Maelestes

Maelestes is a prehistoric shrew-like mammal discovered in 1997 in the Gobi Desert. The animal lived in the late Cretaceous Period, around 71–75 million years ago, and was a contemporary of dinosaurs such as Velociraptor and Oviraptor. According to some scientists, the discovery and analysis of this species suggests that true placental mammals appeared near the time the non-avian dinosaurs became extinct 66 million years ago, not much earlier in the Cretaceous as thought by others.[1] However, the presence of an epipubic bone, among other characteristics, place it as a non-placental eutherian.[1][2]

Maelestes
Temporal range: Late Cretaceous
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Mammalia
Order:
†Cimolesta
Family:
†Cimolestidae
Genus:
†Maelestes

Wible et al., 2007
Species:
†M. gobiensis
Binomial name
†Maelestes gobiensis
Wible et al., 2007

Reproduction

Although Maelestes was a eutherian, it was not a placental mammal. The presence of an epipubic bone suggests that it could not expand its torso the same way placentals can, forcing it to give birth to small, relatively undeveloped young like modern marsupials. Like modern marsupials, it might have had a pouch, though there is no evidence for this and many marsupials like shrew opossums lack pouches.

References
  1. Wible, J.R., G.W. Rougier, M.J. Novacek, and R.J. Asher. (2007). "Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary." Nature, 447: 1003–1006.
  2. Giallombardo, Andres, 2009 New Cretaceous mammals from Mongolia and the early diversification of Eutheria Ph.D. dissertation, Columbia University, 2009402 pages; AAT 3373736 (abstract) The origin of Placental Mammals, Cimolestidae, Zalambdalestidae
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