Molluscan marginalia: serration at the lip edge in gastropods

Abstract

The shells of many marine gastropods have ventrally directed serrations (serial projections) at the edge of the adult outer lip. These poorly studied projections arise as extensions either of external spiral cords or of interspaces between cords. This paper describes taxonomic, phylogenetic, architectural and functional aspects of serrations. Cord-associated serrations occur in cerithiids, strombids, the personid Distorsio anus, ocenebrine muricids and some cancellariids. Interspace-associated serrations are phylogenetically much more widespread, and occur in at least 16 family-level groups. The nature of serration may be taxonomically informative in some fissurellids, littorinids, strombids and costellariids, among other groups. Serrated outer lips occur only in gastropods in which the apex points more backward than upward, but the presence of serrations is not a necessary byproduct of the formation of spiral sculptural elements. In hard-bottom gastropods that do not flee from predators, pointed serrations may resist shear when the shell is clamped firmly to the substratum. The functions of serration in other gastropods are less clear, but likely involve defence against predators with soft feeding structures in some cases.

The varix: evolution, distribution, and phylogenetic clumping of a repeated gastropod innovation

“…In contrast, continuous growth involves more time spent when either the aperture is relatively weak or the cost of producing a constantly thick shell is relatively high. Other shell structures, including siphons and a crenulated outer lip (for clamping the shell onto rock), can be formed discontinuously in varicate gastropods (Seilacher & Gunji, 1993;Sälgeback & Savazzi, 2006;Vermeij, 2014). With periodic growth, the siphon is functional most of the time, without needing constant remodelling.…”

Seven new genera and thirty-four new species of buccinoid gastropods (Neogastropoda: Buccinidae) from the Aleutian Islands, Alaska

“…Perhaps this is a modification for feeding on bivalves as in some other groups. A general discussion of labial "serrations" or dentations is given in Vermeji, 2014. Etymology: Latin, combination of labium "lip" and dentatus "toothed" in reference to the prong-like denticles at the base of the outer lip.…”

Shell features associated with the sand-burying habit in gastropods

“…A distinct callus pad is common in sand-burying nassariids, especially in the IWP; Strombidae, again in the IWP (Eurpotomus, Laevistrombus); and cassids. Surface-dwelling adult personids, cassids and some muricids also have much of the ventral side of the shell covered with a thick callus pad or shield, but in most cases this feature is accompanied by a crenulated outer lip that clamps to hard surfaces (Vermeij, 2014).…”