Caecum heptagonum Carpenter, 1857

Raines, Bret K., 2020, A Rosetta Stone for eastern Pacific Caecidae (Gastropoda: Caenogastropoda), Zootaxa 4827 (1), pp. 1-146 : 49-52

Caecum heptagonum Carpenter, 1857

Figures 33 A–G, 3A–L, 35A–B, 127M

Caecum (Elephantulum) heptagonum Carpenter, 1857: 319 , holotype NHMUK 1857.6.4.1524, Mazatlan.

Caecum heptagonum var. hexagona de Folin, 1867a: 46 , Panama.

Caecum heptagonum var. octogona de Folin, 1867a: 46 , Panama.

Caecum (Elephantulum) heptagonum — Carpenter, 1858: 422; Abbott, 1974: 92, fig. 883.

Caecum heptagonum — Carpenter, 1860: 32; Palmer, 1951: 43; Brann, 1966: pl. 32, fig. 365; Pizzini, 1998: 141, figs. 1–14.

Caecum hexagonum [sic] — Bartsch, 1920: 567.

Elephantanellum heptagonum — Strong & Hertlein, 1939: 226, pl. 20, fig. 9; Keen, 1968: 419, figs. 83a–b; Keen, 1971: 398, fig. 472; Shasky, 1984: 27.

Elephantulum heptagonum — Hertz, 1979b: 32, figs. 1–3; Skoglund, 1992: 29.

Elephantlum [sic] heptagonum— Lightfoot, 1993a: 23, fig. 13.

