Yacimiento de icnitas de dinosaurio de Arén

Yacimiento de icnitas de dinosaurio de Arén is one of Spain's most significant paleontological sites, located in the municipality of Arén, in the province of Huesca, on land belonging to the Sociedad de Montes Comunes de Arén, close to the N-230 national road that links Lleida with the French border. It is a place where nature preserved a direct trace of a world that existed 65 million years ago.

How were the dinosaur footprints in Arén discovered?

The story of the site begins in 1992, when geologist Luis Ardévol was carrying out geological mapping work in this part of the Pyrenees. During routine fieldwork he noticed something that soon turned out to be a find of exceptional scientific value: footprints left by giant reptiles millions of years earlier. At first, nine ichnites — fossilized footprints — were visible across an area of roughly 15 square meters. In the summer of 2000, a broader excavation was carried out, uncovering two distinct levels bearing footprints, designated Arén I and Arén II.

What was found at Arén, and how old are these traces?

The fossils from Arén date to the upper Maastrichtian, the final stage of the Late Cretaceous — the period immediately preceding the mass extinction at the Cretaceous-Paleogene boundary, which brought the age of dinosaurs to an end nearly 65 million years ago. Two types of evidence have been documented at the site: ichnites, meaning footprints left in the sediment of the time, and skeletal remains.

In total, around forty bone pieces have been recovered, including a femur and caudal (tail) vertebrae, along with tibia fragments, numerous ribs, and several teeth. The bone assemblage associated with the footprints at Arén is considered one of the richest in Western Europe from the upper Maastrichtian, both in the number of specimens and in their diversity. Among the finds are exceptional pieces such as cranial fragments and caudal vertebrae preserved in anatomical connection — a rarity in the fossil record that helps researchers better reconstruct the anatomy and movement of these animals.

Can the site be visited?

Yes. One of the locations, Areny-1, has been specially prepared for visitors and has been declared a Bien de Interés Cultural (a protected cultural heritage site). The Ruta de las Icnitas was created here — a fifteen-minute walking trail that leads visitors to a wooden viewing platform, from which the clearly marked dinosaur footprints can be observed. Information panels placed along the route explain how the tracks formed and became preserved in rock, while also introducing visitors to theories about the extinction of the dinosaurs at the end of the Cretaceous.

Frequently asked questions

Where exactly is the site located? In the municipality of Arén, in the province of Huesca, in the Ribagorza region, close to the N-230 road heading toward the French border.

Who discovered the dinosaur footprints in Arén? Geologist Luis Ardévol, while carrying out geological mapping of the area in 1992.

From what period do the footprints and bones date? From the upper Maastrichtian, the final stage of the Late Cretaceous, around 65 million years ago.

Can visitors actually see the footprints? Yes, via the Ruta de las Icnitas trail leading to the Areny-1 site, which features a viewing platform and educational panels.

What other finds, besides footprints, have been made at Arén? Around forty bone pieces, including a femur, caudal vertebrae, tibia fragments, ribs, and teeth, as well as exceptionally well-preserved cranial fragments.