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 wel ...

ns that were distantly related to modern

marsupials Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a ...

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

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

; one species, ''

Gurbanodelta ''Gurbanodelta kara'' is an extinct genus of metatherian mammal. A deltatheroid, it represents the geologically youngest member of this clade, dating to the late Paleocene of China. Description ''Gurbanodelta kata'' is known from upper molars. ...

kara'', is known from the late

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

(

Gashatan The Gashatan is an Asian Land Mammal Age, a large biozone which corresponds to ages between 58.7–55.8 Ma for finds of fossil mammals in Asia. This zone lies within the Thanetian stage of the Paleocene series. It precedes the Bumbanian The Bumbani ...

) of

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. Their fossils are restricted to

Central Asia Central Asia is a region of Asia consisting of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. The countries as a group are also colloquially referred to as the "-stans" as all have names ending with the Persian language, Pers ...

and

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. This order can be defined as all

metatherian 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 ...

s closer to ''

Deltatheridium ''Deltatheridium'' (meaning ''triangle beast'' or ''delta beast'') is an extinct species of metatherian. It lived in what is now Mongolia during the Upper Cretaceous, ''circa'' 80 million years ago. A study in 2022 strongly suggested that ''De ...

'' than to

Marsupialia Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a ...

. When they were first identified in the 1920s, they were believed to be

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 ...

and possible ancestors of the "

creodonts Creodonta ("meat teeth") is a former order of extinct carnivorous placental mammals that lived from the early Paleocene to the late Miocene epochs in North America, Europe, Asia and Africa. Originally thought to be a single group of animals ances ...

" (a

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

group of extinct carnivorous mammals from the

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

and

Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...

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

carnivora Carnivora ( ) is an order of placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at least 279 species. Carnivor ...

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 extinct thylacine. In Australia, the exceptions inc ...

thylacoleonid Thylacoleonidae is a family of extinct carnivorous diprotodontian marsupials from Australia, referred to as marsupial lions. The best known is ''Thylacoleo carnifex'', also called the marsupial lion. The clade ranged from the Late Oligocene to th ...

s and

sparassodonts Sparassodonta (from Greek to tear, rend; and , gen. , ' tooth) is an extinct order of carnivorous metatherian mammals native to South America, related to modern marsupials. They were once considered to be true marsupials, but are now though ...

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, Te ...

''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 (biology), family of basal carnivore, carnivorous Metatheria, metatherians that lived during the Cretaceous and Paleogene. They were closely related to marsupialia, marsupials. Their fossils are restricted to ...

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 ''Oklatheridium'' is an extinct genus of deltatheroidan from the United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic ...

'' 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 ** †''

'' Gregory & Simpson 1926 *** †'' D. pretrituberculare'' Gregory & Simpson 1926 *** †'' D. nesovi'' Averianov 1997 ** †'' Sulestes karakshi'' Nesov 1985 '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

in many details of their dental anatomy, suggesting a carnivorous lifestyle. Deltatheroideans in this regard appear to have replaced

eutriconodont Eutriconodonta is an order (biology), order of early mammals. Eutriconodonts existed in Asia (including Insular India, pre-contact India), Africa, Europe, North America, North and South America during the Jurassic and the Cretaceous periods. The ...

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 and Hell Creek Formation).R. C. Fox, C. S. Scott, and H. N. Bryant. 2007. A new, unusual therian mamm ...

'' came to succeed the larger

gobiconodontid Gobiconodontidae is a family of extinct mammals that ranged from the mid-Jurassic to the early Late Cretaceous, though most common during the Early Cretaceous. The Gobiconodontids form a diverse lineage of carnivorous non-therian mammals, and inc ...

s 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 most eutriconodonts. Evidence of direct predation on dinosaurs may be attested on a skull belonging to ''

Archaeornithoides ''Archaeornithoides'' is a genus of maniraptoran theropod dinosaur of the Late Cretaceous of Mongolia. Discovery and naming In 1965, a Polish-Mongolian paleontological expedition found a fossil of a small dinosaur at Bayn Dzak, Mongolia. In 19 ...

'', which seems to have been punctured by ''

'' 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