Mexican paleontologists uncover bone pathologies in dinosaurs

Mexican paleontologists uncover bone pathologies in dinosaurs

19/09/2019
14:22
Fernando Guzmán Aguilar
Mexico City
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In the study, pieces of dinosaur fossils were identified, analyzed, described, and compared to healthy and sick bones from reptiles, birds, and mammals

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Dinosaurs had illnesses too, but which? Since there are no well-preserved skin fragments nor mummified organs, it is impossible to know which pathogens infected them or which heart or brain diseases they had.

Fortunately, dinosaur fossil bones “talk” about some of their diseases. Thanks to studies carried in the U.S., Canada, Argentina, and Russia, now we know these animals could develop cancer and arthritis.

Ángel Alejandro Ramírez Velasco, a paleontologist from the Sciences Faculty of the National Autonomous University of Mexico (UNAM), performed, under the direction of Elizabeth Morales, from the Veterinary and Zoological Medicine Faculty and of René Hernández, from the Geology Institute – the first study on bone pathologies in Mexican dinosaurs as his Master's dissertation.

For his postgraduate project, the paleontologist identified, analyzed, described, and compared bone pathologies in dinosaur fossils from paleontological collections of the Geology Institute and the Northwest Regional Station of the UNAM, of Borders, of the Museum of the Desert, of the National Institute of Anthropology and History Center of Coahuila and the Teacher’s School of Coahuila, as well as private collections, Claudio Leon’s among them.
 

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Pieces
Ramírez Velasco analyzed 9,446 pieces (they are called pieces and not specimens, because of many dinosaurs there are only fragments, such as a femur, a piece of rib, vertebrae, and other bone fragments.)

Pieces with pathological signs were subject to a comparative analysis with bones (both healthy and sick) of reptiles, birds, and mammals (some paleopathologies behave like those of these animals) and to histological studies.

“As happens with rocks, fossil bones are cut and integrated into a resin; then, they are put in a thin plate that is polished, and they can be observed without tint since they have color from minerals. Other pieces were subject to computed tomography in the PET/CT unit of the Medicine Faculty of the UNAM,” explains the paleontologist.

From all the fossil pieces of Mexican dinosaurs from the Cretaceous, only 1% presented anomalies: physical-traumatic disorders (43%), degenerative and proliferative disorders (18%), neoplasia (18%), development disorders (11%), inflammatory disorders (4%) and uncertain etiology (11%).

 

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In three out of six groups
Ramírez Velasco found paleopathologies only in three of the six groups: in duck-billed dinosaurs (Hadrosaurids), in horn dinosaurs (Ceratopsidae), and in a relative of the Tyrannosaurus rex called Labocania.

From the three groups, the one that presented more paleopathologies were the duck-billed dinosaurs: trauma injuries in ribs, caudal vertebrae, fibulas, and metacarpus, and in one ischium; inflammatory and development disorders in pedal phalanges; degenerative and proliferative injuries in caudal and sacral vertebrae, and in a tibia; neoplastic injuries in a cervical vertebra, a pubic bone and a tooth; and traces of an uncertain etiology in a humerus and a hand phalange.

“Three dinosaurs, possibly of different species, had trauma or fractures in their paws; others had rib injuries. Hadrosaurs, both from Chihuahua and Coahuila, had a common degenerative pathology, the kind of arthritis, in tail vertebrae,” says the paleontologist.

In a duck-billed dinosaur (from the collection of the Geology Institute), Ramírez Velasco identified a cancerous tumor, similar to a gruyere cheese, in the union of two cervical vertebrae. And since the tumor increased the separation between both vertebrae by several centimeters, it possibly cut the spinal cord.
 

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In another duck-billed dinosaur (Huehuecanauhtlus) discovered in Michoacán, he found two ribs and a thoracic vertebra in unusual pathological conditions that could be related to spinal osteomyelitis and a rib fracture.

“By the fracture, the rib was left unstable and fused with the vertebra, generating a bone mass that blocked nerves and caused back pain and partial paralysis in some of the arms of the dinosaur. The mass bone also present injuries caused by infections in the wound that was left open when the rib broke. On the brink of death, the dinosaur was prey to a carnivore because two teeth of carnivore dinosaurs were rescued, as if they were bullets in a crime; or it was devoured after dying.”

Tears or amputations
Regarding Ceratopsidae, quadrupedal herbivores similar to rhinoceros, from 2.5 to 9 meters long, with horns, and plates in the head, only two Coahuilaceratop magnacuerna presented pathologies.

One had a tumor in a skull bone; the other, an injury in the horns. These dinosaurs, according to studies carried in the U.S. and Canada, fractured the horns because they used them to fight between them or to defend themselves from predators.
 

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Lastly, Labocania, relative of the Tyrannosaurus rex, had avulsions (tears or amputations).

“It had a ligament tear in the jaw that must have caused it a lot of pain, reason why it might not have been able to hunt and died.”

As part of his PhD project focused on the taxonomy of Mexican duck-billed dinosaurs, Ramírez Velasco hopes to contribute under the direction of Jesús Alvarado Ortega, from the Geology Institute, with more information about the lives of hadrosaurs, a diverse group and, also, the most abundant in Mexico, and describe a new species.
 

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