Modulus (LINNE, 1758)

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 : 597-598

MODULUS MODULUS (LINNÉ, 1758)

Material examined

Atlantic Ocean : US: Florida: Indian River Lagoon , Fort Pierce Inlet, North Causeway, 27°28.20′N, 80°19.04′W ( USNM 1143356 ); Caribbean Sea: Belize: Twin Cays, Lagoon ( USNM 857810 ) .

Description

Marginal fold S-shaped ( Fig. 8 ), terminating at posterior tip of sorting area; oesophageal aperture at tip of marginal fold recurved segment; sorting area elongately triangular, with rounded posterior margin; left margin of sorting area with slight anterior bulge; accessory marginal fold straight along sorting area left margin, curving around posterior end of sorting area; sorting area pad, anterior flap, and crescentic pads lacking; glandular pad forming elongate, rounded mound projecting short distance posteriorly beyond gastric shield; paired digestive gland ducts opening at left of glandular pad; crescentic ridge long, extending from near oesophageal aperture, past digestive gland ducts, curving around posterior end of glandular pad, fusing to side of pad slightly behind gastric shield; accessory pads, caecum and caecal folds lacking; U-shaped fold present below style sac aperture; typhlosoles fused along distal two-thirds of style sac.

Remarks

Previously described by Houbrick (1980: fig. 3E) and Simone (2001: fig. 304). Houbrick interpreted the posterior tip of the sorting area as a ‘much reduced spiral caecum’; the marginal fold was depicted as a direct extension of the minor typhlosole. Based on the relative position of landmarks in Houbrick’s figure, apparently the caecum (as defined herein) was misidentified as the opening of the digestive gland. Probably as a consequence of poor preservation, both Houbrick (1980) and Simone (2001) overlooked the presence of the crescentic ridge and paired digestive gland ducts.

Figures

Figure 8. Midgut anatomy of Modulidae. Modulus modulus (USNM 1143356). Scale bar: 1.0 mm; refer to the text for a list of anatomical abbreviations.