Caecum laeve C.B. Adams, 1852

Raines, Bret K., 2020, A Rosetta Stone for eastern Pacific Caecidae (Gastropoda: Caenogastropoda), Zootaxa 4827 (1), pp. 1-146 : 17-20

Caecum laeve C.B. Adams, 1852

Figures 9 A–G, 10A–J, 11A–B, 126G

Caecum laeve C.B. Adams, 1852: 162 , holotype MCZ 186581 , Panama.

Caecum laeve var. minus C.B. Adams, 1852: 162 , Panama. (syn. nov.).

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

Caecum leve [ sic] var. cylindrica de Folin, 1867a: 39 , 4 syntypes NHMUK 1868.2 .17.6, Panama. (syn. nov.).

Caecum leve [ sic] var. semi fusca de Folin, 1867a: 39 , 4 syntypes NHMUK 1872.3 .22.7, Panama. (syn. nov.).

Caecum leve [ sic] var. fusca de Folin, 1867a: 39 , 4 syntypes NHMUK 1872.3 .22.7, Panama. (syn. nov.).

? Caecum imperfectum de Folin, 1867a: 40 , holotype MNHN-IM-2000-4598, Panama.

Caecum laeve var. subornata de Folin, 1869: 130 , 4 syntypes NHMUK 1857.6 .4.151, Panama. (syn. nov.).

Caecum (Fartulum) laeve — Carpenter, 1858: 431.

Caecum laeve — Carpenter, 1860: 32; Carpenter, 1863: 350; Tryon, 1886: 215, pl. 66, fig. 52; Palmer, 1951: 44; Turner, 1956: 60, pl. 17, fig. 6.

Fartulum laeve — Keen, 1971: 398, fig. 484; Draper, 1979: 28, fig. 13; Shasky, 1984: 27; Skoglund, 1992: 29.

Meioceras laeve — Lightfoot, 1993b: 84, fig. 33.

