Hyotissa semiplana is an extinct species of large saltwater oysters, a fossil marine bivalve mollusk in the family Gryphaeidae, the foam oysters[1] Fossil shells of Hyotissa semiplana can reach a diameter of about 60 millimetres (2.4 in).

[2] They have thick-walled valves, with rough, nodose surface.

[3][4] Fossils of this species have been found in the Campanian-Maestrichtian of Poland, in the Santonian-Maestrichtian of Europe and North Africa and in the Campanian of South India.

[3][5] This bivalve-related article is a stub.

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