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Temporal range: Aptian–Maastrichtian
Early-Late Cretaceous
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Theria
(unranked): Metatheria
Order: Deltatheroida
Gregory and Simpson, 1926
Families & Genera

Deltatheroida is an extinct group of basal metatherians that lived in the Cretaceous and were closely related to marsupials. Their fossils are restricted to Central Asia and North America. This order can be defined as all metatherians closer to Deltatheridium than to Marsupialia.

These mammals possessed tritubercular lower molars and these were not tribosphenic and were quite primitive. This is awkward because tribosphenic molars are commonly found in most therian mammals (there exist some exceptions such as anteaters and some whales, 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" (extinct carnivorous mammals), but this was later disproven. Nonetheless, deltatheroideans do converge on hyaenodontids, oxyaenids, carnivorans, dasyuromorphs and sparassodonts in many details of their dental anatomy, suggesting a carnivorous lifestyle.[2][3] Oxlestes and Khudulestes in particular are among the largest mammals of the Mesozoic,[3] though at least the former's status as deltathoidans is questionable.[4]

See also[edit]


  1. ^ Averianov, A.; Archibald, J.D. (2005). "Mammals from the mid-Cretaceous Khodzhakul Formation, Kyzylkum Desert, Uzbekistan". Cretaceous Research 26 (4): 593–608. doi:10.1016/j.cretres.2005.03.007. 
  2. ^ 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
  3. ^ a b 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. 
  4. ^ 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

Further reading[edit]

Zofia Kielan-Jaworowska, Richard L. Cifelli, and Zhe-Xi Luo, Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure (New York: Columbia University Press, 2004), 444-448.