Caecum diminutum C.B. Adams, 1852

Raines, Bret K., 2020, A Rosetta Stone for eastern Pacific Caecidae (Gastropoda: Caenogastropoda), Zootaxa 4827 (1), pp. 1-146 : 7-10

publication ID	https://doi.org/ 10.11646/zootaxa.4827.1.1
publication LSID	lsid:zoobank.org:pub:2CE528C2-DE07-4155-B37D-BE2C342A3901
DOI	https://doi.org/10.5281/zenodo.4457757
persistent identifier	https://treatment.plazi.org/id/03A3DF49-FFE4-FF8B-FF44-F9DBFEF7395A
treatment provided by	Plazi
scientific name	Caecum diminutum C.B. Adams, 1852
status

Treatment

Caecum diminutum C.B. Adams, 1852 View in CoL

Figures 3 View FIGURE 3 A–I, 4A–M, 5A–B, 6N–O, 127P

Caecum diminutum C.B. Adams, 1852: 161 View in CoL , holotype MCZ 186574 View Materials , Panama.

Caecum (Fartulum) farcimen Carpenter, 1857 View in CoL (in part): 326, 4 syntypes NHMUK 1857.6 View Materials .4.1544, 1 syntype NHMUK 1857.6 View Materials .4.1545, Mazatlan. (syn. nov.).

Caecum impartitum var. bicolor de Folin, 1867a: 41 View in CoL , 3 syntypes MNHN-IM-2000-4600, Panama. (syn. nov.).

Caecum taeniatum de Folin, 1867b: 43 View in CoL , 3 syntypes MNHN-IM-2000-3115, Panama. (syn. nov.).

Caecum diminutum View in CoL — Turner, 1956: 45, pl. 17, fig. 5; Keen, 1971: 397; Lightfoot, 1993a: 18, fig. 7.

Caecum farcimen View in CoL — Carpenter, 1860: 32; Tryon, 1886: 215, pl. 66, fig. 53; Palmer, 1951: 44; Keen, 1968: 418, figs. 78a–b; Keen, 1971: 397; Shasky, 1984: 27; Skoglund, 1992: 28.

non Brochina farcimen — Lightfoot, 1993b: 80, fig. 27.

Caecum View in CoL sp. “ a ”— Cruz, 2007: 135, fig. 7.

