Ylistrum Mynhardt & Alejandrino, 2014

Dijkstra, Henk H. & Beu, Alan G., 2018, Living Scallops of Australia and Adjacent Waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae), Records of the Australian Museum (Rec. Aust. Mus.) 70 (2), pp. 113-330 : 207

Ylistrum Mynhardt & Alejandrino, 2014

Ylistrum Mynhardt & Alejandrino in Mynhardt et al., 2014: 407. Type species (by original designation): Pecten balloti Bernardi, 1861 ; Pliocene to living, Southwest Pacific.

Diagnosis. Amusiini with (sub)circular shape, up to c. 140 mm high, very weakly inflated, both valves slightly convex; umbonal angle c. 140°; exterior surface of disc and auricles smooth, interior with c. 42–54 narrow, prominent radial riblets arranged irregularly or in vaguely discernable pairs; auricles equal in length, intermediate hinge teeth absent, byssal notch and ctenolium weak in early ontogeny, absent later.

Distribution. Middle Miocene–Recent. The earliest species referable to Ylistrum seems to be Amusium morganense Beu & Darragh (2001: 175, figs 64A, F, 65A–E), from Morgan Limestone (Balcombian Australian local stage, middle Miocene), River Murray cliffs near Blanchetown, South Australia, and Nullarbor Limestone (also Balcombian), Nullarbor Plain, southern Western Australia. Ylistrum morganense is smaller and has larger auricles and much more closely paired internal rib carinae than Y. balloti . Tropical and subtropical Indo-West Pacific, living littorally.

Discussion.As discussed under Annachlamys and Amusium , we retain Ylistrum in Amusiini at present, awaiting a more final molecular phylogeny of Pectinidae .