Mammals were present in higher numbers during the Jurassic Period (from 200 million to 145 million years ago) than previous studies have suggested, according to new research. Furthermore, it appears that small, rodent-like creatures were unexpectedly diverse during this era. In relation to this, researchers from the Beijing Museum of Natural History in collaboration with scientists working at the University of Chicago reported some new discoveries, from the northeastern region of China.
One of the tiny mammals, Agilodocodon scansorius, was arboreal and had long claws and sharp, gnawing teeth. It is considered the earliest tree-living mammal yet found. The other, Docofossor brachydactylus, was burrowed in the ground and is the earliest subterranean-dwelling mammal yet found. The new species, which both belong to an order of extinct mammals known as Docodonta.
Zhe-Xi Luo, University of Chicago biologist and coauthor on both papers, told online magazine Live Science: “What’s new with this discovery of two additional docodonts is that one of them turns out to be a subterranean mammal with highly specialized digit patterns; the other is a bona fide excellent tree climber. From their locomotory functions, we can safely infer that docodonts’ ecological diversity had a tremendous range—far more so than we previously anticipated.”
Interviewed by the website Science, John Wible, an expert in mammalian evolution at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania said that the findings “give us a very different view of mammal life during the age of dinosaurs.” Certainly the range and diversity of mammals was far wider than text books would suggest.
The new findings have been reported in two separate papers, published in the journal Science. The first is titled “An arboreal docodont from the Jurassic and mammaliaform ecological diversification.” The second is headed “Evolutionary development in basal mammaliaforms as revealed by a docodontan.”
