The coarsening-upward clastic sequence at Tebch, Inner Mongolia, China, containing the dinosaur Psittacosaurus mongoliensis, comprises the remains of a fluviolacustrine system deposited in an extensional tectonic setting.The presence of Asteropollis sp. cf. Asteropollis trichotomosulcatus (Singh) Singh, 1983 in conjunction with the absence of tricolpate pollen indicates a Barremian or possibly early Aptian age. The overlying Tebch basalt, dated by the 40Ar/39Ar laser step-heating method, yields a mid-Aptian age of 110 ± 0.52 Ma.This chronology supports the argument that the Juifotang Formation of the Jehe Group in western Liaoning is Early Cretaceous, with the Jurassic–Cretaceous boundary very low within, or below, the base of the Jehe Group. Our data also suggest that the Berriasian–Hauterivian (Neocomian) age suggested for the one known Russian locality that has yielded P. mongoliensis (Shestakovskaya Svita at Gorno-Altayaskaya, Avtonomnaya Oblast) may be excessively old.

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