How much of a dinosaur you see in photographs and museums is the authentic dinosaur? Well, it depends on the dinosaur.
Leroy Kameron Durrant, an undergraduate student at the University of Wyoming (UW), reexamined “Reed’s Allosaurus,” a historically significant dinosaur specimen found near Laramie almost 150 years ago.
The result was a fascinating insight into a thoroughly plastered prehistoric beast.
“There’s plaster and paint over most of the bones, and one bone had three or four metal wires drilled through it,” Durrant told Cowboy State Daily. “But seeing broken bones isn’t fun, so that’s what they did to get it ready for display in the museum.”
Durrant and the other UW researchers had to look inside the bones to determine how much dinosaur they had to work with. To do that, the 150-million-year-old fossils had to go to the hospital.
The project revealed the anarchy of early paleontology and how modern-day technology can restore some of the damage done in the past.
“People are noticing these famous specimens are plastered, which led to many flawed analyses that weren’t flawed at the time,” Durrant said. “We’re in the world of computed systematics, and our view of dinosaur taxonomy is changing because of it.”
Reed’s Allosaurus
The specimen Durrant studied was UW 11541, a partial skeleton of a Late Jurassic Allosaurus from the Morrison Formation. It was discovered by William Harlow Reed, a famous dinosaur hunter and the first curator of the UW Geological Museum.
Reed was one of the dinosaur hunters hired during the Bone Wars, a strange period of scientific advancement and personal rivalry between two paleontologists, Othniel Charles Marsh and Edward Drinker Cope.
The primary battlefield was Como Bluff near Medicine Bow, but Cope and Marsh’s teams scoured several states searching for the biggest and best dinosaur specimens to dig up and send back East to their ultra-petty and competitive bosses.
Reed, who worked for Marsh, didn’t have to search hard to find “his” Allosaurus. He first found the bones already excavated at the Union Pacific depot in Laramie in 1879.
“The story was they were found in some buttes south of Laramie,” said UW Geological Museum volunteer Beth Southwell. “Reed saw them in a little display case at the depot. He sent a message to Marsh once he got to Como, and Marsh wanted him to go back and get the rest of the specimen, but the train ticket cost $10 more than Reed had.”
The rest of the specimen was recovered between 1879 and 1890. Reed acquired it from another of Marsh’s dinosaur hunters on behalf of the UW Geological Museum, and UW 11541 became one of the museum’s centerpiece displays (after some aesthetic enhancement).
In 1921, a burst pipe flooded the basement of UW’s Science Building. Several one-of-a-kind specimens were destroyed, and Reed’s Allosaurus was one of the many casualties.
“The bone was glued with vegetable glue, there was a lot of plaster holding it together, and it was on a very wiggly-looking mount,” Southwell said. “It was one of many things that were ruined in the flood.”
Not as pretty as it used to be, UW 11541 moved into UW’s vast paleontological collections. It’s been studied by other paleontologists since, and a 1976 monograph on Allosaurus by James Madsen determined it was one of the largest Allosaurus specimens ever found.
Like many historical specimens, Reed’s Allosaurus was studied but not scrutinized. Paleontologists weren't overly concerned with how much of the specimen was reconstructed rather than authentic, focusing on what they were looking for rather than taking it all in.
It was time for a critical re-analysis of this significant specimen. With funding from the Wyoming Research Scholars Program, Durrant set out to do just that.
Plastered Dinosaurs
Why would someone take an authentic dinosaur fossil and cover it with plaster? Because it looked better that way.
When Durrant started his re-analysis of Reed’s Allosaurus, he was handed “a ball of plaster with broken bone bits within it,” covered with layers of paint and creosote to obscure the delineation between plaster and prehistoric.
“The main issue wasn’t that the individual bones were destroyed in the flood,” he said, “but that they were being held together by plaster.”
Reed’s Allosaurus consists of several broken backbones, several bones of varying completeness from the left leg, and the left side of the hip. It wouldn’t make for a dynamic display in a museum, so Reed followed the precedent of his peers and used plaster to make it better.
“If you have a public museum, people don’t want to see a bunch of broken bones,” Durrant said. “Because of that, they’d plaster over broken bones to make them whole. Allosaurus is the most common theropod in the Morrison Formation, so they restored the specimen with plaster to show people what the complete fossils looked like.”
