The first occurrence of Troodon-morphotype tooth in Jiayin,Heilongjiang,Northeast China

Abundant dinosaur remains have been discovered from the Heilongjiang/Amur area for over one hundred years.Among these discoveries,an isolated small theropod tooth recently found from the lower part of the Yuliangzi Formation of Jiayin displays highly distinctive morphological features.It can be identified as a Troodon-morphotype tooth based on mesiodistal constriction at the base of the crown and large,hook-like denticles extending the entire length of both carinae.Previously,Troodon remains were mainly found in North America.Some isolated Troodon teeth were also discovered in Blagoveschensk and Kundur localities on the left bank of the Heilongjiang river.This specimen represents the first occurrence of Troodon-morphotype tooth in Jiayin,Heilongjiang,Northeast China.The presence of this taxon in Jiayin,Blagoveschensk and Kundur localities in the Heilongjiang area provides new evidence for faunal exchange between North America and Asia through Cretaceous Beringia.