Around 299 million years ago, in an area corresponding to today’s central Germany, volcanic eruptions produced a large quantity of lava which covered a layer of mud. The study of this made it possible to find imprints of fossilized scales, tails and legs, but also to make a much more singular discovery: that of the oldest cloaca imprint known to date, described in detail in the journal Current Biology.
Present in birds, reptiles, amphibians and certain mammals, the cloaca is a canal-shaped organ, located at the end of the intestinal tube and constituting the common receptacle for excretions from the digestive tract and products from the genital tract. It allows you to have “one opening for everything: defecating, urinating, breeding and laying eggs”summarizes paleontologist Jakob Vinther.
The second (and oldest) in history
Interviewed by Scientific American, the paleontologist from the British University of Bristol is clearly moved by this discovery. “Finding the footprint of an animal crouching in the mud, preserved with such fidelity, is a real find”says the scientist, who did not participate in the study published in Current Biology. “The animal is literally frozen – with its private parts – in eternal history, like movie stars on the Hollywood Walk of Fame.”
Paleontologist at the Berlin Natural History Museum and lead author of the study, Lorenzo Marchetti discovered traces of this cloacal orifice by examining rare diagonal and hexagonal scale imprints in the fossil – no clue should ever be overlooked. “I noticed something unusual; after comparison with modern animals, I understood what it was about.he explains.
The size and shape of cloacal openings vary among reptiles, but the lack of preserved fossils has long kept their evolution mysterious. “Only two examples of this structure are currently known in fossil reptiles”specifies the Italian paleontologist, whose discovery joins an imprint found in 2021, and which was until now the only one known.
Jakob Vinther and his team then found the cloacal imprint of a Psittacosaurus, a 130 million year old herbivorous dinosaur. This will go down in the history of paleontology as the first imprint of this type to have been discovered and identified, but the find by Lorenzo Marchetti’s team is now ahead of it – and by far – in terms of antiquity, since it is approximately 170 million years older.
The scale and footprint prints allowed Lorenzo Marchetti and his colleagues to determine that the famous cloaca belonged to a previously unknown species. The animal, which the researchers named Cabarzichnus pulchruswas a small lizard-like reptile, which probably basked in the mud to cool off, explains the paleontologist.
“It’s quite remarkable to see such fine details preserved from such a small animal”says Phil Bell, a paleontologist at the University of New England in Australia, who was not involved in the research. If it is so rare to find such prints, it is because “the consistency of the mud must be absolutely perfect for such an imprint to form”continues the specialist. “Fossilized cloacas are as rare as hen’s teethconcludes Jakob Vinther. Finding another one is exciting to say the least.”
