Caecum strangulatum de Folin, 1867

Figures 69 A–I, 70A–N, 71A–B, 127L

Caecum strangulatum de Folin, 1867a: 43, 25 syntypes MNHN-IM-2000-4586, Panama.

Caecum strangulatum var. acuta de Folin, 1867a: 44, Panama.

Caecum occultum de Folin, 1867a: 44, holotype MNHN-IM-2000-4590, Panama. (syn. nov.).

Caecum uncinatum de Folin, 1867a: 47, 2 syntypes MNHN-IM-2000-4583, Panama. (syn. nov.).

Caecum strangulatum — Kisch, 1959a: 38.

Caecum richthofeni Strong & Hertlein, 1939: 224; pl. 20, fig. 11, holotype CAS 065658, 1 paratype LACM 1713, Panama. (syn. nov.).

Caecum richthofeni — Keen, 1971: 397; Shasky, 1984: 27; Skoglund, 1992: 28.

Caecum quadratum — Shasky, 1984: 27; Kaiser, 1997: 29; Finet et al. 2016: 28.

Caecum species #2— Lightfoot, 1993a: 22, fig. 12.

Material examined. In addition to the type material the following lots were examined. NHMLAC: LACM 1935 - 170.14, Port Utria, Choco Dept., Colombia, 24 m, 1 sh ; LACM 1935 - 90.12, Secas Islands, Chiriqui Prov., Panama, 45 m, 12 sh ; LACM 1972 - 59.32, Quepos, Puntarenas Prov., Costa Rica, 24 m, 4 sh; LACM 1972 - 58.64, Quepos, Puntarenas Prov., Costa Rica, 10–24 m, 6 sh; LACM 1972 - 30.32, Santa Elena Point, Guanacaste Prov., Costa Rica, 13–16 m, 5 sh; LACM 1935 - 122.21, Salinas Bay, Guanacaste Prov., Costa Rica, 11 m, 7 sh ; LACM 1965 - 12.46, Maria Cleofas Island, Tres Marietas Islands, Mexico, 5–10 m, 2 sh ; LACM 1936 - 169.5, Tiburon Island, Sonora, Mexico, 30 m, 1 sh ; LACM 1964 - 31.26, Puertecitos, Baja California, Mexico, 1–3 m, 7 sh; LACM 1973 - 3.47, Soladita Cove, SE of Guaymas, Sonora, Mexico, intertidal to 3 m, 2 sh ; LACM 1966 - 23.25, Ventana Point, Baja California Sur, Mexico, 22–37 m, 14 sh; LACM 1937 - 173.5, Muertos Bay, Baja California Sur, Mexico, 13 m, 2 sh ; LACM 1965 - 16.100, Banderas Bay, Jalisco, Mexico, 18–27 m, 1 sh ; LACM 1967 - 12.17, Isabel Island, Nayarit, Mexico, 25 m, 1 sh ; LACM 1965 - 21.72, Otoque Island, Panama Bay, Panama, 2–5 m, 19 sh ; LACM 1965 - 25.60, Taboga Island, Panama Bay, Panama, 9–27 m, 6 sh ; LACM 1967 - 15.21, Banderas Bay, Jalisco, Mexico, 10–21 m, 1 sh ; LACM 1978 - 15.2, La Plata Island, Manabi Prov., Ecuador, 13–20 m, 1 sh ; LACM 1972 - 22.18, San Pedrito Island, Murcielagos Islands, Costa Rica, 3–4 m, 9 sh ; LACM 1968 - 45.57, Cuastecomate Bay, Jalisco, Mexico, 18–36 m, 12 sh ; LACM 1972 - 30.33, Santa Elena Point, Guanacaste Prov., Costa Rica, 13–17 m, 20 sh; LACM 1972 - 35.34, Penca Point, Guanacaste Prov., Costa Rica, 8–13 m, 8 sh; LACM 1972 - 43.21, Ballena Bay, Puntarenas Prov., Costa Rica, 11 m, 1 sh ; LACM 1972 - 52.69, Ballena Point, Ballena Bay, Puntarenas Prov., Costa Rica, 3–16 m, 9 sh ; LACM 1972 - 53.37, Herradura Bay, Puntarenas Prov., Costa Rica, 22 m, 7 sh ; LACM 1972 - 63.91, Cano Island, Puntarenas Prov., Costa Rica, 8–13 m, 100+ sh ; LACM 1972 - 64.22, Cano Island, Puntarenas Prov., Costa Rica, 13 m, 1 sh ; LACM 1967 - 9.11, Isabel Island, Nayarit, Mexico, 9 m, 7 sh ; LACM 1934 - 240.7, Tangola Tangola Bay, Oaxaca, Mexico, 27–37 m, 1 sh ; LACM 1972 - 19.51, El Jobo, Salinas Bay, Costa Rica, 2–6 m, 100 sh ; LACM 1933 - 173.5, Indefatigable Island, Galapagos Islands, 110 m, 11 sh ; LACM 1935 - 134.12, Secas Islands, Chiriqui Prov., Panama, 25 m, 2 sh ; LACM 1984 - 44.22, Cousins Island, W of Santiado Island, Galapagos Islands, 21–30 m, 50 sh ; LACM 1984 - 46.11, Plazas Island, E of Santa Cruz Island, Galapagos Islands, 21–30 m, 10 sh ; LACM 1935 - 136.5, Secas Islands, Chiriqui Prov., Panama, 22 m, 10 sh ; LACM 1934 - 297.5, S of Black Beach, Charles Island, Galapagos Islands, 37 m, 11 sh ; LACM 1934 - 290.8, Tagus Cove, Albemarle Island ., Galapagos Islands, 147 m, 9 sh ; LACM 1934 - 289.10, James Bay, James Island, Galapagos Islands, 29 m, 18 sh ; LACM 1978 - 116.18, Cedro Island, Gulf of Nicoya, Puntarenas Prov., Costa Rica, intertidal, 2 sh ; LACM 1935 - 171.12, Port Utria, Choco Dept., Colombia, 14 m, 1 sh ; LACM 1935 - 180.5, Octavia Bay, Choco Dept., Colombia, 136 m, 2 sh ; LACM 1934 - 272.7, James Bay, James Island, Galapagos Islands, 44 m, 14 sh ; LACM 1934 - 267.4, Wreck Bay, Chatham Island, Galapagos Islands, 40 m, 60 sh ; LACM 1933 - 157.9, Post Office Bay, Chatham Island, Galapagos Islands, 16 m, 8 sh ; LACM 1934 - 277.8, James Bay, James Island, Galapagos Islands, 45 sh ; LACM 1934 - 271.12, Sulivan Bay, James Island, Galapagos Islands, 37 m, 57 sh ; LACM 1934 - 273.11, James Bay, James Island, Galapagos Islands, 44 m, 35 sh ; LACM 1934 - 262.3, Albemarle Pt., Albemarle Island, Galapagos Islands, 31 m, 7 sh ; LACM 1934 - 293.5, Black Beach, Charles Island, Galapagos Islands, 18 m, 18 sh ; LACM 1934 - 269.10, Wreck Bay, Chatham Island, Galapagos Islands, 59 m, 35 sh ; LACM 1934 - 281.12, off Post Office Bay, Chatham Island, Galapagos Islands, 120 m, 15 sh ; LACM 1933 - 156.2, Wreck Bay, Chatham Island, Galapagos Islands, 33 m, 125 sh ; LACM 1934 - 300.5, S of Black Beach, Charles Island, Galapagos Islands, 33 m, 1 sh ; LACM 1934 - 287.12, Academy Bay, Indefatigable Island, Galapagos Islands, 27 m, 30 sh ; LACM 1938 - 188.5, Wreck Bay, Chatham Island, Galapagos Islands, 25 sh ; LACM 1934 - 288.4, Tagus