Propeamussiidae Abbott, 1954

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 : 120

Propeamussiidae Abbott, 1954

Propeamussiidae Abbott, 1954: 361 , 369.

Diagnosistic characters. Free or byssate Pectinoidea with outer foliated calcitic layer on left valve and outer prismatic calcitic layer on right valve, present on the main part of the disc; inner layer crossed-lamellar aragonite beyond pallial line, in some species almost to distal margins; byssal notch without ctenolium.

Discussion. Hertlein (1969: N350) placed Propeamussium de Gregorio, 1884 with the subgenus Parvamussium Sacco, 1897a , together with Amusium Röding, 1798 and Korobkovia Glibert & van de Poel, 1965 in his Amusium group, although noting that these genera may have been derived from different groups of Pectinidae . Abbott (1954), however, introduced a new family name Propeamussiidae , emended by Waller (1978: 353), for representative species of Propeamussium . Waller (1972b) compared the microstructure of the shells of Pectinidae and Propeamussiidae and described their evolutionary and functional significance. He pointed out that the extensive layer of prismatic calcite forming the outer surface of the right valve of Propeamussiidae is represented on only a very small umbonal area of the right valve in Pectinidae . Waller (1984) also included several other related genera in Propeamussiidae , viz. Parvamussium Sacco, 1897a , Cyclopecten Verrill, 1897 , Similipecten Winckworth, 1932 , and Catillopecten Iredale, 1939 . Hayami (1988a) mentioned also Polynemamussium Habe, 1951 as an extant genus in Propeamussiidae , and treated Parvamussium as a synonym of Propeamussium . Subsequently, Hayami & Kase (1993: 54) raised Parvamussium in rank to a genus. Schein-Fatton (1985) introduced Bathypecten as a genus of Pectinidae , and Schein (1989) transferred it to the Propeamussiinae , which she regarded as a subfamily of Pectinidae , together with Cyclopecten , Parvamussium , Propeamussium and Similipecten . However, Dijkstra & Gofas (2004) considered Bathypecten to be a junior synonym of Catillopecten . Dijkstra & Maestrati (2012) introduced a new family Cyclochlamydidae for the genera Cyclochlamys and Chlamydella , formerly placed in Propeamussiidae , together with a new genus Micropecten Dijkstra & Maestrati, 2012 . As Hayami (1988b) and Waller (1991, 1993, 2006a) mentioned, the suprageneric classification of the Pectinoidea is still under study and not finalized. Currently Propeamussium , Parvamussium , Cyclopecten , Similipecten and Catillopecten are considered to be valid genera in Propeamussiidae . Table 1 compares the diagnostic characters of genera of Propeamussiidae and Cyclochlamydidae occurring in Australia.