A new docodont mammal from the Late Jurassic of the Junggar Basin in northwest China

Fieldwork in the early Late Jurassic (Oxfordian) Qigu Formation of the Junggar Basin in Northwest China (Xinjiang Autonomous Region) produced teeth and mandibular fragments of a new docodont. The new taxon has a large "pseudotalonid" on the lower molars, and by retention of crest b-g exhibits closer affinities to Simpsonodon and Krusatodon from the Middle Jurassic of Europe than to the other known Asian docodonts Tashkumyrodon,Tegotherium, and Sibirotherium. It differs from the Haldanodon-Docodon-lineage by the "pseudotalonid" and large cusps b and g. A PAUP analysis based on lower molar characters produced a single most parsimonious tree with two main clades. One clade comprises Docodon, Haldanodon, and Borealestes, and the other Dsungarodon, Simpsonodon, and Krusatodon plus the Asian tegotherrids. Analysis of the molar occlusal relationships using epoxy casts mounted on a micromanipulator revealed a four-phase chewing cycle with transverse component. The molars of the new docodont exhibit a well developed grinding function besides cutting and shearing, probably indicating an omnivorous or even herbivorous diet. A grinding and crushing function is also present in the molars of Simpsonodon, Krusatodon, and the Asian tegotheriids, whereas Borealestes, Haldanodon, and Docodon retain the plesiomorphic molar pattern with mainly piercing and cutting function.