Eulimidae (Bertolaso & Garilli, 2009)

Eulimidae View in CoL

The Eulimidae View in CoL (L. Cretaceous- Recent) are almost exclusively echinoderm parasites, with a generally polished, high-spired shell. The varices of eulimids are atypical of gastropods as a whole. In most species, varices appear as periodic axial scars on the shell associated with an internal thickening. In many cases, they are synchronized between whorls, with only one per whorl, although some have two per whorl, and the degree of synchrony varies ( Fig. 2D View Figure 2 ). For example, not all specimens of Melanella martini (A. Adams in Sowerby, 1854) have synchronized varices ( Savazzi & Sasaki, 2004). The varices of eulimids are associated with a growth hiatus and subsequent thickening of the aperture. Interestingly, some eulimids are sequential hermaphrodites, and a varix is associated with the transition from male to female (e.g. Apicalia View in CoL ) ( Warén, 1983). All eulimids with the characteristic curved shell possess a varix every 360°, although the inverse is not true, – not all species with this pattern have curved shells ( Savazzi & Sasaki, 2004). The curving of the shell may be accomplished by slight changes to the axis of coiling at each growth hiatus. The internal nature of the varices helps maintain the ultra-smooth texture of the shell while still providing a thickened aperture during growth stoppages and periodic structural support. Some genera, such as Auriculigerina View in CoL , Chileutomia View in CoL , and Oceanida View in CoL , have more expanded varices, which correspond to a more flaring aperture ( Warén, 1983; Lozouet, 1999; Landau & Marquet, 2001; Garilli & Messina, 2006).