Fossils of the Serra de Alvaiázere

Hills that were once a sea floor

The Serra de Alvaiázere, the highest point of the Sicó massif (618 m), is made of limestone from the Jurassic period. That limestone formed at the bottom of an ancient sea, from mud and the shells of marine animals — which is why fossils turn up in the stones along the paths and in the dry-stone walls.

What you can find

Mostly shells of marine animals set in the stone. With luck, ammonites: ancient relatives of squid and octopus, with a spiral-coiled shell.

Often it is just a fragment, or a raised pattern on the rock. Low-angle light — early in the morning or late in the afternoon — makes them easier to spot. To show someone what you found, photograph it next to a coin for scale.

The oldest dinosaur tracks in the Iberian Peninsula

A study published in 2023 describes dinosaur tracks in Alvaiázere about 195 million years old, from the Early Jurassic — the oldest known in the Iberian Peninsula. The work was led by palaeontologist Silvério Figueiredo, of the Polytechnic Institute of Tomar, with the University of Coimbra and the local association Al-Baiaz, among others, and named a new type of track: Moyenisauropus lusitanicus.

We have no information on visits to the track site — Alvaiázere town council is best placed to advise.

Where to look

Here are three approximate areas where we have found fossils. On purpose, we do not give the exact spot — the rest is up to you.

Rules for fossil hunters

• Take photos, not fossils: leave each one for the next person to discover.
• Don't dig or break rock: the hills are part of the Natura 2000 network (Sicó/Alvaiázere) and any work on the ground needs authorisation.
• Respect private land, walls and crops — stay on the paths.
• Closed shoes and water: limestone is slippery when wet.