Turritella communis, (RISSO, 1826)

Strong, Ellen E., 2011, More than a gut feeling: utility of midgut anatomy in phylogeny of the Cerithioidea (Mollusca: Caenogastropoda), Zoological Journal of the Linnean Society 162 (3), pp. 585-630 : 602

TURRITELLA COMMUNIS (RISSO, 1826)

Material examined

Atlantic Ocean: North Sea: the Netherlands: Texel ( SMF).

Description

Marginal fold S-shaped ( Fig. 11B ), extending beyond posterior tip of sorting area; oesophageal aperture at tip of marginal fold short recurved segment; sorting area broad anteriorly, curving, tapering rapidly to pointed tip; sorting area left margin with prominent bulge; sorting area pad, anterior flap, crescentic pads, and accessory marginal fold lacking; glandular pad forming long, tall, broad mound, extending far posterior to gastric shield; pad posteriorly subdividing gastric chamber into narrow upper chamber on right and lower, broad chamber on left; single digestive gland duct opening at left of glandular pad; crescentic ridge long, bounding shallow, broad crescentic groove; ridge extending posteriorly from digestive gland duct, curving around posterior end of glandular pad, continuing to gastric shield as indistinct ledge bounding shallow cleft alongside glandular pad; crescentic ridge paired, with inner ridge paralleling proximal crescentic ridge from digestive gland duct, and extending to posterior of glandular pad; accessory pads, caecum, and caecal folds lacking; U-shaped fold present below style sac aperture; typhlosoles unfused.

Remarks

Described by Graham (1938: fig. 3) and Fretter & Graham (1962: fig. 121C). The midgut in these figures has been opened ventrally such that the midgut floor between the oesophageal opening and the gastric shield has been removed, or is not visible. Consequently, the description does not convey even the most basic aspect of cerithioidean midgut anatomy – the presence of the large central glandular pad. The only elements remaining are the gastric shield, oesophageal aperture, and the large, curving sorting area with marginal fold; the recurved proximal tip of the marginal fold is not shown. This perspective was fundamental to the interpretation that turritellids possess a vestigial spiral caecum behind the gastric shield on the right (see character 21, below).

Figures

Figure 11. Midgut anatomy of Siliquariidae (A) and Turritellidae (B, C). A, Tenagodus squamatus (USNM 801714). B, Turritella communis (SMF). C, Maoricolpus roseus (ZMB 102.962). Scale bars: 1.0 mm; refer to the text for a list of anatomical abbreviations.