Napaeus arinagaensis Artiles, Deniz & Martín, 2011

Yanes, Yurena, Santana, Jesús, Artiles, Miguel, Deniz, Francisco, Martín, Javier, Alonso, María R. & Ibáñez, Miguel, 2011, Five new Napaeus species (Gastropoda: Pulmonata: Enidae) from Gran Canaria and El Hierro (Canary Islands), Zootaxa 2901 (1), pp. 35-51 : 46

Napaeus arinagaensis Artiles, Deniz & Martín , n. sp.

Figs. 1 , 2 , 3 N , 7 D–F , 9 A

Type locality. North slope of Arinaga Mountain (Gran Canaria; UTM: 28RDR 6182, 180 m altitude).

Holotype ( Figs. 2 , 3 N ; empty shell): TFMC ( MT 0417 ). Leg. M. Valido and M. Ibáñez, 9 July 1989.

Paratypes. 36 shells collected between 1989 and 2010 from Arinaga Mountain (east of Gran Canaria); deposited in AIT and the following collections: JSGC (12 shells); MAGC (10 shells) .

Etymology. The specific name derives from its type locality, Arinaga Mountain.

Distribution and habitat ( Fig. 1 ). Endemic to Gran Canaria, occupying an area of about 6 km 2 of the Arinaga mountain and its surroundings (southeast of the island), associated with lowland vegetation, within an altitudinal range between 30 and 180 m. We only found empty shells of this species, which is possibly extinct as living specimens were not recorded during the fieldwork since 1989, despite intensive searching.

Diagnosis. Shell slender, conic, almost smooth, shiny, with whorls increasing regularly in size. Aperture ovate, rounded at junction of columellar and palatal edges.

Description. Shell ( Figs. 2 , 3 N ) dextral, slender (SB/SH index), conic, with whorls increasing regularly in size; 6¾–7¼ convex whorls, deeply marked suture. Body whorl intermediate (BH/SH index), occupying less than ⅔ of the shell surface area (BS/SS index). Protoconch smooth, shiny, with about 1½ whorls. Aperture short and wide (AH/SH and AB/SB indices), ovate, rounded at junction of columellar and palatal edges. Angle ( Fig. 2 ) between columella and upper palatal margin about 117º. Peristome discontinuous, expanded as narrow whitish lip, more developed in lower part of palatal edge and reflected on columellar edge, partly covering umbilical slit. Older specimens with a callosity between peristome edges and a small nodule at junction of parietal and palatal margins. Aperture extending laterally beyond penultimate whorl by about 42% (ca 0.8 mm).

The majority of the shells collected were bleached and whitish, but some of them, including the holotype, retain a part of the original coloration, being uniformly pale brown, without blotches. Shell ornamentation almost smooth ( Fig. 9 A ), characterised by numerous weak, radial oblique ribs, only a few stronger on the body whorl. The shell has some gloss despite ribs.

Comparison with other taxa. The N. arinagaensis shell ( Fig. 3 N ) is comparable in form and size to five species from Gran Canaria. It is clearly smaller than N. isletae Groh & Ibáñez, 1992 ( Fig. 3 P ) and larger than N. exilis Henríquez, 1995 ( Fig. 3 M ), N. myosotis (Webb & Berthelot, 1833) ( Fig. 3 L ) and N. osoriensis ( Wollaston, 1878) ( Fig. 3 K ). Napaeus arinagaensis is similar in shell size to N. moquinianus (Webb & Berthelot, 1833) ( Fig. 3 O ), however, the latter has irregular whitish blotches on its shell and the surface areas of the first whorls and the entire shell of N. arinagaensis are smaller than those of N. moquinianus . Napaeus arinagaensis ( Fig. 3 N ) and N. myosotis ( Fig. 3 L ) are similar in the degree of convexity of their whorls whereas the other four species have flatter whorls.

Figures

FIGURE 1. Geographical distribution of the new species.

FIGURE 2. Drawings of the shell of the holotype of Napaeus arinagaensis n. sp., showing the placement of the measurements obtained (in º, 2 mm or mm). α, upper palatal angle (i.e. the angle between the columella and the upper palatal margin of the aperture); AB, aperture breadth; AH, aperture height; AP, aperture perimeter; AS, aperture surface area (plane view); BH, body whorl height (at columella level); BP, body whorl perimeter; BS, body whorl surface area (plane view); FB, first whorls breadth; FH, first whorls height; FP, first whorls perimeter; FS, first whorls surface area (plane view); PB, penultimate whorl breadth; PH, penultimate whorl height; PP, penultimate whorl perimeter; PS, penultimate whorl surface area (plane view); SB, shell breadth; SH, shell height; SP, shell perimeter; SS, shell surface area (plane view); T, distance between columella and periphery of penultimate whorl above aperture; U, highest distance between columella and palatal edge of aperture.

FIGURE 3. Shells of: A. Napaeus josei n. sp., holotype. B. N. nanodes, from Barranco del Agua, Tenerife (AIT). C. N. badiosus, from Barranco de Valle Seco, Tenerife. D. N. venegueraensis n. sp., holotype. E. N. chrysaloides, from Tamadaba, Gran Canaria (AIT). F. N. validoi n. sp., holotype. G. N. obesatus, from Barranco del Pagador, Gran Canaria (AIT). H. N. bajamarensis, holotype (from Yanes et al. 2009). J. N. grohi n. sp., holotype. K. N. osoriensis, from Osorio, Gran Canaria (AIT). L. N. myosotis, from Montaña de Guía, Gran Canaria (AIT). M. N. exilis, from Altos de Gáldar, Gran Canaria (AIT). N. N. arinagaensis n. sp., holotype. O. N. moquinianus, from Brezal del Palmital, Gran Canaria (AIT). P. N. isletae, holotype.

FIGURE 7. Scatter plots of some shell measurements for the new species and the most similar species. AS, aperture surface area (plane view); BS, body whorl surface area (plane view); FS, first whorls surface area (plane view); PS, penultimate whorl surface area (plane view); SB, shell breadth; SH, shell height; SS, shell surface area (plane view). The dimensions are in mm (lengths) or mm2 (surface areas).

FIGURE 9. Details of shell ornamentation of holotypes (penultimate whorl). A. Napaeus arinagaensis n. sp. B. N. validoi n. sp. C. N. grohi n. sp.