Hunting dinosaurs in Portugal – Field trip to Lourinhã

Linda and guest bloggers Blandine (hyperlink to Meet the Scientist) and David (hyperlink to Meet the Scientist) here – in August 2021 we packed our bags, hand lenses and sunscreen, and hopped on a plane to go on a field trip in Lourinhã, Portugal [Fig. 1]. This city is known as the Portuguese capital of dinosaurs because of its fossil-rich Jurassic outcrops. It even is the eponym (name giving location) for several taxa: sauropod dinosaur genus Lourinhasaurus, theropod dinosaur genus Lourinhanosaurus, sauropod dinosaur species Supersaurus/Dinheirosaurus lourinhanensis. Today, Lourinhã is located on the Portuguese Atlantic coast. While small beaches exist, the majority of the coastline consists of tall, rocky cliffs. This area looked very different during the Mesozoic Era though.

Fig. 1. Map of Portugal with all locations highlighted that we visited or mention in this text. Figure made by David.

When Pangaea fell apart and the North Atlantic began to open, the Lusitanian rift basin formed due to the extension of the crust in the area that is today western Portugal. The Lusitanian basin was likely bordered by the Berlenga horst in the west and by the Central Plateau of the Iberian Peninsula  (Meseta Central) in the east [Fig. 2]. During the Late Triassic, the evaporation of sea water in the Lusitanian Basin led to the deposition of a thick and ductile salt layer, which later caused instability in the overlying sediments. The formation and movement of salt domes constantly changed the topography and thus modified the course of river beds. The relative sea level at the coast of this area was fluctuating during the Jurassic, and as a result we observe layers representative of large, meandering rivers and layers richer in terrestrial plant material when the sea level was at its lowest, occasionally marine intercalations (with shallow marine fossils such as oysters) and fine, muddy deposits from entirely marine environments. 

Fig. 2. top: Schematic showing today’s coastline (red) and key locations on top of the Jurassic landscape and main geological features. bottom: Artist’s/David’s reconstruction of the Jurassic ecosystem. Figure made by David.

The dinosaur fauna of Portugal is similar to the ones of the Morrison Formation in the US and the Tendaguru Formation in Tanzania, with several genera, such as Allosaurus, Ceratosaurus and Torvosaurus occurring in all three localities [Fig. 3]. This is remarkable since these regions were separated by the sea during the upper Jurassic; the former supercontinent Pangaea was already breaking up. That means that a faunal exchange between North America (Morrison Formation), the island Iberia (Lourinhã Formation) and Gondwana (Tendaguru Formation) was still possible, probably in times when the sea-level was low.

Fig. 3. Paleogeography of the Jurassic, showing possible connectivity between geologic formations with very similar dinosaur fossil assemblage.

Day 1) Praia de Vale Pombas and Dino Parque Lourinhã: 

We spent the morning of our first day at the Praia de Vale Pombas, a small beach south of Peniche. You very quickly forget the beautiful scenery when you spot a fossil. Within minutes we found large fragments of fossilized wood and got very excited when we found bones quickly after that. Most remains were fragmented and we could not identify them, but we found a theropod metatarsal (foot) bone [Fig. 5] as well as a small piece of a rib of an unidentified animal. 

Please note: while fossil collection is permitted at this specific outcrop, the different municipalities in this area handle this matter very differently, many do not allow collection by private collectors but only professional scientific excavations for which you need to file a request. Always follow the local regulations when in the field, many fossils are beautiful, but not yours to take. Also make sure to always inform the authorities when you spot something potentially important. 

Fig. 4. Blandine (left) inspects a find while Linda (right) is busy extracting a dinosaur bone.
Fig. 5. Theropod metatarsal (foot) bone. During the collection process, this fossil cracked and broke into several pieces. But fortunately, we were prepared and glued it back together.

In the afternoon we visited the Dino Parque in Lourinhã. A small museum in the park showcases the locally found dinosaurs with original skeletons and replicas, as well as methods and techniques used in the excavation process and during fossil preparation. The largest section of the park is a huge outside area showing life size reconstructions of different dinosaur species. We received tours behind the scenes and talked to the staff and preparators who explained their work to us. This was so much fun that we wrote a separate post just about our day in this park, check it out here [hyperlink to blog post]

Day 2) Museu da Lourinhã: 

On the second day, we visited the Museu da Lourinhã, the museum of the city of Lourinhã dedicated to the region’s geological and historical heritage. In the paleontological gallery, numerous locally found dinosaur fossils, including eggs with embryos of the theropod Lourinhanosaurus are presented. The museum’s archeological and ethnological exhibitions deal with human history in the region and show how people lived here in the past.

