Caecum subspirale Carpenter, 1857

Raines, Bret K., 2020, A Rosetta Stone for eastern Pacific Caecidae (Gastropoda: Caenogastropoda), Zootaxa 4827 (1), pp. 1-146 : 68-70

Caecum subspirale Carpenter, 1857

Figures 48 A–E, 49A–I, 50A–B, 127G

Caecum (Elephantulum) subspirale Carpenter, 1857: 315 , 4 syntypes NHMUK 1857.6.4.1515, Mazatlan.

Caecum (Elephantulum) abnormale Carpenter, 1857: 316 , 1 syntype NHMUK 1857.6.4.1516, Mazatlan. (syn. nov.).

Caecum (Elephantulum) obtusum Carpenter, 1857: 317 , 2 syntypes NHMUK 1857.6.4.1517, Mazatlan.

? Caecum validum de Folin, 1867a: 40 , 8 syntypes MNHN-IM-2000-4582, Panama

Caecum (Elephantulum) subspirale — Carpenter, 1858: 419.

Caecum subspirale — Carpenter, 1860: 32; Palmer, 1951: 43; Brann, 1966: pl. 32, fig. 361; Raines & Pizzini, 2009: 116, figs. 4g, 5g, 8a–c.

Elephantulum subspirale — Keen, 1968: 419, fig. 90; Keen, 1971: 398.

Brochina subspirale — Lightfoot, 1993b: 76, fig. 22.

Brochina abnormale — Lightfoot, 1993b: 75, fig. 19.

Brochina species #4— Lightfoot, 1993b: 75, fig. 20.

Material examined. In addition to the type material the following lots were examined. NHMLAC: LACM 1978 - 116.17 , Cedro Island , Nicoya, Puntarenas Prov., Costa Rica, intertidal, 2 sh ; LACM 1986 - 195.7 , La Gringa Point, Los Angeles Bay , Baja California, Mexico, 5 m, 1 sh ; LACM 1972 - 30.31 , Santa Elena Point, Guanacaste Prov., Costa Rica, 13–16 m, 1 sh . SBMNH: SBMNH 620308 , Isla Smith, NW, Baja California [Norte], Mexico, 120–183 m, 1 sh ; SBMNH 621376 , Punta la Gringa , Bahia de los Angeles, Baja California [Norte], Mexico, 20–40 m, 1 sh ; SBMNH 620309 , Cabo Tepoca, Sonora, Mexico, 20–30 m, 6 sh ; SBMNH 620846 , Bahia Cuastecomate , Jalisco, Mexico, 5–15 m, 1 sh ; SBMNH 622370 , Puertecitos, Baja California [Norte], Mexico, 2–3 m, 1 sh ; SBMNH 452533 , Bahia de Culebra , Guanacaste, Costa Rica, 13–23 m, 1 sh ; SBMNH 452534 , Las Cocinas, Sonora, Mexico, 13 m, 1 sh ; SBMNH 620310 , La Cruz de Huanacaxtle , Bahia de Banderas, Nayarit, Mexico, 7–20 m, 1 sh ; SBMNH 620312 , Bahia La Choya , Sonora, Mexico, 6–16 m, 1 sh ; SBMNH 620565 , Bahia San Carlos , Sonora, Mexico, 5–7 m, 1 sh ; SBMNH 621557 , Playa Olas Atlas, Sinaloa, Mexico, 10–25 m, 1 sh .

Original diagnosis. “ C. ( Elephantulum ) t. maxime elongata, tenuissime lirata; juxta aperturam annulo subtumente; septo mucronato, superficie subplanato, mucrone laterali, dextrorsum sita, parva, apice rotundato, subspirali: operculo concavo, tenui, anfr. plurimis lira tenui spiraliter ascendente.” Carpenter (1857: 315).

