Losillasaurus (meaning "Losilla lizard") is a genus of sauropod dinosaur from the Jurassic-Cretaceous boundary in the southeast of Spain. The type species of the turiasaurian Losillasaurus giganteus was discovered in the Los Serranos basin in Valencia and formally described by Casanovas, Santafé and Sanz in 2001. The material is from a subadult and includes part of a skull; complete cervical, dorsal, sacral, and caudal vertebrae as well as several fragments; skeletal elements from the limbs including a humerus, ulna, radius, and metacarpal; sternal plates; and from the pelvis: the ilium, ischium, and pubis. The genera is characterized by the dimension and shape of the neural spine of the proximal caudal vertebrae. The humerus is 143 centimetres (56 in) long, which despite being from a subadult specimen is within 20% of the size of Paralititan. The size estimation proposed by Francisco Gascó in his master thesis is 15-18 m (49-59 ft) and 12-15 tons.