Article by Anthony D. Fredericks
Paleontology – February 2009 – Colorado Central Magazine
AS I DRIVE INTO Cañon City I am immediately flanked by long rows of motels, a neon parade of fast food restaurants, and scores of brightly colored gas stations on both sides of the road. I quickly notice that the town is home to the Colorado Woman’s Correctional Facility (Note to self: Talk nice to all the waitresses and leave extra large tips.). Cañon City is also the gateway to the Royal Gorge -a stunning geologic wonder that has literally sucked the breath out of thousands of tourists when seen for the first time -especially if, like me, they have a passionate and abiding respect for very high (and/or very deep) geologic wonders.
However, my immediate destination is the Dinosaur Depot Museum — a former railroad depot lovingly turned into a small, but incredible, museum for dinosaur lovers of all persuasions. Soon after I walk through the door I meet Lois Oxford, who is both the Volunteer Coordinator and Lab Supervisor. A wide smile and an outgoing personality let me know that this will be both a rewarding and pleasant journey back in time. After a brief introduction, she leads me on a personal tour of the Museum which is crammed with dinosaur fossils of every size, shape, and description. The Museum’s space may be limited, but its displays are not.
One of the first displays visitors (especially kids) notice is the Allosaurus skull greeting visitors in the main exhibit room. Lois tells me that most people assume that it’s a T. Rex skull because it is similar in size and shape to that slightly more famous carnivore. However, as Lois points out, there are two ways to distinguish these creatures. For one, Tyrannosaurus was nearly twice as large as an Allosaurus (T. Rex weighed in at about six tons, attained a height of approximately eighteen feet [to the head], and was about forty feet long. Allosaurus, on the other hand, came in at around 1 and 1/2 tons, reached a height of nearly seven feet [at the hips], and had a body length of about twenty-five feet.). Even more significant, is the fact that Allosaurus had three fingers on each hand, while T. Rex only had two. Two fingers, three fingers -no matter, the razor-sharp claws on the ends of those fingers could do a job on any wandering herbivore unfortunate enough to get a little too close.
On the right hand wall of the main exhibit area is the fossil of a complete Stegosaurus stenops. Lois points to the informative sign and tells me, “We put the sign up there to let people know it’s not a fish.
“People would often stop and stare at the fossil thinking it was something other than a dinosaur.” The fossil is actually a full-size replica of the most complete Stegosaurus (only the front legs and shoulder are missing) known to science — one that was prepared and worked on in the Dinosaur Depot lab.
It was June of 1992 when a group of paleontologists from The Denver Museum of Nature and Science was working a dinosaur site at Garden Park Fossil Area just outside Cañon City. As chance would have it, one of the workers was prospecting one evening in a narrow canyon. Poking his rock hammer into an exposure on the rock face he pulled out the neck vertebra of a Stegosaurus dinosaur.
THE NEXT DAY a crew of diggers was dispatched to the site. Millimeter by millimeter and inch by inch the neck vertebrae were unearthed. Then, the most incredible discovery of all — an apparently intact skull (Dinosaur skulls are rare finds because their hollow and fragile nature is no match for intense and constant geological pressures over the millennia!) Using small probes, soft brushes and dilute plastics the fragile bone was slowly and carefully exposed.
The excavation of the skeleton continued in August of that year. A complete and articulated tail (with three of the four tail spikes in place) was also uncovered. As the excavation continued it was realized that this was an almost inclusive and very large specimen. Due to its completeness there was some degree of reluctance in dividing it up into pieces (a common practice in paleontology) for transport out of the isolated canyon. It was decided to contact nearby Fort Carson to see if they would be willing to donate the use of one of their Chinook helicopters to lift the completely jacketed Stegosaurus (with a total weight in excess of six and one-half tons) out of the canyon.
The excavation crew also contacted Colorado Quarries in Cañon City for some heavy machinery to dig out the complete skeleton. Meanwhile, volunteers worked feverishly to jacket the skeleton in layers of protective plaster. All that was left was for the Army to lift the payload out without banging into the narrow canyon walls. The entire crew watched (with the proverbial baited breath) as the helicopter pilot, using only verbal commands from the ground, successfully raised the payload and deposited it on a nearby flatbed truck. From there it was transported to the Dinosaur Depot Museum in Cañon City for preparation. It eventually took more than four years of preparation work before the specimen was ready for public display in the Museum.