Material examined. In addition to the type material the following lots were examined. NHMLAC: LACM 1966 - 8.25 , Santa Margarita Island , Baja California, Mexico, intertidal, 12 sh ; LACM 1968 - 41.88 , Cuastecomate Bay , Jalisco, Mexico, 5–21 m, 4 sh ; LACM 1935 - 166.4 , Gorgona Island , Colombia, 3–7 m, 3 sh ; LACM 1938 - 224.6 , Gorgona Island , Colombia, 64 m, 1 sh ; LACM 1934 - 251.8 , Secas Islands , Panama, 73–148 m, 10 sh ; LACM 1935 - 90.9 , Secas Islands , Panama, 22 m, 1 sh ; LACM 1938 - 184.3 , Secas Islands , Panama, 26 m, 3 sh ; LACM 1937 - 173.4 , Muertos Bay , Baja California, Mexico, 13 m, 4 sh ; LACM 1935 - 134.9 , Secas Islands , Panama, 1 m, 8 sh ; LACM 1935 - 136.2 , Secas Islands , Panama, 45 m, 6 sh ; LACM 1934 - 126.12 , Secas Islands , Panama, 22 m, 3 sh ; LACM 1980 - 65.11 , Salango Island , Manabi, Ecuador, 6–12 m, 5 sh ; LACM 1976 - 7.15 , La Gringa Point, Los Angeles Bay , Baja California, Mexico, 34 m, 40 sh ; LACM 1965 - 21.67 , Otoque Island , Panama Bay, Panama, 9–37 m, 22 sh ; LACM 1965 - 25.58 , Taboga Island , Panama Bay, Panama, 9–37 m, 1 sh ; LACM 1965 - 22.41 , Tortola Island, Panama Bay , Panama, 18–37 m, 1 sh ; LACM 1972 - 53.33 , Herradura Bay , Costa Rica, 23 m, 7 sh ; LACM 1972 - 7.36 , Isla Point, Bahía Elena , Costa Rica, 1–12 m, 9 sh ; LACM 1938 - 39.14 , Chatham Bay , Cocos Island, Costa Rica, 73–90 m, 12 sh ; LACM 1933 - 154.2 , Chatham Bay , Cocos Island, Costa Rica, 31 m, 3 sh ; LACM 1938 - 179.7 , Chatham Bay , Cocos Island, Costa Rica, 25 m, 3 sh ; LACM 1972 - 63.89 , Cano Island , Costa Rica, 8–13 m, 4 sh ; LACM 1934 - 253.8 , Culebra Point , Costa Rica, 37 m, 3 sh ; LACM 1939 - 168.3 , Sulphur Bay , Clarion Island, Revillagigedo Islands, Mexico, 52–64 m, 9 sh ; LACM 1934 - 260.7 , Sulphur Bay , Clarion Island, Revillagigedo Islands, Mexico, 46 m, 12 sh ; LACM 1934 - 245.1 , Sulphur Bay , Clarion Island, Revillagigedo Islands, Mexico, 55 m, 14 sh ; LACM 1968 - 45.52 , Cuastecomate Bay , Jalisco, Mexico, 18–37 m, 32 sh ; LACM 1934 - 2.23 , Braithwaite Bay , Socorro Island, Mexico, 25–34 m, 8 sh ; LACM 1934 - 256.6 , Braithwaite Bay , Socorro Island, Mexico, 30 m, 10 sh ; LACM 1934 - 257.9 , Braithwaite Bay , Socorro Island, Mexico, 24 m, 8 sh ; LACM 1939 - 170.1 , Socorro Island , Braithwaite Bay, Mexico, 18–55 m, 1 sh ; LACM 1934 - 247.6 , Small bay W of Braithwaite Bay, Socorro Island, Mexico, 8–20 m, 4 sh ; LACM 1969 - 17.69 , El Tule, Canelo Bay , Baja California, Mexico, 18–37 m, 160 sh ; LACM 1965 - 12.44 , Maria Cleofas Island , Tres Marias Islands, Mexico, 5–10 m, 26 sh ; LACM 1965 - 10.15 , Maria Magdalena Island , Tres Marias Islands, Mexico, 10 m, 2 sh ; LACM 1933 - 140.4 , Isabel Island , Nayarit, Mexico, 25 m, 1 sh ; LACM 1937 - 223.4 , Isabel Island , Nayarit, Mexico, 33 m, 3 sh ; LACM 1965 - 16.99 , Banderas Bay , Jalisco, Mexico, 18–27 m, 50 sh ; LACM 1971 - 83.55 , Los Arcos, Banderas Bay , Jalisco, Mexico, intertidal to 5 m, 6 sh ; LACM 1964 - 36.52 , San Carlos Bay , Guaymas, Sonora, Mexico, 18–37 m, 65 sh ; LACM 1968 - 13.30 , Point San Antonio, San Carlos Bay , Sonora, Mexico, 18–28 m, 50 sh ; LACM 1936 - 181.2 , San Pedro Nolasco Island , Sonora, Mexico, 22 m, 1 sh ; LACM 1937 - 210.4 , Patos Island , Sonora, Mexico, 23 m, 11 sh ; LACM 1967 - 17.47 , Libertad Port , Sonora, Mexico, intertidal, 8 sh ; LACM 1962 - 22.36 , Cholla Bay , Port Penasco, Sonora, Mexico, intertidal, 5 sh ; LACM 1966 - 19.65 , Pulmo Bay , Baja California Sur, Mexico, 2–6 m, 28 sh ; LACM 1936 - 166.5 , Partida Island , Baja California, Mexico, 26 m, 6 sh ; LACM 1973 - 3.33 , Coyote Bay , Baja California Sur, Mexico, 9–22 m, 50 sh ; LACM 1961 - 1.14 , Final Point , Baja California, Mexico, 37 m, 36 sh ; LACM 1964 - 31.23 , Puertecitos, Baja