smaller and less procumbent than the first two incisors. The first premolariform (p1) was rather similar to the last incisor and canine, being dominated by a large main cusp. In some specimens, there was a second relatively large cusp located distally to (behind) the main cusp, but in other specimens this cusp was much smaller. The premolariforms with prominent distal cusps may represent deciduous teeth and be labelled as dp1.[3] The first premolariform was single-rooted in most species, but double-rooted in G. tomidai.[6][7] The second premolariform was more complex than p1, bearing three well-developed cusps. This tooth was possibly not replaced in Gobiconodon, and in some specimens the tooth is missing and the socket is filled with bone. As a result, the second premolariform may be considered a deciduous tooth and labelled as dp2. The second premolariform was double-rooted in some species, like G. hoburensis, but single-rooted in others like G. borissiaki.[3]
Unlike the anterior dentition, the molariforms of Gobiconodon were relatively unspecialised. There were 5 molariforms in both the upper and lower jaws. The lower molariforms had a typical "triconodont" shape quite similar to that of the "
Classification
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 1984, the subfamily Gobiconodontinae was erected within Amphilestidae, in which the genera Gobiconodon, Guchinodon and Klamelia were included.[16] In 1988, Gobiconodontinae was raised to family rank as Gobiconodontidae.[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.[3]
Along with other gobiconodontids, Gobiconodon has often been placed within Eutriconodonta, a group characterised by their "triconodont" molariforms with cusps placed in a straight line. Phylogenetic analyses have often found eutriconodonts to be closer to
Palaeobiology
Tooth replacement
The
References
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