Australian Aplacophoran molluscs: I. Cheatodermomorpha from Bass Strait and the Continental Slope off south-eastern Australia
Four new species of Chaetodermatidae (Chaetoderma usitatum, Falcidens chiastos, F. lipuros and F. macrafrondis) and a new genus and species of Prochaetodermatidae (Rhabdoderma australe) are the first Chaetodermomorpha described from off Australia; all are from the shelf in Bass Strait or from the continental slope off southeastern Australia. Two species are numerous: F. chiastos occurs at densities sometimes up to 180 m2 from 22 to 120 m in 20 of the 23 shelf samples that contain Chaetodermomorpha, and the prochaetodermatid R. australe is common from deeper water, 1,120 to 2,510 m. Several additional species only recently received or with a single specimen are noted but not described; three belong to Prochaetoderma, Limifossor, or Scutopus, thereby extending the recorded ranges of these genera to the western Pacific. Of the 16 species of Chaetodermomorpha collected, four are shelf species occurring at depths of less than 200 m (F. chiastos, F. lipuros, one Prochaetodermatidae, one undetermined), six are upper slope species extending to 1,000 m (three species of Falcidens, Chaetoderma sp., Scutopus sp., Limifossor sp.) and six extend below 1,000 m (C. usitatum, F. macrafrondis, R. australe, Falcidens sp., Chaetoderma sp., Prochaetoderma sp.). These depth distributions are similar to other Pacific Chaetodermomorpha genera except for Chaetoderma, a genus usually common on the shelf but missing from Bass Strait.