California, Mexico, 8–20 m, 40 sh ; LACM 1967 - 70.28 , Magdalena Island , Magdalena Bay, Baja California Sur, Mexico, 2–10 m, 45 sh ; LACM 1967 - 71.9 , Magdalena Island , Magdalena Bay, Baja California Sur, Mexico, 8–10 m, 23 sh ; LACM 1971 - 183.49 , Man-O-War Cove, Magdalena Bay , Baja California Sur, Mexico, intertidal to 11 m, 40 sh . SBMNH: SBMNH 619633 , Isla Clarion, SE side, Colima, Mexico, 10–15 m, 12 sh ; SBMNH 452370 , Bucerias, Bahia de Banderas , Nayarit, Mexico, 10–25 m, 12 sh ; SBMNH 620767 , Caleta Lalo, Sonora, Mexico, 15 m, 2 sh ; SBMNH 452367 , Punta Doble, 5 mi SW, San Carlos Nuevo Guaymas , Sonora, Mexico, 100–125 m, 1 sh ; SBMNH 619605 , Playas del Coco , Guanacaste, Costa Rica, 16–33 m, 2 sh ; SBMNH 452377 , Punta Coyote, Baja California Sur, Mexico, 20–57 m, 20 sh ; SBMNH 622380 , Isla Salango, N side, Manabi, Ecuador, 10–25 m, 1 sh ; SBMNH 621529 , Bahia Cuastecomate , Jalisco, Mexico, 12–30 m, 10 sh ; SBMNH 452368 , Punta Doble, Sonora, Mexico, 30–45 m, 20 sh ; SBMNH 621386 , Cabo Tepoca, Sonora, Mexico, 20–30 m, 30 sh ; SBMNH 452503 , Bahia Audiencia , Manzanillo, Colima, Mexico, 7–13 m, 50 sh ; SBMNH 620866 , Bahia Cuastecomate , Jalisco, Mexico, 10–15 m, 10 sh ; SBMNH 24444 , Bahia San Luis Gonzaga , San Luis Gonzaga, Baja California [Norte], Mexico, intertidal, 4 sh ; SBMNH 129240 , Teacapan, Sinaloa, Mexico, 25–31 m, 4 sh ; SBMNH 110186 , Acapulco, Guerrero, Mexico, 11–18 m, 100 sh ; SBMNH 452361 , Isla Danzante, W of, Baja California Sur, Mexico, 50–57 m, 30 sh ; SBMNH 452362 , Isla Jaltemba, Nayarit, Mexico, 10–25 m, 30 sh ; SBMNH 452363 , Isla Danzante, NE end, Baja California Sur, Mexico, 67–100 m, 30 sh ; SBMNH 452364 , Bahia Santiago , Colima, Mexico, 27–40 m, 7 sh ; SBMNH 452365 , Isla Danzante, Baja California Sur, Mexico, 67–100 m, 1 sh ; SBMNH 452366 , Puerto Lobos, Sonora, Mexico, 8–9 m, 2 sh ; SBMNH 452369 , Bahia de Culebra , Guanacaste, Costa Rica, 10–30 m, 20 sh ; SBMNH 452371 , Isla Danzante, NE end, Baja California Sur, Mexico, 67–100 m, 20 sh ; SBMNH 452372 , Bahia de los Angeles , Baja California [Norte], Mexico, 6 sh ; SBMNH 452373 , Ensenada San Francisco, Guaymas , Sonora, Mexico, 25–50 m, 20 sh ; SBMNH 452374 , Isla Danzante, NE end, Baja California Sur, Mexico, 67–100 m, 60 sh ; SBMNH 452375 , Las Cocinas, Sonora, Mexico, 13 m, 70 sh ; SBMNH 452376 , Roca Acero, Sonora, Mexico, 30–45 m, 30 sh ; SBMNH 452378 , Isla San Jorge [ Bird Island ], Sonora, Mexico, 10–25 m, 8 sh ; SBMNH 452511 , Las Cocinas, Sonora, Mexico, 13 m, 30 sh ; SBMNH 452523 , Punta San Pedro, Sonora, Mexico, 10–25 m, 40 sh ; SBMNH 616146 , Isla Socorro , Colima, Mexico, 20 sh ; SBMNH 15730 , Isla Carmen, Baja California Sur, Mexico, 30 sh ; SBMNH 18677 , Bahia Cuastecomate , Jalisco, Mexico, 9 m, 1 sh ; SBMNH 18674 , Bahia de los Angeles , Baja California [Norte], Mexico, intertidal, 20 sh ; SBMNH 15733 , Bahia de los Angeles , Baja California [Norte], Mexico, intertidal, 8 sh ; SBMNH 18676 , Punta Final, Baja California [ Norte ], Mexico, intertidal, 12 sh ; SBMNH 619537 , Isla Manuelita, Puntarenas, Costa Rica, 120 m, 7 sh ; SBMNH 619539 , Bahia Ballena , Puntarenas, Costa Rica, 13–15 m, 2 sh ; SBMNH 619601 , Roca Blanca, Nayarit, Mexico, 55–60 m, 2 sh ; SBMNH 619602 , Punta Mareno, Sonora, Mexico, 10–25 m, 3 sh ; SBMNH 619603 , Roca Acero, Sonora, Mexico, 28 m, 1 sh ; SBMNH 128788 , Bahia de los Angeles , Baja California [Norte], Mexico, intertidal, 10 sh ; SBMNH 119743 , Punta Colorada, Baja California Sur, Mexico, intertidal, 10 sh ; SBMNH 619604 , Punta Colorada, Baja California Sur, Mexico, intertidal, 5 sh ; SBMNH 115006 , Punta Penasco, Sonora, Mexico, Intertida , 3 sh ; SBMNH 619616 , El Submarino, Sonora, Mexico, 11 m, 20 sh ; SBMNH 619619 , Isla Ildefonso, Baja California