Cove, Albemarle Island, Galapagos Islands, 42 sh ; LACM 1972 - 196.29, Espinoza Point, Fernandina Island, Galapagos Islands, 15–30 m, 175 sh ; LACM 1938 - 223.7, Gorgona Island, Cauca Dept., Colombia, 10 m, 1 sh . SBMNH: SBMNH 214938, Islas Viradores, Playas del Coco, Guanacaste, Costa Rica, 20–30 m, 6 sh ; SBMNH 132265, Bahia de los Angeles, Baja California [Norte], Mexico, 14–29 m, 1 sh; SBMNH 620480, Bahia Ballena, Puntarenas, Costa Rica, 17–23 m, 1 sh ; SBMNH 620492, Bahia San Carlos, San Carlos Nuevo Guaymas, Sonora, Mexico, 15–30 m, 1 sh ; SBMNH 619789, Islas Viradores, Playas del Coco, Guanacaste, Costa Rica, 20–30 m, 20 sh ; SBMNH 622319, Isla Salango, N side, Manabi, Ecuador, 10–25 m, 15 sh; SBMNH 622360, Isla La Plata, N side, Manabi, Ecuador, 12–20 m, 4 sh; SBMNH 620527, Bahia Cuastecomate, Jalisco, Mexico, 12–30 m, 12 sh ; SBMNH 142629, Isla Perico, Panama Prov., Panama, intertidal, 1 sh; SBMNH 214993, Las Hadas, Colima, Mexico, 1–2 m, 1 sh; SBMNH 142630, Bahia Cuastecomate, Jalisco, Mexico, intertidal, 2 sh ; SBMNH 142631, Bahia Tenacatita, Jalisco, Mexico, 1 sh ; SBMNH 132835, Isla Santa Cruz, Bahia Academy, Galapagos, Ecuador, intertidal, 1 sh ; SBMNH 110188, Acapulco, Guerrero, Mexico, 11–18 m, 1 sh; SBMNH 618583, Isla Espanola, Isla Espanola, Galapagos, Ecuador, 17 m, 7 sh; SBMNH 619787, Bahia Audiencia, Manzanillo, Colima, Mexico, 7–13 m, 1 sh ; SBMNH 619788, Isla Jaltemba, Nayarit, Mexico, 10–25 m, 5 sh; SBMNH 619888, Bahia Santiago, Colima, Mexico, 27–40 m, 25 sh ; SBMNH 619891, Bahia de Culebra, Guanacaste, Costa Rica, 13–23 m, 25 sh ; SBMNH 620471, Isla Gardner, Galapagos, Ecuador, 10–25 m, 1 sh; SBMNH 620472, Roca Cousins, Isla Santiago, Galapagos, Ecuador, 10–25 m, 6 sh; SBMNH 620473, Punta Cormorant, Isla Floreana, Galapagos, Ecuador, intertidal, 10 sh; SBMNH 620474, Isla Floreana [Isla Charles], Isla Champion, Galapagos, Ecuador, 10–13 m, 1 sh; SBMNH 620494, Bahia de Culebra, Guanacaste, Costa Rica, 10–25 m, 2 sh ; SBMNH 620495, Bahia Santiago, Colima, Mexico, 8–20 m, 1 sh ; SBMNH 620497, Barra de Navidad, Jalisco, Mexico, 3–45 m, 12 sh ; SBMNH 620498, Bahia Banderas, Nayarit, Mexico, 10–25 m, 1 sh ; SBMNH 620499, Balboa, Panama Prov., Panama, 15 sh; SBMNH 622329, Isla Baltra, Galapagos, Ecuador, 10–25 m, 12 sh; SBMNH 622358, Isla Salango, Manabi, Ecuador, 30–45 m, 2 sh; SBMNH 622496, Punta Juluapan, Colima, Mexico, 31 m, 4 sh; SBMNH 622505, Bahia Santiago, Colima, Mexico, 13 m, 5 sh. BCD: Navidad Bar, Jalisco, Mexico, 16–30 m, 13 sh; Wreck Bay, Chatham Is., Galapagos Islands, 40 m, 6 sh .

