The earliest evolution of mammals and origins of mammalian features can be traced to the mammaliaforms of the Triassic and Jurassic periods that are extinct relatives to living mammals. Here we describe a new fossil from the Middle Jurassic that has a mandibular middle ear, a gradational transition of thoracolumbar vertebrae and primitive ankle features, but highly derived molars with a high crown and multiple roots that are partially fused. The upper molars have longitudinal cusp rows that occlude alternately with those of the lower molars. This specialization for masticating plants indicates that herbivory evolved among mammaliaforms, before the rise of crown mammals. The new species shares the distinctive dental features of the eleutherodontid clade, previously represented only by isolated teeth despite its extensive geographic distribution during the Jurassic. This eleutherodontid was terrestrial and had ambulatory gaits, analogous to extant terrestrial mammals such as armadillos or rock hyrax. Its fur corroborates that mammalian integument had originated well before the common ancestor of living mammals.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
We thank G. Sun for proposing this research, and for his encouragement and support throughout; O. Dülfer for preparation of the fossil; P. Göddertz and K. Jäger for their CT scanning and virtual reconstructions; G. Oleschinski for SEM photography; and A. Isch for graphics support. We benefited from discussion with K. C. Beard, W. A. Clemens, M. R. Dawson, D. Y. Hu, W. v. Koenigswald, G. Sun and J.R. Wible. J. R. Wible and M. R. Dawson helped to improve the manuscript. Support was from the Key Lab for Paleobiological Evolution of Northeastern Asia, Ministry of Land Resources of China, and Shenyang Normal University and Paleontological Museum of Liaoning (C.Z. and S.W.), Deutsche Forschungsmeinschaft (DFG) (T.M.), Alexander von Humboldt-Foundation, National Science Foundation and the University of Chicago (Z.-X.L.). This is publication no. 60 from DFG Research Unit 771, Universität Bonn.
Video of virtual reconstruction from the micro-CT scanning and the animation before and after the correction of the fracture through M1. Lower teeth m1-m2: video of virtual reconstruction from the micro CT scanning and the animation of the correction for the taphonomic compression of lower m1 and m2. See Supplementary Information file for Technical details on CT scanning parameters and virtual reconstruction software.
About this article
Skin mites in mice (Mus musculus): high prevalence of Myobia sp. (Acari, Arachnida) in Robertsonian mice
Parasitology Research (2018)