Sur, Mexico, 5–10 m, 6 sh ; SBMNH 619620 , Isla Maria Madre, SE Cabo Alto , Nayarit, Mexico, 15–20 m, 1 sh ; SBMNH 619623 , Playa Las Gaviotas, Mazatlan , Sinaloa, Mexico, 0–3 m, 2 sh ; SBMNH 619624 , Punta Camaron, Mazatlan , Sinaloa, Mexico, intertidal, 2 sh ; SBMNH 619628 , Bahia San Carlos , Sonora, Mexico, 31 m, 50 sh ; SBMNH 619629 , Roca Blanca, Nayarit, Mexico, 55–60 m, 15 sh ; SBMNH 128592 , Isla San Marcos, S end, Baja California Sur, Mexico, 5–9 m, 15 sh ; SBMNH 132343 , Bahia de los Angeles, Baja California [ Norte ], Mexico, 16–31 m, 50 sh ; SBMNH 129978 , Puertecitos, 1.5 mi N [ Playa Curbina ], Baja California [Norte], Mexico, intertidal, 1 sh ; SBMNH 619634 , Isla Maria Madre, N side, Nayarit, Mexico, 12–18 m, 7 sh ; SBMNH 619644 , Estero Morua, Sonora, Mexico, 7–10 m, 20 sh ; SBMNH 619645 , Las Hadas, Manzanillo , Colima, Mexico, 0–2 m, 4 sh ; SBMNH 619795 , Bahia de las Palmas, Baja California Sur, Mexico, 67–133 m, 2 sh ; SBMNH 619796 , Isla San Jorge [ Bird Island ], Sonora, Mexico, 0–5 m, 15 sh ; SBMNH 116600 , Punta Colorada, Baja California Sur, Mexico, intertidal, 1 sh ; SBMNH 619799 , Isla Cleopha, Nayarit, Mexico, 12–15 m, 1 sh ; SBMNH 128461 , Bahia Salinas , Baja California Sur, Mexico, 5–18 m, 100 sh ; SBMNH 619853 , Isla Cleopha, SE offshore, Nayarit, Mexico, 60–75 m, 6 sh ; SBMNH 620175 , Isla Maria Cleofas, Nayarit, Mexico, 10–25 m, 1 sh ; SBMNH 620561 , Bahia Banderas , Nayarit, Mexico, 7–20 m, 1 sh ; SBMNH 620566 , Playa Cochorit , Sonora, Mexico, 3 sh ; SBMNH 620578 , Barra de Navidad , Jalisco, Mexico, 2 sh ; SBMNH 620675 , Bahia San Carlos , San Carlos Nuevo Guaymas, Sonora, Mexico, 10–25 m, 25 sh ; SBMNH 620686 , Bahia San Carlos , San Carlos Nuevo Guaymas, Sonora, Mexico, 10–25 m, 12 sh ; SBMNH 620775 , Bahia Tenacatita , Cabo Tamarino, Jalisco, Mexico, 8–10 m, 2 sh ; SBMNH 620776 , Bahia San Carlos , San Carlos Nuevo Guaymas, Sonora, Mexico, 13–36 m, 40 sh ; SBMNH 620778 , Bahia Saladita , Sonora, Mexico, 12 m, 12 sh ; SBMNH 620782 , Bahia Bocochibampo , Sonora, Mexico, 15–17 m, 2 sh ; SBMNH 620788 , Punta Colorado, Sonora, Mexico, 18 m, 1 sh ; SBMNH 620801 , Bahia San Carlos , San Carlos Nuevo Guaymas, Sonora, Mexico, 10–25 m, 8 sh ; SBMNH 620811 , Bahia San Carlos , San Carlos Nuevo Guaymas, Sonora, Mexico, 60–90 m, 3 sh ; SBMNH 620861 , Cabo Pulmo, Baja California Sur, Mexico, 7–20 m, 4 sh ; SBMNH 620862 , Caletilla Banda, Colima, Mexico, 27–30 m, 2 sh ; SBMNH 620864 , Bahia Bocochibampo , Sonora, Mexico, intertidal, 1 sh ; SBMNH 621303 , Puerto San Carlos, Bahia Magdalena , Baja California Sur, Mexico, 2–10 m, 3 sh ; SBMNH 621317 , Estero Morua, Sonora, Mexico, intertidal, 15 sh ; SBMNH 621352 , Isla Danzante, S of, Baja California Sur, Mexico, 45 m, 4 sh ; SBMNH 621354 , Santa Rosalia, Baja California Sur, Mexico, 13 m, 12 sh ; SBMNH 621411 , Bahia San Carlos , San Carlos Nuevo Guaymas, Sonora, Mexico, 15–30 m, 20 sh ; SBMNH 621511 , Punta la Gringa , Bahia de los Angeles, Baja California [Norte], Mexico, 20–40 m, 25 sh ; SBMNH 621512 , Barra de Navidad , Jalisco, Mexico, 1–5 m, 1 sh ; SBMNH 621633 , Isla Maria Cleofas, Nayarit, Mexico, 16–23 m, 1 sh ; SBMNH 621658 , ICP-03-012, Coiba National Park , Veraguas, Panama, 5–19 m, 3 sh ; SBMNH 621659 , Punta Entrada, Baja California Sur, Mexico, 10–13 m, 1 sh ; SBMNH 621672 , Isla San Pedro Martir , Sonora, Mexico, 120 m, 12 sh ; SBMNH 622332 , Isla Perico, Panama Prov. , Panama, intertidal, 3 sh ; SBMNH 622355 , Isla San Pedro Nolasco, SE tip, Sonora, Mexico, 17 m, 6 sh ; SBMNH 622388 , Isla Ballena, Baja California Sur, Mexico, 12–17 m, 2 sh ; SBMNH 622495 , Bahia Santiago , Colima, Mexico, 13 m, 3 sh. BKR: Navidad Bar, Colima, Mexico, 16–32 m, 3 sh ; off Piedras Blancas, Nayarit, Mexico, 18 m, 10 sh .

