Plicatostylid bivalves were large sized, with the
spoon-shaped
Lithiotis reaching heights of 25-30 cm and a thickness of up to 1.5-3 cm, with the largest as high as 50 cm and some specimens of
Lithioperna reaching 70 cm and 4 cm thick. They developed in large
reef systems like modern
Crassostrea, but in warm, shallow seas, with some
bioherms attaining lengths over 60 m and thicknesses of 3-5 m. This facies not only include this family, but also the
myalinid Pseudopachymytilus, the
carditid Opisoma, and the
megalodontids or potential stem
hippuritids Pachymegalodon and
Protodiceras. These bivalves were major players in their marine ecosystems, contributing to the geological structure of
carbonate platforms. Some endemic species (ex.
Lithiotis timorensis) were described from
Timor. Other faunas are seen in the
Himalayas. The oldest records are Middle-Late Sinemurian specimens of
Gervilleioperna. Most of these bivalves met their end during a significant environmental upheaval known as the
Toarcian Oceanic Anoxic Event, which altered ocean chemistry and made survival challenging. Yet, in some areas like
Morocco or the
Apennine Mountains, they persisted, showing some adaptability.
Gervilleioperna survived until at least the
Aalenian in
Chile, likely due to having a small shell. The genus
Pachyperna is known from the Eocene (
Bartonian-
Priabonian?), revelating the group also survived the
Cretaceous–Paleogene extinction event.
Genera Subfamily Pachygervilliinae: • †
Gervilleioperna • †
Lithioperna • †
Pachygervillia • †
Pachyperna Subfamily Plicatostylinae: • †
Cochlearites • †
Lithiotis • †
Plicatostylus (type) == References ==