In Provence, they walked the earth before the dinosaurs

The “Pictures of Science” format allows you to decode an image of particular interest from a scientific point of view, describe it and understand its challenges.

If we love Provence for its wines, cicadas, and art of living, we don’t know it so much for its natural resources: a unique heritage (fauna, flora and geographic diversity) inextricably linked with the history and extraordinary landscapes of this land caught between the Mediterranean, the Alps and the Rhone Pass. Among this heritage, The new fossils are dated to the Archaic period (Middle Permian, about 265 million years ago), which was recently discovered, provides insight into the evolution of species and ecosystems before the dinosaurs.

Exceptional fossilized traces of a walking animal

These are traces of fossilized biological activities: when animals move on a fairly loose substrate, they leave their footprints on the ground. With luck, these prints can be covered in fine clay and petrify over time. These fossilized remains are called “ichnofossils fossils” (from the Greek ikhnos : trace) exceptional. Paleontologists use it to try to identify the animal, but also its movement and environment at the time: like the more “classic” fossils (bones, teeth, shells, etc.), fish fossils are valuable clues. To better understand the evolution of species.

fossil traces Hyloidichnus, Permian of Gunfron, with its fingers and a trail of tail.
Roman Garrost / MNHNAnd the Introduction by the author

In the red clay rocks (sandstone and pallet) of the Junfaron region, in the Var, we have already discovered fossil traces attributed to insects, reptiles and amphibians as well as fossils: a real frozen ecosystem that is being revealed little by little, as the fossils continue. Among our discoveries, well-preserved traces of reptiles even show traces of the tail and claws: they allow us to reconstruct the gait of the animal that passed there 265 million years ago.

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Fingerprints to understand movement … and body pose

More precisely, this track is called Hyloidichnus Corresponds to the footprints left by a representative of the captorinid, a group of extinct reptiles. Similar to their distant dinosaur cousins, captorinids are monitor lizards and can reach large sizes as shown by other fossils found in Africa.

Our findings from Gonfaron show that this very ancient reptile moved on dry ground with agility and flexibility, using its front and hind legs for both traction and propulsion, and the body undulating slightly while the tail worked for balance. These dynamic quadrilaterals can function even by leaning on the base of the fingers only (that is, “almost digital”) like the bottom of many modern reptiles.

path drawing Hyloidichnus With the tail trail in the middle (red arrows).
Antoine Logy / MNHNAnd the Introduction by the author

Photogrammetry, 3D imaging in paleontology

All these valuable clues were obtained thanks to a modern 3D imaging method, photogrammetry, which consists in modeling the slightest relief found on the fossil. Thus the sample is digitized with very fine contour lines, which makes it possible to observe the smallest details of the morphology of the fingerprint. Besides more detailed observation, this method also allows traces to be traced on fossil skeletons.

This article was co-written by Antoine Loegue, MSc student in Paleontology at MNHN (CR2P/ISYEB), first author of the scientific article cited in the reference, which corresponds to part of his MSc thesis.

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