Material examined. In addition to the type material the following lots were examined. NHMLAC: LACM 1946 - 10.14 , Creston Island , Mazatlan, Sinaloa, Mexico, intertidal, 19 sh ; LACM 1966 - 19.62 , Pulmo Bay , Baja California Sur, Mexico, 2–6 m, 80 sh ; LACM 1961 - 2.8 , San Carlos Bay , Guaymas, Sonora, Mexico, intertidal, 30 sh ; LACM 1966 - 20.23 , S end of Pulmo Bay , Baja California Sur, Mexico, 7 m, 9 sh ; LACM 1972 - 38.31 , Penca Point , Costa Rica, 8–13 m, 7 sh ; LACM 1966 - 15.31 , El Tule, Canelo Bay , Baja California Sur, Mexico, intertidal, 60 sh ; LACM 1975 - 54.28 , Venado Island , Panama, intertidal, 7 sh ; LACM 1975 - 55.32 , San Carlos, Panama, intertidal, 7 sh ; LACM 1966 - 13.30 , Cape San Lucas, Baja California Sur, Mexico, intertidal, 8 sh ; LACM 1946 - 4.10 , Cabeza de Ballena , Baja California Sur, Mexico, intertidal, 38 sh ; LACM 1966 - 11.28 , Palmilla Point, Baja California Sur, Mexico, intertidal, 5 sh ; LACM 1946 - 11.8 , Camaron Point, Mazatlan, Mexico, intertidal, 3 sh ; LACM 1946 - 9.13 , Mazatlan, Mexico, intertidal, 29 sh ; LACM 1965 - 28.33 , Barra de Navidad , Jalisco, Mexico, 2–7 m, 9 sh ; LACM 1965 - 21.64 , Otoque Island , Panama Bay, Panama, 9–27 m, 3 sh ; LACM 1938 - 131.21 , Honda Bay , Panama, 55–90 m, 1 sh ; LACM 1975 - 56.20 , Farfan Beach, Panama Prov., Panama, intertidal, 2 sh ; LACM 1972 - 75.32 , off Bique, Panama, intertidal, 9 sh ; LACM 182099 , Taboga Island , Panama Bay, Panama, intertidal, 2 sh ; LACM 1968 - 18.16 , Banderas Bay , Jalisco, Mexico, intertidal, 6 sh ; LACM 1968 - 41.85 , Cuastecomate Bay , Jalisco, Mexico, 5–20 m, 1 sh ; LACM 1970 - 11.53 , Ancon Point, Santa Elena, Ecuador, intertidal, 67 sh ; LACM 1974 - 86.14 , El Velero , Nicaragua, 2 m, 1 sh ; LACM 1986 - 369.3 , Cocos Island , Costa Rica, 91–122 m, 3 sh ; LACM 1972 - 63.85 , Cano Island , Costa Rica, 8–13 m, 1 sh ; LACM 1935 - 106.40 , Blanca Beach, Costa Rica, intertidal, 1 sh ; LACM 1935 - 136.1 , Secas Islands , Panama, 22 m, 1 sh ; LACM 1972 - 51.58 , Herradura Bay , Costa Rica, 37 m, 1 sh ; LACM 1984 - 29.25 , Arch Rock at SE of Darwin Island, Galapagos Islands, 6–9 m, 2 sh ; LACM 1935 - 7.3 , Fronton Island , near Callao, Peru, 9 m, 1 sh ; LACM 1972 - 81.20 , S of Bocapan , Tumbes, Peru, intertidal, 1 sh ; LACM 1934 - 320.1 , Port Utria , Colombia, 36 m, 1 sh ; LACM 1935 - 170.11 , Port Utria , Colombia, 24 m, 8 sh ; LACM 1935 - 179.7 , Octavia Bay , Colombia, 83 m, 5 sh ; LACM 1934 - 304.2 , Gorgona Island , Colombia, 60 m, 1 sh ; LACM 1938 - 224.5 , Gorgona Island , Colombia, 18–36 m, 3 sh ; LACM 1974 - 24.17 , San Lorenzo Island , Peru, intertidal to 5 m, 70 sh . SBMNH: SBMNH 620843 , Bahia Cuastecomate , Jalisco, Mexico, 10–15 m, 4 sh ; SBMNH 452524 , Salinas, Guayas, Ecuador, intertidal, 1 sh ; SBMNH 452525 , Punta