Character matrix for Cokotherium from A new mammal from the Lower Cretaceous Jehol Biota and implications for eutherian evolution

Here we report on a new Early Cretaceous eutherian represented by a partial skeleton from the Jiufotang Formation at Sihedang site, Lingyuan City, Liaoning Province that fills a crucial gap between the earliest eutherians from the Yixian Formation and later Cretaceous eutherians. The new specimen reveals, for the first time in eutherians, that the Meckelian cartilage was ossified but reduced in size, confirming a complete detachment of the middle ear from the lower jaw. Seven hyoid elements, including paired stylohyals, epihyals and thyrohyals and the single basihyal are preserved. For the inner ear the ossified primary lamina, base of the secondary lamina, ossified cochlear ganglion and secondary crus commune are present and the cochlear canal is coiled through 360^°. In addition, plesiomorphic features of the dentition include weak conules, lack of pre- and post-cingula and less expanded protocones on the upper molars and height differential between the trigonid and talonid, a large protoconid and a small paraconid on the lower molars. <i>Cokotherium</i> displays an alternating pattern of tooth replacement with P3 being the last upper premolar to erupt similar to the basal eutherian <i>Juramaia</i>. Parsimony analysis places <i>Cokotherium</i> with <i>Montanalestes</i>, <i>Sinodelphys</i> and <i>Ambolestes</i> as a sister group to other eutherians.This article is part of the theme issue ‘How Chinese fossils and palaeontological research impact our understanding of major evolutionary transitions’.