The reconstruction of the only existing dinosaur cloaca fossil may help clarify how this prehistoric animal mates. Related papers were recently published in “Contemporary Biology”.
The cloaca is an “omnipotent” opening in many animals, which can be used for mating, laying eggs, urinating and defecation, etc. Many animals including lizards, turtles and birds have this organ.
In 2016, Jakob Vinther of the University of Bristol in the United Kingdom and his colleagues analyzed the well-preserved skin of a parrot-billed dragon about 1 meter long. They noticed that the cloaca of this dinosaur also seemed surprisingly complete.
The Vinther team transformed this fossil, compressed and flattened for hundreds of millions of years, from a two-dimensional “pancake” to a three-dimensional digital model.
The research team then compared the cloaca of Psittacosaurus with that of other animals.
Most birds that evolved from dinosaurs reproduce mainly through “cloaca kisses.” Vinther believes that Psittacosaurus did not do this.
Most of its cloaca mouth is covered by two layers of skin, which makes the cloaca look more like a crocodile rather than a bird.
The male crocodile has a genital that extends from the cloaca, and Vinther’s team suspects Psittacosaurus also.
Moreover, the skin of this dinosaur may hide musk glands that can produce an attractive smell.
This conclusion echoes the previous conclusion reached by another team, who analyzed the same psittacius fossil.
The new analysis also showed that dinosaur cloacas contained large amounts of melanin.
Vinther originally thought that melanin was to prevent microbial infections, but melanin was on the outside of the skin, not inside the body, so researchers speculated that it might make the cloaca stand out.
Vinther said this visual signal is unusual.
He hypothesized that Psittacosaurus might attract partners like dogs, for example through sight and sniffing around the tail.
Thomas Holtz of the University of Maryland said: “We have never had such a close and personalized observation of dinosaurs before, at least in this part.”
But he pointed out that a sample makes it difficult to infer how typical these features are in Psittacosaurus or how typical they are in general dinosaurs.
However, he admitted that the possibility of finding a fossil with a soft structure intact is very low, but “I will not hold my breath.”
Related paper information:https://doi.org/10.1016/j.cub.2020.12.039