An archival photo from 1910 shows Reed’s Allosaurus on display in the UW Geological Museum. The fossils look exquisite to the untrained eye, despite the plethora of plaster used to make them look this way.
Durrant’s goal was to determine the percentage of fossils versus plaster. However, he couldn’t remove the plaster, which was keeping the delicate fragments together.
Time for a doctor’s visit.
Parts Of A Plastered Whole
Durrant and Laura Vietti, the collections manager of the UW Geological Museum, arranged for the fossils to be sent to Ivinson Memorial Hospital in Laramie for an inside look at the plastered dinosaur.
CT scans are valuable tools for paleontologists, as they can reveal the internal structure of dinosaur bones that can’t be studied without damaging the specimens. In this case, the CT scans would help determine the ratio of fossil and plaster for each bone of Reed’s Allosaurus.
“Ivinson Memorial Hospital did the CT scan as a generous gift,” Vietti said. “They didn’t charge us for the time or technology. That was a very nice thing they did for us.”
The CT scans uncovered the truth without disturbing the fossils. Using a program called 3D Slicer, Durrant examined the digital data and determined how much of Reed’s Allosaurus was Reed’s Allosaurus.
“Half of the ischium, the backwards bone in the hip, was fake,” he said. “The pubis was broken up, but all there. The tibia survived quite well, with all the plaster and paint still intact. The femur took some damage, and the ilium is unrecognizable in its current state.
Durrant was able to make a revised skeletal diagram of Reed’s Allosaurus. Many of the fossilized bones were still intact, but they were far from the picture of perfection displayed in 1910.
The CT scans also solved another amusing mystery. One of the bones defied description until it was revealed to be more than one bone.
“There was a little bone that I couldn’t identify for the life of me,” Durrant said. “The CT scan showed it was two different bones, glued and wired together in a way we couldn’t see from the surface.”
Fragilis Unambiguous
Another goal of Durrant’s re-analysis of Reed’s Allosaurus was to determine which species of Allosaurus the bones belonged to. That’s easier said than done.
In 1890, there was only one species of Allosaurus: A. fragilis. In 2025, there are four species, and more could be identified as the field of paleontology advances.
This is part of a field called taxonomy. It can be hard enough to do with living animals, let alone ones that have been extinct for 150 million years.
“Allosaurus has had a strange taxonomic history,” Durrant said. “It's gone through a bunch of different names and people named animals that were clearly Allosaurus as something new. But since the 1970s, all of the Allosaurus specimens in the Morrison Formation were lumped into A. fragilis.”
Marsh, Reed’s employer, named Allosaurus in 1877. He also named Apatodon, Creosaurus, and Labrosaurus based on specimens found at Como Bluff that have all been reassessed as Allosaurus.
Big Al, the most famous Allosaurus specimen in the world, was found near Shell in the 1990s. It’s been classified as the species A. jimmadseni.
Specimens of Allosaurus found in Portugal were classified as A. europaeus. In 2024, a new species – A. anax – was described from an Allosaurus specimen found in Oklahoma in 1931, previously known as Saurophaganax.
Taxonomy is tricky, but Durrant knew what to look for. The definitive 1976 Allosaurus monograph classified Reed’s Allosaurus as A. fragilis, but Durrant’s concern was that the identification may have come from plastered pieces rather than the original fossil.
“There’s a circular notch near the top of the pubis that is one of the few features that can be used to identify the species of Allosaurus,” he said. “The notch on this specimen is fairly small and very circular, which shows we were looking at a specimen of A. fragilis.”
Durrant confirmed that Madsen got it right in 1976. The bones used to identify the species in that study “matched one for one” with this study.
Plaster Disasters
CT scanning has proven to be an immensely valuable tool in the paleontology arsenal, but that doesn’t mean it’s a universal solution. The nice thing about Reed’s Allosaurus was that its bones could fit inside the CT machine at Ivinson Memorial Hospital.
That’s a problem for Julian Hernandez Diepenbrock, a graduate student at UW’s Department of Geology and Geophysics who assisted with Durrant’s project. He’s doing a similar project with a much larger historic specimen.