Description. Protoconch and teleoconch I unknown. Teleoconch II sculptured with weak longitudinal threads ( Fig. 49A ), assumed transition to teleoconch III marked by incised axial line. Teleoconch III sculptured with thin longitudinal cords ( Figs. 49 B–G), mucro low, pointed, positioned along dorsal margin ( Fig. 49B ), transition to teleoconch IV marked by low, rounded varix ( Fig. 49B ). Teleoconch IV sculptured with strong longitudinal cords ( Fig. 49H ), transition to teleoconch V marked by abrupt, somewhat squared varix ( Fig. 49C ). Teleoconch V with identical characters as previous stage ( Fig. 49D ), transition to teleoconch VI marked by abrupt, well-developed, squared varix ( Fig. 49F ). Teleoconch VI (last growth stage) large for genus [Tol 3.45–4.35 mm], tubular, moderately and regularly arched [Larc: 1.11–1.48 mm; Arc: 0.21–0.39 mm], subcylindrical, semi-translucent white ( Figs. 48 A–B). Surface with numerous longitudinal cords, irregular in strength and spacing and with fine longitudinal lines in interspaces ( Fig. 49I ). Longitudinal interspaces wider than cords ( Figs. 49E, I ). Fine axial threads may be present near apertural end, giving cancellated appearance ( Fig. 49E ). Posterior [Dpe: 0.61–1.00 mm] with somewhat thick edge, squared shoulder ( Fig. 48D ). Septum hemispherical, slightly flattened ( Fig. 48E ). Mucro normally covered by septum. Aperture [Da: 0.87–1.12 mm] with abrupt varix, fine axial threads ( Fig. 49E ). Varix well-developed, abrupt squared shoulder, followed by abrupt constriction ( Fig. 49E ). Lip smooth, with slightly deflected peristome ( Fig. 48D ). Periostracum thin, smooth, light brown ( Fig. 48A ). Operculum unknown. Conceptual reconstruction of growth stages shown in Fig. 50A .

Distribution and Habitat. From Cholla Bay, Sonora, Mexico to Venado Beach, Panama. Intertidal to 180 m. Uncommon subtidally on sand and mud substrates.

Remarks. The type material of Caecum subspirale consists of subadult stages (NHMUK 1857.6.4.1515, Fig. 48E ). Although Lightfoot (1993b: 76) correctly synonymized C. obtusum with C. subspirale , she must have overlooked the species’ varix or that it changes at different stages, because she did not include C. abnormale or her Brochina species #4. The C. abnormale type material (NHMUK 1857.6.4.1516, Fig. 48F ) is simply an example of a late subadult stage C. subspirale with an early developed varix. The type material of C. validum de Folin, 1867 (MNHN-IM-2000-4582, Fig. 48H ) consists of both badly worn specimens and fragments. However, the presence of longitudinal cords on a few specimens suggests they are examples of early subadult C. subspirale .

Figures

FIGURE 48. Caecum subspirale. A. Profile view with periostracum (LACM 1978-116.17). B. Profile view without periostracum (LACM 1978-116.17). C. Profile view (SBMNH 620309). D. Ventral view (LACM 1978-116.17). E. Syntype, NHMUK 1857.6.4.1515. F. C. abnormale Syntype, NHMUK 1857.6.4.1516. G. C. obtusum, syntype, NHMUK 1857.6.4.1517. H. C. validum, syntype MNHN-IM-2000-4582.

FIGURE 49. Caecum subspirale shells at different growth stages. A. Teleoconch II (NHMUK 1857.6.4.1517). B. Teleoconch III (NHMUK 1857.6.4.1515). C. Teleoconchs IV to V (SBMNH 620309). D. Teleoconch V (LACM 1986-195.7). E. Teleoconch VI (SBMNH 620309). F. Teleoconchs V to VI (LACM 1972-30.31). G. Surface of teleoconch III (NHMUK 1857.6.4.1515). H. Surface of teleoconchs IV to V (LACM 1986-195.7). I. Surface of teleoconch VI (SBMNH 620309).

FIGURE 50. Caecum subspirale. A. Conceptual reconstruction of growth stages. B. Species distribution map.