Scientists Discovered How Dinosaurs Mate By Reconstructing Its Cloacal Region

Humans have studied dinosaurs for many years using the several bones these creatures left behind. However, these durable and long-lasting remains of dinosaurs do not tell scientists how they mate. The organs responsible for reproduction are soft tissues that are harder to come by.

But experts from the United Kingdom were able to reconstruct the cloacal regions of Psittacosaurus from the fossil specimen unearthed in Sihetun, in northeast China's Liaoning Province. Psittacosaurus is a Labrador dog-sized dinosaur that lived from around 145-100.5 million years ago.

According to BGR, examining that fossil would provide a wealth of detail in the hindquarters of the dinosaur. The reconstructed cloaca is a 0.7-inch-long opening that would have been used for excretory purposes, like defecating or urinating, and also for mating.

Science Times reported that cloacas are primarily found in vertebrate animals but not on humans. For example, birds bring together their genitalia for a few seconds when they mate to exchange fluids in a process that experts dubbed as a 'cloacal kiss.'

The researchers published their study in Current Biology.

ALSO READ : What is Cloaca? And Why Do Most Animals Have it Except Humans?

Mates Like Modern Crocodiles

The researchers said that the cloacal region of Psittacosaurus bears some similarities with modern crocodiles, like having lips on either side. They also noticed that the outer margins of the cloaca's vent area were highly pigmented, which could mean that they use it for signaling displays.

This is a similar mating tactic that baboons and some salamanders use today and some birds like the alpine accentor and the spotted bowerbird. The researchers also think that the lobes of the cloaca contain musky scent glands like the ones seen in modern crocodiles.

Paleontologist Jakob Vinther of the University of Bristol explained that they had reconstructed the cloaca's colorful patterns using a remarkable fossil of Psittacosaurus at the Senckenberg Museum in Germany. But since it is something new, it took a while for the team to reconstruct it fully.

Looking at the similarities of the modern crocodiles' fossilized vent, the researchers said that it is also likely that the Psittacosaurus may similarly have a penis concealed within its cloaca. But since soft tissues are not well-preserved compared to bones, the researchers cannot confirm the sex of the fossilized dinosaur.

Last Missing Piece

Brittanica defined cloaca in a vertebrate animal as a common chamber and outlet that the animal uses to defecate and urinate, as well as in mating. It is commonly found in amphibians, birds, reptiles, elasmobranch fishes (such as sharks), and monotremes.

However, the cloaca is not present in placental mammals and most bony fishes. Those who have cloaca usually have an accessory organ or a penis to direct their sperm into the female animal's cloaca, just like in some birds and ducks. But in most bords, they join their cloacas in a cloacal kiss when mating.

University of Bristol paleoartist Robert Nicholls said that reconstructing the cloacal region of Psittacosaurus helped them understand how dinosaurs mate, which is the last remaining feature that scientists do not know anything about. He called it a game-changer in studying the ancient animals that once roamed the Earth.

"Knowing that at least some dinosaurs were signaling to each other gives paleoartist exciting freedom to speculate on a whole variety of now plausible interactions during dinosaur courtship. 'It is a game-changer!" he concluded.