Sometimes time doesn't heal all wounds. Between mangled shoulder blades, fused vertebrae and hollowed out hips, several of the National Museum of Natural History’s dinosaur specimens still display the signs of diseases and injuries that date back more than 150 million years to the late Jurassic period.
According to paleontologist Matthew Carrano, the museum’s curator of Dinosauria, the signs of these ancient traumas are vital clues to what life was like during the Mesozoic. “It’s cool to think about how these animals were dealing with pathogens 80 or 100 million years ago,” he said.
But pinpointing prehistoric pathologies is no easy feat. Because paleontologists predominantly study fossilized bones, they can only diagnose diseases that leave marks on the animal’s bones. This makes it difficult to discover traces of ailments like stomach bugs, pneumonia or soft tissue injuries. And only certain types of clues make it into the fossil record. “It has to be this kind of middle of the road problem where it's not so small that it didn't leave a mark, but it's not so big that it killed the animal before it had time to affect the skeleton,” Carrano said.
In anticipation of this weekend’s World Veterinary Day (April 29), Carrano gave several prehistoric reptiles in the museum’s Deep Time Hall of Fossils a belated physical to diagnose the Mesozoic maladies these animals dealt with millions of years ago.
The museum’s toothy Smilosuchus mount could easily be mistaken for a crouching crocodilian. But the prehistoric creature, which terrorized Triassic waterways during the early days of dinosaurs, is not closely related to modern alligators or crocodiles. Instead it belongs to an ancient clade of armored reptiles called phytosaurs.
Similar to their modern look-alikes, phytosaurs like Smilosuchus were apex aquatic predators in many Triassic ecosystems. However the museum’s remarkably complete skeleton shows that life was not always easy for these burly beasts. According to Carrano, most of the skeleton’s limb bones are warped by disease. In 2021, he worked with a veterinarian to publish a paper outlining the many ailments across this skeleton which appear to be consistent with a pervasive infection.
But an exact diagnosis for this Smilosuchus, and nearly all other prehistoric creatures outside of rare freeze-dried ice-age mummies, is almost impossible. “In ancient animals you rarely can know which disease because you're not getting a fossil of that microbe,” Carrano said. “We can compare it to certain diseases in the modern world, but we can't do the ultimate test where we put it in a petri dish and see what bacteria grows.”
The museum’s adult Camptosaurus skeleton is surrounded by a slew of iconic Jurassic-age dinosaurs, which makes it easy to overlook. But this humble herbivore was no prehistoric pushover. Camptosaurus could grow up to 20 feet long and sported spur-like thumb spikes to ward off predators.
However, the Camptosaurus specimen in the museum’s fossil hall looks to be a little worse for wear. Carrano points out a deep, bowl-like cavity on the top of its hip.
“We see this giant pocket that shouldn't be there,” Carrano said. “What that looks like is a huge infection with a drainage space at the bottom.” He thinks it could have been caused by an injury that became infected or as a result of a bone disease. The size of the abscess tells Carrano that the Camptosaurus lived with this injury for a while.
The museum’s Ceratosaurus mount is in a tough spot. The Jurassic predator, which is known for its distinctive facial horns, is stuck on its back alongside an ornery Stegosaurus wielding its spike-covered tail.
While the dramatic set piece gives visitors an idea of the dangerous ramifications of a botched Stegosaurus hunt, it’s tough to get a sense of this Ceratosaurus specimen’s actual injuries without examining its real bones, which are stored in the museum’s collection (while many of the mounts in the fossil hall are composed of both real and cast bones, this Ceratosaurus mount is entirely a cast).
One of the specimen’s most striking features are several fused bones in the animal’s foot. “Where they should be three separate bones, these bones have grown together,” Carrano said. He also notes the fossilized hand of a duck-billed hadrosaur dinosaur in the museum’s collection displays a similar pathology. Its fingers are connected by excess bone growth that likely would have made it difficult for the dinosaur to use its hand.
Stretching nearly 100 feet, the museum’s Diplodocus specimen looks impenetrable. But even this colossal sauropod skeleton exhibits signs of wear. Carrano points out several vertebrae in the dinosaur’s elongated tail that appear to have fused together. Where the tops of other vertebrae point straight up, these compromised vertebrae are capped with bony growths of ossified tendons that give them a distinct ‘T-shape.’ “You've got these two chunks of the tail vertebrae that would have been immobile,” Carrano said.
The museum’s Diplodocus is not the only sauropod skeleton to sport these gnarled tail vertebrae. According to Carrano, “these fused vertebrae show up in a bunch of these dinosaurs and seem to show up in a certain part of the tail.” Possible explanations range from the sauropods repeatedly smacking this section of their tails against the ground when rearing up to their whip-like tails being arthritis-prone.
The museum’s remarkably complete Allosaurus specimen, which is posed tending to a nestful of fossilized eggs, has been studied for more than a century. But few have looked in depth at one of the apex predator’s striking abnormalities: a mangled shoulder.
According to Carrano, the Allosaurus’s left shoulder blade appears to have been broken and healed out of place. “There's a sharp bend in a bone that should otherwise be straight and there's an extra piece of bone that's also grown out” in the opposite direction, Carrano said. Instead of being shaped like an upside down spoon, the specimen’s shoulder resembles a two-pronged fork. “It's pretty ugly looking,” Carrano said.
This injury highlights how rough and tumble life during the Jurassic was when giant predators like Allosaurus were pursuing even bigger game. But to Carrano, it also illustrates the durability of dinosaurs. “For all I know that injury happened 10 years before the animal died and the Allosaurus just had to live with that problem,” Carrano said. “Life is just rough sometimes.”
Smithsonian Scientists Discover One of the Earliest Mammal Ancestors That Ate Its Veggies
What We’ve Discovered About the ‘Tyrant Lizard King’ Since the Nation’s T. rex Was Unearthed
2022 in Review: Smithsonian Staff Sifts Through an Ocean of Fossils
2022 in Review: The Year’s Top Discoveries by Museum Researchers