UV light reveals possible camouflage on a 125-million-year-old crocodile
Scientists examined a 125‑million‑year‑old crocodile fossil from Spain under ultraviolet light and uncovered preserved skin, possible sensory organs, advanced respiratory structures, and an alternating band pattern on the tail that could represent ancient camouflage. The discovery offers the earlie…
A fossil of a small crocodile that lived 125 million years ago has yielded a treasure trove of soft‑tissue details when examined under ultraviolet light. The specimen, catalogued as MGB‑512 and housed in the Museum of Natural Sciences of Barcelona, was found in the limestone deposits of Pedrera de Meià, a UNESCO‑listed site in Catalonia, Spain. The new study, published in the Zoological Journal of the Linnean Society, is the first to describe the preserved skin, possible sensory structures, and a striking tail pattern that may be the oldest known coloration in a crocodylomorph.
Exceptional Preservation in Pedrera de Meià
The fossil was deposited in a karstic lake near the coast of the Catalan Pre‑Pyrenees. Fine lake sediments quickly covered the carcass, creating an environment that prevented decay and allowed delicate tissues to fossilise. Over millions of years those sediments turned into the lithographic limestones that now form the Pedrera de Meià, a Konservat‑Lagerstätte known for its exceptional preservation of fish, amphibians, reptiles and plants. The site has yielded more than 8,000 specimens, including the first angiosperm, Montsechia, and a diverse array of insects and vertebrates.
UV Light Reveals Skin and Soft Tissues
When paleontologists Oscar Castillo and Jesús Serrano scanned the holotype of Montsecosuchus depereti under ultraviolet light, they saw structures that were invisible under normal lighting. UV illumination causes fossilised tissues and the surrounding matrix to fluoresce differently, making hidden details stand out. The team documented a variety of soft‑tissue features, including epidermal scales that varied in shape and size across the body. The fossil also shows a lack of the high caudal fin seen in modern crocodiles, indicating a different tail morphology.
Possible Sensory Organs and Respiratory Adaptations
Within some of the preserved scales, especially around the neck, limbs, and along the trunk and tail, the researchers identified structures that resemble sensory organs found in living crocodiles. These organs can detect touch, water pressure, temperature, and chemical cues. In Montsecosuchus, they appear only in small scales along the body edges, suggesting that such sensory systems may have evolved in localized regions before becoming widespread in later crocodylomorphs.
UV analysis also exposed cartilaginous elements in the chest, indicating that Montsecosuchus possessed a sophisticated respiratory system similar to that of modern crocodiles. This finding shows that complex thoracic anatomy evolved earlier than previously thought, allowing the animal to thrive in a semi‑aquatic environment.
Unexpected Tail Pattern: The Oldest Known Coloration?
The most striking discovery came from the tail. Several scales in the caudal region display alternating light and dark bands when viewed under UV light. Researchers interpret these bands as possible remnants of the animal’s original coloration, potentially serving as disruptive camouflage to break up the outline of the crocodile in its watery habitat. If confirmed, this would make Montsecosuchus the oldest crocodylomorph with preserved evidence of coloration, a record previously limited to much younger species.
While the exact hues cannot be determined from the fossil, the pattern aligns with the idea that early crocodylomorphs may have had coloration similar to modern relatives. The discovery underscores the value of UV imaging in paleontology and highlights the Catalan fossil record’s importance for understanding vertebrate evolution.
Future Directions and Unresolved Questions
Further studies will aim to confirm the nature of the tail pattern and to determine whether similar coloration existed in other early crocodylomorphs. Researchers also plan to investigate the distribution of sensory organs in related species to trace the evolution of these structures. The Pedrera de Meià site continues to be a rich source of well‑preserved fossils, offering opportunities to uncover more soft‑tissue details in the future.
The research was led by the Institut Català de Paleontologia Miquel Crusafont and supported by multiple funding bodies, including the Ministry of Science, Innovation and Universities and the NextGenerationEU/PRTR program. The findings were presented by Oscar Castillo‑Visa, Albert G. Sellés, Àngel Galobart, and Phil Bell, among others.
About the Pedrera de Meià Fossil Site
Pedrera de Meià is a Konservat‑Lagerstätte that preserves not only bones but also delicate soft tissues. The site’s exceptional conditions have allowed scientists to study Lower Cretaceous fish, amphibians, reptiles, and plants in remarkable detail. Exhibits are available at the Montsec de Meià Interpretation Center in Vilanova de Meià, and the Orígens Geopark hosts an online showcase of the site’s most representative fossils.
With its rich diversity of fossils—from insects to early flowering plants—Pedrera de Meià remains a cornerstone for paleontological research in the Catalan Pyrenees.
Why it matters
The study provides the earliest direct evidence of coloration in a crocodylomorph, offering new insights into the evolution of skin, sensory systems, and respiratory anatomy in early reptiles.
Key points
- UV imaging uncovered skin, sensory structures, and a tail band pattern in a 125‑million‑year‑old crocodile.
- The fossil shows advanced respiratory features similar to modern crocodiles.
- Alternating bands on the tail may represent the oldest known coloration in a crocodylomorph.
- Pedrera de Meià is a Konservat‑Lagerstätte with exceptional soft‑tissue preservation.
- The discovery highlights the importance of Catalan fossil sites for vertebrate evolution studies.
Frequently asked questions
What makes Pedrera de Meià a special fossil site?
It is a Konservat‑Lagerstätte where fine lake sediments preserved not only bones but also delicate soft tissues, allowing researchers to study skin, organs, and even coloration in fossils.
How does ultraviolet light help in paleontology?
UV light causes fossilised tissues and surrounding rock to fluoresce differently, revealing hidden structures such as scales, sensory organs, and cartilage that are invisible under normal lighting.
Why is the tail pattern significant?
If the alternating bands are indeed coloration, they would be the oldest known evidence of skin patterning in a crocodylomorph, shedding light on early reptile camouflage strategies.
