A 280-million-year-old fossil from the Italian Alps is pretty much just black paint in the lizard-shaped grooves of a rock. So say researchers who examined the specimen and laid to rest questions that have long puzzled paleontologists.
The fossil, known as Tridentinosaurus antiquus, was found in 1931. Based on what looked like the imprint of preserved soft tissue, it was classified as a protorosauria, a now-extinct long-necked reptile group that is believed to contain the precursors of the archosaur group which, in turn, includes dinosaurs and crocodiles. Over the years, the fossil has been referred to in paleontological articles and has helped shape the way scientists viewed the evolution of reptiles.
However, T. antiquus has long puzzled some paleontologists because it would be extremely rare to find a fossil from the time of the protorosaurs with so much soft tissue so well-preserved. So a research team led by Valentina Rossi from University College Cork in Ireland decided to have a closer look.
The scientists examined the fossil using a wide array of different chemical and visual observation methods including ultraviolet light analysis, 3D surface modeling, scanning electron microscopy, and spectroscopy. The analysis revealed that there was some kind of coating applied on top of the painted outline. This would not have been unusual as such preservation techniques were often employed as a means of preserving fossils stored or shown in museums. But beneath that, the team concluded that the body outline wasn't carbonized soft tissue as has been assumed for nearly a century. It was, instead, simply black pigment painted into a lizard-shaped carving in the rock.
“Fossil soft tissues are rare, but when found in a fossil they can reveal important biological information, for instance, the external colouration, internal anatomy and physiology," said Rossi. “The answer to all our questions was right in front of us, we had to study this fossil specimen in detail to reveal its secrets – even those that perhaps we did not want to know.”
The painted outline was no doubt intended to enhance what is otherwise a poorly preserved fossil, but the researchers say they can't be sure of the original intent.
The study wasn't all disappointing news, paleontologically speaking. The team's analysis did reveal some poorly preserved long bones that would have helped constitute the animal's hindlimbs which, the researchers say, resemble similar bones found from Late Triassic pterosauromorphs, a group of extinct flying reptiles. They also discovered osteoderms – tiny crocodile-like scales that might have covered the animal's back.
While they say that further analysis of these skeletal remains might shed more light on the animal, for now, they advise other researchers to use caution when referencing T. antiquus, or any literature based on its original – false – description.
The findings have been reported in the journal Paleontology.
Source: University College Cork