Pycnodonte
Pycnodonte is a genus of extinct oysters, fossil marine bivalve mollusks in the family Gryphaeidae, the foam oysters or honeycomb oysters. 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). They are a commonly found fossil in Cretaceous shellbeds of the Navesink Formation in New Jersey. Species. Species within the genus "Pycnodonte" include: 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. In the Hanksville, Utah area, the "Pycnodonte newberryi" oyster bed is exposed over a large area. Studies are currently being conducted to determine whether there is more than one species in these beds.