Chame, Panama Prov., Panama, 1 sh ; SBMNH 452526 , Bahia de Culebra , Guanacaste, Costa Rica, 13–23 m, 7 sh ; SBMNH 452527 , Bahia Santiago , Colima, Mexico, 27–40 m, 3 sh ; SBMNH 454726 , Punta Camaron, Mazatlan, Sinaloa, Mexico, 1 sh ; SBMNH 619530 , Bahia Ballena , Puntarenas, Costa Rica, 13–15 m, 5 sh ; SBMNH 12371 , Melaque, Jalisco, Mexico, intertidal, 1 sh ; SBMNH 127141 , Chacala , Nayarit, Mexico, 3 m, 1 sh ; SBMNH 619781 , Punta Mita, Nayarit, Mexico, intertidal, 2 sh ; SBMNH 619782 , Isla Jaltemba , Nayarit, Mexico, 10–25 m, 4 sh ; SBMNH 619822 , Bahia Chamela , Jalisco, Mexico, intertidal, 1 sh ; SBMNH 620177 , Roca Prospera , Coiba National Park, Veraguas, Panama, 10–21 m, 8 sh ; SBMNH 620560 , Tisate, Bahia Banderas , Jalisco, Mexico, intertidal, 2 sh ; SBMNH 620574 , Salinas, Guayas, Ecuador, intertidal, 3 sh ; SBMNH 620618 , Isla Venado, Panama Prov., Panama, intertidal, 10 sh ; SBMNH 620646 , Isla Perico, Panama Prov., Panama, intertidal, 15 sh ; SBMNH 620677 , Cabo Pulmo , Baja California Sur, Mexico, 1–3 m, 1 sh ; SBMNH 620682 , Veracruz, West Panama, Panama, intertidal, 5 sh ; SBMNH 620689 , Isla Pajaro [Mogo Mogo], Panama Prov., Panama, intertidal, 15 sh ; SBMNH 620812 , Punta Paitilla, Panama City, Panama Prov., Panama, intertidal, 40 sh ; SBMNH 620845 , La Cruz de Huanacaxtle , Nayarit, Mexico, 9–14 m, 15 sh ; SBMNH 620860 , Bahia Tenacatita , Cabo Tamarino, Jalisco, Mexico, 8–10 m, 1 sh ; SBMNH 620873 , Cabo San Lucas , Baja California Sur, Mexico, 10–25 m, 2 sh ; SBMNH 621300 , Punta Mita, Nayarit, Mexico, intertidal, 20 sh ; SBMNH 621343 , Barra de Navidad , Jalisco, Mexico, 3–45 m, 5 sh ; SBMNH 621361 , Santa Cruz, Nayarit, Mexico, 2 sh ; SBMNH 621417 , Punta Rosales, Jalisco, Mexico, intertidal, 12 sh ; SBMNH 621500 , La Puntilla, Salinas, Guayas, Ecuador, intertidal, 40 sh ; SBMNH 621505 , Playas de Villamil , Guayas, Ecuador, intertidal, 5 sh ; SBMNH 621510 , Punta Mita, Nayarit, Mexico, intertidal, 10 sh ; SBMNH 621562 , Isla Venado, Panama Prov., Panama, intertidal, 30 sh ; SBMNH 621632 , Careyes , Nayarit, Mexico, 3–10 m, 2 sh ; SBMNH 621635 , Isla del Coco , Puntarenas, Costa Rica, 10–25 m, 1 sh ; SBMNH 621653 , Isla Maria Magdalena , Nayarit, Mexico, 8–12 m, 1 sh ; SBMNH 621660 , Isla Meanguera , Golfo de Fonseca, La Union, El Salvador, 5 m, 1 sh ; SBMNH 622317 , Playas de Villamil , Guayas, Ecuador, intertidal, 12 sh ; SBMNH 622375 , Isla Pedro Gonzalez, Balboa District , Panama Prov., Panama, intertidal, 1 sh ; SBMNH 622501 , Isla Chapetona , Sonora, Mexico, 0–2 m, 1 sh ; SBMNH 622502 , Las Hadas , Colima, Mexico, 1–3 m, 7 sh ; SBMNH 622503 , Bahia Santiago , Colima, Mexico, 13 m, 4 sh ; SBMNH 622504 , Punta Juluapan , Colima, Mexico, 31 m, 2 sh. BCD: Coyote Pt., Conception Bay, Baja California, Mexico, intertidal, 1 sh .

