The genus was described based on a fossil molar that was found in the Danian part of the Cretaceous-Paleogene Lefipán Formation in the Cañadón Asfalto Basin in north-central Patagonia, Argentina.

[8] The Danian section of the formation shows a remarkably rapid recovery from the extinction event,[9] with aquatic plant taxa virtually undisturbed and other flora reappearing quickly.

[10] A layer in the formation, known as the Turitella bed, is considered closest to the onset of the Paleogene and the fossil of Cocatherium, as well as the bivalve Meretrix chalcedonica, was found approximately 5 metres (16 ft) above the estimated K/Pg boundary.

[11] The formation has provided several macro- and microfossils of flora, which has led researchers to conclude the rapid recovery and low extinction rate of several genera and families of plants.

[13] While Cocatherium is the only mammal found in the formation, shark,[3] and ray teeth of Hypolophodon patagoniensis,[14] occur in the Danian section and are indicative of a shallow marine to littoral (coastal) environment.