Dinosaur Diseases and Injuries: What Fossils Reveal About Prehistoric Health

Dinosaurs may have been the most successful land animals in history, but they were far from invincible. Their bones carry evidence of broken limbs, infected wounds, aggressive cancers, parasitic infections, and degenerative diseases that are strikingly similar to those affecting modern animals—and even humans. The field of paleopathology (the study of ancient diseases) has turned dinosaur fossils into medical case files millions of years old.

Broken Bones and Traumatic Injuries

Healed Fractures

Dinosaur bones frequently show evidence of breaks that healed during the animal’s lifetime, proving these injuries were survivable:

Allosaurus “Big Al”: One of the most studied dinosaur specimens ever found, this juvenile Allosaurus had 19 separate injuries including broken ribs, infected foot bones, and a fractured shoulder blade—yet survived long enough for many injuries to partially heal
Tyrannosaurus rex “Sue”: The most complete T-Rex ever found had healed rib fractures, fused tail vertebrae, a torn tendon in the right arm, and signs of a severe leg infection. Despite these injuries, Sue lived to an estimated 28 years—a long life for a T-Rex
Triceratops: Many specimens show healed fractures on the frill and horns, consistent with horn-to-horn combat with other Triceratops
Sauropods: Healed rib and tail fractures are common, possibly from falls, predator attacks, or intra-species conflicts

Bite Marks

Some of the most dramatic injuries come from predator bites:

Specimen	Evidence	Interpretation
Edmontosaurus tail	Chunk bitten off and healed	Survived a T-Rex attack
Triceratops frill	Puncture wounds matching T-Rex teeth	Predator-prey combat
Tenontosaurus bones	Deinonychus tooth marks	Attacked by raptors
T-Rex face bones	Bite marks from another T-Rex	Intraspecific combat

The most remarkable example is an Edmontosaurus specimen with a large bite taken from its tail—the wound shows extensive bone regrowth, meaning this hadrosaur survived a T-Rex attack and lived for months or years afterward. This tells us that predator attacks were not always fatal, and dinosaurs had remarkable healing abilities.

Face-Biting in Tyrannosaurs

Multiple T-Rex skulls show healed bite marks on the face and jaw that match the teeth of other T-Rex individuals:

These injuries are concentrated on the lower jaw and snout
They are consistent with face-biting during dominance disputes or mating competition
Some bites were severe enough to crush and deform facial bones, yet the animals survived
Similar face-biting behavior is seen in modern crocodilians during territorial disputes

Infections and Diseases

Osteomyelitis (Bone Infections)

When bacteria infect bone, they leave distinctive marks that are preserved in fossils:

“Big Al” the Allosaurus: Multiple foot bones show severe osteomyelitis—the infection likely entered through a wound and spread through the bone, causing swelling and pain that would have made walking agonizing
T-Rex “Sue”: A massive infection in the left leg created a large abscess visible in the bone. Some researchers suggest this infection may have ultimately contributed to her death
Hadrosaurs: Several specimens show infected jaw bones, possibly from dental abscesses (infected teeth)

Trichomonosis: The Jaw-Eating Parasite

In 2009, researchers identified lesions in T-Rex jaws that match those caused by Trichomonas gallinae, a protozoan parasite that causes devastating oral infections in modern birds:

The parasite erodes holes in the jaw bones—and identical holes are found in multiple tyrannosaur specimens
The infection would have made eating extremely painful or impossible
In severe cases, the animal may have starved to death due to inability to feed
This suggests that T-Rex—the ultimate apex predator—could be brought down by a microscopic parasite

Respiratory Infections

A specimen of the sauropod Dolly (a diplodocid) shows abnormal bony growths in the neck vertebrae where air sacs connected to the respiratory system
These growths are consistent with a respiratory infection (like pneumonia or aspergillosis)
This is the first evidence of respiratory illness in a dinosaur and suggests dinosaur lungs were vulnerable to similar infections as modern birds

Cancer in Dinosaurs

The First Diagnosed Dinosaur Cancer

In 2020, scientists published a landmark study confirming osteosarcoma (aggressive bone cancer) in a Centrosaurus leg bone:

The fossil had been known since the 1980s but was originally misidentified as a healed fracture
Advanced medical imaging (CT scans) and comparison with human osteosarcoma samples confirmed it was cancer
The tumor had progressed significantly, meaning the animal lived with cancer for some time
Being part of a protective herd may have allowed the weakened individual to survive longer than a solitary animal would have

Other Cancerous Growths

Hadrosaur tumors: Several hadrosaur specimens show bony growths consistent with benign tumors (osteomas)
Hemangioma: A type of blood vessel tumor has been identified in dinosaur vertebrae
Osteochondroma: Benign bone tumors found in several dinosaur species

Cancer is not a modern disease—it has plagued vertebrates for hundreds of millions of years. Dinosaur cancers tell us that cancer is an inherent vulnerability of complex multicellular life.

