Planodasys littoralis Rao, 1993

Records from India. ANDAMAN & NICOBAR ISLANDS: Harminder Bay—Rao (1993); GENERAL RECORD: Naidu & Rao (2004).

Habitat. Marine, intertidal, subtidal; medium sand with little detritus, 10 cm below surface, between low and mid water level.

Distribution. India (Bay of Bengal).

Remarks. Currently, the genus Planodasys includes two species both of which are from India (see also below). Description of both species are based on bright-field microscopy only; it is possible that advanced optical techniques (e.g., DIC) may reveal internal structures so far undetected (e.g., the frontal organ) and/or may provide a better insight on the structure of the very long cylindrical caudal organ (bursa copulatrix in the original description). As the layout of the reproductive system has been demonstrated to be of phylogenetic significance (e.g., Todaro et al. 2011), reliable information in this regard is relevant beyond taxonomy. Likewise, the inclusion of Planodasys species in the ongoing phylogenetic studies based on molecular markers (e.g., Todaro et al. 2012, 2014, 2015) could confirm or disprove the current in-group systematization of the family Planodasyidae (Guidi et al. 2014) . In our opinion, and as a possible working hypothesis, Planodasys should be considered a junior synonym of Crasiella as it lacks reliable autapomorphic traits that could make it a distinct taxon. However, until additional information will be gathered, we continue to consider Planodasys to be a separate genus.