Skin and color pattern of 125-million-year-old crocodile revealed by extraordinary fossil from the Pyrenees

A newly uncovered fossil of a 125-million-year-old crocodile, found in the Pyrenees region of Catalonia, Spain, has revealed detailed insights into its skin structure and color patterns, offering scientists a rare glimpse into the evolutionary history of ancient crocodilians. The discovery, made through advanced imaging techniques using ultraviolet light, was published in the Zoological Journal of the Linnean Society and highlights the preservation of soft tissues in a specimen named Montsecosuchus depereti. The fossil, housed at the Museum of Natural Sciences of Barcelona, was originally discovered over a century ago but has now yielded previously unseen data thanks to modern analytical methods. The crocodile lived during the Lower Cretaceous period, approximately 125 million years ago, in what is now the Catalan Pre-Pyrenees. It perished in the waters of a karstic lake, where its body became embedded in fine sediments that eventually solidified into the lithographic limestones of the Pedrera de Meià. These rocks are part of the UNESCO Orígens Global Geopark, a site renowned for its rich geological and paleontological heritage. The fossil’s exceptional preservation has enabled researchers to examine features that were previously inaccessible due to their delicate nature. The study was conducted by a team of paleontologists from the Institut Català de Paleontologia Miquel Crusafont, led by Oscar Castillo-Visa and Jesús Serrano. During efforts to compile a comprehensive database of fossils from the Montsec lithographic limestones stored in Catalan and European museums, the researchers noticed unusual structures on the holotype of Montsecosuchus depereti when exposed to ultraviolet light. This technique illuminated differences between the fossilized tissues and the surrounding rock, revealing details invisible under standard lighting conditions. Under UV light, the team documented various types of soft tissues, including epidermal scales. While the species had been known since the early 20th century, this study marks the first detailed description of its skin structure. The findings show significant variation in the size and shape of the scales along the body, with no evidence of the large caudal fin characteristic of modern crocodiles. Additionally, the researchers identified potential sensory organs located primarily in smaller, peripheral scales, particularly on the neck, limbs, and sides of the trunk and tail. These structures, similar to those found in contemporary crocodiles, likely served as receptors for detecting changes in water pressure, temperature, and chemical stimuli. The UV imaging also revealed cartilaginous structures in the thorax, suggesting that Montsecosuchus depereti possessed a respiratory system comparable to that of modern crocodiles. This indicates that even at an early stage of crocodylomorph evolution, certain members of the group had developed complex anatomical adaptations suited for a semi-aquatic lifestyle. Such features suggest a level of sophistication in their physiology that challenges previous assumptions about the developmental trajectory of these prehistoric reptiles. Oscar Castillo-Visa emphasized the significance of the discovery, stating that UV light allowed the team to observe details that would otherwise have remained hidden. “This method has opened up new possibilities for studying the soft tissues of ancient organisms,” he noted. The research underscores the importance of revisiting historical specimens with modern technology, as many fossils hold untapped information waiting to be uncovered. The fossil, cataloged as MGB-512, measures approximately 50 centimeters in length and represents one of the few examples of a crocodile-like creature from the Early Cretaceous era in Europe. Its location in the Pedrera de Meià site, combined with the unique preservation of its soft tissues, positions it as a critical piece of evidence in understanding the evolution of crocodylomorphs. Scientists plan to continue analyzing other fossils from the same geological layer to determine whether similar characteristics exist in related species, potentially shedding further light on the broader evolutionary trends of these ancient predators.