EVER SINCE THE FIRST SPECIMEN was discovered just north of Morrison, Colorado, Stegosaurus has been a prehistoric puzzle. It’s name (“roofed lizard” ) comes from its most distinguishing feature -the double row of 17 tall, triangular plates rising from its neck, back, and tail. O.C. Marsh, who originally named the creature, mistakenly believed that the plates overlaid each other much like the shingles on a roof.
To date, approximately 80 specimens have been recovered in North America — primarily throughout the Morrison Formation. However, most recently (2007), a partial specimen from Portugal has been unearthed. This new discovery provides additional evidence in support of a prehistoric terrestrial connection between North America and Europe.
As I stare at the specimen on the wall of the Museum, I am taken by the excessive mass of this creature. In fact, an average adult Stegosaurus reached a length of about twenty-five feet and weighed in at around 5 to 5½ tons.
This would have made it equivalent to a modern-day Minke Whale. It was also distinguished by a seemingly under-sized head and an arched back that tapered at both ends to a tail (as long as its body). Its head was held low to the ground — an obvious advantage for a herbivorous dinosaur. It also possessed a toothless beak at the front of its mouth which it used to tear away low-lying vegetation. With a little imagination one could say that this creature looked like a small-headed elephant with severely shortened legs. It is speculated that it had a voracious appetite — feasting primarily on conifers, cycads, horsetails, ferns, and mosses. And, just like modern-day birds and crocodiles, it swallowed gastroliths to aid in the internal processing of food.
SCIENTISTS HAVE BEEN PUZZLED by the fact that Stegosaurus possessed a very small skull in proportion to the rest of its body. Analysis of the skull also suggests that they possessed an extremely small brain -about the size of a golf ball. In fact, while the overall weight of the Stegosaurus was in excess of five tons, its brain was a mere 2.8 ounces — an unbelievable ratio of brain weight to body weight of 1:57,142. Modern day creatures exhibit significantly higher ratios of brain weight to body weight as follows: fish — 1:5,000; reptiles: 1:1,500; birds — 1:220; most mammals — 1:180; and humans — 1:50 (It would be appropriate to mention that the ratio of brain weight to body weight for certain creatures — authors, for example — has yet to be determined.) Indeed, the brain of a Stegosaurus was one of the smallest among all the dinosaurs and was a factor that contributed to the mistaken and persistent belief that dinosaurs were dim-witted and unintelligent.
Another erroneous assumption was that this diminutive brain was insufficient to control such a large creature. As most anatomy professors will tell you, brain size is a rudimentary indicator of the intelligence of the animal to whom it belongs. That’s primarily because there is a complex and interlocking set of factors that affect a creature’s overall intelligence. There appears to be some degree of agreement, however, for the notion that higher ratios of brain to body mass (humans, for example) may increase the amount of brain mass available for high-level cognitive tasks (such as rocket science, quantum mechanics, or understanding the incredible popularity of Hannah Montana).
One of the ongoing conundrums of Stegosaurus research was the discovery of an enlarged region of the spinal column near the hip region. Initially, some scientists believed that this was a “second brain” — something that controlled the creature’s hind limbs. This theory has now been discounted and it is currently believed that the enlargement was not brain tissue, but a complex nerve center called the “sacral plexus.” The sacral plexis was, quite possibly, a secondary control center for the creature’s spinal cord.
ANOTHER ENDURING MYSTERY associated with this beast pertains to the dermal plates along its backside. Although these plates arose from the surface of the skin, rather than from its skeleton, their function has never been clear. Original theories suggested that the plates were used primarily as defensive structures — protecting the animal from attacks by large predators. This idea has been largely discounted, yet modern-day paleontologists still can’t agree on their function. One theory postulates that, because the plates had blood vessels running through them, they helped control the body temperature of the animals. Other researchers suggest that the plates were used to intimidate enemies by making the Stegosaurus look larger than it was. Still others suggest that they were used in some form of sexual display (“I’ll show you my dermal plates if you show me yours!”) or as a way to identify members of the same species.
