Eomaia scansoria (Ji et al. 2002) Barremian, Early Cretaceous ~125 mya, ~10 cm in length) was originally considered a basal eutherian mammal, but not a placental mammal. Here it nests as a basal marsupial.
Distinct from Didelphis the mandible of Eomaia had a larger canine and three fewer molars. The coronoid process was tall without any posterior process. The molars were more asymmetrical in shape, with taller cusps.
The slender scapula included a central ridge and the coracoid was greatly reduced and invisible in lateral view. The shoulder joint was ventrally oriented, indicating a parasagittal motion for the forelimbs to finally match the hind limbs. The humerus and radius/ulna were more gracile and elongated.
The pelvis was relatively smaller with fewer protruding processes. The fibula was more gracile. The metatarsals were more nearly subequal as were all the non-ungual phalanges. |
