Deltatheroida is an extinct group of basal

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 w ...

ns that were distantly related to modern

marsupials Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

. The majority of known members of the group lived in the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

; one species, '' Gurbanodelta kara'', is known from the late

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pala ...

( Gashatan) of

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...

. Their fossils are restricted to

Central Asia Central Asia, also known as Middle Asia, is a region of Asia that stretches from the Caspian Sea in the west to western China and Mongolia in the east, and from Afghanistan and Iran in the south to Russia in the north. It includes the fo ...

and

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

. This order can be defined as all metatherians closer to '' Deltatheridium'' than to

Marsupialia Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

. These mammals possessed primitive tritubercular (three-cusped) lower molars that were not tribosphenic. This is awkward because tribosphenic

molars The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

are commonly found in most

theria Theria (; Greek: , wild beast) is a subclass of mammals amongst the Theriiformes. Theria includes the eutherians (including the placental mammals) and the metatherians (including the marsupials) but excludes the egg-laying monotremes. ...

n mammals (there exist some exceptions such as

anteater Anteater is a common name for the four extant mammal species of the suborder Vermilingua (meaning "worm tongue") commonly known for eating ants and termites. The individual species have other names in English and other languages. Together wit ...

s and some

whale Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...

s, which have no teeth at all). When they were first identified in the 1920s, they were believed to be placentals and possible ancestors of the " creodonts" (a

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...

group of extinct carnivorous mammals from the

Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...

and

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

), but this was later disproven. Nonetheless, deltatheroideans do converge on hyaenodontids, oxyaenids,

carnivora Carnivora is a Clade, monophyletic order of Placentalia, placental mammals consisting of the most recent common ancestor of all felidae, cat-like and canidae, dog-like animals, and all descendants of that ancestor. Members of this group are f ...

ns,

dasyuromorphs Dasyuromorphia (, meaning "hairy tail" in Greek) is an order comprising most of the Australian carnivorous marsupials, including quolls, dunnarts, the numbat, the Tasmanian devil, and the thylacine. In Australia, the exceptions include the ...

and sparassodonts in many details of their dental anatomy, suggesting a carnivorous lifestyle.CHRISTIAN DE MUIZON and BRIGITTE LANGE-BADRÉ, Carnivorous dental adaptations in tribosphenic mammals and phylogenetic reconstruction, Article first published online: 29 MAR 2007 DOI: 10.1111/j.1502-3931.1997.tb00481

Taxonomy

The following is a species list of Deltatheroida.Mikko's Phylogeny Archiv

†Deltatheroida Kielan-Jaworowska 1982 eltatheralia Marshall & Kielan-Jaworowska 1992; Holarctidelphia Szalay 1993* †

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

** †''

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

''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.S. Bi, X. Jin, S. Li and T. Du. 2015. A new Cretaceous metatherian mammal from Henan, China. PeerJ 3:e896 * †

Deltatheridiidae 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 (Mongolia and Uzbekistan) and North America (United States - ...

Gregory & Simpson 1926 eltatheridia Van Valen 1965; Nanocuridae Fox, Scott & Bryant 2007; Sulestinae Nessov 1985; Deltatheroididae Kielan-Jaworowska & Nesov 1990** †'' Hyotheridium dobsoni'' Gregory & Simpson 1926 ** †'' Lotheridium mengi'' Bi et al. 2015 ** †'' Nanocuris improvida'' Fox, Scott & Bryant 2007 ** †'' Prodeltitheridium kalandadze'' Trofimov 1984 ** †'' Oklatheridium'' Davis, Cifelli & Kielan-Jaworowska 2008 *** †'' O. szalayi'' Davis, Cifelli & Kielan-Jaworowska 2008 *** †'' O. minax'' Davis & Cifelli 2011 *** †'' O. wiblei'' Cifelli & Davis 2015 ** †'' Atokatheridium boreni'' Kielan-Jaworowska & Cifelli 2001 ** †'' Deltatheridium'' Gregory & Simpson 1926 *** †'' D. pretrituberculare'' Gregory & Simpson 1926 *** †'' D. nesovi'' Averianov 1997 ** †''

Sulestes karakshi ''Sulestes'' is an extinct genus of Deltatheridiidae from Cretaceous of Uzbekistan Uzbekistan (, ; uz, Ozbekiston, italic=yes / , ; russian: Узбекистан), officially the Republic of Uzbekistan ( uz, Ozbekiston Respublikasi, italic= ...

'' Nesov 1985 'Deltatherus''_Nesov_1997;_''Marsasia.html" ;"title="Deltatherus.html" ;"title="'Deltatherus">'Deltatherus'' Nesov 1997; ''Marsasia">Deltatherus.html" ;"title="'Deltatherus">'Deltatherus'' Nesov 1997; ''Marsasia'' Nesov 1997; ''Deltatheroides kizylkumensis'' Nesov 1993; ''Deltatherus kizylkumensis'' (Nesov 1993) Nesov 1997; ''Marsasia aenigma'' Nesov 1997] ** †''Tsagandelta, Tsagandelta dashzevegi'' Rougier, Davis & Novacek 2015 ** †'' Deltatheroides, Deltatheroides cretacicus'' Gregory & Simpson 1926 ** †'' Gurbanodelta kara'' Ni ''et al.'' 2016

Biology

Deltatheroideans are thought to be carnivorous mammals, converging on hyaenodontids, oxyaenids,

ns,

and sparassodonts in many details of their dental anatomy, suggesting a carnivorous lifestyle. Deltatheroideans in this regard appear to have replaced eutriconodont mammals as the dominant carnivorous mammals of the Mesozoic, either directly through competition or occupying vacant ecological niches; in

, ''

Nanocuris ''Nanocuris'' is an extinct genus of Deltatheridiidae from the Cretaceous of Canada (Saskatchewan) and United States ( Wyoming - Lance Formation).R. C. Fox, C. S. Scott, and H. N. Bryant. 2007. A new, unusual therian mammal from the Upper Creta ...

'' came to succeed the larger gobiconodontids and ''

Jugulator ''Jugulator'' is the thirteenth studio album by English heavy metal band Judas Priest. It was released in Japan on 16 October 1997 and the rest of the world on 28 October 1997. It was their first studio album since ''Painkiller'' in 1990 an ...

'', while in Asia the Early Cretaceous gobiconodontid radiation is replaced in the Late Cretaceous by a deltatheroidean one. Given that all insectivorous and carnivorous mammals groups suffered heavy losses during the mid-Cretaceous, it seems likely these metatherians simply occupied niches left after the extinction of eutriconodonts. Evidence of direct predation on dinosaurs may be attested on a skull belonging to '' Archaeornithoides'', which seems to have been punctured by '' Deltatheridium'' teeth and later healed.Elżanowski, A. Wellnhoffer, P. (1993). "Skull of Archaeornithoides From the Upper Cretaceous of Mongolia". earth.geology.yale.edu/~ajs/1993/11.1993.08Elzanowski.pdf . American Journal of Science

Taxonomy

Biology

See also

References

Further reading