Genus: Demandasaurus FERANDEZ-BALDOR, CANUDO, HUERTA, MONTERO, PEREDA SUBERBIOLA, & SALGADO, 2011
Etymology: In reference to the Sierra de la Demanda, Burgos Province, Spain, the mountain chain where the type specimen was found, and Greek, sauros, "lizard."

Species: darwini FERANDEZ-BALDOR, CANUDO, HUERTA, MONTERO, PEREDA SUBERBIOLA, & SALGADO, 2011
Etymology: In honor of the naturalist Charles R. Darwin (1809-1882)

Holotype: MDS-RVIL, 275 (See below)

Locality: Tenados de los Vallejos II Locality, Burgos Province, Spain.

Horizon: Upper section of the Castrillo de la Reina Formation.

Biostratigraphy:

Age: Late Barremian Stage, Lower Gallic Subepoch, Middle Early Cretaceous Epoch to Early Aptian Stage, Middle Gallic Subepoch, Upper Early Cretaceous Epoch, Early Cretaceous.

Material: Right premaxilla.

MDS-RVII 332: Left premaxilla.

MDS-RVII 443: Left dentary.

MDS-RVII 340, 436, 437, 438, 440, 441: 6 isolated teeth.

MDS-RVII 589, 806: 2 cervical vertebrae.

MDS-RVII 606: Axis.

MDS-RVII 379, 458, 466, 487, 811: 5 cervical ribs.

MDS-RVII 242, 798: 2 dorsal vertebrae.

MDS-RVII 14, 301, 364, 365, 368, 382, 592, 600, 611: 9 dorsal ribs.

MDS-RVII 2, 3, 4, 9, 10, 11, 12, 15, 101, 216, 217, 217, 470, 602, 605, 609, 610, 629, 805: 19 caudal vertebrae.

MDS-RVII 21, 99, 231, 232, 590, 591, 594, 796, 797: 9 haemal arches.

MDS-RVII 18: Left ischium.

MDS-RVII 18: Right ischium.

MDS-RVII 16: Left femur.