Splendrillia abdita, 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 : 280-282

Splendrillia abdita , new species

( Plate 142 )

Drillia thea var. carminura Dall, 1889a: 91 , in part. Only the specimens from Barbados are incorporated into this new taxon.

Type material. Holotype 9.7 x 3.6 mm (USNM 87468); two paratypes: 9.5 x 3.2 & 9.8 x 3.5 mm, from the type locality (MCZ 7074). A third specimen, in lot MCZ 7074, of an unidentified but different species (not a drilliid) was moved to MCZ 383692. Dall did not unequivocally state that the specimens were the same as the one from USFC Sta. 2404, which was the model for his description and holotype of Drillia carminura . As such they are not considered part of a type series of that species. See under Cerodrillia carminura (Dall, 1889) for further explanation. The specimen in USNM 87468, the designated holotype of this new species, and two paratypes are believed to originally have been in the same lot. At the time it was customary to divide lots between the Smithsonian and Museum of Comparative Zoology. The single specimen in USNM 87468 is labeled “ Drillia thea var.” and lacks a varietal name. It is the best preserved specimen and so has been selected as the holotype.

Type locality. Off Barbados, R/V Blake expedition 1877-78, in 100 fms [183 m].

Range and habitat. Known only from the type locality.

Description. Shell very small (to 9.8 mm total shell length), fusiform, truncated anteriorly, glossy, with a total of up to about 8 strongly convex whorls, with a large, gradually tapering last whorl that is approximately 60% of the total shell length; sutures appressed. Protoconch of 1¾ smooth round whorls, the first not immersed. Axial sculpture of broad, convex ribs that run from sulcus or suture to succeeding suture on spire whorls, and evanesce before the anterior fasciole on the last. Ribs mostly obsolete in the sulcus, slightly opisthocline, knob-like below sulcus of first 2 whorls, elongate below; 10 on penultimate, 6 on last whorl to varix. Microscopic growth striae present. Varix convex, higher and wider than nearby ribs, hump-like, positioned ⅓-turn from the edge of the outer lip. Spiral sculpture absent except for about 5 threads on the anterior fasciole. Microsculpture is not evident on the worn type specimens. Sulcus slightly concave, about ⅓-height of the spire whorls, bare, except for a few reduced ribs that extend to the suture. Outer lip somewhat flattened from varix, re-grown from varix on holotype, broken off on paratypes; strengthening axial folds present. Edge of lip forms a low arc from anal sinus to anterior canal. Stromboid notch obscured by damaged. Anal sinus a deep notch that adjoins the suture at its apex, behind the parietal lobe. Edges parallel to slightly convergent; inner rim of sinus flared out. Inner lip narrow, emarginated; erect at anterior end of canal, recumbent elsewhere; with a low parietal lobe posteriorly. Anterior canal well defined, short, straight, open; fasciole not swollen. Color off-white, with faint golden-yellow spots in sulcus corresponding to rib intercostal space. Color may be more vivid in fresh specimens; the ones in hand are old and faded.

Remarks. Taxonomy. Splendrillia abdita has all the distinctive features of Splendrillia : an anal sinus that adjoins the suture behind the parietal lobe, ribs that are mostly absent in the sulcus, a hump-like varix, and spiral sculpture confined to the anterior fasciole. This species is unique with its golden-yellow spots in the sulcus. Variability. The average total length of the three type specimens is 9.67 mm (9.5–9.8 mm), their color pattern appears to be consistent. Identification. Splendrillia abdita is very similar in appearance and size to S. subtilis , new species, S. panamensis , new species S. interpunctata (E.A. Smith, 1882) , and S. alticostata , new species. It can be distinguished from all four by its color pattern. From S. subtilis it also differs in the form of the last whorl, which is more convex, not as angled as that of S. subtilis . From S. panamensis it also somewhat smaller (9.67 versus 11.68 mm in total length), has ribs that extend farther down the last whorl, and lacks a strong spout-like anal sinus. From S. interpunctata it also differs in having longer, less oblique ribs. From S. alticostata it also differs in having less angular ribs.

Etymology. The Hidden Splendrillia , from the Latin adjective abditus (=hidden, secret, out of the way), a reference to all known specimens’ more than 100 years’ hidden residence under other identifications in museum trays.

Figures

PLATE 142. Splendrillia abdita, new species. Figs. 1 – 2: holotype, offshore, Barbados (USNM 87468). Fig. 1: ventral, lateral & dorsal views; Fig. 2: enlarged view of protoconch (not to scale). Figs. 3 – 4: paratypes, offshore, Barbados (MCZ 7074).