Clathrodrillia parva, Fallon, Phillip J., 2016

Fallon, Phillip J., 2016, Taxonomic review of tropical western Atlantic shallow water Drilliidae (Mollusca: Gastropoda: Conoidea) including descriptions of 100 new species, Zootaxa 4090 (1), pp. 1-363 : 102-103

Clathrodrillia parva , new species

(Fig. 45)

Type material. Holotype 10.5 x 4.0 mm (USNM 1291333); one paratype, 9.8 x 3.6 mm, in 20 m, 0.4 km N of Turtle Harbor, Utila I., Honduras (ANSP 464985). Both types R. Masino!

Type locality. New Guinea Reef, Questelles Bay, St. Vincent I., SVG, in 34 m.

Range and habitat. Honduras (Utila I.) and SVG ( St. Vincent I.). A large disjunct distribution, but perhaps overlooked elsewhere because of its small size and deep reef-dwelling habitat (20–34 m). It has been found on coarse mineral sand with sponge (holotype) and on sand and coral rubble at the base of coral rock wall (paratype) in 20– 34 m.

Description. Shell small (to 10.5 mm total length), fusiform, glossy; to about 9 convex whorls; shoulders sloping on early whorls, more acute on penultimate and last whorls; body whorl approximately 59% of overall length. Aperture narrowly oval, only slightly wider centrally than anal sinus and anterior canal. Surface sculpture of heavy axial ribs and fine spiral cords. Protoconch of approximately 1½–1¾ smooth round whorls. Axial sculpture of broad axial ribs, suture-to-suture on spire whorls, evanescent near anterior fasciole on shell base, 9–10 on penultimate and 7 on last whorl to varix; ribs reduced and recurved in sulcus, almost obsolete in sulcus of last whorl. Narrower, shorter ribs are present on shell base between each regular rib and begin below periphery of last whorl. Varix broad and hump-like, about ⅓-turn from the edge of outer lip. Spiral sculpture of fine spiral cords 2– 3 on early, 4–5 on the penultimate whorls, and 6 on last whorl below suture line. Spiral cords override axials; growth striae dense but microscopic between cords. Sulcus concave, smooth, without ornamentation except reduced ends of axials; about ⅓-height of spire whorls. Outer lip thin, somewhat flattened from varix to lip edge; lip edge forms an arc from and congruent with anal sinus to stromboid notch. Stromboid notch a wide, shallow indentation. Anal sinus deep, U-shaped, flared and offset from suture by parietal callus. Inner lip thin, recumbent, emarginated; with a parietal callus posteriorly. Anterior canal moderately long, open, twisted to the right when viewed ventrally; unnotched; fasciole not swollen. Color white with a light orange-brown patch on varix shoulder.

Remarks. Taxonomy. Clathrodrillia parva is the smallest member of the genus; nonetheless, important shell characters are typical of Clathrodrillia : a tall, turreted spire; axial ribs with overriding spiral cords; a hump-like varix with a darker blotch; a narrow aperture, a short but well-developed anterior canal, and an anal sinus spoutlike, laterally directed from the shell’s axis. Variability. The two type specimens have an average total length of 10.15 mm (9.8–10.5 mm) and average W/ L ratio of 0.374. Identification. This small white shell may be mistaken for similar-sized drilliids in other genera that possess well-defined anterior canals, namely Cerodrillia, Decoradrillia , Syntomodrillia , or Leptadrillia , but the combination of a turreted shell, varical hump, and spiral cords overriding the ribs is unique to Clathrodrillia . From C. guadeloupensis , new species it differs in being smaller (10.5 versus 20.7 mm maximum total length) and in possessing somewhat more angular shoulders. From C. wolfei (Tippett, 1995) it differs in having more robust ribs with more angular shoulders, and in being smaller (10.15 versus 12.68 mm average total length). From C. dautzenbergi (Tippett, 1995) it differs in being smaller and in having fewer, more robust ribs.

This taxon is represented by only two specimens but is nonetheless believed to merit description. They are mature, of similar size, have very similar morphological characteristics, and so are very likely representative of the species as whole. They are the smallest representatives of a genus otherwise comprised of mostly much larger species and thus important to illustrate the adaptive size range of the genus-group.

Etymology. The Little Clathrodrillia . From the Latin adjective parvus, feminine parva , meaning little. The name is a reference to its size—the smallest of the clathrodrillias.