Roots of the Mammalian Family Tree


Filling in the Gaps in Evolutionary History
Because very few skeletons of early mammals have been found, scientists have had only vague ideas about their lifestyles. The completeness of the Jeholodens jenkinsi skeleton, however, has allowed Dr. Luo and his collaborators to reconstruct some of the complexities of mammalian evolution. Studies of Jeholodens jenkinsi have shown that this early mammal had a very advanced shoulder blade and collarbone. The flexible connections of these bones indicate that its forelimb was capable of an almost erect gait. It walked with an erect posture indicative of an active lifestyle, rather than with the sprawling gait of primitive mammals and reptiles. Yet, in contrast to the advanced shoulder and forelimb, Jeholodens had a very primitive pelvis, sprawling hind limbs, and splayed hind feet. Many of its hind limb features are comparable to those of reptiles. These features reveal a more complex early evolution of the mammalian skeleton than previously imagined. The enigmatic combination of advanced features with primitive features in Jeholodens jenkinsi suggests that different parts of organisms evolve at different evolutionary rates. Unearthing \| Early Mammals \| Filling in the Gaps \| Beyond Liaoning