Original diagnosis. “Shell well arcuated, rather stout, of nearly uniform diameter; white; smooth and shining; apex very prominent.” Adams (1852: 162).

Description. Protoconch multispiral (about 1.75 whorls), planispiral, smooth ( Fig. 10A ), transition to teleoconch I marked by apertural varix ( Fig. 10A ). Teleoconch II short, about 2 times length of teleoconch I, smooth ( Fig. 10B ), transition to teleoconch II marked by very slight axial incised line ( Fig. 10A ). Teleoconch II sculptured with weak axial growth lines ( Fig. 10C ), transition to teleoconch III marked by axial incised line ( Figs. 10A, D ). Teleoconch III sculptured with axial growth lines stronger than previous stage ( Fig. 10E ), transition to teleoconch IV marked by axial incised line ( Fig. 10D ). Teleoconch IV with numerous axial growth lines, transition to teleoconch V marked by rapid increase in diameter ( Figs. 10D, G ). Teleoconch V surface smooth ( Fig. 10H ), transition to teleoconch VI marked by apertural swelling followed by increase in diameter ( Figs. 10G, I ). Teleoconch VI (last growth stage) average size for genus [Tol 1.43–2.64 mm], tubular, robust, mildly and regularly arched [Larc: 0.40–0.55 mm; Arc: 0.09–0.14 mm], nearly uniform in diameter from posterior to aperture, translucent, often with tan mottling ( Figs. 9 A–C). Surface smooth ( Fig. 10H ). Posterior [Dpe: 0.30–0.36 mm], with thin edge, squared shoulder ( Fig. 9D ). Septum mucronate ( Fig. 9D ). Mucro heel-like, positioned along dorsal margin ( Fig. 9D ). Aperture [Da: 0.40–0.45 mm] oblique, slightly constricted ( Fig. 9D ). No varix. Lip smooth, with deflected peristome ( Fig. 9D ). Periostracum very thin, smooth or with nearly obsolete microsculpture, tan to reddish brown ( Fig. 9A ). Operculum thin, light brown; exterior surface with 8–10 fine concentric rings ( Figs. 9 E–F). Conceptual reconstruction of growth stages shown in Fig. 11A .

Distribution and Habitat. From Conception Bay, Baja California, Mexico to Callao, Peru, including Cocos Island and the Galapagos Islands. Intertidal to 122 m. Abundant intertidally on sand and rocky substrates.

Remarks. The holotype of Caecum laeve is a slightly worn adult specimen (MCZ 186581, Fig. 9G ). Caecum laeve is similar to C. parvum Adams, 1852 . However, C. laeve lacks the moderately prominent annular rings seen on C. parvum . When Carpenter (1857) described C. farcimen (NHMUK 1857.6.4.1545), he noted one specimen on tablet 1545 as only “probably belonging to” his new species. After comparing the holotype of C. laeve with that specimen ( Fig. 9H ), it has proven to be conspecific with C. laeve . The remaining C. farcimen (NHMUK 1857.6.4.1544) type specimens found on tablet 1544 are actually C. diminutum as discussed previously.

Lightfoot (1993b: 84) placed Caecum laeve in the genus Meioceras . However, Carpenter (1859) erected Meioceras for western Atlantic caecids with a helical spiral in their early growth stages. After studying the growth morphology, it was determined that C. laeve lacks the helical spiral characteristic of Meioceras .

Pizzini et al. (2007) suggested that Caecum imperfectum de Folin, 1867 was a junior synonym of C. dextroversum Carpenter, 1857 . However, after further examination, the holotype of C. imperfectum (MNHN-IM-2000-4598, Fig. 9I ) is most likely a badly worn early subadult stage of C. laeve .

Figures

FIGURE 9. Caecum laeve. A. Profile view with periostracum (SBMNH 620845). B–C. Profile views without periostracum depicting color variations (SBMNH 620618). D. Ventral view (LACM 1965-28.33). E. Operculum, exterior surface (LACM 1965- 28.33). F. Operculum, interior surface (LACM 1965-28.33). G. Holotype, MCZ 186581. H. C. farcimen, syntype, NHMUK 1857.6.4.1545. I. C. imperfectum, holotype, MNHN-IM-2000-4598.

FIGURE 10. Caecum laeve shells at different growth stages. A. Protoconch and teleoconchs I to II (LACM 1974-24.17). B. Surface of teleoconch I (LACM 1974-24.17). C. Surface of teleoconch II (LACM 1974-24.17). D. Teleoconchs II to V (LACM 1965-28.33). E. Surface of teleoconch III (LACM 1965-28.33). F. Surface of teleoconch IV (LACM 1965-28.33). G. Teleoconchs IV to V (LACM 1965-28.33). H. Surface of teleoconch V to VI (LACM 1965-28.33). I. Teleoconch V (SBMNH 621500). J. Teleoconch VI (LACM 1965-28.33).

FIGURE 11. Caecum laeve. A. Conceptual reconstruction of growth stages. B. Species distribution map.