Yanbeilong

MEANING: North of Yanmen Pass dragon

PERIOD: Early Cretaceous

CONTINENT: Asia

Yanbeilong is one of the most recent stegosaurians, being from the Cretaceous while the majority went extinct in the Jurassic. It is closely related to Stegosaurus itself, and likely had two rows of large plates running down its back and the length of the tail, ending 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 Early Cretaceous. The Cretaceous is the third and final geological period of the Mesozoic Era, with the Early Cretaceous making up roughly the first half, lasting from about 143 to 100 million years ago. The poles were ice-free, due to the relatively warm climate, and forests extended into high latitudes. The continued breakup of the continents created new coastlines and isolated landmasses, influencing the evolution of distinct dinosaur faunas.

It was a time of transition, as many groups of animals and plants began to take on more modern forms while others declined or disappeared. Pterosaurs continued to thrive, though early birds were becoming more diverse and widespread. Mammals remained small but adapted to a variety of ecological niches. In the oceans, ichthyosaurs and plesiosaurs were common, and early mosasaurs began to appear.

Dinosaurs remained the dominant land animals, with groups like iguanodontians, spinosaurids, and carcharodontosaurids rising to prominence. While sauropods declined in some regions, they remained abundant in the Southern Hemisphere. The first true ceratopsians appeared, and ankylosaurs replaced stegosaurs in their niche. Dromaeosaurs and other small theropods diversified. During this time, the first flowering plants evolved, gradually changing global ecosystems by providing new food sources for herbivores.

Yanbeilong is a stegosaur. Stegosauria is a group of herbivorous ornithischian dinosaurs best known for their distinctive back plates and tail spikes. They first appeared in the Middle Jurassic and were most diverse during the Late Jurassic, although a few persisted into the Early Cretaceous. Stegosaurian fossils have primarily been discovered in the Northern Hemisphere, particularly in North America, Europe, and Asia, with fewer remains found in the Southern Hemisphere. Their distribution suggests they were successful in a range of environments, from floodplains to more arid regions, though they eventually declined in diversity as other herbivorous groups rose to prominence.

Stegosaurians were part of a larger group called Thyreophora, which also includes the heavily armored ankylosaurs. Early in their evolutionary history, stegosaurs developed simple rows of bony osteoderms for defense. Over time, these structures became more elaborate, evolving into the tall, broad plates and formidable tail spikes that characterize the group. These plates typically ran in two rows along the back and may have served multiple purposes including defense, thermoregulation, and display, though their exact function is still debated. At the end of the tail, most stegosaurs bore a set of long paired spikes which could have been used as a powerful weapon against predators.