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Othnielosaurus It was a small bipedal dinosaur of less than two meters in length and 15 kilos in weight that lived to late Jurassic in what is now North America. The fossils of an individual of this species, of vegetarian habits, reveal that he suffered two fractures in his left foot, in addition to arthritis, which caused a limp that could hasten his death.
Thefossils dinosaurs say much more about these animals than we think. They not only allow us to identify a species or deduce its size.
Through thepaleopathology, paleontologists can also indicate what diseases or ailments they could suffer millions of years ago and if these were the causes of theirdeath.
“The study of the pathologies of animals of the past is an open window to know thebehavior and the biology of organisms that lived many millions of years ago”, He says Penelope Crusader-Knight, scientist at the Research Institute in Paleobiology and Geology of the National University of Río Negro in Argentina.
When analyzing thefractures of the fossils, can clarify if these were caused byrandom hits or bystruggles in mating seasons, and especially if they survived them. If they did, this would show how having these injuries or ailments affected them in their day-to-day lives.
In a study, published in the journalHistorical Biology, the scientist, together with the groupAragosaurus from the University of Zaragoza, researchers from the University of the Basque Country and other US centers, analyzed the bones of the apparently damaged left foot (phalanges) of a small bipedal dinosaur, calledOthnielosaurus consors, found in the 19th century in the Morrison Formation in the western US state of Wyoming, dating back about 150 million years.
The results confirm that this animal, with a vegetarian habit and weighing about 15 kilos, hadthree types of pathologies in itsfoot left: a form ofarthritis of metabolic, familial, or possibly idiopathic origin, and twofractures –One of impact and the other of pylon– that could have been caused by two accidents throughout his life.
"Both fractures were probably quitepainful and reduced the activity of the animal to some degree. We have been able to observe that the fractures show a certain degree of healing, so it can be thought thatOthnielosaurus survived with them for a time, although this made it difficult to walk and possibly caused alimp”Says Cruzado-Caballero.
A fatal outcome
According to the researchers, the pathologies in this individual prevented him from moving normally, limited him when it came to obtaining food and caused a more fragile state of health.
"This couldweaken it and make it easy prey for predators. Lameness and malnutrition could be the ultimate causes that led to thisOthnielosaurus to a fatal outcome ”, emphasizes the researcher.
The survival of this animal, also known asmarsh reptile in honor of its discoverer in 1879, - the famous American paleontologist Othniel Charles Marsh who starred in the War of the Bones along with rival Edward Drinker Cope - it shouldn't have lasted long, say the authors. The proof is that the impact fracture was not fully healed at the time of his death.
However, it is not entirely clear whether these ailments contributed directly or indirectly to its end, as the dinosaur was effectively able to avoid predators for a time. What the work does confirm is that the presence of pathologies in the feet of dinosaurs and other land vertebrates of the past “couldcondition the daily life of these animals ”, concludes Cruzado-Caballero.
P. Cruzado-Caballero et al. "A limping dinosaur in the Late Jurassic: Pathologies in the pes of the neornithischian Othnielosaurus consors from the Morrison Formation (Upper Jurassic, USA)"Biology History February 2020.