MEANING: North of Yanmen Pass dragon
PERIOD: Early Cretaceous
CONTINENT: Asia
Yanbeilong is a stegosaurian dinosaur from the Early Cretaceous of what is now China. It is one of the most recent members of the group, being from the Cretaceous while the majority of stegosaurs went extinct in the Jurassic. Yanbeilong is a derived stegosaurian, closely related to Stegosaurus itself. Though absent from fossil remains, it likely would have had two rows of large plates running down its back and the length of the tail, which ended in long spikes. It also whould have had a long narrow skull, and longer hindlimbs than forelimbs.
Abstract from paper: Stegosaurs are a minor but iconic clade of ornithischian dinosaurs, and along with their sister taxon ankylosaurs form the clade Eurypoda, the major radiation of Thyreophora (armoured dinosaurs). We here report some stegosaurian materials from the Lower Cretaceous Hekou Group of the Zhongpu area, Lanzhou-Minhe Basin, Gansu Province, China. Most of the morphology of the specimen is similar to Stegosaurus stenops and Stegosaurus homheni. However, its dorsal vertebrae have a higher neural arch and smaller neural canal than Stegosaurus stenops. The neural arches of the dorsal vertebrae of Stegosaurus homheni are deeply excavated dorsal to the neural canal in anterior view, which is not present in GSAU 201201. Because the material is fragmentary, we consider the new specimen as Stegosaurus sp. In phylogenetic analysis, it is also recovered as the sister taxon of Stegosaurus stenops. This is the first stegosaurian dinosaur from Gansu Province, which extends the geographical range of Stegosauria and enriches the Cretaceous stegosaurian record. The Ankylosaur Taohelong jinchengensis is also from the same area and same layer as this stegosaur, which is new evidence that they lived in the same ecosystems alongside each other.
Yanbeilong is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.
The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.
The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.
Yanbeilong is a stegosaurian. Stegosauria is a group of herbivorous ornithischian dinosaurs that lived mainly during the Jurassic period, though there are some members known from the early Cretaceous. Stegosaurian fossils have been found mostly in the Northern Hemisphere.
Stegosaurians were armored dinosaurs; together with the ankylosaurs, they make up a larger group known as the thyreophorans. An early evolutionary innovation was the development of spikes as defensive weapons. Over time, these developed into much larger plates and spikes as the species within the group grew to larger size. These plates usually tend to run in two rows down the back, and end as spikes, known as thagomizers, at the tip of the tail.