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.
In a paper published today in Proceedings of the National Academy of Sciences, Nick Longrich, a paleontology research associate in the University of Calgary's Department of Biological Sciences, 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.
Illustration of Hesperonychus elizabethae by University of Calgary
paleontologist Nick Longrich. Credit: Nick Longrich
"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 Longrich. "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."
"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.
Article: Nicholas R. Longrich and Philip J. Currie, "A microraptorine (Dinosauria–Dromaeosauridae) from the Late Cretaceous of North America", PNAS, March 16 advanced online edition
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Wait, Let's Not Be In Such A Rush To Go Multiplanetary Or Interstellar - A Comment On Elon Musk's Vision
- Petition To Youtube To Halt Ads On Doomsday Videos - They Make The Vulnerable Suicidal
- Paleo: In A Clinical Trial, Bread Made With Ancient Grains Could Benefit Heart Health
- Why Psychology Lost Its Soul - Science Replaced It
- Hubble Spots Europa Geysers Again - How They Did It - And What Next? Flyby? Lander?
- Chatelperronian Hominins: Disputed Neanderthal Region Confirmed In France
- No Go Area! What? What is that?
- "Seems you agree with me a few things. How would you make your own scale? (ignoring desire for the..."
- "Well, first there's the timescale. If you build a dyson sphere, you don't have the capability to..."
- "I don't think that much of the Kardashev scale. Especially L2,3 star vs galaxy. How would it be..."
- "When Descartes claimed ... the soul ... is eternal and indivisible... it's obvious he starts with..."
- "Oh, sorry to hear that, I hear this so often. Basically it's like propoganda I think. Propoganda..."
- Is Parenting Kids of Human and Canine Persuasion the Same? Yes!
- Diabetes: MiniMed 670G Hybrid Closed-Loop Insulin System Is A Waypoint To An Artificial Pancreas
- Celebrate Oktoberfest with Beer Chemistry
- Littlest Consumers Doing Well, Nutrition-wise
- Herpes Vaccine Update: Exciting News, But Don't Throw Away Condoms Just Yet
- Ben & Jerry’s Asks Us to Take Big Lick of Fear & Hype
- Antipsychotic medications linked to increased risk of pneumonia in persons with Alzheimer's disease
- Multiple sclerosis misdiagnosis shows need for improved education of clinicians
- Brown adipose tissue can secrete factors that activate fat and carbohydrate metabolism
- Therapeutic Gene Delivery for Inherited Retinal Degeneration in Children
- Molecular atlas of the pancreas