Deltatheroida

Deltatheroida
Temporal range: Aptian–Paleocene

Early Cretaceous-Paleocene

Lotheridium mengi
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Class: Mammalia
Clade: Metatheria
Order: †Deltatheroida
Gregory and Simpson, 1926
Families & Genera

Deltatheroida is an extinct group of basal metatherians that were distantly related to modern marsupials.[3] 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.[4] 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" (a polyphyletic group of extinct carnivorous mammals from the Paleogene and Miocene), 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.[5]

Taxonomy

The following is a species list of Deltatheroida.[6][7]

†Deltatheroida Kielan-Jaworowska 1982 [Deltatheralia Marshall & Kielan-Jaworowska 1992; Holarctidelphia Szalay 1993]

Biology

Deltatheroideans are thought to be carnivorous mammals, converging on hyaenodontids, oxyaenids, carnivorans, dasyuromorphs and sparassodonts in many details of their dental anatomy, suggesting a carnivorous lifestyle.[5][9] Oxlestes and Khuduklestes in particular are among the largest mammals of the Mesozoic,[9] though at least the former's status as deltatheroideans is questionable.[10]

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 North America, Nanocuris came to succeed the larger gobiconodontids and Jugulator, while in Asia the Early Cretaceous gobiconodontid radiation is replaced in the Late Cretaceous by a deltatheroidean one.[11] 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.[12]

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.[13]

At least some deltatheroideans were sabertoothed predators.[8]

See also

References

  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. 1 2 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.
  3. ↑ Wilson, G.P.; Ekdale, E.G.; Hoganson, J.W.; Calede, J.J.; Linden, A.V. (2016). "A large carnivorous mammal from the Late Cretaceous and the North American origin of marsupials". Nature Communications. 7. doi:10.1038/ncomms13734.
  4. ↑ Xijun Ni; Qiang Li; Thomas A. Stidham; Lüzhou Li; Xiaoyu Lu; Jin Meng (2016). "A late Paleocene probable metatherian (?deltatheroidan) survivor of the Cretaceous mass extinction". Scientific Reports. 6: Article number 38547. doi:10.1038/srep38547.
  5. 1 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
  6. ↑ Mikko's Phylogeny Archive Haaramo, Mikko (2007). "†Deltatheroida – deltatherids". Retrieved 30 December 2015.
  7. ↑ Paleofile.com (net, info) "Archived copy". Archived from the original on 2016-01-11. Retrieved 2015-12-30.. "Taxonomic lists- Mammals". Archived from the original on 11 January 2016. Retrieved 30 December 2015.
  8. 1 2 S. Bi, X. Jin, S. Li and T. Du. 2015. A new Cretaceous metatherian mammal from Henan, China. PeerJ 3:e896
  9. 1 2 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.
  10. ↑ 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
  11. ↑ G. W. Rougier, B. M. Davis, and M. J. Novacek. 2015. A deltatheroidan mammal from the Upper Cretaceous Baynshiree Formation, eastern Mongolia. Cretaceous Research 52:167-177
  12. ↑ David M. Grossnickle, P. David Polly, Mammal disparity decreases during the Cretaceous angiosperm radiation, Published 2 October 2013.DOI: 10.1098/rspb.2013.2110
  13. ↑ 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

Further reading

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.

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