Bonapartenykus

Bonapartenykus (meaning "José F. Bonaparte's claw") is an extinct genus of alvarezsauroid dinosaur that lived during the Late Cretaceous (Campanian–Maastrichtian) of what is now the Allen Formation of the Río Negro Province, Argentina. The genus contains a single species, Bonapartenykus ultimus, known from a partially articulated, incomplete skeleton that was found in close association to two incomplete eggs and several clusters of eggshells belonging to the oogenus Arriagadoolithus. Bonapartenykus was named in 2012. It has an estimated length of and weight of , making it the largest member of the clade Alvarezsauroidea. Additional skeletons referrable to this genus have subsequently been described.

==Discovery and naming== thumb|left|Outcrops of the Allen Formation in Argentina A partial skeleton of a theropod with eggs was collected in a surface of approximately 30 m2 in fluvial sandstones of the upper Allen Formation in northwestern Patagonia, Argentina. The locality has also produced specimens of hadrosaurids, ankylosaurs, several titanosaur sauropods, several abelisaurids, indeterminate tetanurans, an incomplete large alvarezsaurid and a large unenlagiid. The skeleton was originally reported and described by Salgado et al. (2009) as an indeterminate alvarezsaurid. The specimen was later redescribed and named in 2012 by Federico L. Agnolin, Jaime E. Powell, Fernando E. Novas and Martin Kundrát. The holotype specimen, MPCA, 1290, consists of a mid-dorsal vertebra, both scapulocoracoids, left tibia and femur, left pubis articulated with the pubic peduncle of the ilium, the anterior blade of the left ilium, and two partially preserved eggs that were separated from the holotype by less than 20 cm (7.9 inches). Two specimens were referred to Bonapartenykus: MGPIFD-GR 166 and MGPIFD-GR 184, a blade of the left scapula, a left coracoid, a distal right pubis, four cervical vertebrae and a single caudal vertebra which all belong to the same individual.