Caecum adamsi

Raines, Bret K., 2020, A Rosetta Stone for eastern Pacific Caecidae (Gastropoda: Caenogastropoda), Zootaxa 4827 (1), pp. 1-146 : 124-125

Caecum adamsi nomen novum

Figures 105 A–G, 106A–F, 107A–B, 126A

Elephantanellum carpenteri Bartsch, 1920: 567 , holotype USNM 340727, San Diego, California. [non Deshayes, 1861 †]. Elephantanellum carpenteri — Keen, 1971: 398.

Caecum (Elephantulum) carpenteri —Abbott, 1974: 92, fig. 882.

Elephantulum carpenteri — Skoglund, 1992: 29.

non Brochina carpenteri — Lightfoot, 1993b: 82, fig. 30.

Caecum carpenteri — Raines, 2019: 101, fig. 3C.

Material examined. In addition to the type material the following lots were examined. SBMNH: SBMNH 115808 , Bahia La Choya , Sonora, Mexico, intertidal, 1 sh ; SBMNH 620157 , Puerto San Carlos , Bahia Magdalena, Baja California Sur, Mexico, 2–10 m, 15 sh; SBMNH 621392 , Estero Morua , Sonora, Mexico, intertidal, 4 sh ; SBMNH 622342 , Punta Tormenta , Sonora, Mexico, intertidal, 1 sh .

Original diagnosis. “This is a large thin shell, in which the segments of all stages are marked by very fine spiral sculpture and a little stronger incremental lines, while the last portion of these stages bears well developed annuli. These increase in number in succeeding stages.” Bartsch (1920: 567).

Description. Protoconch and teleoconchs I, II, III unknown. Teleoconch IV smooth with weak axial growth lines, axial rings developing near aperture ( Fig. 106A, C ), transition to teleoconch V marked by suture ( Fig. 107A ). Teleoconch V sculptured with weak axial growth lines and weak, longitudinal striae ( Figs. 106B, D ), transition to teleoconch VI marked by suture ( Fig. 107A ). Teleoconch VI (last growth stage) large for genus [Tol 4.57–4.80 mm], tubular, thin, fragile, moderately to strongly and regularly arched [Larc: 2.12–2.18 mm; Arc: 0.40–0.41 mm], subcylindrical, semi-translucent white ( Figs. 105 A–B). Surface sculptured with longitudinal striae crossed by axial threads, which become raised annuli toward apertural end ( Figs. 106 E–F). Posterior [Dpe: 0.76–0.80 mm] with rather thin edge, squared shoulder ( Fig. 105D ). Septum slightly inflated ( Fig. 105G ). Mucro not visible. Aperture [Da: 0.80–0.85 mm] thin ( Fig. 105D ). No varix. Lip smooth ( Fig. 105D ). Periostracum thin, smooth, yellowish ( Fig. 105A ). Operculum thin, light brown; exterior surface with 7–9 concentric rings ( Fig. 105E ). Conceptual reconstruction of growth stages shown in Fig. 107A .

Etymology. The replacement name honors Charles B. Adams, who described the first caecids from the eastern Pacific region.

Distribution and Habitat. From Santa Monica, Los Angeles County, California south to the Gulf of California, Mexico. Intertidal to 18 m. Uncommon to rare on sandy substrates.

Remarks. Caecum carpenteri ( Bartsch, 1920) described in the original combination of Elephantulum carpenteri Bartsch, 1920 is a secondary homonym of, and preoccupied by Caecum carpenteri Deshayes, 1861 †. As there are no known synonyms of Bartsch’s species, Caecum adamsi nomen novum is here introduced for Caecum carpenteri ( Bartsch, 1920) .

Caecum adamsi is quite fragile and for many years had only been known from its holotype (USNM 340727, Fig. 105G ). It also has a more restricted range than had been suggested by both Keen (1971) and Lightfoot (1993b). Lastly, it should be noted there is an error in Bartsch’s original type number. The catalog number for the holotype is USNM 340727, not 340726. The latter number is for the holotype of Caecum diegense Bartsch, 1920 , which has been missing since the 1960s.

Figures

FIGURE 105. Caecum adamsi nom. nov. A. Profile view with periostracum (SBMNH 620157). B. Profile view without periostracum (SBMNH 620157). C. Profile view (SBMNH 621392). D. Ventral view (SBMNH 621392). E. Operculum, exterior surface (SBMNH 620157). F. Close-up of apertural rings (SBMNH 621392). G. Elephantanellum carpenteri holotype, USNM 340727.

FIGURE 106. Caecum adamsi nom. nov. shells at different growth stages. A. Teleoconch IV (SBMNH 620157). B. Teleoconch V (SBMNH 621392). C. Surface of teleoconch IV (SBMNH 620157). D. Surface of teleoconch V (SBMNH 621392). E. Surface of teleoconch VI (USNM 340727). F. Teleoconch VI (USNM 340727).

FIGURE 107. Caecum adamsi nom. nov. A. Conceptual reconstruction of growth stages. B. Species distribution map.