We were given a thorough tour of the geological and paleontological section by Carla Tómas, one of the museum’s preparators, who also led us behind the scenes into the preparators’ laboratory. Here, the preparator team works on the preparation and study of local and international vertebrate remains. While we were there, Carla explained to us that her specialty is to find new methods to stabilize very fragile fossils by preparing and treating them chemically. Some geological properties can lead to poor bone preservation, for example the presence of salt can result in extremely brittle fossils. It is therefore important to understand the chemical processes happening and stop the degradation of the material to preserve the fossil.

Day 3) Ponta do Trovão, the Toarcian GSSP

Not far away from our accommodation in the town of Peniche, just north of Lourinhã, there is a GSSP [Fig. 6]. GSSP stands for Global Boundary Stratotype Section and Point and refers to physical markers between specific layers of rock, marking the lower boundary of a stratigraphic unit. For each stage on the geologic time scale, scientists are trying to identify one GSSP somewhere in the world, indicating exactly the boundary between two stages. The end/beginning of a geological stage is defined by a change, commonly a change in fossil assemblages such as an extinction event or the first appearance of an index fossil. Currently, less than 80 GSSPs have been ratified, the vast majority of which are located in Europe. The GSSP we visited is located at Ponta do Trovão in Peniche, and marks the beginning of the Toarcian (early Jurassic, 182.7 million years ago). It is defined by the very first appearance of the ammonite genus Dactylioceras (Eodactylites)

Fig. 6 Information board and GSSP ‘spike’ at Ponta do Trovão, marking the exact end of the Pliensbachian (below the spike) and the beginning of the Toarcian (above the spike).

We spent the rest of the day exploring the area, looking for fossils in the layers below the GSSP (thus not in the Toarcian, but the previous stage, the Pliensbachian) and found thousands of belemnites [Fig. 7]. Belemnites are an extinct group of cephalopods, which looked similar to today’s squids but with hooks on their ten arms. They had an internal skeleton called the cone, of which only the calcitic guard (called rostrum) commonly fossilizes. In addition to belemnite rostra scattered around, we also spotted a few coprolites, the fossil remains of poop [Fig. 8]. It appears that something has been snacking on ancient “calamari”, but could not digest the hard, calcite guards. Between the large number of rostrum fragments, we also discovered a number of ammonites, some of which – especially when they were located in the intertidal zone and thus currently in contact with sea water – were beautifully pyritized [Fig. 9]. 

Since this is a special outcrop, a GSSP, we did not collect fossils here, but only marveled at their beauty. 

Fig.7 Fragments of belemnite rostra found at Ponta do Trovão.
Fig. 8 Coprolite (fossil poop) consisting of indigestible belemnite remains. Scale in cm.
Fig. 9. Fragment of a small ammonite, shimmering golden because of pyrite, an iron sulfide mineral also known as fool’s gold.

Day 4) Praia Formosa, Praia de Santa Cruz, Praia Azul and excavation sites of the municipality of Torres Vedras

In the morning we joined a guided tour given by Bruno Camilo Silva, a local paleontologist. We learned about the geology at Praia Formosa and Praia de Santa Cruz, two beaches south of Peniche. The tall cliffs here show wonderful profiles of the rock layers of the Lower Jurassic, providing insight into the sedimentological history of this place. At the time, tectonic movements and underwater currents would cause sediments to slide down the Berlenga Horst from time to time. Those events formed a sediment known as turbidite, occurring here as massive conglomerates. We can see clearly where these turbiditic flows eroded the older sea-floor sediments, leaving irregular contacts between the layers [Fig. 10]. Considering that the Berlenga Horst was quite far away from the location these layers were deposited, it is difficult to imagine the sheer size of the sediment flows and the amount of material that must have been transported.

Fig.10 This outcrop at Praia de Santa Cruz shows fine, gray, sea sediments which are disturbed and eroded by badly sorted reddish brown sediments, a turbidite.

The layers below the turbidite in this area are unfortunately quite poor in body fossil content, despite numerous traces of invertebrate activity in the sediments. Based on those ichnofossils such as burrows, it is assumed the area had probably a rich benthic fauna, which has not been preserved in the sediment because the conditions were too unfavorable for fossilization. The fact that we know there was abundant life but all that’s left of it now are ichnofossils and we may never know which organisms once roamed the seabed here is quite humbling. After brooding about this, we chose to have our lunch break at Praia Azul, the blue beach. We used this occasion to search for fossils at the foot of the cliffs near the beach while eating our sandwiches. The most common fossils that can be found here are oysters, marking times of shallow marine conditions. Several large oyster banks are preserved [Fig. 10], though wood and other isolated plant fragments also occur frequently. In addition to these finds, coprolites, signs of bioturbation such as re-filled burrows, and – very rarely – small bones can be spotted in the cliffs of this beach. 

