Shells of species in this genus are found around the world in fossil shell beds from the Valanginian (140.2 Ma) to the Early Pleistocene (0.781 Ma).

[2] They are a commonly found fossil in Cretaceous shellbeds of the Navesink Formation in New Jersey.

[3] Species within the genus Pycnodonte include:[4] Fossils of species within this genus have been found all over the world in sediments from Cretaceous to Quaternary (age range: 140.2 to 0.0781 million years ago).

The fossils generally exist in large layers or beds.

In Utah, in the Capital Reef National Park area, this layer of fossils is up to ten feet thick, and is present in the lower Tununk section of the Mancos Shale Fraction, just above the Dakota Sandstone and below the Blue Gate Shale layer.