Gobiconodonta
| Gobiconodonts Temporal range: Middle Jurassic-Early Cretaceous, 167–100 Ma | |
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| Life restoration of a Gobiconodon | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Synapsida |
| Class: | Mammalia |
| Clade: | Holotheria |
| Order: | †Gobiconodonta Averianov & Lopatin, 2011 |
| Families | |
The Gobiconodonta are a group of extinct mammals known from the Middle Jurassic (klameliids)[1] to Early Cretaceous.
Biology
Like many other non-therian mammals, gobiconodonts retained classical mammalian synapomorphies like epipubic bones (and likely the associated reproductive constrictions), venomous spurs and sprawling limbs. However, the forelimb and shoulder anatomy of at least some species like Jeholodens are similar to those of therian mammals, though the hindlimbs remain more conservative.[2]
Some information on gobiconodont soft-tissues can be seen in Spinolestes, which was very well preserved, showing evidence of fur and internal organs. Spinolestes shows hair similar to that of modern mammals, with compound hair follicles with primary and secondary hair, even preserving traces of a pore infection. It also possesses a clear thoracic diaphragm like modern mammals, as well as spines, dermal scutes and an ossified Meckel's cartilage.[3]
The gobiconodont triconodont dentition has no analogue among living mammals, so comparisons are difficult. However, its clear that most if not all gobiconodonts were primarily carnivorous, given the presence of long, sharp canines, premolars with trenchant main cusps that were well suited to grasp and pierce prey, strong development of the madibular abductor musculature, bone crushing ability in at least some species and several other features.[2]
Gobiconodonts are often among the largest mammals in Mesozoic faunal assemblages, displaying a broad size range from small shrew-like insectivores to large forms like Repenomamus and Gobiconodon. They were among the first mammals to be specialised for vertebrate prey, and likely occupied the highest trophic levels among mammals in their faunal communities. Several forms like Gobiconodon and Repenomamus show evidence of scavenging, being among the few Mesozoic mammals to have significantly exploited that.[2]
At least in carnivorous niches, gobiconodonts were probably replaced by deltatheroidean metatherians, which are the dominant carnivorous mammals in Late Cretaceous faunal assemblages.[4]
At least Spinolestes had xenarthrous vertebrae and osseous scutes, convergent to those of modern xenarthrans and to a lesser extent the hero shrew.[3]
Classification
Cladogram after Averianov & Lopatin, 2011:[5]
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Gobiconodonta was named by Averianov & Lopatin (2011); according to the authors it contained two families of mammals (gobiconodontids and klameliids)[5] that were traditionally assigned to Eutriconodonta.[1][2] The exact phylogenetic position of these families within Mammaliaformes is uncertain. Some analyses using only dental and mandibular characters (the first analysis of Gao et al., 2010,[6] Meng, Wang & Li, 2011,[7] Averianov & Lopatin, 2011[5]) found that gobiconodonts and eutriconodonts did not form a clade that wouldn't also include trechnotherians; however, some other analyses of dental and mandibular characters (Gaetano and Rougier, 2011,[8] 2012[9]) did recover gobiconodontids as eutriconodonts. The analysis conducted by Luo et al. (2007)[10] and the second analysis of Gao et al. (2010),[6] involving a broader range of Mesozoic mammaliaforms and more characters (including postcranial ones) recovered gobiconodontids as eutriconodonts as well. However, Gao et al. (2010) stressed that jeholodentids and gobiconodontids are the only eutriconodonts with known postcranial skeletons; according to the authors, it remains uncertain whether the results of their second analysis represent true phylogeny or are merely "a by-product of long branch attraction of jeholodentids and gobiconodontids".[6]
References
- 1 2 Thomas Martin and Alexander O. Averianov (2006). "A previously unrecognized group of Middle Jurassic triconodontan mammals from Central Asia". Naturwissenschaften 94 (1): 43–48. doi:10.1007/s00114-006-0155-5. PMID 17016686.
- 1 2 3 4 Zofia Kielan-Jaworowska, Richard L. Cifelli, Zhe-Xi Luo (2004). "Chapter 7: Eutriconodontans". Mammals from the Age of Dinosaurs: origins, evolution, and structure. New York: Columbia University Press. pp. 216–248. ISBN 0-231-11918-6.
- 1 2 Martin, Thomas; Marugán-Lobón, Jesús; Vullo, Romain; Martín-Abad, Hugo; Luo, Zhe-Xi; Buscalioni, Angela D. (2015). "A Cretaceous eutriconodont and integument evolution in early mammals". Nature 526 (7573): 380–384. doi:10.1038/nature14905.
- ↑ Zofia Kielan-Jaworowska, Richard L. Cifelli, Zhe-Xi Luo (2004). "Chapter 12: Metaherians". Mammals from the Age of Dinosaurs: origins, evolution, and structure. New York: Columbia University Press. pp. 425–462. ISBN 0-231-11918-6.
- 1 2 3 A. O. Averianov and A. V. Lopatin (2011). "Phylogeny of Triconodonts and Symmetrodonts and the Origin of Extant Mammals". Doklady Biological Sciences 436 (1): 32–35. doi:10.1134/s0012496611010042.
- 1 2 3 Chun-Ling Gao, Gregory P. Wilson, Zhe-Xi Luo, A. Murat Maga, Qingjin Meng and Xuri Wang (2010). "A new mammal skull from the Lower Cretaceous of China with implications for the evolution of obtuse-angled molars and ‘amphilestid’ eutriconodonts". Proceedings of the Royal Society B: Biological sciences 277 (1679): 237–246. doi:10.1098/rspb.2009.1014. PMC 2842676. PMID 19726475.
- ↑ Jin Meng, Yuanqing Wang and Chuankui Li (2011). "Transitional mammalian middle ear from a new Cretaceous Jehol eutriconodont". Nature 472 (7342): 181–185. doi:10.1038/nature09921. PMID 21490668.
- ↑ Leandro C. Gaetano and Guillermo W. Rougier (2011). "New materials of Argentoconodon fariasorum (Mammaliaformes, Triconodontidae) from the Jurassic of Argentina and its bearing on triconodont phylogeny". Journal of Vertebrate Paleontology 31 (4): 829–843. doi:10.1080/02724634.2011.589877.
- ↑ Leandro C. Gaetano and Guillermo W. Rougier (2012). "First Amphilestid from South America: A Molariform from the Jurassic Cañadón Asfalto Formation, Patagonia, Argentina". Journal of Mammalian Evolution 19 (4): 235–248. doi:10.1007/s10914-012-9194-1.
- ↑ Luo, Z.-X.; Chen, P.; Li, G. and Chen, M. (2007). "A new eutriconodont mammal and evolutionary development in early mammals.". Nature 446 (7133): 288–293. doi:10.1038/nature05627. PMID 17361176.