Oxlestes

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Oxlestes
Temporal range: Late Cretaceous, 93  Ma
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Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Eutheria
Genus:† Oxlestes
Nessov et al., 1982
Type species
†Oxlestes grandis
Nessov et al., 1982

Oxlestes is an extinct mammal from the Late Cretaceous of Asia, more specifically from the Cenomanian of Uzbekistan. A carnivorous species of uncertain affinities, it is notable for its relatively large size, being among the largest of all Mesozoic mammals. [1] [2] Due to the limited amount of material, it has been considered a nomen dubium . [3]

Contents

Description

Oxlestes is currently a monotypic genus, containing a single species, O. grandis. Its specimens were recovered in the Cenomanian-aged Khodzhakul Formation of Uzbekistan. The holotype, CCMGE 6/11758, is composed of an axis vertebra, dentaries, canine teeth and a sagittal crest. [2]

The axis is relatively narrow, with a long, pointed anterior process. There are two pairs of distinct foramina anterior and posterior to the dorsal transverse suture; modern placentals only bear one. [3] It is about 1.9 centimeters long. [1]

The dentaries are short and robust, with a convex central border. The masseteric fossa is deep, and the canine is long and deep. The skull has been suggested to be about 10 centimeters long; [1] one axis and dentary comparison to zhelestids and rabbits would make it somewhat smaller at 7.5 centimeters, though this has since been contested. [4]

Overall, the available proportions seem to indicate an animal comparable in size to the largest of modern mustelids and mid-sized felines. [1]

Classification

Oxlestes was initially referred to Palaeoryctidae, a eutherian family, based on comparisons with several other Cretaceous eutherians like Zalambdalestes , Barunlestes and Asioryctes (none of which considered to be palaeoryctids anymore; Palaeoryctidae as a whole may be invalid). [1] Posterior efforts have cautiously referred it to the metatherian clade Deltatheroida, [2] [5] mostly based on size and its carnivorous speciations, but recent studies have shown no evidence of specifically deltatheroidean or even metatherian characters. [3] [6] [7] [8] Averinov and Archibald et al. 2005 referred it to the eutherian clade Zhelestidae, suggesting a close relation to Sheikhdzheilia [3] though this too is not entirely certain. [9]

Ecology

Oxlestes was among the largest mammals of the Mesozoic, being comparable in size to modern mammalian predators such as wolverines and mid-sized cats. Its deep sagittal crest and masseteric fossae are indicative of powerful jaw musculature, and it possessed deep canines, both characteristics of predatory mammals. Some of these are shared with the contemporary deltatheroidean mammals, to which it could be related. [1] [2] If Oxlestes was a zhelestid, it would set a precedent in an otherwise herbivorous clade. [10]

It is larger than some contemporary dinosaur species. Some researchers have even suggested that it could have predated on the local small ceratopsians such as Asiaceratops . [10]

Related Research Articles

<span class="mw-page-title-main">Eutheria</span> Clade of mammals in the subclass Theria

Eutheria, also called Pan-Placentalia, is the clade consisting of placental mammals and all therian mammals that are more closely related to placentals than to marsupials.

<i>Pucadelphys</i> Extinct genus of mammals

Pucadelphys is an extinct genus of non-marsupial metatherian. The genus contains a single species, P. andinus. Fossils of Pucadelphys have been found in the Santa Lucía Formation in Tiupampa in Bolivia.

<i>Alphadon</i> Extinct genus of mammals

Alphadon is an extinct genus of small, primitive mammal that was a member of the metatherians, a group of mammals that includes modern-day marsupials. Its fossils were first discovered and named by George Gaylord Simpson in 1929.

<i>Gobiconodon</i> Extinct genus of mammals

Gobiconodon is an extinct genus of carnivorous mammals 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. Species of Gobiconodon varied considerably in size, with G. ostromi, one of the larger species, being around the size of a modern Virginia opossum. 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. Unusually among predatory mammals and other eutriconodonts, the lower canines were vestigial, with the first lower incisor pair having become massive and canine-like. Like the larger Repenomamus there might be some evidence of scavenging.

Deltatheroida is an extinct group of basal metatherians that were distantly related to modern marsupials. The majority of known members of the group lived in the Cretaceous; one species, Gurbanodelta kara, is known from the late Paleocene (Gashatan) of China. Their fossils are restricted to Central Asia and North America. This order can be defined as all metatherians closer to Deltatheridium than to Marsupialia.

The Bissekty Formation is a geologic formation and Lagerstätte which crops out in the Kyzyl Kum desert of Uzbekistan, and dates to the Late Cretaceous Period. Laid down in the mid to late Turonian, it is dated to about 92 to 90 Ma.

The Khodzhakul Formation is a Cenomanian aged geologic formation in Uzbekistan. Dinosaur remains are among the fossils that have been recovered from the formation. As well as those of Mammals. It is part of the same stratigraphic succession as the overlying Bissekty Formation.

<span class="mw-page-title-main">Deltatheridiidae</span> Extinct family of mammals

Deltatheridiidae is an extinct family of basal carnivorous metatherians that lived in the Cretaceous and were closely related to marsupials. Their fossils are restricted to Central Asia and North America. They mostly disappeared in the KT event, but a ghost lineage, currently represented by Gurbanodelta, survived until the late Paleocene by decreasing in size and becoming insectivorous.

Sulestes is an extinct genus of Deltatheridiidae from Cretaceous of Uzbekistan.

Deltatheroides is an extinct genus of Deltatheridiidae from Cretaceous of Mongolia.

