Genus: Menucocelsior ROLANDO, MARSA, AGNOLIN, MOTTA, ROZADILLA & NOVAS, 2022
Etymology: Mapundungun, menuco, "waterhole", inreference to the fossil site "Salitral Ojo de Agua", and Latin, celsior, "major."

Species: arriagadaroum emend ROLANDO, MARSA, AGNOLIN, MOTTA, ROZADILLA & NOVAS, 2022
= Menucocelsior arriagadai ROLANDO, MARSA, AGNOLIN, MOTTA, ROZADILLA & NOVAS, 2022
Etymology: In honor of "Beto" Arriagada and his family, the owners of the Farm that includes the fossil sites here reported, which are also enthusiastic on preserving fossils form the arm and usually help us to find fossil sites during our fieldtrips.
Note: The authors use the ending 'ai' and not '0rum' which is used for multiple people and is here emened.

Holotype: MPCN-PV-798

Locality: Cerro Matadero Site, 67°23'22.13"W, 39°30'27.08"S, locates within the Arriagada Farm, 70 km south from General Roca city, Rio Negro Province, Patagonia, Argentina. Note: This area is known as "Salitral Ojo de Agua" Agnolin et. al., 2012.

Horizon: Allen Formation.

Biostratigraphy:

Age: Maastrachtina Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.

Material: Second and probably third caudal vertebrae, 3 distal anterior-caudals, 6 proximal mid-caudals, and 5 distal mid-caudals, right humerus, left fibula and incomplete metapodial.