The Tertiary-Recent bivalve Noetiella (Arcacea) and its evolutionary relationships

The arcoid genus Noetiella is defined to include small, non umbonate trapezoidal taxa possessing a prosodetic ligament and simple radial costae. Two subgenera are described; N. (Noetiella) – Pliocene to Recent and N. (Scalenonoetia) subg. nov. — Eocene. N. (Noetiella) contains three species; N. (N.) congoenis Thiele and Jaeckel, N. (N.) minor (Pallary) comb. nov. and N. (N.) tethyensis sp. nov. N (Scalenonoetia) contains a single species N. (S.) africana (Newton). The anatomy of N. congoensis is described and reflects the infaunal habits in the form of the foot, musculature, lack of byssus and large palp size. Noetiella is compared with other infaunal noetids and shown to differ significantly from Noetia, Eontia, Verilarca, Trinacria, Linter and Pachecoa. The traditional subfamily trichotomy of Noetiinae, Striarcinae and Trinacriinae is questioned. The affinity of Noetiella is discussed on an individual lineage basis and is believed to belong to a distinct lineage separate from that of Noetia. A late Cretaceous ancestor is hypothesised which most probably resembled some of the more trapezoidal forms of Breviarca