Genus: Bonapartenykus AGNOLIN, POWELL, NOVAS & KUNDRAT, 2012
Etymology: The generic name honors the surname of the great Argentinean palaeontologist Jose F. Bonaparte, and Latin, onykus, "claw."

Species: ultimus AGNOLIN, POWELL, NOVAS & KUNDRAT, 2012
Etymology: Latin, ultimus, "latest"; in reference of the present record constitutes the geological youngest alvarezsaurid from South America.

Holotype: MPCA 1290

Locality: "Arrigada III", Salitral Ojo de Agua, 39°25'55"S, 67°17'40"O, Rio Negro Province, northwestern Patagonia, Argentina.

Horizon: "Egg level 2", Upper levels of the Allen Formation, Lower Malargue Group.

Biostratigraphy:

Age: Middle Campanian-Lower Maastrichtian Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.

Material: A nearly articulated but badly preserved partial skeleton consisting of an incomplete mid-dorsal vertebra, a nearly comlpete left scapulocoracoid, incomplete right scapulocoracoid, incomplete left tibia and femur, nearly complete left pubis articulated with the incomplete pubic peduncle of ilium, and the anteior blade of the left ilium.

Note: Also associated with the skeletal elements are 2 partially preserved eggs.

Referred material:

MESO, CHOINIERE, BAIANO, BRUSATTE, CANALE, SALGADO, POL & PITTMAN, 2025

MPCN-PV 738.1 (formerly MEPyG 177): Almost comlpete right femur.

MPCN-PV 738.2: Almost complete left coracoid.

MPCN-PV 738.3 (formerly MGPIFD-GR 184): Proximal end of a left scapula.

MPCN-PV 738.4 (formerly MGPIFD-GR 194): Partial eft pubis.

MPCN-PV 738.5: Proximal end of a right metatarsal II

MPCN-PV 738.6: Distal end of a metatarsal I.

MPCN-PV 738.7: Proximal end of a chevron.

MPCN-PV 738.8: Almost complete mid caudal vertebra.

MPCN-PV 738.9: Caudal prezygapophysis.

MPCN-PV 738.10: Almost complete proximal caudal centrum.

MPCN-PV 738.11: Caudal centrum.

MPCN-PV 738.12: Discal caudal centrum.

MPCN-PV 738.13: Proximal end of a right fibula.

MPCN-PV 738.14 (formerly MGPIFD-GR 171): 2 inconplete fused sacral centra.

MPCN-PV 738.15-16: 2 almost complete cervico-dorsal neural ach.

MPCN-PV 738.17: Fragment of an pedal non-ungual phalanx.

MPCN-PV 738.18: Left pedal phalanx III-2.

MPCN-PV 738.19: Right pedal phalanx IV-3.

MPCN-PV 738.20: Left pedal phalanx IV-4.

MPCN-PV 738.21: Right pedal phalanx IV-4.

MPCN-PV 738.22: Proximal fragment of a right pedal phalanx.

MPCN-PV 738.23: Left pedal phalanx IV-2.

MPCN-PV 738.24: Fragment of a right tibia.

MPCN-PV 738.25: Fragment of a right metatarsal III.

MPCN-PV 738.26: Fragment of a middle neural arch.

MPCN-PV 738.27: Almost complete middle crvical neural arch.

MPCN-PV 738.28: Fragment of a cervical neural arch.

MPCN-PV 738.29: Almost complete caudal centrum.

MPCN-PV 738.30: Distal fragment of a caudal centrum.

MPCN-PV 738.31: Fragment of a possible last sacral vertebra.

MPCN-PV 738.32: Fragment of a cervical centrum.

MPCN-PV 738.33: Fragment of a left metatarsal III.

MPCN-PV 738.34: Fragment of a left metatarsal III-2.

MPCN-PV 738.35: Proximal end of a dorsal rib.

MPCN-PV 738.36: Almost complete dorsal rib.

MPCN-PV 738.37: Proximal fragment of a caudal centrum.

MPCN-PV 738.38: Distal fragment of a caudal centrum.

MPCN-PV 738.39: Proximal fragment of an indeterminate pedal non-ungual phalanx.

MPCN-PV 738.40: Distal fragment fo a caudal centrum.

MPCN-PV 738.41: Proximal fragment of an indeterminate pedal non-unbual phalanx.

MPCN-PV 738.43: Fragment of a cervical neural arch.

MPCN-PV 738.44: Almost pedal phalanx.

MPCN-PV 738.45: Almost compelte pedal ungual phalanx III.

MPCN-PV 738.46: Pedal ungual phalanx II.

MPCN-PV 738.47: Neural arch fragment of a proximal cervical vertebra.

MPCN-PV 738.48: Fragment of a cervical postzygapophysis.

MPCN-PV 738.49: Fragment of a dorsal postzygapophysis.

MPCN-PV 738.50: Fragment of a cervical postzygapophysis.

MPCN-PV 738.51: Cervical prezaygapphysis.

MPCN-PV 738.52: Neural arch fragment of a cervical vertebra.

MPCN-PV 738.54: Proximal fragmetn of indetermiante pedal ungual phalanx.

MPCN-PV 738.55: Fragment of a cervical postzygapophysis.

MPCN-PV 738.58: Almost complete caudal neural arch.

Numbers: Not given: Several indeterminate fragments.

 

SALGADO, CORIA, ARUCCI & CHIAPPE, 2009

Locality: 'Arriagada III', 39°25'55"S, 67°17'40"N, Salitral Ojo de Agua, Rio Negro Province, Argentina.

Horizon: Allen Formation.

Biostratigraphy:

Age: Campanian-Maastrichtian Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.

Material:

MGPIFD-GR 166: 4 fragmentary cervical and a single caudal.

MGPIFD-GR 184: Fragmentary blade of a left scapula, an incomplete left coracoid, distal right pubis

MGPIFD-GR 166, 184: Both appear to belong to the same individual.