<span class="mw-page-title-main">Stagodontidae</span> Extinct family of mammals

Stagodontidae is an extinct family of carnivorous metatherian mammals that inhabited North America and Europe during the late Cretaceous, and possibly to the Eocene in South America.

<i>Pappotherium</i> Extinct family of mammals

Pappotherium is an extinct genus of mammals from the Albian of Texas, US, known from a fossilized maxilla fragment bearing two tribosphenic molars, discovered within the Glen Rose Formation near Decatur, Wise County, Texas.

Patagonia is an extinct genus of non-placental mammal from the Miocene of Argentina. Traditionally considered a metatherian incertae sedis, one analysis suggested it to be a gondwanathere. However, this has been rejected by other authors.

The "Gurlin Tsav" skull is a currently unnamed carnivorous metatherian fossil from the Nemegt Formation of Mongolia. Composed of a single semi-complete skull, this specimen is notable in regards to the evolution and systematics of Metatheria as a whole, and thus nigh-omnipresent in phylogenetic analyses of this group.

Khuduklestes is a genus of extinct mammal of uncertain affinities from the Late Cretaceous of China. It is rather similar to the also carnivorous and taxonomically uncertain Oxlestes, being slightly smaller.

<i>Tsagandelta</i> Extinct family of mammals

Tsagandelta is a genus of deltatheroidean therian mammal that lived in Asia during the Late Cretaceous. Distantly related to modern marsupials, it is part of Deltatheroida, a lineage of carnivorous metatherians common in the Cretaceous of Asia and among the most successful non-theropod carnivores of the region. It represents the first known mammal from the Bayan Shireh Formation.

Zhelestidae is a lineage of extinct eutherian mammals. Occurring in the Late Cretaceous from the Turonian to the Maastrichtian, they were an extremely successful group, with representatives present in Europe, Asia, India, Africa and North America, ostensibly rendering them a cosmopolitan clade. They were specialised towards an herbivorous lifestyle and were in fact initially considered stem-ungulates, but the presence of epipubics and "archaic" dental characters render them as non-placental eutherians.

<span class="mw-page-title-main">Zalambdalestidae</span> Extinct family of mammals

Zalambdalestidae is a clade of Asian eutherians occurring during the Late Cretaceous. Once classified as Glires, features like epipubic bones and various cranial elements have identified these animals as outside of Placentalia, representing thus a specialised clade of non-placental eutherians without any living descendants, and potentially rather different from modern placentals in at least reproductive anatomy.

Valentinella is a Late Cretaceous genus of eutherian mammal from France, Europe. It was originally known from some damaged lower and upper jaws, and was cautiously referred to the lainodontine zhelestid mammals. This identification was later questioned and even considered a nomen dubium by some researchers, and remains uncertain due to the scarcity and fragmentary nature of the fossils.

Azilestes is a genus of probable zhelestid eutherian mammal, a family consisting of small herbivores, that was discovered in the early Maastrichtian Grès de Labarre Formation of France. It is a monotypic genus, with only type species A. ragei being known. Only one specimen, the holotype described in 2021, is known. It consists of a partial dentary with teeth.

References

  1. 1 2 3 4 5 6 L. A. Nessov. 1982. Drevneishie mlekopitaiushchie SSSR [Ancient mammals of the USSR]. Palyentologicheskogo Obshchyestva 25:228-243
  2. 1 2 3 4 Zofia Kielan-Jaworowska; Richard L. Cifelli; Zhe-Xi Luo (2004). "Chapter 12: Metatherians". Mammals from the Age of Dinosaurs: origins, evolution, and structure . New York: Columbia University Press. pp.  425–262. ISBN   0-231-11918-6.
  3. 1 2 3 4 Averianov, A.; Archibald, J.D. (2005). "Mammals from the mid-Cretaceous Khodzhakul Formation, Kyzylkum Desert, Uzbekistan" (PDF). Cretaceous Research. 26 (4): 593–608. Bibcode:2005CrRes..26..593A. doi:10.1016/j.cretres.2005.03.007.
  4. ↑ Alexander O. Averianov, J. David Archibald & Eric G. Ekdale, New material of the Late Cretaceous deltatheroidan mammal Sulestes from Uzbekistan and phylogenetic reassessment of the metatherian-eutherian dichotomy, doi : 10.1080/14772011003603499
  5. ↑ Khuduklestes Nessov, Sigogneau-Russell & Russe, 1994
  6. ↑ S. Bi, X. Jin, S. Li and T. Du. 2015. A new Cretaceous metatherian mammal from Henan, China. PeerJ 3:e896
  7. ↑ Guillermo Rougier, New specimen of Deltatheroides cretacicus (Metatheria, Deltatheroida) from the Late Cretaceous of Mongolia, BULLETIN OF CARNEGIE MUSEUM OF NATURAL HISTORY 36(DEC 2004):245-266 · SEPTEMBER 2009
  8. ↑ Guillermo W. Rougier; Brian M. Davis; Michael J. Novacek (2015). "A deltatheroidan mammal from the Upper Cretaceous Baynshiree Formation, eastern Mongolia". Cretaceous Research. 52, Part A: 167–177. doi : 10.1016/j.cretres.2014.09.009.
  9. ↑ J. DAVID ARCHIBALD and ALEXANDER AVERIANOV, Phylogenetic analysis, taxonomic revision, and dental ontogeny of the Cretaceous Zhelestidae (Mammalia: Eutheria), Version of Record online: 25 JAN 2012 doi : 10.1111/j.1096-3642.2011.00771.x
  10. 1 2 Michael J. Benton, Mikhail A. Shishkin, David M. Unwin, The Age of Dinosaurs in Russia and Mongolia, Cambridge University Press, 04/12/2003 - 740 páginas
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