It is estimated to weigh over 14 kilograms (31 lb), narrowly beating the previous Mesozoic mammal contender, Repenomamus giganticus.

However, it does not match any early Cenozoic South American therian group.

[1] Püschel et al. (2024) subsequently argued that Patagomaia might be a large gondwanatherian, possibly synonymous with Magallanodon,[3] but Chimento, Agnolín & Novas (2024) did not consider their arguments to be conclusive.

[4] Patagomaia chainko was found alongside the monotreme Patagorhynchus, the meridiolestidan Orretherium, the gondwanathere Magallanodon and several dinosaurs.

[1] Alongside Malagasy gondwanatheres like Adalatherium and Vintana and South American mesungulatid meridiolestidans, Patagomaia chainko provides evidence that Late Cretaceous Gondwanan mammal faunas tended to achieve larger sizes than their northern counterparts.