Archierato galapagensis ( Schilder, 1933 )

Fehse, Dirk & Simone, Luiz Ricardo L., 2020, Contributions to the knowledge of the Eratoidae. X. Revision of the genus Archierato Schilder, 1933 (Mollusca: Gastropoda), Zootaxa 4851 (1), pp. 81-110 : 87-88

Archierato galapagensis ( Schilder, 1933)

( Fig. 19 , 46 )

Hespererato marginata galapagensis Schilder, 1933: 249 , 254, 264 (text fig. 46); Allan,1956: 144.

Erato (Hespererato) galapagensis: Keen, 1971: 488 (fig. 913).

Hespererato galapagensis: Cate, 1977: 363 (text figs. 47, 47a−47c).

Holotype. CS 3728 . L 4.1 mm, W 2.5 mm, D 2.1 mm, CT 15, LT 17

Type locality. Albemarle (Isabela) Island, Galapagos Archipelago.

Etymology. Named after the type locality.

Diagnosis. Shell mid-sized with length 4 to 5 mm, robust, ovate, with close-set, coarse labral and irregular, less developed columellar dentition; ventral fold thin, 17 labral and 15 columellar teeth; maximum globosity at posterior third.

Description. Shell mid-sized, narrowly ovate, with elevated spire. Protoconch and subsequent whorls covered by thin callus. Suture indistinct. Body whorl ~80% of total height, maximum diameter at posterior third, convexly tapered anteriorly. Anterior ventral margin indented. Dorsum rounded. Dorsal sulcus absent. Whole shell surface covered by very thin, sub-glossy callus. Aperture comprises ~80% of total height, straight, narrow. Labrum narrow, thickened, smooth, flattened ventrally, anteriorly slightly declivous. Outer labral margin rounded, callused, edged at inner margin. Labral teeth coarse, less developed, close-set, irregular, 17 in number, restricted to labral edge. Siphonal canal short, rounded and blunt. Anal canal simple, sloping. Columella straight, curved without inner carinal ridge and less developed parietal lip. Columellar denticles 15 in number, coarse, spaced, anterior most forming terminal ridge. Fossula obscured, not delimited from columella. Callosities white; dorsum and apex red-brown.

Variability. Not enough specimens were available to assess the intraspecific variability.

Distribution. Known only from type locality.

Material examined. Only the type shells were available for study.

Remarks. Archierato galapagensis is restricted to the Galapagos Archipelago. Unfortunately, Schilder (1933: 249, 254, 264) based his description on a beached and damaged holotype. Therefore, its coloration is not representative. However, the shell morphology is distinctive from A. columbella and A. panamaensis . The ovate shell outline is in great contrast to the pyriform shells of the latter two species.

Rather smooth specimens of Hespererato scabriuscula are usually offered by shell dealers and others (e.g. Femorale website) as H. galapagensis . However, A. galapagensis is a much smaller species with finer dentition, narrow aperture and completely smooth shell.

Figures

FIGURES 19–20. Archierato specimens. 19. Archierato galapagensis (Schilder, 1933), holotype CS 3728, L 4.1 mm, Albemarle (Isabela) Island, Galapagos. 20. Hespererato scabriuscula (Gray in Sowerby I, 1832) DFB 5616-2, L 7.3 mm, off Salango, Manabi, Ecuador (less pustulated specimen often misinterpreted as A. galapagensis).

FIGURES 42–46. Comparison of the E Pacific Archierato species (the shells are equally sized for better comparison, consider, e.g., Tab. 1 for their real dimension). 42. A. michaelmonti, holotype. 43. A. rhondae, holotype. 44. A. panamaensis, lectotype. 45. A. columbella, neotype. 46. A. galapagensis, holotype.