Nonetheless, a fossil from China of a Psittacosaurus is so effectively preserved that the opening the Labrador-size dinosaur used to pee, poop and reproduce is seen, permitting paleontologists to check it for the primary time.
Whereas it would not supply any concrete solutions on how dinosaurs might have procreated, it does give some hints.
“We have no dinosaur fossils the place you might be assured they have been caught within the act,” mentioned Jakob Vinther, a paleontologist and senior lecturer on the College of Bristol’s College of Earth Sciences.
What we all know is “based mostly on pure historical past the place we evaluate it to residing teams of animals.”
Whereas most mammals have separate holes for bodily features, many different animals — together with birds and reptiles — have only one and it is referred to as the cloaca.
The fossilized cloaca confirms that dinosaurs had one nevertheless it would not appear like that of every other residing animals.
“It is rather distinctive. Most cloacas kind a type of slit. Typically it is a vertical break up, generally it is a smiley face, generally it is a bitter face. This factor has a V-shaped construction with a pair of good flaring lips and there is not a residing teams of animals which have morphology like that,” Vinther mentioned. “It’s considerably much like crocodiles however nonetheless distinctive.”
The examine, which printed within the journal Present Biology on Tuesday, mentioned that enormous, pigmented lobes on both facet of the opening might have harbored musky scent glands, as seen in residing crocodiles and alligators.
What’s extra, the outer margins of the cloaca are extremely pigmented with melanin. Whereas they do not know for certain what shade it was, it probably would have contrasted with the dinosaur’s pale underbelly, Vinther mentioned.
This distinctive pigmentation might imply the vent was used to show and sign, much like residing baboons and some breeding salamanders.
The fossil is displayed on the Senckenberg Museum of Pure Historical past in Frankfurt, Germany, however was present in a fossil-rich space of Liaoning in northern China.
Vinther had labored on the fossil earlier than in 2016, reconstructing the dinosaur’s shade patterns, and it was solely on the finish of that examine that he realized that the cloaca was very well preserved, he mentioned.
In animals with cloacal vents, the genitals are tucked contained in the physique and have not been preserved so it isn’t identified whether or not this explicit dinosaur was male or feminine.
Most birds, the one residing relative of dinosaurs, mate by “cloacal kissing” — by urgent collectively their openings. Some paleontologists assume dinosaurs might have mated like this.
Vinther, nevertheless, believes that this dinosaur would have had a penis — the fossilized opening is extra much like a crocodile’s, which do, and there are some birds, like ostriches and geese, which even have penises.
“From what we will see, this cloaca wouldn’t have been appropriate for cloacal kissing,” Vinther mentioned. “It appears like it will have been penetrative intercourse.”