Paleontologist George Callison knew as soon as he found the bones that he had something good. The new field site, which would eventually be designated the Fruita Paleo Area, was yielding the smaller fossils which could be so hard to find. Dr. Callison had done his doctoral research on snake evolution and hoped to find an early snake species among these tiny fossils. This find was no snake, but it was exciting. The distal tibia of the tiny leg bone he uncovered was distinctive, and unlike any he had seen before. Dr. Callison likens it to finding a random car part. “If you find a spark plug, all you can conclude is that you’ve found something with an internal combustion engine. But if you find the hood ornament, then you know the make and model of the car you’ve found” says Callison. These bones were a hood ornament, and they told Callison that he had found something new, a whole new species in fact- the tiny dinosaur that would later be named Fruitadens haagarorum.
Dr. Callison found the first Fruitadens fossil in 1975, but it would take many years of study before the fossils would be formally described and named Fruitadens in 2009. Paleontologists now believe Fruitadens was about 26 to 30 inches long and weighed about 1.1 to 1.7 pounds, smaller than your average chicken. Like a chicken, it probably ate plant material as well as insects and other invertebrates. Fruitadens walked on two legs like a bird and its front limbs were shortened, making it look vaguely like a miniature Tyrannosaurus rex – but not as fierce.
Fruitadens is not the only species that has been discovered at the Fruita Paleo Area and named for Fruita. In the late Jurassic period, about 150 million years ago, Fruita was in a floodplain, there were braided stream channels lined with gallery forests, while away from the water the land was relatively dry, much like today. Fruitadens shared this habitat with other animals like Fruitachampsa. Dubbed “the housecat of the Jurassic” by Dinosaur Journey’s John Foster, Fruitachampsa was related to modern crocodiles, but it was entirely terrestrial and had the size and posture of a cat. A tiny mammal, named Fruitafossor gobbled termites like an armadillo. With oversized forearms for digging, it earned the nickname: “Popeye.” But unlike Popeye or an armadillo, Fruitafossor was tiny– when curled up in a ball, it could fit under a quarter.
Terrestrial crocs and miniature mammals may be very cool, but Fruitadens had an outsized impact on the world of paleontology for such a small creature. Prior to the discovery of Fruitadens, most paleontologists did not realize that dinosaurs could be tiny. Small dinosaur fossils were thought to be juvenile specimens of larger species. But Dr. Callison and his student, Helen Quimby, examined the Fruitadens fossils and realized that the ends of the long bones were fused as they are in adult vertebrates that have finished growing. Also, the relative sizes of different parts of the bones suggested that they were from an adult. Callison and Quimby looked at how the bones of birds like turkeys, ostriches and chickens changed as they grew up. (Birds are dinosaurs’ closest living relatives.) When these animals are young, the ends of the limb bones are large relative to their length giving them a “knobby” kneed look. But the Fruitadens bones had adult proportions. Based on these two lines of evidence, Callison and Quimby made a convincing case that Fruitadens was a small, but fully grown dinosaur. This caused paleontologists to go back and look at other small fossils and realize that many of them were indeed tiny dinosaur species – not just young.
Fruitadens is in fact the smallest dinosaur discovered in North America. Now you may be thinking: “Tiny dinosaur, don’t we call that a lizard?” But Callison explains that, unlike other reptiles, dinosaurs had a unique hip structure that gave them an erect posture. Picture how a Tyrannosaurus stands upright like a bird, or how a Triceratops’s belly is raised up off the ground like a cow’s compared to how an alligator’s belly drags on the ground with its legs sprawling out sideways. This difference in posture also suggests that dinosaurs had a higher activity level than other reptiles, meaning they spent a lot less time sunbathing. So while they are related, dinosaurs are not simply overgrown lizards.
The city of Fruita has rightfully embraced its paleontological prominence. We have a stylized Apatosaurus on our town logo and Greta the T-rex stands guard in Circle Park. But perhaps we have embraced the wrong species – those giant dinosaurs get all the glory. Shouldn’t a small town like Fruita appreciate the little guy? Shouldn’t a town that celebrates a headless chicken that refused to die also celebrate a tiny dinosaur that dodged 1,500-pound predators like Allosaurus? Greta the T-rex is here to stay, after all we need someone to protect us from the Grinch at Christmas. But I think that Fruita needs another dinosaur monument: a tiny Fruitadens– right next to Greta.
Thanks to Dr. George Callison for teaching me about tiny dinosaurs. Dr. Callison is not only a terrifically interesting scientist, but also a very talented landscape painter. You can check out his work on this website: http://georgecallison.com/. To learn more about Fruitadens and see a model, visit the Dinosaur Journey Museum here in Fruita, https://www.museumofwesternco.com/visit/dinosaur-journey/ -it’s fantastic. This post is soon to be published at www.fruitapulp.com, check it out there and learn more about life in Fruita, CO.