The Lourinhã Formation

The Lourinhã Formation, situated in Portugal’s Lusitanian Basin, is a Late Jurassic (Kimmeridgian–Tithonian, 157–145 million years ago) geological unit composed of fluvial and deltaic sandstones, mudstones, and conglomerates, deposited in a coastal floodplain environment with rivers, lakes, and seasonal wetlands. It is renowned for its exceptional dinosaur fossil record, yielding theropods like Torvosaurus and Ceratosaurus, sauropods such as Lusotitan and Dinheirosaurus, and ornithischians like Draconyx, alongside dinosaur eggs, tracks, and small vertebrates such as turtles and crocodiles. Exposed along Portugal’s western coast between Peniche and Santa Cruz, key sites like Porto das Barcas feature cliffs where fossils, including theropod teeth, erode onto beaches, providing a window into a vibrant Jurassic ecosystem.

The Lourinhã Formation is often compared to North America’s Morrison Formation due to striking similarities in age, fauna, and depositional setting, reflecting their close geological connection during the Late Jurassic. Both formations, dated to the same period, preserve similar dinosaur genera, such as Allosaurus, Torvosaurus, and Stegosaurus, suggesting shared ecosystems across the proto-Atlantic before the supercontinent Pangaea fully split. During the Late Jurassic, the Iberian Peninsula (where the Lourinhã Formation lies) and Laurentia (where the Morrison Formation is located) were still relatively close, separated by a narrow, forming rift basin as the Atlantic began to open. This proximity allowed for faunal exchange, making the Lourinhã Formation a critical European counterpart to the Morrison, offering insights into the global distribution and diversity of Late Jurassic dinosaurs.