How would you like to look out your second-story window one day and gaze into the eyes of a giant predator with serrated teeth the size of bananas? It could certainly jump-start your workday with more power than a slug of espresso.
This impressive dinosaur lived west of Fort Collins, on the east shore of what is now Horsetooth Reservoir—hence its nickname the “Monster of Masonville.” But while we share this creature’s territory, it lived 150 million years ago—before Colorado’s mountains powered their way upward, at the growth rate of a fingernail, through the rich sediments of ancient wetlands now described by geologists as the Morrison Formation.
I’ve known about the Monster of Masonville since 1990, when a Coloradoan writer named Madonna Kukay wrote about its discovery. But I didn’t ferret out the details until March 5, when I attended the Western Interior Paleontological Society’s symposium, “Journey to the Jurassic,” at the Colorado School of Mines.
Dr. Joe Sertich from the Denver Museum of Nature and Science discussed the Monster of Masonville fossils, including parts of the giant’s skull, that reside in the museum’s modern catacombs. Then, Dr. James Kirkland, who discovered the predator when he was a graduate student, talked about his current work in Utah, describing the rich trove of dinosaur fossils there. The colorful and sometimes controversial Dr. Robert Bakker, then at the University of Colorado, described Kirkland in a Los Angeles Times article as the “Dinosaur Dundee of Colorado” for his ability to sniff out dinosaur bones a mile away.
Our local dinosaur resembled the better-known Tyrannosaurus rex, but lived far before T. rex’s time. Scientists first named it Epanterias, believing it was a genus related to isolated bones found near Canon City in 1877 and in Oklahoma in 1934.
But Sertich and other scientists now believe the Monster of Masonville was a super-sized version of Allosaurus, which is usually a somewhat more modest-sized predator (only 25 feet long and two tons in weight). Our monster weighed closer to four tons and stretched 50 feet long—clearly a predator with some gravitas in his day and time. Moreover, instead of the wimpy forelimbs of T. rex, Allosaurus sported impressive and highly functional hands capable of toying effectively with any struggling prey.
A geologist friend of mine, Herb Saperstone, wondered why our local museum didn’t have at least a copy of this incredible find. Being compulsively curious, he checked into the matter. It turns out that the Fort Collins Museum of Discovery does have Monster of Masonville replicas tucked away in a classroom. The giant jaws, a vertebra and a piece of the tail rest safely encased under plexiglass, prodding us to ponder the times when the echo of this dinosaur’s steps gave shivers to those creatures that might become its next meal.
The Los Angeles Times article indicates that Bakker & Co. found significant portions of an Allosaurus post-cranial skeleton, along with the remains of “a smaller beast that may have served as its last meal.” Sertich failed to cite any references about a formal description of the find, so perhaps an eager graduate student someday can reveal more secrets of our resident monster.
If you would like to see our local monster, contact Kirk Wilkinson, public programs coordinator at the Museum of Discovery, to make arrangements. I plan to return to the museum later this year with paleo friends of mine from the Denver area to show them one of the dinosaurian wonders of Northern Colorado.
As an artist with a penchant for time traveling, it’s always exciting to have the past revealed in startling and unexpected detail — as long as it’s not giving me a hungry stare through a second-story window.
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