''Oxlestes'' is an extinct mammal from the
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...
of
Asia
Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...
, more specifically from the
Cenomanian
The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...
of
Uzbekistan
Uzbekistan (, ; uz, Ozbekiston, italic=yes / , ; russian: Узбекистан), officially the Republic of Uzbekistan ( uz, Ozbekiston Respublikasi, italic=yes / ; russian: Республика Узбекистан), is a doubly landlocked cou ...
. A
carnivorous
A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...
species of uncertain affinities, it is notable for its relatively large size, being among the largest of all Mesozoic mammals.
[L. A. Nessov. 1982. Drevneishie mlekopitaiushchie SSSR ncient mammals of the USSR Palyentologicheskogo Obshchyestva 25:228-243] Due to the limited amount of material, it has been considered a ''
nomen dubium
In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application.
Zoology
In case of a ''nomen dubium'' it may be impossible to determine whether a s ...
''.
Description
''Oxlestes'' is currently a
monotypic
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...
genus, containing a single species, ''O. grandis''. Its specimens were recovered in the
Cenomanian
The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...
-aged
Khodzhakul Formation
The Khodzhakul Formation is a Cenomanian aged geologic formation in Uzbekistan. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel, et al., 2004, "Dinosaur distribution." pp.517-607 As well as those of ...
of
Uzbekistan
Uzbekistan (, ; uz, Ozbekiston, italic=yes / , ; russian: Узбекистан), officially the Republic of Uzbekistan ( uz, Ozbekiston Respublikasi, italic=yes / ; russian: Республика Узбекистан), is a doubly landlocked cou ...
. The
holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
, CCMGE 6/11758, is composed of an
axis
An axis (plural ''axes'') is an imaginary line around which an object rotates or is symmetrical. Axis may also refer to:
Mathematics
* Axis of rotation: see rotation around a fixed axis
* Axis (mathematics), a designator for a Cartesian-coordinat ...
vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
,
dentaries
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
,
canine teeth
A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...
and a
sagittal crest
A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptiona ...
.
The axis is relatively narrow, with a long, pointed anterior process. There are two pairs of distinct
anterior and posterior to the dorsal transverse suture; modern
placentals
Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguishe ...
only bear one.
It is about 1.9 centimeters long.
The dentaries are short and robust, with a convex central border. The
masseter
In human anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it ...
ic fossa is deep, and the canine is long and deep. The skull has been suggested to be about 10 centimeters long;
one axis and dentary comparison to
zhelestids and
rabbits
Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit specie ...
would make it somewhat smaller at 7.5 centimeters, though this has since been contested.
Overall, the available proportions seem to indicate an animal comparable in size to the largest of modern
mustelids
The Mustelidae (; from Latin ''mustela'', weasel) are a family of carnivorous mammals, including weasels, badgers, otters, ferrets, martens, minks and wolverines, among others. Mustelids () are a diverse group and form the largest famil ...
and mid-sized
felines.
Classification
''Oxlestes'' was initially referred to
Palaeoryctidae
Palaeoryctidae or Palaeoryctoidea ("old/stony digger", from Greek: ὀρύκτης, ''oryctes'') is an extinct group of relatively non-specialized non-placental eutherian mammals that lived in North America during the late Cretaceous and took par ...
, an
eutheria
Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all therian mammals that are more closely related to placentals than to marsupials.
Eutherians are distinguished from noneutherians by various phenotypic tra ...
n family, based on comparions with several other Cretaceous eutherians like ''
Zalambdalestes
''Zalambdalestes'' (meaning ''much-like-lambda robber'') was a eutherian mammal, most likely not a placental due to the presence of an epipubic bone, living during the Upper Cretaceous in Mongolia.
''Zalambdalestes'' was a hopping animal with ...
'', ''
Barunlestes'' and ''
Asioryctes'' (none of which considered to be palaeoryctids anymore; Palaeoryctidae as a whole may be invalid).
Posterior efforts have cautiously referred it to the
metatheria
Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as well ...
n clade
Deltatheroida
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 (G ...
,
mostly based on size and its carnivorous speciations, but recent studies have shown no evidence of specifically deltatheroidean or even metatherian characters.
Averinov and Archibald et al. 2005 referred it to the eutherian clade
Zhelestidae
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 (and subsequently in Mad ...
, suggesting a close relation to ''
Sheikhdzheilia''
though this too is not entirely certain.
[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 ]
Ecology
''Oxlestes'' was among the largest mammals of the Mesozoic, being comparable in size to modern mammalian predators such as
wolverines
The wolverine (), (''Gulo gulo''; ''Gulo'' is Latin for " glutton"), also referred to as the glutton, carcajou, or quickhatch (from East Cree, ''kwiihkwahaacheew''), is the largest land-dwelling species of the family Mustelidae. It is a muscul ...
and mid-sized
cats
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of t ...
. 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
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 ( ...
mammals, to which it could be related.
If ''Oxlestes'' was a
zhelestid, it would set a precedent in an otherwise herbivorous clade.
[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]
It is larger than some contemporary
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
species. Some researchers have even suggested that it could have predated on the local small
ceratopsia
Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. ...
ns such as ''
Asiaceratops
''Asiaceratops'' (meaning "Asian horned face") is a genus of herbivorous ceratopsian dinosaur. It lived during the Early-Late Cretaceous. The type species, ''A. salsopaludalis'' is known from Uzbekistan, while ''A. sulcidens'' is known from China ...
''.
References
{{Taxonbar, from=Q24883317
Cretaceous animals of Asia
Prehistoric eutherians
Cretaceous mammals
Late Cretaceous mammals of Asia
Fossil taxa described in 1982
Prehistoric mammal genera