Genus: Notosphenos AGNOLIN, ROLANDO, MANABE, TSUIHIJI & NOVAS, 2024
Etymology: Greek, noto, "south" and Greek, sphenos, "wedge.": in reference to teh general terms applied to Tuatara (Sphenodon punctatus) and all its kin.

Species: finisterre AGNOLIN, ROLANDO, MANABE, TSUIHIJI & NOVAS, 2024
Etymology: Latin, finisterre, refers to the 'end of the earth.'

Holotype: MPM-PV-23097

Locality: Monotreme site, LA Anita Farm, S 50°31.128', W72°33.845', located approximately 30 km SW from El Calafate City, Santa Cruz Province, Argentina.

Horizon: Upper levels, Chorrillo Formation.

Biostratigraphy:

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

Material: Incomplete right maxilla preserving 2 complete and 1 partial tooth.