Original diagnosis. “Testa (quoad genus) magna, elongata, robusta, subcylindrica, arcuata; annulis numerosis (XL–L), planatis, creberrimis, primum latioribus, dein tenuissimis ornata; ante aperturam valde et profunde strangulata; interstitiis vix impressis; apertura paululo declivi, haud contracta, marginata; septo mucronato, mucrone subdactyliformi, dorsum versus paulo reverso, interdum dextroverso; margine laterali paulo convexo; operculo subconvexo, apice prominente, sutura vix definita.” de Folin (1867a: 43).

Description. Protoconch multispiral (about 2.0 whorls), planispiral, smooth (Fig. 70A), transition to teleoconch I marked by well-defined apertural varix (Fig. 70A). Teleoconch I short, sculptured with axial threads, crossed by weak irregular longitudinal sculpture (Fig. 70B), transition to teleoconch II marked by change in sculpture (Fig. 70A). Teleoconch II about same length as teleoconch I, sculptured with stronger irregular longitudinal sculpture (Fig. 70C), transition to teleoconch III marked by change in sculpture (Fig. 70D). Teleoconch III sculptured with numerous, short, close-set, longitudinal striae, beneath sporadic, longitudinal, sinuous, raised cords (Fig. 70E), may develop low annuli (Figs. 70D, J–K), transition to teleoconch IV marked by change in sculpture (Figs. 70D, J–K). Teleoconch IV may have narrow annuli, otherwise sculptured with similar characters as in previous stage, increasing in strength and density (Fig. 70F, J–K), transition to teleoconch V marked by suture and increase in width (Figs. 70D, J–K). Teleoconch V (last growth stage) average size for genus [Tol 2.07–2.72 mm], tubular, thick, robust, moderately and regularly arched [Larc: 0.58–0.89 mm; Arc: 0.18–0.25 mm], subcylindrical with increase in diameter from posterior to aperture, creamy white (Figs. 69 A–C). Axial sculpture of 23–50 raised, strong, thick, narrow to wide, quadrangular ribs, closely arranged and regularly spaced, except last 3–5 preceding aperture, which narrow slightly on ventral side (Figs. 70G, L). Axial interspaces rather deep, narrower than ribs (Figs. 70G, L). Surface sculptured with numerous, conspicuous, dense, longitudinal striae on axial ribs and interspaces (Figs. 70H, M). Striae strength alternates in intensity, with 2–4 faintly more impressed (Figs. 70H, M). Posterior [Dpe: 0.44–0.52 mm] with thick edge, squared shoulder (Fig. 69H). Septum mucronate, flattened to deeply recessed (Figs. 69 A–C). Mucro with rounded point or finger-like, conical, blunt, positioned on dorsal margin, straight to slightly curved toward dorsal margin (Figs. 69 D–E. H). Aperture [Da: 0.59–0.79 mm] with abrupt deep sulcus followed by varix (Figs. 70G, L), sculpture of sulcus and varix more uniform than posterior end (Figs. 70I, N). Varix well-defined, with large ring consisting of 3–5 axial ribs, last 1–2 sharply narrowed on ventral side (Figs. 70G, L). Lip smooth, weakly developed, with slightly deflected peristome (Figs. 69D, E). Periostracum not observed. Operculum thin, light brown; exterior surface with 7–8 concentric rings (Figs. 69 F–G). Conceptual reconstruction of growth stages shown in Fig. 71A.

Distribution and Habitat. From Saladita Cove, Guaymas, Mexico to La Plata Island, Ecuador, including the Galapagos Islands. Intertidal to 120 m. Common on sand and mud substrates.

Remarks. Caecum strangulatum is a unique species and extremely variable. De Folin (1867) described a variation of the species, that he called “ acuta ” for specimens with “...annulis latioribus, septo elongato, valde mucronato, subcylindraceo, vel conico, interdum in cavitate incluso...”, or with wider rings and a more pronounced mucro that is sometimes enclosed within the septum cavity (Figs. 69C, E, H, J, 70 J–L).

Strong & Hertlein (1939) overlooked Caecum strangulatum when describing C. richthofeni from the same type locality (Fig. 69J). The holotype of C. richthofeni (CAS 065658) is a perfect example of De Folin’s “ acuta ” variation. De Folin (1867) also described two other species: C. occultum (Fig. 69K) and C. uncinatum (Fig. 69L) as separate species. However, C. occultum is actually a transitional subadult stage and C. uncinatum is a worn fragment of teleoconch III.

Lightfoot (1993a: 22) described and illustrated a species she dubbed “ Caecum sp. #2”, which is in fact C. strangulatum . Sadly for Lightfoot, she did not have access to all of de Folin’s work, which is most likely why she tentatively considered C. richthofeni to be a synonym of C. quadratum . Kaiser (1997) and Finet et al. (2016) followed this error.