Caecum shaskyi, Raines, 2020

Caecum shaskyi species novum

Figures 114 View FIGURE 114 A–I, 115A–E, 116A–B, 128E

Fartulum farcimen — Shasky, 1984: 27, [non Carpenter, 1857].

Type material. Holotype, SBMNH 637732 View Materials ; paratypes, SBMNH 637733 View Materials (4 figured).

Additional material examined. NHMLAC: LACM 1938 View Materials - 218.5 View Materials , 18 miles SE of Foca Island , Piura Dept., Peru, 21 m, 2 sh . SBMNH: SBMNH 637731 View Materials , Salango Island , Manabí Province, Ecuador 11–27 m, 1 sh. BCD: N. side of La Plata Island, Ecuador, 12–30 m, 1 sh .

Type locality. La Plata Island , Manabí Province, Ecuador .

Diagnosis. Teleoconch subcylindrical, with increase in diameter from posterior end to aperture. Surface smooth and glossy, yellowish-orange to orange in color. Septum mucronate, with pronounced finger-like, blunt mucro. Aperture with slight swelling and pronounced axial rings. Periostracum sculptured with dense, sinuous striae.

Description. Protoconch and teleoconchs I, II unknown. Teleoconch III surface smooth with weak axial growth lines ( Fig. 115B View FIGURE 115 ), transition to teleoconch IV marked by slight axial constriction ( Fig. 115A View FIGURE 115 ). Teleoconch IV surface smooth, glossy, with occasional axial growth lines ( Fig. 115C View FIGURE 115 ), transition to teleoconch V marked by slight axial constriction ( Fig. 115A View FIGURE 115 ). Teleoconch V with identical characters as previous stage, transition to teleoconch VI marked by axial constriction ( Fig. 115D View FIGURE 115 ). Teleoconch VI (last growth stage) large for genus [Tol 3.41–3.60 mm], tubular, thick, robust, moderately and regularly arched [Larc: 1.22–1.41 mm; Arc: 0.30–0.35 mm], subcylindrical with increase in diameter from posterior to aperture, yellowish-orange to orange ( Fig. 114B View FIGURE 114 ). Surface smooth, glossy ( Fig. 115C View FIGURE 115 ). Posterior [Dpe: 0.60–0.61 mm] with thick edge, squared shoulder ( Fig. 114E View FIGURE 114 ). Septum mucronate, deeply recessed ( Fig. 114E View FIGURE 114 ). Mucro finger-like, conical, blunt, positioned near dorsal margin, straight to slightly curved toward dorsal margin ( Fig. 114E View FIGURE 114 ). Aperture [Da: 0.72–0.79 mm] with slight swelling followed by rapid constriction, with 4–5 distally spaced axial rings, interspace narrowing with constriction ( Figs. 114E View FIGURE 114 , 115E View FIGURE 115 ). No varix. Lip smooth, with deflected peristome ( Fig. 114E View FIGURE 114 ). Periostracum rather thick, with dense, sinuous striae, yellow-orange ( Figs. 114A, C, F View FIGURE 114 ). Operculum thin, light brown; exterior surface with 5–6 concentric rings ( Figs. 114 View FIGURE 114 H–I). Conceptual reconstruction of growth stages shown in Fig. 116A View FIGURE 116 .

Etymology. The species is named in honor of the late Donald R. Shasky (1925–2002), for his work on eastern Pacific molluscs.

Distribution and Habitat. Known from La Plata Island, Manabí Province, Ecuador to Foca Island, Piura Dept., Peru. Subtidal, 11– 30 m. Uncommon on sandy substrates.

Remarks. Caecum shaskyi cannot be mistaken for any other eastern Pacific caecid. Its robust, glossy, yelloworange teleoconch along with its blunt finger-like mucro has no contenders. While several western Atlantic species such as C. floridanum Stimpson, 1851 , C. lineicinctum de Folin, 1880 , and C. carolinianum Dall, 1892 also have recessed, blunt, finger-like mucros, only C. carolinianum is comparable. Both C. shaskyi and C. carolinianum have smooth, glossy teleoconchs with longitudinal striae on the periostracum. Both species are rather robust with apertural swelling. Where C. shaskyi differs from C. carolinianum is in microsculpture, size and coloration. Caecum shaskyi lacks surface microsculpture, while C. carolinianum has both axial growth lines and longitudinal striae. The only axial rings present on C. shaskyi are those on the apertural swelling. Caecum shaskyi has a yellow-orange teleoconch with an average size of 3.5 mm. Caecum carolinianum is creamy white with a larger average size teleoconch of 4.2 mm.