Original diagnosis. “ C. ( Elephantulum ) t. septangulata, angulis valde prominentibus; annulis rotundatis confertis cincta, angulos longitudinales supracurrentibus; apertura planata, extus heptagonis forma, intus circulari, sulco concentrico ornata; operculo?” Carpenter (1857: 319).

Description. Protoconch multispiral (about 1.8 whorls), planispiral, smooth ( Fig. 34A ), transition to teleoconch I marked by well-defined apertural varix ( Fig. 34A ). Teleoconch I short, with dense sinuous longitudinal sculpture ( Fig. 34B ), transition to teleoconch II marked by axial incised line ( Fig. 34A ). Teleoconch II about 2.5 times length of teleoconch I, with dense reticulated sculpture and weak, longitudinal, dextrally wound threads ( Fig. 34C ), transition to teleoconch III marked by slight axial constriction ( Figs. 34A, D ). Teleoconch III sculptured with longitudinal ridges crossed by dense axial threads ( Fig. 34E ), transition to teleoconch IV marked by suture followed by increase in diameter ( Figs. 34D, G ). Teleoconch IV sculptured comprised of 6–12 regularly spaced longitudinal ridges and flattened annuli covered with dense longitudinal threads ( Fig. 34F ), transition to teleoconch V marked by varix ( Figs. 34H , 36A ). Teleoconch V sculptured similar to previous stage with stronger longitudinal striae ( Fig. 34I ), transition to teleoconch VI marked by varix ( Figs. 34K , 35A ). Teleoconch VI (last growth stage) average size for genus [Tol 2.40–2.67 mm], tubular, thick, robust, moderately and regularly arched [Larc: 0.80–0.89 mm; Arc: 0.22–0.29 mm], larger than previous stage, subcylindrical with increase in diameter from posterior to aperture, cream to light brown ( Figs. 33 A–B). Surface sculptured comprised of 6–12 pronounced longitudinal ridges and broad, flattened annuli covered with dense longitudinal threads, interspaces narrow ( Figs. 33 A–D, 34J–L). Posterior polygonal [Dpe: 0.40–0.49 mm], with 6–12 sides, and thick edge ( Fig. 33D ). Septum mucronate, recessed ( Fig. 33D ). Mucro finger-like, conical, pointed, positioned along dorsal margin ( Fig. 33D ). Aperture polygonal with 6–12 sides [Da: 0.61–0.70 mm], thick ( Figs. 33 A–C, 34K–L). Lip smooth, weak, with deflected peristome ( Fig. 33D ). Varix obsolete to well-developed with 2–3 ribs separated by shallow sulcus ( Figs. 33 A–C, 34K–L). Periostracum not observed. Operculum thin, light brown; exterior surface with 6–7 concentric rings ( Figs. 33 F–G). Conceptual reconstruction of growth stages shown in Fig. 35A .

