An analysis of a small dinosaur specimen may have solved the mystery of how horned dinosaurs arrived in North America. 

Paleontologists working with the oldest horned dinosaur ever found on the continent claim that they migrated from Asia via a land bridge between 113 million and 105 million years ago. The skull of the dinosaur was first uncovered in 1997, and up until that point early horned North American dinosaurs were only known by a small collection of teeth, bones and a tail.

Crow-Sized Horned Dinosaur The Oldest In North America

Crow-sized horned dinosaur: Filling in the gaps

Scientists have now named the new species Aquilops americanus, which lived during the Early Cretaceous, around 107 million years ago. Andrew Farke, a paleontologist at the Raymond M. Alf Museum of Paleontology in Claremont, California said: “It’s the first complete specimen of a horned dinosaur found in North America from that time. And it’s even more exciting because it’s not at all closely related to later horned dinosaurs from North America.”

Aquilops is actually closely related to Archaeoceratops oshimai and Leptoceratops gracilis, among others, which lived in Asia. “In most features, it’s virtually identical to them,” Farke told Live Science. “And that’s cool because it adds support for this idea that, around 110 million years ago or so, there was a big influx of animals from Asia into North America.”

Analyzing ancestry

The skull measures 3.3 inches in length, and doesn’t actually sport horns, but it does have other features that are unique to horned dinosaurs, such as a toothless beak known as a rostral bone. In Aquilops this bone has a small bump on the end, which might be the first stage of the horn seen on later relatives.

Other features include cheek spikes, possibly for defense, and around a dozen flat teeth which were probably used for cutting vegetation to eat, before it was mashed by other rounder teeth.

The finding is a leap forward in tracking the evolution of horned dinosaurs. The next known example did not live until around 20 million years later in North America, and the Triceratops is known to have lived 40 million years later.