Class BIVALVIA Linné, 1758?

Subclass PTERIOMORPHA Beurlen, 1944?

Superfamily OSTREOIDEA Rafinesque, 1815?

Family OSTREIDAE Rafinesque, 1815?

Subfamily LIOSTREINAE Vyalov, 1983?

Genus Agerostrea Vyalov, 1936

The?species?is?distinguished?from?falcate?congeners?and??species?of?Rastellum?(Faujas-Saint-Fond,?1799)?by?its??smooth?central?field?in?both?valves?and?general?absence?of??shell?chambers?(with?respect?to?Rastellum).??According?to?Stenzel?(1971),?chomata?are?tubercle-like?and?surround?the??commissure;??however,?this?is?a?character?Malchus?et?al.?(1994)?found?on?Rastellum?diluvianum?(Linné)?rather?than?Agerostrea.

Agerostrea?is?a?Late?Cretaceous?(and?possibly?Pliocene)?genus?while?Rastellum?ranges?from?the?Callovian?(end?of?the?Middle?Jurassic)?to?the?end?of?the?Creatceous,?so?they?overlap.?
Although?they?are?both?in?the?true?oyster?family?Ostreidae,?they?belong?to?different?subfamilies

The?clue?someone?used?is:?Agerostrea?has?shorter?ribs,?and?even?smooth?surfaces?(externally?and?internally).?Rastellum?have?long?ribs,?forming?a?sort?of?spike.
As?example, In fig2?Agerostrea?is on?the?left?side.

參考：The first record of Agerostrea ungulata (von Schlotheim, 1813) (Bivalvia: Ostreoidea) from the Upper Maastrichtian of KwaZulu, South Africa, with a discussion of its distribution in southeast Africa and Madagascar
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