North America’s smallest dinosaur discovered

From the University of Calgary in Canada:

Mini dinosaurs prowled North America

Paleontologists unlocking the diversity of prehistoric hunters with discovery of pint-sized cousin of Velociraptor

Massive predators like Albertosaurus and Tyrannosaurus rex may have been at the top of the food chain, but they were not the only meat-eating dinosaurs to roam North America, according to Canadian researchers who have discovered the smallest dinosaur species on the continent to date. Their work is also helping re-draw the picture of North America’s ecosystem at the height of the dinosaur age 75 million years ago.

“Hesperonychus is currently the smallest dinosaur known from North America. But its discovery just emphasizes how little we actually know, and it raises the possibility that there are even smaller ones out there waiting to be found,” said Nick Longrich, a paleontology research associate in the University of Calgary’s Department of Biological Sciences. “Small carnivorous dinosaurs seemed to be completely absent from the environment, which seemed bizarre because today the small carnivores outnumber the big ones,” he said. “It turns out that they were here and they played a more important role in the ecosystem than we realized. So for the past 100 years, we’ve completely overlooked a major part of North America’s dinosaur community.”

In a paper published today in the scientific journal Proceedings of the National Academy of Sciences, Longrich and University of Alberta paleontologist Philip Currie describe a new genus of carnivorous dinosaur that was smaller than a modern housecat and likely hunted insects, small mammals and other prey through the swamps and forests of the late Cretaceous period in southeastern Alberta, Canada. Weighing approximately two kilograms and standing about 50 centimetres tall, Hesperonychus elizabethae resembled a miniature version of the famous bipedal predator Velociraptor, to which it was closely related. Hesperonychus ran about on two legs and had razor-like claws and an enlarged sickle-shaped claw on its second toe. It had a slender build and slender head with dagger-like teeth.

“It was half the size of a domestic cat and probably hunted and ate whatever it could for its size – insects, mammals, amphibians and maybe even baby dinosaurs,” Longrich said. “It probably spent most of its time close to the ground searching through the marshes and forests that characterized the area at the end of the Cretaceous.”

Fossilized remains of Hesperonychus, which means “western claw,” were collected in 1982 from several locations including Dinosaur Provincial Park. The most important specimen, a well-preserved pelvis, was recovered by legendary Alberta paleontologist Elizabeth (Betsy) Nicholls, after which the species is named. Nicholls was the curator of marine reptiles at the Royal Tyrrell Museum in Drumheller and earned her MSc and PhD degrees at U of C. She passed away in 2004. The fossils remained unstudied for 25 years until Longrich came across them in the University of Alberta’s collection in 2007. Longrich and Currie focused on fossilized claws and a well-preserved pelvis for their description.

“The claws were thought to come from juveniles- they were just so small. But when we studied the pelvis, we found the hip bones were fused, which would only have happened once the animal was fully grown”, Longrich said. “Until now, the smallest carnivorous dinosaurs we have seen in North America have been about the size of a wolf. Judging by the amount of material that was collected, we believe animals the size of Hesperonychus must have been quite common on the landscape.”

Currie and Longrich last year described the previous record-setting small North American dinosaur, a chicken-sized insectivore named Albertonykus borealis.

The discovery of Hesperonychus is the first sign of small carnivorous dinosaurs in North America and also extends the timeframe of small, birdlike dromaeosaurs known as the Microraptorinae in the fossil record by approximately 45 million years. Specimens from China have been found dating to 120 million years ago, while Hesperonychus appeared to have thrived until the end of dinosaur age in the late Cretaceous.


The paper “A microraptorine (Dinosauria–Dromaeosauridae) from the Late Cretaceous of North America” by Nicholas R. Longrich and Philip J. Currie is published in the March 16 advanced online edition of the Proceedings of the National Academy of Sciences at:

See also here.

About Albertonykus, smallest dinosaur of North America before this discovery: here.

See also here.

Dino Mites: A Diminutive Dinosaur in North America and a Rare Mass Death of Young Relatives in China: here.

Walking With Dinosaurs steps off the TV screen: here.

2 thoughts on “North America’s smallest dinosaur discovered

  1. Many dinosaurs once found Alaska hospitable

    SCIENCE LESSON: Kids learn about far-away times when giants walked tundra.

    Fairbanks Daily News-Miner

    Published: March 16th, 2009 01:38 AM
    Last Modified: March 16th, 2009 01:38 AM

    FAIRBANKS — The Arnold Espe Auditorium at the University of Alaska Museum of the North was filled to capacity last week with people hoping to learn about dinosaurs that roamed across Alaska 70 million years ago.

    The program began with “Arctic Dinosaurs,” a one-hour documentary produced by NOVA that presented different theories surrounding dinosaur survival in the polar north during the late Cretaceous period. The film speculated on the effects of four months of continuous darkness on dinosaurs, although, based on plant evidence, temperatures weren’t nearly as cold as today’s, and also hypothesized about adaptations and migratory theories.

    Linked to all these possibilities is the extensive Liscomb fossil bed on the banks of the Colville River and the construction of a permafrost tunnel dug in 2006 to excavate fossils from the bed, which is estimated to be 3 feet thick. The idea was to access large fossils deep in the bed, as well as examine better-preserved fossils not exposed to repeated freeze-thaw cycles, such as those at the top of the bed.

    The tunnel might provide some answers to the mysteries of arctic dinosaurs, said Patrick Druckenmiller, a paleontologist, assistant professor with the Department of Geology and Geophysics and curator of earth sciences at the museum.

    “It seems like we’ve just started to figure things out with those dinosaurs on the North Slope,” Druckenmiller said. “I think we’re really going to start finding some good stuff in there.”

    The 40 or so children in the audience, when not wowed by the documentary’s computer-generated dinosaur footage, appeared restless during scientists’ interviews and theoretical analysis.

    Following a brief question and answer period after the film, when children wondered if dinosaurs lived in the ocean and which was the tallest, the key point of interest was made available for viewing and touching: three tables of fossilized bones, teeth and tracks.

    Most of the kids couldn’t wait to get their hands on a Tyrannosaurus Rex tooth or hold a Velociraptor skull.

    “Dinosaurs are pretty cool,” said Aidan Mulrooney, 6. “And I know quite a lot.”

    Did he know dinosaurs once roamed Alaska?

    “No, that’s one thing I learned,” he admitted with a good-natured smile.

    Some attendees weren’t as concerned with Alaska dinosaurs in particular but brought their kids for the rare chance to handle some of the bones and replica casts on display.

    “It’s neat that they are able to touch things,” said Amy Olsen, whose 4-year-old son, Samuel, poked at the teeth of a Brachylophosaurus while her younger son, Silas, gazed sleepily at the proceedings while resting on her back. “He asked if we’d see dinosaurs here. I didn’t think so, so this is a real bonus.”

    “We had to bring them here; they love dinosaurs,” Beth Poisson said. Her two boys, Carter, 4, and Reece, 3, busily examined anything within reach. “The older one wants to do his own excavations in the backyard. He’s been burying pillows and stuffed animals.”

    “When it comes to dinosaurs and kids, they are inseparable,” Druckenmiller said.


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