CLAREMONT, Calif., Dec. 10 (UPI) -- How did Triceratops end up in North America? Apparently it all started with a dino several thousand times smaller -- the Aquilops americanus, literally "American eagle face."
The new species is the oldest horned dinosaur discovered in North America; at more than 108 million years old, Aquilops americanus is 40 million years older than Triceratops and 20 million years older than the previous oldest horned dinosaur.
New fossils were discovered by a group of paleontologists from the University of Oklahoma. Unearthed in Montana, the bones have allowed scientists a fresh glimpse at the beginnings of the ceratopsian group in North America -- a group featuring a wide disparity in size. The Aquilops americanus fossils suggest the ancient horned dino weighed no more than three-and-a-half pounds and was roughly the size of a rabbit. The later-arriving Triceratops was thought to weigh as much as 25,000 pounds.
Aquilops' skull, in contrast, fits in the palm of a human hand; and at full maturity, researchers say, the dinosaur wouldn't have stretched longer than two feet. The new discovery is described in the journal PLOS ONE.
"Aquilops is the first fossil to show what the earliest horned dinosaurs in North America looked like," study author Andrew Farke, a curator at the Raymond M. Alf Museum of Paleontology, said in a press release. "Scattered teeth and bones from around the same time showed us that these animals were here, but not much else was known."
The newly discovered species mostly closely resembles ceratopsians from Asia, suggesting the mini dino -- which scavenged the forest for plants to munch on -- first migrated from the Far East beginning more than 110 million years ago. Researchers say it was part of the first of three waves of horned dinosaurs to travel, over a span of 60 million years, from Asia to North America, when the two continents were connected by a land bridge.