Sunday, March 05, 2006
[evomech] In the News: More info on "'Jurassic Beaver' find stuns experts"
Early Mammalian Evolutionary Experiments
Mammals of the Mesozoic era (248 to 65 million years ago) generally are considered to be primitive, shrew-like creatures living in the shadow of the dinosaurs (1). Only after the extinction of the dinosaurs at the end of the Cretaceous era (144 to 65 million years ago) did they have a chance to explore a greater variety of ecological niches. During the adaptive radiation that began about 65 million years ago, mammals were able to invade all kinds of terrestrial environments, even the aquatic and aerial realms. Pushing back the mammalian conquest of the waters by more than 100 million years, Ji et al. (2) report on page 1123 of this issue a Middle Jurassic, 164-million-year-old skeleton with a beaverlike tail and seal-like teeth perfectly adapted for an aquatic lifestyle.
Research Article the above Perspective refers to:The links work OK but email me if you have any problems (I made a typo on the research article url and got "We've redesigned our Web site, and some Carnegie Museum of Natural History pages have gone the way of the dinosaurs."!)
A Swimming Mammaliaform from the Middle Jurassic and Ecomorphological Diversification of Early Mammals
Qiang Ji,1,3 Zhe-Xi Luo,2,1* Chong-Xi Yuan,3 Alan R. Tabrum2
A docodontan mammaliaform from the Middle Jurassic of China possesses swimming and burrowing skeletal adaptations and some dental features for aquatic feeding. It is the most primitive taxon in the mammalian lineage known to have fur and has a broad, flattened, partly scaly tail analogous to that of modern beavers. We infer that docodontans were semiaquatic, convergent to the modern platypus and many Cenozoic placentals. This fossil demonstrates that some mammaliaforms, or proximal relatives to modern mammals, developed diverse locomotory and feeding adaptations and were ecomorphologically different from the majority of generalized small terrestrial Mesozoic mammalian insectivores.
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