In the Triassic, some 240 million years ago, the small part of the world later called Catalonia was very different from now. We have to imagine a coastal area in equatorial latitudes, where we could find from floodplains with small river channels to very extensive tidal flats and calm waters, explains Eudald Munjal, a researcher at the Staatliches Museum für Naturkunde Stuttgart (SMNS, Germany) who adds that a large part of the faunas that existed then do not have current representatives or the forms were very different from those we know today.
Thus, researchers linked to the Institut Català de Paleontologia Miquel Crusafont (ICP) have published several articles in which they describe 219 fossil footprints, also called ichnites, of different animals that lived at that time, long before the arrival of the dinosaurs. From the study of these traces, nine different forms of footprints have been found that correspond to small therapsids (precursors of mammals), possible large amphibians or precursors of turtles, small lepidosauromorphic or archosauromorphs reptiles, and large archosaur reptiles, a species of primitive crocodile. Some of these fossils are remarkably well preserved, even showing the patterns of skin, fingertips, and claws.
Traces of a xiphosuran, an antecedent of the current horseshoe or pan crabs of the Moluccas, in the Pena Rubi deposit in Vallirana are also described in another investigation. The study highlights that it is these crab-like invertebrates are more closely related to spiders than to crustaceans. They are often called living fossils because their morphology has changed very little in the last 400 million years and because they have survived several mass extinctions. The presence of this trial confirms that during the Triassic these coastal environments were full of life.
It is very interesting to see how the faunas are distributed in the different environments that we have identified, explains Chabier de Jaime, ICP predoctoral researcher who has co-led the research. Despite the presence of a xiphosuran, an animal linked to coastal environments, we have found that terrestrial environments were much richer in biodiversity than those near the coast, he adds. Among the 219 fossils found, the researchers highlight the ichnite of Puigventos (Olesa de Montserrat) which is extraordinarily well preserved and was found by chance by a hiker five years ago after a walk in the mountains. In this fossil, the claws and even the relief of the skin can be perfectly observed.
A study by the Institut Catala de Paleontologia Miquel Crusafont (ICP) revealed that it was an impression of the left foot of an archosaur, a primitive group of relatively large reptiles that are considered ancestors of dinosaurs and crocodiles. The appearance of these archosaurs was similar to that of current crocodiles, They also walked on all fours, but these were relatively long and in a more upright position than crocodiles. Archosaurs dominated terrestrial ecosystems after the Late Permian extinction, also called “the great death.
It happened shortly before the appearance of the dinosaurs and it is the greatest extinction to have occurred on Earth, much more devastating in the one that later wiped out the dinosaurs. From the study of ichnites, we can analyze how ecosystems evolved after the great climatic and biotic crisis at the end of the Permian, says Munjal. The later period was not too quiet for the species that survived, either. During the Triassic, rising Tetis sea levels flooded what is now Europe and North Africa from east to west.
In Olesa de Montserrat more remains of the Middle Triassic were found, as in the deposits of Pena Rubi (in the municipality of Vallirana) and Montmagny (in Figaro-Montmagny). These new towns are added to the only two known so far (Collcardus and Pedrera de Can Sallent). According to the researchers, these sites are the only ones in the entire Iberian Peninsula of this chronology. The study concludes that the observations made in the Catalan Triassic basin can be extrapolated to the rest of Europe and North Africa.