Eomaia
Early Cretaceous eutherian mammal from China, debated as basal eutherian.
The single fossil specimen is 10 centimeters in length, virtually complete, and exceptionally well-preserved, showing traces of hair, teeth, tiny foot bones, cartilages, and fur. Eomaia is significant in the study of early mammal evolution, particularly regarding the origins of placental mammals, though its exact classification has been subject to debate.
- Species
- Eomaia scansoria
- Location
- Yixian Formation, Liaoning Province, China
- Size
- 10 centimeters (3.9 in) in length
- Weight
- 20–25 grams (0.71–0.88 oz)
- Known for
- Early eutherian mammal with features intermediate between metatherians and placentals
Lore & Background
The specimen's skull is squashed flat, but its teeth, tiny foot bones, cartilages, and fur are visible. Its body weight is estimated at 20–25 grams.
Reader's Guide
Eomaia is significant for its combination of features that are intermediate between metatherians (marsupials) and placental mammals. It possessed several placental-like traits, such as an enlarged malleolus on the tibia and a specific offset joint in the foot, but lacked key placental features like a malleolus on the fibula and a complete mortise-and-tenon ankle joint. Its dental formula (5.1.5.3/4.1.5.3) is more typical of metatherians in incisor count, but its premolar-to-molar ratio resembles placentals. The presence of epipubic bones, absent in placentals but found in other mammals, suggests it gave birth to small, undeveloped neonates requiring extensive nurturing. This uncertainty reflects ongoing debate about the timing and relationships of early placental mammal origins.
Did You Know?
- Eomaia scansoria is known from a single, virtually complete fossil specimen about 10 cm long.
- Eomaia had epipubic bones, which are absent in placental mammals but found in all other mammals.
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