Name: Eomaia ‭(‬Dawn mother‭)‬.
Phonetic: E-oh-my-ah.
Named By: Ji,‭ ‬Luo,‭ ‬Yuan,‭ ‬Wible,‭ ‬Zhang‭ & ‬Georgi‭ ‬-‭ ‬2002.
Classification: Chordata,‭ ‬Mammalia,‭ ‬Theria,‭ ‬Eutheria.
Species: E.‭ ‬scanosoria (type).
Diet: Insectivore.
Size: 10‭ ‬centimetres long.
Known locations: China,‭ ‬Liaoning Province‭ ‬-‭ ‬Yixian Formation.
Time period: Barremian of the Cretaceous.
Fossil representation: Single well preserved specimen that includes the impression of its fur.

       Eomaia was a ground breaking discovery as this little mammal is the oldest known placental mammal in the fossil record.‭ ‬Placental mammals are those that have young that develop inside their mother’s womb and are connected to their mother’s body via a placenta until they are ready to be born.‭ ‬Earlier Mammaliaformes such as Megazostrodon are thought to have still laid eggs similar to monotreme mammals,‭ ‬which today make up the smallest proportion of known mammals,‭ ‬whereas placental mammals are the largest‭ (‬marsupials are the other group,‭ ‬and have external pouches where the young develop inside‭)‬.‭
       However because Eomaia is in a very basal position,‭ ‬it still lacks some features that are seen in later and modern placental mammals.‭ ‬Eomaia also has epipubic bones that project forwards from the pubis,‭ ‬features that stiffen the body when in movement.‭ ‬These bones are a benefit to non-placental mammals‭ (‬and are even seen in the much earlier therapsids‭)‬,‭ ‬but would get in the way of embryonic development in placental mammals,‭ ‬which is why they are not seen in modern forms.‭ ‬Eomaia also has an arrangement of teeth types that are more similar to those of earlier Mammaliaformes.
       The identification of Eomaia as a placental mammal was made possible by the exquisitely well preserved specimen that was discovered in China's Liaoning Province,‭ ‬an area that is now world famous for producing finely detailed fossils,‭ ‬particularly of feathered dinosaurs like Microraptor.‭

Further reading
- The earliest known eutherian mammal. - Nature 416:816-822. - Q. Ji, Z.-X. Luo, C.-X. J.R. Yuan Wible, J.-P. Zhang & J.A. Georgi - 2002.


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