Who would have told a Psittacosaurus (the size of a dog) that approximately 120 million years later, scientists would be looking closely at its cloaca. That’s how it is. For the first time, a team of researchers from the University of Bristol (England) has described in detail the cloaca of a dinosaur, the hole that these creatures used to do everything: defecate, urinate, mate and lay eggs.
Although most mammals can have different openings for these functions, it is common among vertebrate animals to have a cloaca. And it’s funny that by now we already know so much about their appearance, their horns, their diet … we don’t know anything about this very important part of their anatomy .
Jakob Vinther from the University of Bristol School of Earth Sciences, along with colleagues Robert Nicholls, a paleoartist, and Diane Kelly, an expert on vertebrate penises and copulatory systems from the University of Massachusetts Amherst, have described in the journal Current Biology the first cloacal duct of a small labrador-sized dinosaur called Psittacosaurus, comparing it to the cloacas of modern vertebrate animals that live on Earth.
Experts examined a fairly well-preserved specimen of Psittacosaurus that was discovered in northwestern China (and on display at the Senckenberg Museum of Natural History in Frankfurt, Germany) and whose 120-million-year-old remains are in very good condition . so it has been the subject of many studies on primitive feathers and the coloring of these dinosaurs. But this is the first time that her genital opening has come to the fore.
Fortunately, this soft tissue structure is still visible in the fossil and is seen as a black striated area under the tail. According to scientists , there are not enough sexually dimorphic characteristics in the non-avian dinosaur to guess its sex , but the structure of the cloaca is similar to that of existing crocodiles, giving us an idea of its function and even how they mated. these creatures.
The cloaca of this dinosaur is an opening 1.7 centimeters long that it would have used for all these functions. The researchers found that the outer margins of this area were highly pigmented with melanin, suggesting that they also used it for visualization signals, to attract the attention of the other sex. In fact, modern baboons and some salamanders use similar mating tactics, as do a limited number of birds, including the eastern spotted pergolero.
Experts compared the fossilized sewer with modern sewers. His specimen is the only known non-avian dinosaur fossil that has a preserved cloaca , but due to the way the fossil is positioned, the internal anatomy of this opening has not been preserved; only the external vent is visible. This means that there is a lot of information left that scientists have not been able to discern.
The authors speculate that the large pigmented lobes on either side of the opening may have harbored musky scent glands, as we can see in today’s crocodiles.
“ As a paleoartist, it has been absolutely amazing to have the opportunity to reconstruct one of the last remaining features that we didn’t know about in dinosaurs. Knowing that at least some dinosaurs were communicating with each other gives paleoartists exciting freedom to speculate on a whole variety of now plausible interactions during dinosaur courtship. It’s a game changer! “Says Robert Nicholls.
It is the first and only sewer ever described, so it will be necessary to wait until the next fortuitous fossil appears.
Referencia: “A cloacal opening in a non-avian dinosaur,” J. Vinther, R. Nicholls and D. Kelly, Current Biology, 2021.