As I continue to examine the specimen on the wall, I’m curious about the placement of the plates. As Lois tells me, one of the enduring “questions of the plates was whether they were alternating or straight-across from each other.” This particular specimen convincingly proved that the plates occurred as two rows of alternating plates, one running down each side of the midline of the creature’s back. Interestingly, in the 1933 version of King Kong, a Stegosaurus attacks the landing party sent to rescue Miss Driscoll (Fay Wray) from the hairy clutches of Mr. Kong. That particular Stegosaurus had its plates paired in a double row down its back. This was a popular interpretation in the 19thh and 20th centuries until the discovery of the specimen near Cañon City proved otherwise.
Many paleontologists will tell you that the Stegosaurus is, quite simply, a most mysterious dinosaur (“A puzzle wrapped inside an enigma and surrounded by a riddle.”). It has baffled scientists and perplexed the public ever since it was first discovered in the late 1800’s. One persistent mystery associated with Stegosaurus is the function of its thagomizer (tail spikes). Speculation in the early part of the 20th century postulated that these four spikes were used for display purposes only. However, paleontologist Robert Bakker provides some evidence (a tail more flexible than many other dinosaurs) that these spikes were used primarily as both defensive and offensive weapons. Ken Carpenter, a paleontologist who has done extensive field work at the Garden Park Fossil Area, offers additional evidence for this theory through an analysis of a punctured tail vertebra of Allosaurus into which a Stegosaurus tail spike fit perfectly.
When the Cañon City specimen was recovered two additional features about the spikes were noted. First, in opposition to some beliefs, it was discovered that the spikes came out from the sides of the tail, unlike old-fashioned models where the spikes would be arranged straight up and down. Second, it was noted that the bottom tail spike on this particular specimen was broken. The broken spike was immediately sent to Denver for a CAT scan which determined that the spike had been broken when the creature was alive — however, it never healed properly. As a result, a bone infection set in which eventually worked its way up the backbone of the creature.
AS MUSEUM PREPARERS WERE CLEANING the specimen they noted a series of brown markings near the front plate. These turned out to be pus pockets indicating that the creature was seriously infected as a result of the broken spike. It is now believed that the animal died from that infection. When I asked Lois more about the animal’s death, she tells me that the Stegosaurus probably “… went down to a pond and slid over on its side in the mud. That’s why the fossil is in the lying position. It got covered up fairly quickly which is why it’s pretty much intact.”
While the fossil replica is perched on the wall in the main room, the real bones are safely tucked in a climate-controlled room in the back of the Museum. “That’s because if they were exposed to the air — because of that bone disease — they would start to fall apart,” Lois tells me. That exposure to air would undoubtedly cause the complete skeleton to essentially disintegrate in about ten years or so. While the public can see a very detailed and very well-articulated skeleton perched on the east wall of the Museum, the actual bones are reserved for scientists to study in a more controlled environment.
There was another “Stegosaurus event” that took place in the 1980’s and which cemented this prehistoric wonder firmly in the minds of every Coloradan. In 1980 a fourth grade class at McElwain Elementary School in Denver noted that Colorado did not have (at that time) an official state fossil. After considerable discussion, the students decided to push for Stegosaurus as the official state fossil (since it had been first discovered in the state). As an extended lesson on legislation, the students learned about and went through all the appropriate procedures for proposing a bill. They also spent considerable time lobbying for its approval. The students traveled all over Colorado to post displays (at other schools) and rally at various community events. Finally, in 1982 Governor Richard Lamm issued the order establishing the Stegosaurus as the Colorado State Fossil. Then in 1991, the state Legislature passed another bill making it official. The lesson: Never underestimate the power of kids in love with a dinosaur!
Anthony D. Fredericks lives in a state with absolutely no Stegosaurs and whose highest mountain is a puny 3,213 feet in elevation. He is the author of more than 400 articles and 115 books. His latest book, Walking with Dinosaurs: Rediscovering Colorado’s Prehistoric Beasts (from which this article was extracted), will be published by Johnson Books (Boulder, Colo.) in the fall of 2009.
