A 78-million-year-old herbivorous horned dinosaur has been identified from a fossil found in the Tar Heel Formation (Black Creek Group) in North Carolina.
The Black Creek horned dinosaur was about the size of a large dog. Image credit: Nicholas Longrich / University of Bath.
Dr Nick Longrich, a paleontologist at the University of Bath, UK, encountered fossil in question in Yale University’s Peabody Museum collections.
The specimen – a fragment of a jaw bone – comes from a smaller cousin of the famous ceratopsian dinosaur Triceratops.
According to a study published in the journal Cretaceous Research, this unusual specimen is the first ceratopsian dinosaur known from the Late Cretaceous period of eastern North America.
“The Black Creek ceratopsian represents a highly derived member of the Leptoceratopsidae,” Dr Longrich said. “Along with basal tyrannosauroids, hadrosaurines, ornithomimosaurs, and nodosaurs, it was part of a distinctive fauna that emerged during the Late Cretaceous in eastern North America.”
Because the fossil is incomplete, the paleontologist isn’t able to identify the exact dinosaur species it belonged to.
But the specimen shows a strange twist to the jaw, causing the teeth to curve downward and outwards in a beak shape. It is more slender than that of ceratopsid dinosaurs found in western North America, suggesting that these dinosaurs had a different diet to their western relatives, and had evolved along a distinct evolutionary path.
A section of leptoceratopsid dinosaur jaw bone from the Tar Heel Formation. The fossil provides evidence of an east-west divide in North American dinosaur evolution. Abbreviations: ag – alveolar groove; dp – dentigerous process. Image credit: Nicholas Longrich.
“During the Late Cretaceous period (100 to 66 million years ago), the land mass that is now North America was split in two continents by a sea, which ran from the Gulf of Mexico to the Arctic Ocean,” Dr Longrich said.
Dinosaurs living in the western continent, called Laramidia, were similar to those found in Asia. However, few fossils of creatures from the eastern continent, Appalachia, have been found because these areas being densely vegetated, making it difficult to discover and excavate fossils.
“The presence of a highly specialized ceratopsian in eastern North America supports the hypothesis that Appalachia underwent an extended period of isolation during the Late Cretaceous, leading the evolution of a distinct dinosaur fauna dominated by basal tyrannosauroids, basal hadrosaurs, ornithimimosaurs, nodosaurs, and leptoceratopsids,” Dr Longrich said.
“Appalachian vertebrate communities are most similar to those of Laramidia. However some taxa – including the Black Creek dinosaur and other leptoceratopsids – are also shared with western Europe, raising the possibility of a Late Cretaceous dispersal route connecting Appalachia and Europe.”
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Nicholas R. Longrich. 2016. A ceratopsian dinosaur from the Late Cretaceous of eastern North America, and implications for dinosaur biogeography. Cretaceous Research, vol. 57, pp. 199-207; doi: 10.1016/j.cretres.2015.08.004
