Friday, August 16, 2013

[PaleoMammalogy • 2013] Rugosodon eurasiaticus • Earliest Evolution of Multituberculate Mammals Revealed by a New Jurassic Fossil from China


Rugosodon eurasiaticus Yuan,  Ji,  Meng,  Tabrum & Luo 2013
lived 160-million years ago on the lakeshores of what is now China

Abstract
Multituberculates were successful herbivorous mammals and were more diverse and numerically abundant than any other mammal groups in Mesozoic ecosystems. The clade also developed diverse locomotor adaptations in the Cretaceous and Paleogene. We report a new fossil skeleton from the Late Jurassic of China that belongs to the basalmost multituberculate family. Dental features of this new Jurassic multituberculate show omnivorous adaptation, and its well-preserved skeleton sheds light on ancestral skeletal features of all multituberculates, especially the highly mobile joints of the ankle, crucial for later evolutionary success of multituberculates in the Cretaceous and Paleogene.

A reconstruction of the extinct rodentlike creature, now called Rugosodon eurasiaticus, which lived 160-million years ago on the lakeshores of what is now China.
 Illustration by April Isch, University of Chicago

'Rugosodon' refers to the rugosity, or wrinkliness, of the mammal's distinctively shaped teeth.

For instance, multituberculates that lived 100 million years or more after R. eurasiaticus and were capable of tree climbing and jumping "had the most interesting ankle bones, capable of 'hyper-back-rotation' of the hind feet." Luo said. "What is surprising about this discovery is that these ankle features were already present in Rugosodon — a land-dwelling mammal."


The fossil of Rugosodon eurasiaticus is preserved in two shale slabs in part (left) and counterpart (right). It is about 6.5 inches (17 cm) long from head to rump, and is estimated to have weighed about 2.8 ounces (80 grams).
 Photographed by Zhe-Xi Luo of University of Chicago and Chongxi Yuan of Chinese Academy of Geological Sciences


Yuan, C.-X., Ji, Q., Meng, Q.-J., Tabrum, A. R. & Luo, Z.-X. 2013. Earliest Evolution of Multituberculate Mammals Revealed by a New Jurassic Fossil. Science. 341, 779–783. 


Fossil reveals features of mammal line that outlived dinosaurs
: Rodent-like animals were deft movers and flexible feeders.

Ancient Rodentlike Creature Once Dominated Earth

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