Petta Malmgren 1866

Genus Petta Malmgren, 1866

Type species. Petta pusilla Malmgren, 1866, by monotypy.

Diagnosis. Pectinariids with smooth cephalic veil, with medial tentacular extension, free from opercular lobe, smooth margin of opercular lobe, poorly-marked separation between scaphe and abdomen, and avicular uncini with transverse rows of progressively shorter teeth distalwards (Hutchings & Peart 2002). In addition, the branchiae and the anal flaps are distinctly shorter than among members of other genera of pectinariids, the latter shorter than scaphal lateral papillae, while the anal cirrus is remarkably longer.

Remarks. Prior to the present study, Petta was a genus comprising only four species. The type species is known from off Sweden, and the other species were described from specimens collected as far apart as in the Caribbean and Gulf of Mexico, Kerguelen Islands and Indonesia. Therefore, the present study brings the first record for species of this genus for the southern Atlantic.

Although Petta has few valid species currently, in most cases they are known only from type material, which in some cases is lost or in poor condition, and the descriptions do not include several important taxonomic characters. A revision of the genus is currently under preparation by Zhang et al.