Material examined. In addition to the type material the following lots were examined. NHMLAC: LACM 1986 View Materials - 195.6 View Materials , La Gringa Point, Los Angeles Bay , Baja California, Mexico, 5 m, 6 sh ; LACM 1946 View Materials - 10.12 View Materials , Creston Island , Mazatlan, Sinaloa, Mexico, intertidal, 1 sh ; LACM 1972 View Materials - 42.64 View Materials , Ballena Point , Ballena Bay, Puntarenas Prov., Costa Rica, 3–17 m, 30 sh ; LACM 1975 View Materials - 54.26 View Materials , Venado Island , Panama Prov., Panama, intertidal, 3 sh ; LACM 1933 View Materials - 10.13 View Materials , Santa Elena Beach, Guayas Prov., Ecuador, intertidal, 10 sh ; LACM 1970 View Materials - 11.52 View Materials , Ancon Point, Guayas Prov., Santa Elena, Ecuador, intertidal, 17 sh ; LACM 1970 View Materials - 12.41 View Materials , Ancon Point, Guayas Prov., Santa Elena, Ecuador, intertidal, 87 sh ; LACM 1935 View Materials - 106.39 View Materials , Blanca Beach, Guanacaste Prov., Costa Rica, intertidal, 1 sh ; LACM 1967 View Materials - 12.14 View Materials , Isabel Island , Nayarit, Mexico, 24 m, 3 sh ; LACM 1965 View Materials - 65.2 View Materials , Caraya Island , Panama Bay, Panama Prov., Panama, intertidal, 1 sh ; LACM 182097 View Materials , Taboga Island , Panama Bay, Panama Prov., Panama, intertidal, 2 sh ; LACM 1965 View Materials - 25.56 View Materials , Taboga Island , Panama Bay, Panama Prov., Panama, 9–27 m, 11 sh ; LACM 1938 View Materials - 131.20 View Materials , Honda Bay , Veraguas Prov., Panama, intertidal to 17 m, 2 sh ; LACM 1972 View Materials - 22.14 View Materials , San Pedrito Island , Murcielagos Islands, Guanacaste Prov., Costa Rica, 3–4 m, 1 sh ; LACM 1972 View Materials - 46.61 View Materials , Alcatraz Island , Tortugas Islands, Puntarenas Prov., Costa Rica, 2–8 m, 120 sh ; LACM 1972 View Materials - 52.66 View Materials , Herradura Bay , Puntarenas Prov., Costa Rica, 3–16 m, 50 sh ; LACM 1935 View Materials - 122.18 View Materials , Salinas Bay , Costa Rica, 10 m, 4 sh ; LACM 1972 View Materials - 17.44 View Materials , Jobo Bay , Costa Rica, 2–8 m, 100 sh ; LACM 1972 View Materials - 58.61 View Materials , Culebra Point , Costa Rica, 10–25 m, 27 sh ; LACM 1970 View Materials - 9.30 View Materials , Salinas, Ecuador, intertidal, 95 sh ; LACM 1972 View Materials - 85.33 View Materials , Mero Pt., Tumbes Dept., Peru, intertidal, 7 sh ; LACM 1973 View Materials - 57.6 View Materials , Zacatillo Island , El Salvador, intertidal, 30 sh ; LACM 1973 View Materials - 95.2 View Materials , Los Cobanos , El Salvador, 2 m, 65 sh ; LACM 1972 View Materials - 81.19 View Materials , S of Bocapan , Tumbes Dept., Peru, intertidal, 1 sh . SBMNH: SBMNH 620188 View Materials , La Puntilla, Salinas, Guayas, Ecuador, intertidal, 20 sh ; SBMNH 619893 View Materials , La Puntilla, Salinas, Guayas, Ecuador, intertidal, 1 sh ; SBMNH 620178 View Materials , Sayulita, Nayarit, Mexico, intertidal, 1 sh ; SBMNH 620187 View Materials , Bahia Herradura , Puntarenas, Costa Rica, intertidal, 1 sh ; SBMNH 621307 View Materials , La Cruz de Huanacaxtle , Bahia de Banderas, Nayarit, Mexico, intertidal, 3 sh ; SBMNH 621313 View Materials , Punta Rosales, Jalisco, Mexico, intertidal, 5 sh ; SBMNH 128133 View Materials , Isla Lobos, Mazatlan, Sinaloa, Mexico, intertidal, 24 sh ; SBMNH 126597 View Materials , Playa Las Gaviotas, Mazatlan, Sinaloa, Mexico, intertidal, 24 sh ; SBMNH 621401 View Materials , Punta Jacinto, Guayas, Ecuador, intertidal, 3 sh ; SBMNH 620756 View Materials , La Cruz de Huanacaxtle , Nayarit, Mexico, intertidal, 40 sh ; SBMNH 620692 View Materials , Lo de Marcos , Nayarit, Mexico, intertidal, 30 sh ; SBMNH 620849 View Materials , Punta Tiburon, Mazatlan, Sinaloa, Mexico, intertidal, 2 sh ; SBMNH 620863 View Materials , Punta Ursula , Veraguas, Panama, 5–10 m, 1 sh ; SBMNH 620867 View Materials , La Cruz de Huanacaxtle , Nayarit, Mexico, 9–14 m, 6 sh ; SBMNH 621362 View Materials , Santa Cruz, Nayarit, Mexico, intertidal, 10 sh ; SBMNH 621645 View Materials , Sayulita, Nayarit, Mexico, intertidal, 1 sh ; SBMNH 622338 View Materials , El Rubio, Tumbes, Peru, intertidal, 1 sh .

