Abbottella (Abbottella) dichroa Watters, 2013, new species
Creators: name: Watters, G. Thomas
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Neotaenioglossa
Pomatiidae
Abbottella
Abbottella dichroa

description: Abbottella (Abbottella) dichroa new species
Figures 1 K–O, 5 Q, 7 C
Type material. UF 456801, holotype; length, 6.5 mm; width, 9.9 mm. UF 216112, 31 paratypes, from the type locality.
Type locality. Dominican Republic, Samaná Province, just E of El Limón, 10 km E of Las Terrenas, at sea level. ca. 19.29° N, - 69.44° W.
Other material examined. UF 216112, 4 broken, weathered, or immature specimens, from the type locality; UF 216116, 118 specimens, 7 km E of Sánchez, Samaná Province, Dominican Republic; UF 236229, 18 specimens, 11 km E of Sánchez, Samaná Province, Dominican Republic; UF 216114, 10 specimens, 5 km E of Sánchez, Samaná Province, Dominican Republic; Grego coll., 1 specimen, Nagua, María Trinidad Sánchez Province, Dominican Republic.
Distribution and habitat. Known from the type locality on the north coast of the Sierra de Samaná of the Cordillera Septentrional to as far west as Nagua, also the region of Sánchez at three sites from 7–11 km E of the town along the south shore of the Samaná Peninsula. Individuals were found crawling on damp, algae-covered rocks on a shaded limestone hillside in a tropical forest.
Description. Shell small (largest specimen, 6.7 mm total length x 10.2 mm total width; smallest specimen, 5.3 mm total length x 8.0 mm total width; holotype, 6.5 mm total length including peristome x 9.9 mm total width including peristome), turbinate, whorls adnate except just before lip. Umbilicus wide, ca. 37% of total width, open to earliest whorls. Protoconch of ca. 1.25 smooth whorls but demarcation between protoconch and teleoconch not well-defined. Teleoconch of 3–3.5 whorls. Axial sculpture of ca. 100 extremely fine lamellae of two strengths on the final whorl, more widely spaced in earlier whorls, often arranged in groups of 1–7 primary lamellae with irregular “empty” spaces interspersed that may be growth stops. Spiral sculpture of 30–36 low, weak cords, slightly stronger in umbilicus, occasionally stronger at periphery and elsewhere. Intersections of primary axial and spiral sculpture form minute elongated pustules or fine prickly sculpture; the sculpture appears more scalloped than serrate on the final whorl but often is more pronounced and prickly on earlier whorls. Suture narrowly channeled, serrate. Aperture double, circular (4.4 mm maximum width in holotype), solute or barely adnate with the auricle joining the final whorl, deflected to various degrees. Inner lip smooth, well-exserted. Outer lip expanded, composed of numerous lamellae, narrowest at the 10–11 o’clock position, auriculate. Base color of shell uniformly white or brown, rarely light tan, without any indication of bands on the whorls, although bands are apparent on both sides of outer lip. Sculpture white. Operculum multispiral with a calcareous, vertical lamella.
Variation in specimens. 183 specimens seen. The most obvious variation is in color; this species occurs in two colors, white or brown, with little evidence of intergrades, although all have a white outer lip banded with brown. Specimens also vary in the degree of deflection of the aperture and the height of the spire.
Comparison with other species. Abbottella adolfi peninsularis (Figure 3 J–L) and A. sanchezi (Figure 4 J–N) have much finer, denser sculpture resembling sandpaper and the umbilicus of those species has two or more strong spiral cords; A. dichroa lacks these cords. Abbottella sosuaensis (Figure 4 O–S) has fewer, almost obsolete, axial lamellae, the sculpture is weakly beaded rather than scalloped or prickly, the outer lip is narrower and deflected abaperturally. In A. tenebrosa (Figure 1 U–Y) the axial sculpture is obsolete and the opercular lamella is oblique. The peculiar sculpture of A. dichroa, arranged in “blocks” separated by smooth areas, is shared by A. adolfi peninsularis, A. sanchezi, and A. sosuaensis.
Remarks. This species is peculiar in having two color morphs in the same population: white or brown. Like other species on the Samaná Peninsula, specimens have been broken through on the first half of the final whorl by a predator (Figure 5 Q).
Etymology. Gr. di -, two + Gr. chroa, color of the skin; in reference to the two color morphs.
description: Published as part of Watters, G. Thomas, 2013, New taxa and distributional notes on Abbottella and related taxa (Gastropoda: Littorinoidea: Annulariidae), pp. 1-22 in Zootaxa 3646 (1) on pages 6-7, DOI: 10.11646/zootaxa.3646.1.1, http://zenodo.org/record/283728