Today, Callison is a happy retiree living in the Grand Junction area, where he spends his free time painting landscapes; check out his work here. But back in the mid- to late-'70s, he and the rest of a Southern California-based paleontological team that regularly ventured to a site near the small Western Colorado town of Fruita discovered the bones of what appeared to be a miniature dinosaur that would have stood about six inches tall -- and only three decades-plus later, they've been proven correct. A scholarly article for the Royal Society of Biological Sciences has formally dubbed the critter "Fruitadens haagarorum."
"I think we realized in a few hours" that they'd stumbled upon a previously unknown dino, Callison says. "But these things can take a while" -- to put it mildly.
The researchers didn't locate just one Fruitadens haagarorum. "Actually, there were three or four specimens, and we found them over a period of two or three years," Callison says. At the time, "I was working on a field expedition sponsored by California State Long Beach and the Los Angeles County Museum of Natural History, and we were exploring and discovering fossils at what was known as the Fruita Paleontological Area. We were looking for fossils of tiny animals that lived with gigantic dinosaurs, and it turned out in three or four instances that those tiny animals turned out to be dinosaurs themselves."
Spotting such small skeletal bits isn't easy. "The way they're discovered is by crawling around on the ground -- keeping our eyeballs close to the ground surface, so we can see tiny fragments that have weathered out onto the surface," he explains. "Once we start finding these fragments, we start looking uphill and try to find exactly the layer they're coming from. Once we find the layer, we hope maybe there will be more, and in this case, there were. Then we excavate around them and above them very carefully, so we can extract them as intactly as we possibly can and take them back to a laboratory so they can be carefully prepared for study."
Upon the completion of the steps in this case, the picture quickly grew clear.
"There were a few other kinds of vertebrates in that size and class that could have been confused for dinosaurs, so we didn't know for sure what we had until we found certain diagnostic pieces," Callison says. "The real clinchers were the ankle bones. Dinosaur ankles aren't unique, but they're nearly so among vertebrates. They're shared only with birds. When you're having fried chicken and eating a drumstick, the shape and combination of bones that hook to the foot can be found not only on chickens, but on small dinosaurs."
If the evidence was so convincing, why the delay between discovery and the official recognition of the dino?
"Preparing them for study can take some time," Callison allows. "And finding somebody who's interested and competent enough to study and publish on that particular kind of animal -- well, that doesn't come along every day. There aren't that many of us, so the field work frequently gets ahead of the lab and publishing work. In this case, it's been over thirty years, but it finally happened -- all the connections and interpretations were made, and it got published, thank goodness."
As for the name, Callison concedes that it's a bit confusing. For one thing, the "haagarorum " part of the moniker is actually a reference to an L.A. natural-history-museum benefactor. Moreover, "the 'Fruitadens' part of it is a combination of where we found it, near Fruita, and 'dens,' from the Latin root for 'teeth,' because it has odd teeth. But that makes it sound like a fruit eater, and even though its prominent food was plant material, there weren't any fruit-bearing plants until that time. They didn't come along until later."
Factoids like this explains why Callison, who retired in 1996 and subsequently moved to the Western Slope, doesn't paint dinosaurs, despite his paleontological background. "I guess I'm not brave enough to do it," he says. "Not only do you have to know a dinosaur's skeletal anatomy, and to be able to flesh it out with the muscle matches, you have to put them in a lifelike setting, and that requires a lot of research to know what kinds of plant were around during their time period and so on. Paleo-artists are very special people, and I haven't risen to that level yet."
Maybe not -- but he has a few other notable qualifications for the job.
