Ceratopsians are best known for the triceratopsbut the family of herbivorous birds with beaks dinosaurs also numerous other relatives during the Late Jurassic to Late Cretaceous periods. Recently, however, a series of bone fragments revealed an entirely new, much smaller, primitive ceratopsian species—the easternmost of its kind ever found in Asia. Given initial dating estimates, the dinosaur may also bolster theories about how these unique animals migrated to present-day North America some 110 million years ago.
Sasayamagnomus saegusai is described in a study published September 2 by an international research team in the journal Articles in paleontology. Based on their analysis, they believe that Sasayamagnomus helped form a distinct neoceratopsian clade — a phylogenetic group consisting of one ancestor and all of its lineal descendants — along with North America’s Aquilops americanus and that of China Auroraceratops rugosusWith this new information, researchers argue for a revised evolutionary timeline that shows ceratopsians’ migration across continents occurred during the late Aptian or early Albian period, sometime between 113-110 million years ago.
(Related: Dinosaur footprints from Africa and South America match.)
According to a report dated September 4, announcement From Carleton University in Canada, paleontologists discovered the fossils in the city of Tambasasayama in southwestern Japan, most of which belonged to a single, young dinosaur that died before fully maturing. With a genus name that translates as “a (gnome) who guards hidden treasures beneath the ground of Sasayama,” an adult Sasayamagnomus was likely only about 80 cm (31.5 in) long and weighed just 10 kg (22 lbs). The neoceratopsian lacked the recognizable large horns and frills of its descendants, but an accompanying illustration indicates it still had the distinctive beak.
Due to their similarities to other primitive North American ceratopsians, researchers believe it’s likely that these dinosaurs began their march from eastern Eurasia to the continent during the mid-Cretaceous via the Bering Land Bridge. Depending on the era, the Bering Land Bridge was sometimes as much as 1,000 km (620 miles) wide, covering a total area of 1.6 million square kilometers (620,000 square miles) — the size of Alberta and British Columbia combined. However, unlike today’s Arctic climate, temperatures during the Cretaceous allowed for large forests that supported the biodiversity needed for the ceratopsian descendants of Sasayamagnomus to arrive in present-day Canada and the Americas.
Although researchers can only describe the young Sasayamagnomus with certainty based on a collection of skull, tibia, and coracoid fragments, this likely won’t be the last study paleontologists will undertake. At least some of the 17 fossils cited in the paper likely come from a second Sasayamagnomus.
