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" is known from the formation, alongside somphospondylan "Europatitan" as well as indeterminate small ornithopods, iguanodonts and spinosaurids, the earliest known stem-rhabdodontid (indeterminate) and the lizard "Arcanosaurus".