Fordilla troyensis Barrande: The Oldest Known Pelecypod

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Science  25 May 1973:
Vol. 180, Issue 4088, pp. 866-868
DOI: 10.1126/science.180.4088.866


Specimens of the small bivalved animal Fordilla troyensis Barrande from New York State show that this fossil is the oldest known pelecypod mollusk and not a conchostracan arthropod. This finding extends the range of the class Pelecypoda backward in time from the Early Ordovician (about 495 million years ago) to the Early Cambrian (about 540 to 570 million years ago). The morphology of Fordilla troyensis suggests that it lived infaunally and that it was ancestral to the pelecypod subclasses Heteroconchia and Isofilibranchia.