Fig. 11. Fossil oyster bed at Praia Azul, shoe for scale.

In the afternoon, we visited active paleontological excavation sites, of which we promised to keep the locations secret in order to avoid people disturbing the ongoing work/research. A team composed of local volunteers, international students and experts, and employees of the municipality of Torres Vedras were excavating turtle and crocodylomorph remains. At a second location nearby an almost complete but at the moment of our visit still unidentified theropod dinosaur was excavated, ready to be covered in plaster and to be lifted and transported to a preparation lab to finally see the light of day again. Blandine picked up a rock very close to one of the sites and found a small tooth (identified by staff on site as possibly hybodontiformes, a sister taxon of sharks and rays), which she handed over to the excavation team so it can be included in the research. In the evening, to finish an exciting day, we paid another visit to Ponta do Trovão to search for fossils with the sun setting over the Berlengas archipelago, the remnant and eponym of the aforementioned Mesozoic horst structure, on the horizon [Fig. 12].

Fig. 12. Sunset over the Atlantic ocean, the Berlengas archipelago in the background.

Day 5) Foz do Arelho and Parque de Merendas

While we spent most of our Portugal trip in the fossil rich localities along the coast south of Peniche, we planned to explore some places north of the city on day 5. After checking geological maps of the region in order to find promising localities we decided to head to the cliffs of Foz do Arelho first. While the place itself was a spectacular sight, we didn’t find any fossils there. So, we went further north to the cliffs of Parque de Merendas near Serra do Bouro. Again, this was an amazing locality, but with very few fossils. We found interesting green minerals on and around plant remains. Bone fossils, however, were very rare, but Blandine, our dinosaur expert, found a large fragment of a dinosaur bone that could not be further identified [Fig. 13].

Fig. 13. Dinosaur bone fragment found at the cliffs of Parque de Merendas.

Day 6) Praia de Porto Dinheiro, Praia do Zimbral and cliffs near Porto Batel

Fig. 14. David extracting a small piece of dinosaur bone from the rock.

We spent the next day going to Praia de Porto Dinheiro (the town is the eponym of the dinosaur genus Dinheirosaurus) near Rebamar and to Praia do Zimbral, where we met with the local paleontologist and the geologists we had already encountered a few days earlier. While the group was excavating an unidentified fossil bone fragment, David found another piece in the rubble that had fallen from the cliff into the beach, extracted it [Fig. 14], and handed it to the local paleontologist so it could be included in their work.

For lunch we went to a local restaurant just next to Praia de Porto Dinheiro, which has a large Sauropod bone being showcased under glass plates below the floor in the entrance. The owner of the restaurant showed us a large Torvosaurus tooth from his private collection. Even the sink in the bathroom is made out of a piece of fossil oyster bank. Later that day we met again with the other geologists and paleontologists at the cliffs near Porto Batel. At this locality dinosaur footprints can be found: The group showed us large theropod tracks [Fig. 15], and the filling (negative) of a deep Sauropod footprint up in the cliff [Fig. 16]. Although way too far above for us to check, we were told that skin impressions can be found in this footprint.

Fig. 15. Large theropod dinosaur footprints at the cliffs near Porto Batel, hammer for scale.
Fig. 16. The infill of a sauropod footprint at the cliffs near Porto Batel, David for scale. The cliff is slowly eroding, endangering the track.

All in all, our trip to Portugal was very exciting. We could observe plenty of fossils including dinosaur bones in the beautiful scenery where the Atlantic ocean is inexorably gnawing away at the rocks that once were the walking grounds of the giants of the past. If you know where to search it is impossible not to find nice fossils, though please remember: Collecting fossils is not permitted everywhere  in this area! Inform yourself prior to your trip and stick to the local laws and regulations! The city of Lourinhã itself, its museum, and dinosaur park are also worth a visit; the geological heritage of the region is felt everywhere in the streets, the people in this area live and breathe dinosaurs, with many shops, restaurants, businesses and cafés including the term ‘dino’ in their names and life-size dinosaur models and art found in many places.

In case you haven’t had enough, here are some additional impressions of our trip [Fig. 17-22]: 

Fig. 17. Sauropod graffiti on a no entry sign in Lourinhã.
Fig. 18. Blandine (left) and David (right) inspecting the outcrop at Ponta do Trovão.
Fig. 19. Pterodactyl reconstruction in the streets of Lourinhã.
Fig. 20. Linda (left) and Blandine (right) at the cliffs at Serra do Bouro.
Fig. 21. Lourinhanosaurus antunesi replica in the Museu da Lourinhã.
Fig. 22. Blandine’s hand on top of theropod footprints at the cliffs near Porto Batel.

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