Cerodrillia arubensis, 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 : 58

Cerodrillia arubensis , new species

( Plate 22 )

Splendrillia sp. Jong & Coomans, 1988: 113; pl. 43, fig. 598.

Type material. Holotype 7.0 x 2.8 mm, frère Verberne! roughly 1970–85 (ANSP 465010). Two paratypes: 1 spec., 7.8 x 3.1 mm, from beach drift, Malmok beach, Aruba, A.N. de Man! 1966 (USNM 1291328); 1 spec., 7.2 x 2.8 mm, from harbor dredgings, Oranjestad, 12°32'N, 070°02'W, F. Fredericus! (ANSP 349130). The holotype is the same specimen described as Splendrillia sp. in Jong & Coomans (1988: 113) and depicted on their plate 43, fig. 598 (per note on sample label).

Type locality. Aruba, Netherlands Antilles.

Range and habitat. Known only from Aruba. Its habitat is also unknown because specimens were taken from beach drift or harbor dredgings.

Description. Shell very small (to 7.8 mm total length), fusiform, with up to approximately 7¼ glossy whorls, sutures appressed, the last whorl approximately 58% of the shell’s total length. Whorls convex below sulcus, sculpted by bold, rounded axial ribs. Protoconch conical, of approximately 1¾ glossy-smooth whorls, the first not immersed in the second. Axial sculpture of broad, round-crested opisthocline ribs that are reduced on whorl shoulder, obsolete in sulcus on last whorl, where they evanesce on shell base below whorl periphery. Ribs are spaced about the same as their width, 7 on the penultimate, 5 on the last whorl to the varix. Growth striae are very fine. Spiral sculpture consists of fine ridges on shell base and anterior fasciole. Shell surface microsculpture, as viewed under a dissecting microscope, consists of groups of 1 or more very fine threads separated by a single somewhat wider but still microscopic space. SEM images of the shell surface show that the pattern of narrow threads and wide spaces is created by groups of closely spaced rows of punctae (in the image about 5–6 rows) separated by wider spaces where punctae are sparse and placed randomly ( Plate 22 , Fig. 7). Sulcus narrow, concave, with low and slightly arcuate ribs. Varix larger than preceding rib, cup handle-like, within ¼-turn of edge of outer lip. Outer lip edge thin and produced in a low arc from the anal sinus to a weak stromboid notch anteriorly. A strengthening fold is located near the edge of the outer lip of the holotype (outer lip missing on paratypes). Anal sinus located on the shoulder, deep, U-shaped with a slightly flared inner edge; offset from the wall by a parietal callus; sides parallel. Inner lip thin, recumbent, “pinched” erect anteriorly, thin and unemarginate in parietal area; parietal callus at posterior end weak, forming one side of anal sinus. Anterior canal short but well defined, curved to the right when viewed ventrally, unnotched; anterior fasciole not swollen, with about 6–9 fine spiral threads. Color white to off-white, protoconch darker on holotype, the best specimen.

Remarks. The holotype was originally identified as Splendrillia sp. by Jong & Coomans (fig. 598) but later recognized as an undescribed Cerodrillia by Faber (unpublished MS). Since the Drilliidae portion of Faber’s manuscript was not published, the specimen was donated to the ANSP for use in this project (Faber, pers. comm.. 22 Apr 2011). Two other specimens were subsequently found during the course of this work and are included as paratypes. Taxonomy. Cerodrillia arubensis has the characteristics of the genus: a glossy shell with spiral sculpture confined to the anterior portion of the shell base and anterior fasciole, a sulcus with reduced ribs, obsolete on last whorl, a varix within ¼-turn from the edge of the outer lip, and a short but well defined anterior canal. The coarse microsculpture is somewhat unusual compared to other members of the genus, but differs from examined specimens of Decoradrillia , Fenimorea , and Splendrillia (compare with SEMs in Plates 49 , 62 & 130–131, respectively). Where present, most of its congeners have fainter spiral lines. Like most members of the genus, its shell is nearly monochromatic. Variability. The average total length of three specimens is 7.33 mm (7.0– 7.8 mm), and average W/L is 0.395. Little variability in form and color is exhibited by this small sample size. Identification. Splendrillia stellae , new species, is very similar and also found in Aruba but differs in having a smooth, narrower shell without spiral microsculpture except for spiral ridges on anterior fasciole, a varix hump-like about ⅓-turn from edge of outer lip, and a shorter anterior canal.

Etymology. The Aruba Cerodrillia . Named for the type locality.

Figures

PLATE 22. Cerodrillia arubensis, new species. Figs. 1 – 3: holotype, Aruba, Neth. Antilles ANSP 465010). Fig. 1: ventral, lateral & dorsal views; Fig. 2: enlarged view of protoconch (not to scale); Fig. 3: apical view, V = varix, L = edge of outer lip. Figs. 4 – 5: paratypes. Fig. 4: Malmok beach, Aruba, Neth. Antilles (USNM 1291328); Fig. 5: Oranjestad, Aruba, Neth. Antilles (ANSP 349130). Figs. 6 – 7: holotype, SEM images of shell surface, 250 x & 900 x, respectively (SEM images courtesy Paul Callomon of the ANSP).

PLATE 49. Clathrodrillia wolfei (Tippett, 1995). Upper panel. Figs. 1 – 2: holotype, E of Cape Lookout, North Carolina (USNM 880070). Fig. 1: ventral, lateral & dorsal view; Fig. 2: enlarged view of protoconch (not to scale). Fig. 3: apical view of paratype in Fig. 4: V = varix, L = edge of outer lip. Lower panel. Fig. 4: paratype, E of Cape Lookout, North Carolina (ANSP 399201); Figs. 5 – 6: off Dry Tortugas (UF 155372); Fig. 7: off Key West (UF 155359); Figs. 8 – 9: SW of Sombrero Light, Florida Keys (DMNH 114865); Figs. 10 – 11, 18: Gulf of Mexico (USNM 900283); Figs. 12, 14: SW of Johns Pass, Pinellas Co., W Florida (DMNH 114854); Figs. 13, 16: off Ft. Myers, Lee Co., W Florida (USNM 900284); Fig. 15: W of St. Johns Pass, Collier Co., W Florida (UF 158174); Fig. 17: off Collier Co., W Florida (USNM 900282); Fig. 19: W coast of Yucatan Peninsula (DMNH 114884).