Distribution and Habitat. From Magdalena Bay, Baja California, Mexico to Manabi, Ecuador, including Revillagigedo Islands and Cocos Island. Intertidal to 148 m. Common subtidally on coarse sand substrates.

Remarks. The type of Caecum heptagonum is an anterior end fragment (NHMUK 1857.6.4.1524, Fig. 33E ). Caecum heptagonum is quite variable in the number of longitudinal ribs (6–12) and strength of the axial threads. Specimens with a higher number of ribs and strong axial threads may even appear to be a distinct species. Figured is an extreme example of a late subadult ( Fig. 33C ).

Figures

FIGURE 33. Caecum heptagonum. A–C. Profile views depicting sculpture variations (LACM 1976-7.15). D. Ventral view (SBMNH 452511). E. Holotype, NHMUK 1857.6.4.1524. F. Operculum, exterior surface (SBMNH 452511). G. Operculum, interior surface (SBMNH 452511).

FIGURE 34. Caecum heptagonum shells at different growth stages. A. Protoconch and teleoconchs I to III (LACM 1968- 13.30). B. Surface of teleoconch I (LACM 1968-13.30). C. Surface of teleoconch II (LACM 1968-13.30). D. Teleoconchs II to IV (LACM 1968-13.30). E. Surface of teleoconch III (SBMNH 452511). F. Surface of teleoconch IV (SBMNH 452511). G. Teleoconchs III to IV (SBMNH 452511). H. Teleoconchs IV to V (SBMNH 452511). I. Surface of teleoconch V (SBMNH 452511). J. Surface of teleoconch VI (SBMNH 452511). K. Teleoconchs V to VI (SBMNH 452511). L. Teleoconch VI (LACM 1976-7.15).

FIGURE 35. Caecum heptagonum. A. Conceptual reconstruction of growth stages. B. Species distribution map.

FIGURE 36. Caecum insculptum. A. Profile view with periostracum (LACM 1972-57.44). B. Profile view without periostracum (LACM 1972-57.44). C. Ventral view (LACM 1972-58.63). D. Operculum, exterior surface (LACM 1972-57.44). E. Operculum, interior surface (LACM 1972-57.44). F. Syntype, NHMUK 1857.6.4.1514. G. C. mirabile, syntype, MNHN-IM- 2000-4593.