Until recently the genus Colpodaspis (as well as the non-Australian genus Colobocephalus) was considered part of the Diaphanidae. However, they are now placed into their own family because of the completely internal, globose shell with a short but protruding spire, a radula that lacks central (rachidian) teeth, and hook-shaped lateral teeth. Members of this family are small to very small in size. Like the Diaphanidae, the distribution is remarkably wide, both geographically and bathymetrically.
Ohnheiser, L.T. & Malaquais, M.A. 2014. The family Diaphanidae (Gastropoda: Heterobranchia: Cephalaspidea) in Europe, with a redescription of the enigmatic species Colobocephalus costellatus M. Sars, 1870. Zootaxa 3774: 501-522.
The only species known from NSW is Colpodaspis thompsoni Brown, 1979
Shells in this family are completely internal in very small (3 mm) slugs. Anteriorly the foot is expanded into rounded lobes and the tail extends a long way posteriorly.
Colpodaspis thompsoni Brown, 1979
Description: Animal small, dark brown with raised white patches on mantle containing yellow spots or splotches. Shell completely internal, white (Marshall & Willan, 1999).
Size: Animal length 3 mm.
Distribution: Indo-West Pacific.
Habitat: This small but distinctive species was recorded for the first time in NSW in 2015 at the Solitary Islands (Nimbs et al., 2015). This record was interpreted then as a product of a shift of southern range resulting from warming of the global oceans, but it could equally result from being overlooked in the past because of its small size.
Figures: See the Sea Slug Forum for a figure
Copyright Des Beechey 2018