“We have a very nice Apatosaurus on display in the museum,” he said. “The specimen was intended for display at multiple times and multiple places, so there was a need to make it look a little prettier. That means we’ve got some pretty heavy plaster reconstruction.”
Diepenbrock says UW’s Apatosaurus is still remarkably complete, around 60-65% actual fossil. However, some of its diagnostic features, which previous paleontologists used to describe it as an Apatosaurus, are plaster reconstructions.
The entirety of Reed’s Allosaurus weighs less than one of the bigger bones in the UW Apatosaurus.
“We're not getting this one to a hospital CT scanner anytime soon,” Diepenbrock said. “Or any time ever, really.”
Diepenbrock is conducting a thorough re-analysis of the UW Apatosaurus to determine its fossil vs. plaster content and whether it’s really an Apatosaurus or some other Jurassic sauropod.
He won’t be able to use the same technology as Durrant, but is utilizing the same principles and informed skepticism to get closer to the truth beneath the plaster.
“(Plaster reconstruction) is a problem that's common with a lot of dinosaur specimens from the 1800s,” he said. “It’s a function of what we knew back then versus what we know now, and changing scientific priorities when it comes to how the bones should look.”
The CT scan and a segmented render of the tibia and ischium (hip and leg bones) of UW 11541, "Reed's Allosaurus." The bright sections of the CT scan are actual fossilized bone, while the dark sections are plaster reconstructions. Using CT scanning allows paleontologists to determine how much of a historic fossil is real or reconstruction without having to damage the fossils themselves. (Courtesy Leory Kameron Durrant) 
The left pubis, one of the hip bones, of UW 11541, "Reed's Allosaurus," next to its CT scan. This 150-million-year-old bone is mostly completely, but the dark spots on the CT scan show where plaster was used to fill in missing pieces and present a "complete" fossil for display. (Courtesy Leory Kameron Durrant) 
Fossilized bones from the foot of UW 11541, "Reed's Allosaurus," next to their CT scans. The digital data reveals that sections of these fossils have been reconstructed with plaster, and one fossil was sculpted entirely of plaster without any fossilized material inside. (Courtesy Leory Kameron Durrant)
Better Than Before
Reed’s Allosaurus is thoroughly smothered in plaster, obscuring valuable fossil material under a thick veneer of plaster and paint. And it’s going to stay that way.
While it’s theoretically possible to separate modern plaster from prehistoric bones, there isn’t the time or the need to do so. Reed's plastered Allosaurus has value as a historical and paleontological object.
“It’s important to keep it as it is,” Durrant said. “That’s the beauty of CT scanning. We can keep the plastered specimen as it is for historical purposes while looking at the real specimen, internally and externally. “
Durrant knows Reed’s Allosaurus inside and out and didn’t have to dismember the historical objects to ascertain their paleontological significance. He was also able to reconfirm that it’s one of the top three largest Allosaurus specimens ever found, which will undoubtedly be of interest to others studying the dynamics of the Late Jurassic Period.
Thanks to modern technology, paleontologists can study the structure and shape of fossilized bones without having to cut through the plaster encasing them. Durrant sees his project as an important reminder for other paleontologists to examine historic dinosaur specimens with a degree of informed distrust.
“People are noticing that these famous specimens are largely plastered, and basing many of our guesses on those reconstructions and illustrations wasn't the best idea,” he said. “Our view of dinosaur taxonomy is changing because of research pointing out these flawed analyses.”
Vietti, who oversaw Durrant’s project and is overseeing Diepenbrock’s work on the UW Apatosaurus, finds this new, technological approach vindicating for paleontology, even if it shatters some long-held assumptions from historic specimens like Reed’s Allosaurus.
“We're continuously studying and restudying specimens, and sometimes we don't always see the results we want,” she said. “At the same time, we are getting a better handle on what we have and what we understand about it. That’s science.”
Double Check It
Plastered specimens have been proliferating paleontological research since before the Bone Wars. If Durrant has learned anything from his project, it’s not to study superficially regarding historic dinosaur specimens.
“If you have a historic specimen that's been described, but it was described over 100 years ago, double-check it,” he said.
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
