TYPE GENUS. — Cyclochlamys Finlay, 1926: 245. — Type species (by original designation): Pecten transenna [sic] Suter, 1913. Recent, New Zealand.
DIAGNOSIS. — Very small Pectinoidea (c. 1.2 up to 6 mm in height) with a smooth or variously sculptured left valve with a flat, weakly to strongly inflated or even conical and pointed sculptured prodissoconch, sometimes bordered by a strong flange-like commarginal lamella or rim (Dijkstra & Marshall 2008: 24, fig. 20D) Right valve with a flattened sculptured prodissoconch, and commonly a smooth, rarely antimarginally sculptured, right valve with a simple outer prismatic layer of longitudinally hexagonal microstructure; internal riblets lacking.
REMARKS
This newly named family of micro-scallops includes three genera (Cyclochlamys, Chlamydella Iredale, 1929 and Micropecten n. gen.) formerly classified in Propeamussiidae. Cyclochlamydidae n.fam. comprises c. 30 Recent species mainly recorded from southern Australia, eastwards to New Zealand,but also recorded from the West Pacific (southern Japan and Indonesia), southwestern Indian Ocean (Rodrigues), and the Falkland Islands.It is absent in the Arctic, the Atlantic, and the northern and eastern Pacific.
Cyclochlamydidae n. fam. differs from Propeamussiidae by the following morphological characters: – a sculptured prodissoconch in Cyclochlamydidae n. fam. (uniformly smooth in Propeamussiidae); – a sometimes antimarginally sculptured right valve in Cyclochlamydidae n. fam. (smooth or weak commarginally sculptured in Propeamussiidae); – a simple outer prismatic layer of longitudinally hexagonal microstructure on the right valve in Cyclochlamydidae n. fam. (an outer layer of columnar calcite in Propeamussiidae).
Size: species of Cyclochlamydidae n. fam. measure 1.2 to 6 mm, whereas Propeamussiidae measure typically 5 to 120 mm in height.
Results of phylogenetic research attesting the monophyly of Cyclochlamydidae n. fam. will be published elsewhere.