Chong-Xi Yuan from the Chinese Academy of Geological Sciences in Beijing, China, and colleagues from Carnegie Museum and the University of Chicago reported the discovery of the oldest rodent fossil ever found in the Aug. 15, 2013, issue of journal Science.
Rugosodon eurasiaticus is the oldest known fossil specimen of a rodent. The 160 million-year –old fossil is the earliest representative of the rodent-like group of mammals called multituberculates that inhabited Earth beginning in the Jurassic period and went extinct in the Oligocene epoch.
Rugosodon eurasiaticus was an omnivore based on the animal’s dental structure. The animal was most probably a land dweller but could have inhabited trees part of the time based on the structure of the ankles. The ankles allow for a higher level of rotation than most mammals that are not tree dwellers. The fossil was found in lake sediment and suggests the animal’s main habitat may have been lake shores. The animal was 6.5 inches long and weighed almost three ounces.
This is the most complete multituberculate fossil ever found and is very similar to another sample found in Spain. This similarity indicates the large range and large variety of adaptation that this group of rodents displayed during their long existence.
Rugosodon eurasiaticus and its kin lasted for a little more than 100 million years making these animals one of the longest enduring groups that ever existed.