Jurassic Reptiles Beneath the World's Tallest Bridge
Fossil beds containing complete skeletons of 180-million-year-old marine reptiles; discovered during construction of the world's tallest bridge.
A Discovery of Toarcian Proportions
During the early 2000s, engineers and construction crews were focused on erecting the Millau Viaduct, a structure that would become the world's tallest bridge with a structural height of 343 meters. As they prepared the foundations for its seven massive piers, they cut deep into the Jurassic-era rock of the Tarn valley. This excavation unexpectedly exposed a record of a prehistoric world. The earthmoving equipment uncovered a large deposit of marine fossils dating back approximately 180 million years to the Toarcian Age of the Lower Jurassic.
The region was then submerged beneath a warm, shallow body of water called the Tethys Ocean. The sedimentary rocks that formed on this ancient seafloor, primarily fine-grained marls and limestones, created ideal conditions for fossilization. The discovery was not of isolated bones, but of remarkably well-preserved, and in some cases nearly complete, skeletons of the animals that swam in this sea long before the dinosaurs dominated the land. The construction of a 21st-century engineering marvel had revealed an ecosystem from the deep past.
The Creatures of the Tethyan Sea
The most famous fossil found here is a species of plesiosaur, a group of marine reptiles known for their long necks and paddle-like limbs. The most significant specimen is a nearly complete skeleton of Occitanosaurus tournemirensis, a four-meter-long plesiosaur. This specific animal is considered an elasmosaur, a family of plesiosaurs characterized by extremely long necks which, in some species, contained up to 80 vertebrae. The Occitanosaurus skeleton, now housed in the Musée de Millau, is the first complete elasmosaur discovered in France.
Alongside the plesiosaur, the fossil beds contained a variety of other marine life that showed details of the Toarcian environment. Remains of ichthyosaurs, another group of marine reptiles with a more dolphin-like body shape, were also found near Millau. The ecosystem had many cephalopods, including ammonites, nautiluses, and belemnites, which were likely prey for the larger reptiles. The excellent preservation suggests the animals were buried quickly in sediment on the seafloor, protecting them from scavengers and decay. In addition to marine reptiles, the broader Grands Causses area contains slabs with dinosaur footprints, including those of large carnivorous theropods up to nine meters in length.
💡Fun Facts
The Millau Viaduct, where the fossil beds were found, has a structural height of 343 meters, making it taller than the Eiffel Tower.
The name *Occitanosaurus tournemirensis* honors Occitania, the region of France where it was found, and the nearby village of Tournemire.
The Toarcian Age (184.2 to 174.7 million years ago) began with a major oceanic anoxic event, which may have contributed to the exceptional preservation of marine fossils.
The nearly complete *Occitanosaurus* skeleton is the star of the paleontology collection at the Musée de Millau et des Grands Causses.
From January to April and October to December, the museum is open Tuesday to Saturday. In May, June, and September, it is open Wednesday to Sunday. Hours are generally 10:30 AM to 12:30 PM and 2:00 PM to 6:00 PM.
Admission
Free.
Accessibility
The museum is housed in an 18th-century private mansion (Hôtel de Pégayrolles) and may have accessibility challenges; it is best to contact the museum directly for specific information.