- Source: Castrillo de la Reina Formation
The Castrillo de la Reina Formation is a geological formation in Spain. It is late Barremian to early Aptian in age. It interpreted as a fluvial deposit. It primarily consists of red clay, with ribbon shaped sandstone channel fills. The rebbachisaurid dinosaur Demandasaurus occurs in the formation, alongside somphospondylan Europatitan as well as indeterminate small ornithopods, iguanodonts (including members of the Hadrosauriformes) and spinosaurids, the earliest known stem-rhabdodontid (indeterminate) and the lizard Arcanosaurus.