Arthritis and Degenerative Diseases

Osteoarthritis

Just like aging humans, elderly dinosaurs developed joint problems:

Iguanodon: Multiple specimens show fused vertebrae and eroded joint surfaces—classic signs of osteoarthritis
Hadrosaurs: Joint degeneration in the legs, especially in larger, older individuals
Sauropods: Fused tail vertebrae are extremely common, suggesting that arthritis was nearly universal in long-lived sauropods
T-Rex “Sue”: Fused tail vertebrae and eroded leg joints indicate significant arthritis in her later years

Gout

Some theropod specimens show crystal deposits in joint tissues consistent with gout—a painful condition caused by uric acid buildup
Modern birds excrete uric acid (rather than urea like mammals), making them susceptible to gout. Dinosaurs likely had the same metabolism, making gout a plausible condition

Spondyloarthropathy

A condition causing inflammation and fusion of vertebrae, similar to ankylosing spondylitis in humans
Found in multiple hadrosaur and sauropod specimens
Would have caused progressive stiffness and pain in the spine

Dental Problems

Dental Abscesses

Hadrosaurs had dental batteries of hundreds of tightly packed teeth. When teeth broke or wore unevenly, bacteria could invade, causing painful abscesses
Several hadrosaur jaw bones show large holes from burst abscesses, with surrounding bone showing infection damage
T-Rex specimens also show dental infections—biting through bone regularly must have cracked and damaged teeth

Tooth Wear and Replacement

Most dinosaurs continuously replaced their teeth throughout life, which limited dental problems
Sauropods like Diplodocus replaced individual teeth roughly every 35 days
Hadrosaurs could have over 1,000 teeth in their jaws at once, with new teeth constantly growing in
Ceratopsians had unique self-sharpening tooth batteries that wore in specific patterns

Parasites

While soft-bodied parasites rarely fossilize, indirect evidence is abundant:

Coprolites (fossilized feces) from dinosaurs contain parasite eggs and cysts, proving internal parasites were common
Biting insects preserved in amber (including ticks and biting flies) were certainly parasitizing dinosaurs—a tick engorged with dinosaur blood was found preserved in Cretaceous amber in 2017
Bone lesions caused by blood-borne parasites have been identified in several dinosaur species
Trichomonosis (described above) represents a devastating parasitic infection

What Injuries Tell Us About Dinosaur Life

Paleopathology reveals important aspects of dinosaur biology:

Dinosaurs could survive severe injuries: Healed fractures and survived predator attacks prove remarkable resilience and healing ability
Social structure mattered: Injured herd animals (like the cancerous Centrosaurus) could survive because the herd provided protection
Intraspecific combat was common: Face-biting in tyrannosaurs and horn injuries in ceratopsians show that dinosaurs fought each other regularly
Dinosaurs aged: Arthritis, gout, and degenerative diseases prove that some dinosaurs lived long enough to develop age-related conditions
Predation was dangerous for both sides: Predators suffered injuries too—“Big Al” the Allosaurus was riddled with hunting-related injuries

Frequently Asked Questions

Q: Did dinosaurs get colds or flu? A: They likely suffered from respiratory infections, as evidenced by the Dolly specimen. However, “colds” and “flu” are caused by specific viruses that target mammals, so dinosaurs would have had their own viral diseases—which don’t preserve in fossils.

Q: Could diseases cause dinosaur extinctions? A: While disease alone probably couldn’t wipe out all dinosaurs, epidemics may have stressed populations. Some researchers have proposed that diseases spread by migrating species could have contributed to localized extinctions. However, the asteroid impact remains the accepted cause of the mass extinction.

Q: How do paleontologists distinguish injury from disease? A: Injuries typically show a clear point of trauma (fracture line, bite mark) with healing radiating outward. Diseases tend to show more diffuse changes across larger areas of bone. CT scanning and histological analysis (microscopic bone structure) help differentiate the two.

Q: Did dinosaurs have immune systems? A: Absolutely. The presence of healed infections and survived injuries proves that dinosaurs had functioning immune systems. As vertebrates closely related to birds and crocodilians—both of which have robust immune systems—dinosaurs certainly possessed sophisticated immune defenses.

The study of dinosaur diseases and injuries humanizes these ancient animals in a way that few other fields can. They suffered pain, fought infections, healed from wounds, developed cancer, and grew old with arthritis. In sickness and in health, dinosaurs were far more like us than we might expect.