Yanbeilong

Yanbeilong (meaning "north of Yanmen Pass dragon") is an extinct genus of stegosaurian dinosaur from the Early Cretaceous (Albian) Zuoyun Formation of Shanxi, China. The type and only species is Y. ultimus. It is considered one of the youngest definitive records of the group, alongside Mongolostegus from Mongolia and possible Stegosaurus remains from the Hekou Group of China, both of which date to the Aptian–Albian.

Discovery and naming
The Yanbeilong holotype specimen, SXMG V 00006, was discovered in 2011 in sediments of the Zuoyun Formation near Madaotou Township in Zuoyun County of Datong City, Shanxi Province, China. The specimen consists of the sacrum, both ilia, the left ischium, right pubis, seven dorsal vertebrae (two of which were isolated, the other five found in association with the ilio-sacral block), and a caudal vertebra.

In 2024, Jia et al. described Yanbeilong ultimus as a new genus and species of stegosaur based on these fossil remains. The generic name, "Yanbeilong", combines the Chinese "Yanbei", meaning "North of Yanmen Pass"—referencing the general area of the type locality—and "long", meaning "dragon". The specific name, "ultimus", is a Latin word meaning "last", referencing the fact that this taxon represents a late-surviving member of the stegosaur lineage.

Classification
Jia et al. (2024) recovered Yanbeilong as a deeply-nested member of the Stegosauria, as the sister taxon to a clade containing Stegosaurus stenops and Wuerhosaurus. The results of their phylogenetic analyses are shown in the cladogram below: