When talking about paleontology , the first thing that usually comes to mind is the image of those huge dinosaurs that inhabited the earth between 210 and 66 million years ago. However, in the study of the life of the past, not only what those beings were like is analyzed. Many other animals and plants , the relationships between different species, and even ecosystems are also studied. The climate of the past is studied, or what the geomorphology of a given place was like.
Among the most interesting aspects that can be inferred from the fossil remains of extinct living beings is their behavior . After all, those animals ate, related and, of course, reproduced. And although there are many remains of nests, eggs and hatchlings, what is not so clear is how they copulated .
Of course, each species would have its own way of doing it , and given the enormous variety of species during the 115 million years that non-avian dinosaurs ruled the earth, talking about how they all did it would be as extensive as talking about how they all copulate. mammals .
Among the dinosaurs, one of the most famous is Tyrannosaurus rex , perhaps due to the influence of cinema, or because it is unfairly considered the largest land predator.
sexual dimorphism
Tyrannosaurs had what in biology is called sexual dimorphism , that is, males and females have apparent differences , as happens with the peacock.
Of the fifteen specimens of sufficient quality of Tyrannosaurus discovered, two forms have been distinguished, one more robust and the other more graceful . This is an age-independent trait, which is also found in modern dinosaurs—birds—and in animals closely related to them, such as crocodiles. And in these animals, these differences are usually associated with this sexual dimorphism.
There is an aspect, both in birds and in crocodiles, that is optimal to be able to differentiate males from females, and it is the way in which the hip is attached to the vertebral column . Thanks to the observation of this trait in the skeletons of Tyrannosaurus , it was possible to successfully identify that the robust form corresponds to the females, and the gracile form to the males .
This particular aspect that the robust form corresponds to the female and the graceful to the male could probably be extrapolated to all theropod dinosaurs —a group that, in addition to Tyrannosaurus , includes the well-known Compsognathus , Velociraptor, Spinosaurus or Giganotosaurus— .
However, to assume that this is a trait common to all dinosaurs is presumptuous to say the least. Not only are there no data to support such a conclusion, but there are observations that point in another direction. Ornithopods such as Edmontosaurus were large herd animals , and their behavior could be similar to that displayed by some mammals, with a dominant male and a group of females forming a harem . In those cases, the most plausible is that the more robust form coincided with the male.
How did they do it?
A study carried out by the paleontologist Peter L. Larson in 1994, published in the journal of the Paleontological Society , made it possible to verify this fact, and also infer how tyrannosaurs copulate . Most birds copulate by contacting their cloacae, and there is no intromittent organ. The exceptions to this rule are very specific and include mainly ducks and ostriches.
However, the data indicates that male Tyrannosaurus rex did, in fact, have a penis with which they penetrated their partner, similar to ostriches . Incidentally, the authors also infer from their study that tyrannosaurs were monogamous and probably maintained family groups .
Regarding posture, it probably also had similarities to how ostriches do. There would be a mount in which the male’s body would be placed on top of the female’s , and he would penetrate her from behind. That was the position they chose for the Cretaceous room in the Jurassic Museum of Asturias (MUJA) , in Colunga, where an impressive reconstruction of a pair of tyrannosaurs mating is exhibited.
REFERENCES:
Kauffman, GB 1988. How Dinosaurs Did It. Journal of College Science Teaching , 18 (2), 135-135.
Larson, P. L. 1994. Tyrannosaurus sex. The Paleontological Society Special Publications , 7 , 139-156. DOI: 10.1017/S2475262200009485
