The spinicaudatan Tylestheria and biostratigraphic significance for the age of dinosaur eggs in the Upper Cretaceous Majiacun Formation, Xixia Basin, Henan Province, China

The spinicaudatan Tylestheria was first described from the clam shrimp (“conchostracan”) Halysestheria yui Zone in the upper Turonian First Member of the Nenjiang Formation, which crops out in the Songliao Basin in Heilongjiang and Jilin provinces, north-east China. Representatives of the genus have been found previously only in this basin. The species described herein as Tylestheria xixiaensis sp. nov. was recovered from the dinosaur-egg-bearing Majiacun Formation in the Xixia Basin, south-west Henan Province. The age of this formation has been uncertain hitherto, with both Early and Late Cretaceous determinations having been made. The recovery of T. xixiaensis from it suggests that the fossil bearing strata can be correlated with the First Member of the Nenjiang Formation and are, therefore, also of Turonian age.