Small dinosaur size of dog lived in North America 60 to 100 million years ago

A small horned dinosaur, about the size of a large modern dog, with a puffin-like beak, lived in North America during the Late Cretaceous period, i.e. between 66 and 100 million years ago. Dr. Nick Longrich, a senior lecturer in palaeontology at the Milner Centre for Evolution, part of the University of Bath, England, who identified the fossil, said the very rare find provides evidence of an east-west divide in the evolution of North American dinosaurs.

North America looked very different during the Late Cretaceous period. It was really two continents – Laramida in the west and Appalachia in the east – divided by the Western Interior Seaway, a shallow sea that extended from the Gulf of Mexico to the Arctic Ocean.

The dinosaurs that lived in Laramida were similar to their cousins in Asia.

Small horned dinosaur
Dr. Longrich said this dinosaur’s jaw was slender, suggesting a diet of soft plants. The tooth rows also had an unusual twist – the upper jaw bent down and out – unlike any other dinosaur he had ever seen. (Image: University of Bath)

Fossil specimens are extremely hard to come by from the ‘lost continent’ of Appalachia because much of its fossil formations were destroyed by the Pleistocene ice age (5 million years ago).

Dr. Longrich studied a jaw fragment kept at the Peabody Museum at Yale University. The specimen had been collected 30 years earlier from a farm in North Carolina. He identified it as a member of the horned dinosaurs – the Ceratopsia. He wrote about his study in the peer-reviewed Elsevier journal Cretaceous Research.

Dr. Longrich wrote in The Conversation:

“It had been labelled as a duckbill dinosaur, but it didn’t look like any of the duckbills I’d seen in the field and museums. Instead, after comparing it with a range of species, the shape of the tooth sockets and curve of the jaw identified it as a Leptoceratopsid – a small, sheep-sized cousin of the giant Ceratopsids, such as Triceratops, that roamed in the west.”

Ceratopsia were herbivorous horned dinosaurs

Ceratopsia were herbivorous (plant-eating) dinosaurs that existed during the Cretaceous period. The specimen studied by Dr. Longrich was a smaller cousin of Triceratops – the Leptoceratopsids.

He was unable to accurately identify the species because the fossil was too incomplete. However, he detected an unusual twist in the jaw, which caused the teeth to curve downward and outwards, in a puffin-like beak shape.

North America millions of years ago
During the Late Cretaceous period, North America was two continents divided by the Western Interior Sea. The small dinosaur fossil was unearthed in Appalachia.

Compared to Ceratopsia found in the Laramida, its jaw was quite slender. Dr. Longrich believes this suggests that these dinosaurs’ diet was different from their western cousins’, and had evolved along a distinct evolutionary path.

Dr. Longrich explained:

“Just as many animals and plants found in Australia today are quite different to those found in other parts of the world, it seems that animals in the eastern part of North America in the Late Cretaceous period evolved in a completely different way to those found in the western part of what is now North America due to a long period of isolation.”

“This adds to the theory that these two land masses were separated by a stretch of water, stopping animals from moving between them, causing the animals in Appalachia to evolve in a completely different direction, resulting in some pretty weird looking dinosaurs.”

“Studying fossils from this period, when the sea levels were very high and the landmasses across the Earth were very fragmented, is like looking at several independent experiments in dinosaur evolution. At the time, many land masses – eastern North America, Europe, Africa, South America, India, and Australia – were isolated by water.”

“Each one of these island continents would have evolved its own unique dinosaurs – so there are probably many more species out there to find.”

Dr Nick Longrich – Profile

Dr. Longrich’s research focuses on using fossil records to understand major evolutionary transitions, both at the organism and ecosystem levels.

Dr Nick Longrich
“My goals are to continue work on the end-Cretaceous extinction event, and to launch new projects aimed at understanding vertebrate radiations and extinctions during the Cretaceous and Paleogene,” says Dr. Longrich, who says he also has a new theory on Brontosaurus. (Image: facebook)

He is interested in the origins of new types of organisms, including the evolution of snakes from lizards and birds from dinosaurs, as well as significant changes to the biosphere caused by ecologic events, especially the asteroid that we believe wiped out the dinosaurs – the Chicxulub asteroid.

According to Dr. Longrich:

“These transitions, which are responsible for the organisms and ecosystems all around us today, can only be understood using the paleontological record: a complete understanding of the patterns and processes of evolution requires fossils.”


“A ceratopsian dinosaur from the Late Cretaceous of eastern North America, and implications for dinosaur biogeography,” Nicholas R. Longrich. Cretaceous Research. January 2016, Pages 199–207. DOI: 10.1016/j.cretres.2015.08.004.