Plekocheilus (Plekocheilus) bigener, Borrero, Francisco J. & Breure, Abraham S. H., 2011

Borrero, Francisco J. & Breure, Abraham S. H., 2011, The Amphibulimidae (Mollusca: Gastropoda: Orthalicoidea) from Colombia and adjacent areas, Zootaxa 3054, pp. 1-59 : 22-24

Plekocheilus (Plekocheilus) bigener spec. nov.

( Figs 8 J–O, 9D)

Diagnosis. A small species of Plekocheilus s. str., characterized by its relatively slender form, (dark) chestnut color with axial, lighter (yellowish) irregular streaks.

Description. Shell up to 38.2 mm, 1.72 times as high as wide, imperforate, ovate, sides of spire slightly convex, moderately solid. Color light to dark chestnut-brown, with irregular, axial streaks of a lighter color; in lighter colored specimens these streaks are almost yellowish. Upper whorls paler, mostly eroded. Surface somewhat shining, with a very fine malleation and a minute granulation; growth striae irregularly thickened as flat riblets for part of their length, with irregular riblets on the upper whorls. Protoconch eroded. Whorls up to 4.2, slightly convex, the last whorl height 0.87 times the total height, not decidedly swollen; suture impressed, not descending in front. Aperture elongate-ovate, whitish inside, 1.4 times as long as wide, height 0.55 times the shell height. Peristome slightly expanded and reflexed, whitish or pinkish; slightly curved at the insertion to the parietal wall. Columellar margin slightly curved, above with a weak fold entering the aperture; narrowly dilated at the insertion to the parietal wall, which has a thin, whitish callus.

Dimensions in mm: H 28.6–38.2, D 16.6–22.0, HA 16.2–22.0, WA 11.2–15.0, LW 25.5–32.8, 3.5–4.2 whorls; holotype H 38.2, D 22.0, HA 22.0, WA 15.0, LW 32.8, 4.1 whorls.

Type locality. Colombia, Risaralda, Parque Nacional Natural Tatamá, Cerro Tatamá, 3600–3770 m, van der Hammen et al. leg./ 20.i.1983.

Type material. Holotype: RMNH 125626. Paratypes (same data as holotype): CMC C14186/1, ICNB /4; ibidem, 3300 m, van der Hammen et al. leg./ 5.ii.1983: ICNB /1; Chocó, Parque Nacional Natural Tatamá, Valle San Francisco [approx. 5°07ʹN 76°42ʹW], 3335 m, van der Hammen et al. leg/ 14.ii.1983: RMNH 125627/3, ICNB /2.

Remarks. The specimens from San Francisco valley show a pink coloration in the lip instead of white; this may be due to the freshness at the time of collection. This species differs from P. glandiformis ( Lea, 1838) by (1) being more slender, (2) having the lip more curved near the palatal insertion at the last whorl, (3) the suture not descending in front. From P. taquinensis (Pfeiffer, 1855) the new species differs by (1) being smaller, (2) somewhat stouter, (3) the suture not descending in front.

Ecology. The species was found in “páramos” with Espeletia frontinoensis (Asteraceae) and Chusquea tessellata (Poaceae) .

Etymology. bigener (Latin) , hybrid; referring to the hybrid nature of the shell sculpture, occurring both in Plekocheilus s. str. and P. ( Eurytus ). The epithet is used as an adjective.

Figures

FIGURE 8. Plekocheilus s. str. A – F. P. (P.) glandiformis (Lea, 1838). A – C. Holotype, USNM 105045 (H 33 mm). D – F. Holotype of couturesi Ancey, NMW 1955.158. 24074 (H 35.7 mm). G – I. P. (P.) taquinensis (Pfeiffer, 1855), lectotype BMNH 1957.6. 3.1 (H 40.2 mm), photo P. Crabb. J – O. P. (P.) bigener spec. nov. J – L. Holotype RMNH 125626 (H 38.5 mm). M – O. Paratype RMNH 125627.