Original diagnosis. “Shell well arcuated, slender, with the diameter uniform, except near the summit: white: with about 17 stout rings, which are rather distant and are but slightly flattened at the summits, followed by about 10 rings which are small and less prominent: apex lateral, not prominent.” Adams (1852: 161).

Description. Protoconch and teleoconch I unknown. Teleoconch II short, sculptured with axial growth lines increasing in strength, transition to teleoconch III marked by axial incised line followed by increase in diameter ( Fig. 4A View FIGURE 4 ). Teleoconch III about 2.5 times length of teleoconch II, smooth or sculptured with narrow rudimentary ribs and short longitudinal striae ( Figs. 4C, E, F View FIGURE 4 ), transition to teleoconch IV marked by a slight axial constriction ( Figs. 4A, D, G View FIGURE 4 ). Teleoconch IV with identical characters as previous stage, transition to teleoconch V marked by a rapid increase in diameter ( Figs. 4A, D, G View FIGURE 4 ). Teleoconch V (last growth stage) small for genus [Tol 1.40–1.68 mm], tubular, robust, strongly and regularly arched [Larc: 0.40–0.44 mm; Arc: 0.14–0.18 mm], nearly uniform in diameter from posterior to aperture, cream to semi-translucent brown, or mottled ( Figs. 3 View FIGURE 3 A–C). Surface smooth or sculptured with numerous, wavy longitudinal striae in the interspaces ( Figs. 4K, M View FIGURE 4 ). Axial sculpture from nearly absent to consisting of 20–30 ribs, which vary greatly in strength and spacing ( Figs. 4H, K, M View FIGURE 4 ). Axial interspaces vary greatly in width, rather shallow ( Fig. 4L View FIGURE 4 ). Posterior [Dpe: 0.34–0.39 mm] with moderately thick edge ( Fig. 3F View FIGURE 3 ). Septum mucronate ( Fig. 3F View FIGURE 3 ). Mucro with low rounded point, positioned along dorsal margin ( Fig. 3F View FIGURE 3 ). Aperture [Da: 0.42–0.45 mm] simple, slightly constricted ( Figs. 4H, K, M View FIGURE 4 ). No varix. Lip smooth, weakly developed, with slightly deflected peristome ( Fig. 3F View FIGURE 3 ). Periostracum not observed. Operculum thin, light brown; exterior surface with 8–10 concentric rings ( Figs. 3 View FIGURE 3 G–H). Conceptual reconstruction of growth stages shown in Fig. 5A View FIGURE 5 .

Distribution and Habitat. From Sinaloa, Mexico to Tumbes, Peru. Intertidal to 27 m. Common intertidally on rocky substrates.

Remarks. The holotype of Caecum diminutum (MCZ 186574) is an adult specimen ( Fig. 3F, I View FIGURE 3 ). Width of axial interspaces varies greatly. At some points they are so narrow they appear almost absent even within a single population. Neither locality nor depth appears to influence the surface sculpture. Carpenter (1857) was unaware of this variability when describing C. farcimen . Although the four specimens on Carpenter’s tablet 1544 are subadult (NHMUK 1857.6.4.1544, Fig. 3J View FIGURE 3 ), they clearly represent the smoother form of C. diminutum . The remaining C. farcimen type specimen (NHMUK 1857.6.4.1545) found on tablet 1545 is actually a junior synonym of another species, which is discussed later. Ribbed forms of C. diminutum can appear somewhat similar to C. firmatum Adams, 1852 . In fact, Carpenter (1863) considered it to be a synonym. However, differences in growth morphology and microsculpture do not support this position. Lightfoot (1993a: 18) correctly identified and illustrated C. diminutum . However, in the second part of her work, Lightfoot (1993b: 80) considered C. farcimen to be a separate unrelated species. De Folin (1867a,b) overlooked C. diminutum when describing C. impartitum var. bicolor ( Fig. 3K View FIGURE 3 ) and C. taeniatum ( Fig. 3L View FIGURE 3 ).

Kingdom	Animalia
Phylum	Mollusca
Class	Gastropoda
Order	Littorinimorpha
Family	Caecidae
Genus	Caecum