Sinodelphys

Sinodelphys is an extinct mammal from the Early Cretaceous. To date, it is the oldest metatherian fossil known,[1] estimated to be 125 million years old. It was discovered and described in 2003 in rocks of the Yixian Formation in Liaoning Province, China, by a team of scientists including Zhe-Xi Luo and John Wible.

Sinodelphys Temporal range: Early Cretaceous, 125 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Fossil specimen, Hong Kong Science Museum
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Clade:	Marsupialiformes
Genus:	†Sinodelphys Luo et al., 2003
Type species
†Sinodelphys szalayi Luo et al., 2003

Fossil record

Specimen at the French National Museum of Natural History, Paris

Only one fossil specimen is known, a slab and counterslab given catalog number CAGS00-IG03. It is in the collection of the Chinese Academy of Geological Sciences.

Sinodelphys szalayi grew only 15 cm (5.9 in) long and possibly weighed about 30 g (1.05 oz). Its fossilized skeleton is surrounded by impressions of fur and soft tissue, thanks to the exceptional sediment that preserves such details. Luo et al. (2003) inferred from the foot structure of Sinodelphys that it was a scansorial tree-dweller, like its non-marsupial contemporary Eomaia and modern opossums such as Didelphis. Sinodelphys probably hunted worms and insects. Most Mesozoic metatherians have been found in North America and Asia. Most lived during the Late Cretaceous between 90 and 66 million years ago.[2]

Evolution of marsupials

Sinodelphys szalayi, living in China around 125 million years ago, is the earliest known metatherian.[2][3][4] This makes it almost contemporary to the eutherian Acristatherium, which has been found in the same area.[5]

	Metatheria    Sinodelphys szalayi      Cenozoic metatherian      Eutheria    Juramaia sinensis      Montanalestes keeblerorum        Murtoilestes abramovi      Acristatherium yanensis      Prokennalestes trofimovi        Cenozoic placentalia

However, Bi et al. (2018) reinterpreted Sinodelphys as an early member of Eutheria.[6]

See also

• Eomaia
• Evolution of mammals

References

1. O'Leary, M.A.; Bloch, J.I.; Flynn, J.J.; Gaudin, T.J.; Giallombardo, A.; Giannini, N.P.; Goldberg, S.L.; Kraatz, B.P.; Luo, Z.-X.; Meng, J.; Ni, X.; Novacek, M.J.; Perini, F.A.; Randall, Z.S.; Rougier, G.W.; Sargis, E.J.; Silcox, M.T.; Simmons, N.B.; Spaulding, M.; Velazco, P.M.; Weksler, M.; Wible, J.R.; Cirranello, A.L. (2013). "The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals". Science. 339 (6120): 662–667. doi:10.1126/science.1229237. PMID 23393258.
2. Luo, Zhe-Xi; Ji, Qiang; Wible, John R.; Yuan, Chong-Xi (2003-12-12). "An early Cretaceous tribosphenic mammal and metatherian evolution". Science. 302 (5652): 1934–1940. doi:10.1126/science.1090718. PMID 14671295.
3. Rincon, P. Oldest Marsupial Ancestor Found, BBC, December 2003.
4. Pickrell, J. Oldest Marsupial Fossil Found in China, National Geographic, December 2003.
5. Yaoming Hu; Jin Meng; Chuankui Li & Yuanqing Wang (2010). Xing Xu; Zhe-Xi Luo & Jia-Yu Rong (eds.). "New basal eutherian mammal from the Early Cretaceous Jehol biota, Liaoning, China". Proceedings of the Royal Society B. 277 (1679): 229–236. doi:10.1098/rspb.2009.0203. PMC 2842663. PMID 19419990.
6. Shundong Bi; Xiaoting Zheng; Xiaoli Wang; Natalie E. Cignetti; Shiling Yang; John R. Wible (2018). "An Early Cretaceous eutherian and the placental–marsupial dichotomy". Nature. 558 (7710): 390–395. doi:10.1038/s41586-018-0210-3. PMID 29899454.