Since the first discoveries of dinosaurs in the 19th century, when they were classified as reptiles, they were assumed to have a typically reptilian lifestyle and metabolism . This, applied to animals weighing several tons, resulted in the image of dinosaurs as clumsy, dumb, slow and lumbering reptiles. Failed experiments of nature, which were doomed to go extinct.
Throughout the 20th century, discoveries of new species of dinosaurs accumulated, that old image continued to prevail, and along with the dinosaurs, the entire Mesozoic world suffered from terrible prejudices. How could a world dominated by reptiles be if not a world doomed to disappear?
But things changed over time. In 1931, during an expedition to Montana by the American Museum of Natural History, paleontologist Barnum Brown found the skeleton of an ornithopod dinosaur, Tenontosaurus. Alongside the bones of this animal, bones of a small theropod dinosaur turned up, but its remains turned up inside a particularly hard rock. Thirty years had to pass before that site was returned to recover more fossils of this mysterious theropod.
In 1969 the paleontologist John Harold Ostrom published that new dinosaur, which he called Deinonychus antirrhopus , which means “terrible claw with counterweight”, referring on the one hand to the enormous curved claw on its foot and on the other hand to its apparently rigid tail. , which would help maintain balance during running and jumping. The result of these investigations shook the image we had of dinosaurs. So much so that this work by Ostrom is considered one of the most important milestones in paleontology in the mid-20th century: the definitive proof that not all dinosaurs were big, slow and heavy.
Deinonychus was slender and graceful. It had long hind legs, perfect for running and jumping, finished off with sharp claws, especially its “terrible claw”, typical of dromis or raptors. His arms were long and closely resembled the wing bones of birds. The tail, long and raised in a horizontal position, would help as a counterweight during running and jumping. We were facing a graceful and fast dinosaur, a predator that has nothing to do with that image of silly and slow dinosaurs doomed to extinction.
But the discovery of agile predators was only the beginning of this revolution. In 1975, paleontologists John R. “Jack” Horner and Bob Makela traveled to Montana looking for the origin of some fossils of eggshells and very small bones that had come to their laboratory. Asking local merchants, they came across some outcrops of the Two Medicine Formation, from the Upper Cretaceous. In the deposit they found nest-shaped structures, inside which they found fossil bones of hatchlings. What really constituted a great discovery was that the teeth of the hatchlings inside the nests showed signs of wear, which showed that they had been feeding in the nest itself. And that only had one possible interpretation: their parents fed them , took care of them. A real bombshell that helped to see dinosaurs as animals that could be social, that built nests and took care of their offspring, moving even further away from the image of a stupid and slow reptile that was held for decades.
The Dinosaur Renaissance had another discovery as an ally: the very biology of the dinosaurs, through paleohistological studies . We owe this new impetus to the French paleontologist Armand de Ricqlès , who applied his bone histology studies of modern animals to fossil vertebrates, with a special interest in dinosaurs. In his work, he revealed that sauropod dinosaurs were characterized by the abundance of a characteristic bone tissue, the fibrolamellar bone. This bone tissue is typical of fast-growing, high-metabolism animals , demonstrating that dinosaurs did not have a typically reptilian metabolism.
This new image of dinosaurs was much more than a “change in fashion”, it was a change in the scientific paradigm, which over time gradually permeated all the sub-disciplines of dinosaur paleontology. And it had consequences: their excavations were promoted again and their studies from a paleobiological perspective increased. And their reconstructions also began to change , since paleoart is a reflection of the scientific knowledge of the moment. At a popular level, this change was very slow, but the definitive shelving that transmitted this new image of dinosaurs to the entire public was the premiere of Jurassic Park in 1993.
Before the Dinosaur Renaissance , considering dinosaurs as obsolete reptiles, their extinction kept no one awake at night. Now, we value them in a way that is very close to us, the mammals. And if they disappeared, being well adapted to their environment , could we also disappear?
References:
Sanz, JL 2007. Dragon Hunters: History of the paleontologists who discovered and studied the dinosaurs. Ed. Ariel.
Gascó, F. 2021. That was not in my dinosaur history book. Guadalmazán.
Paul, G. 1988. Predatory dinosaurs of the world. New York, Simon and Schuster, 464 p.
Horner, J.R.; Makela, R. 1979. Nest of juveniles provides evidence of family structure among dinosaurs. Nature, 282 (5736): 296-298.
Ostrom, J. H. 1970. Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana. Bulletin of the Peabody Museum of Natural History, 35: 1-234.
