In 2011, remains of a new species in this genus, Protungulatum coombsi from the Hell Creek Formation suggested that Protungulatum was present in both the Cretaceous and the Paleocene. However, some later studies questioned this Late Cretaceous age for the genus, considering Protungulatum to be exclusively Paleocene in age.
In 2011, remains of a new species within the Protungulatum genus from the Hell Creek Formation suggested that Protungulatum existed during both the Cretaceous and the Paleocene periods. However, some later studies challenged this Late Cretaceous age for the genus, proposing instead that it was solely present in the Paleocene.