Wollastonia vermetiformis (R. T. Lowe, 1855) R. T. Lowe, 1855

Mattia, Willy De, Neiber, Marco T. & Groh, Klaus, 2018, Revision of the genus-group Hystricella R. T. Lowe, 1855 from Porto Santo (Madeira Archipelago), with descriptions of new recent and fossil taxa (Gastropoda, Helicoidea, Geomitridae), ZooKeys 732, pp. 1-125 : 31-33

Wollastonia vermetiformis (R. T. Lowe, 1855) comb. n. Figs 118-120

List of synonyms.

1855 Helix (Hystricella) vermetiformis R. T. Lowe: 186.

1867 Helix (Octephila) vermetiformis - Paiva: 47-48.

1867 Helix (Octephila) vermetiformis var. α minor Paiva: 48.

1878 Helix (Hystricella) vermetiformis - Wollaston: 163.

1894 Geomitra vermetiformis - Pilsbry in Pilsbry 1893-1895: 242.

1931 Geomitra (Actinella) bicarinata var. vermetiformis - Nobre: 87.

1950 Discula (Hystricella) vermetiformis - Mandahl-Barth: 31, 55.

1983 Discula (Hystricella) oxytropis vermetiformis - Waldén: 267.

2002 Geomitra vermetiformis - Bank et al.: 124.

2006 Discula oxytropis - Cameron et al.: 40 [partim].

2008 Hystricella oxytropis - Seddon: pl. 29 fig. C, map 177 [partim; in her “Corrigenda” Seddon (2009) mentions for pl. 29 fig. C in Seddon (2008) that the "Shell of Hystricella oxytropis is normally approx. 8 mm wide, not 5 mm, and does not always have a double keel"].

2009 Hystricella oxytropis - Seddon: 80 [partim].

2009 Hystricella vermetiformis vermetiformis - Groh et al.: 21, fig. 29.

2017 Hystricella vermetiformis - Groh: e.T107396913A107396917.

Type material.

NHM 1968.588, lectotype (herewith designated), from loc. typ. ex coll. R. T. Lowe. The lectotype is depicted in the Fig. 118.

Locus typicus.

[vermetiformis] "Hab. fossilis in Portu Sto" (= Porto Santo, fossil); [minor] rara ad Zimbral d'Aréa [= Zimbral da Areia (at the SE coast of Porto Santo, N of Barbinha-Porto dos Frades), 33°04'25"N / 16°17'46"W].

Additional material.

All from Porto Santo. Fossil: CWDM/4, Barbinha, a little distance south along the old rough road, mud fossil deposits, 33°03'56"N / 16°17'49"W, 10 m, leg. W. De Mattia & J. Macor, May 2015; CKG/3, W coast, Ribeiro de Agua, 33°02'11"N / 16°23'34"W, 50 m, leg. C. Groh, Jul. 27 1983; CKG/1, approx. 800 m E Vila Baleira, approx. 60 m N of oil tanks at bridge over Vale do Touro, from Quaternary tuffite layers, 33°03'51"N / 16°19'20"W, 30 m, leg. K. Groh & J. Hemmen, Jul. 27 1983; CKG/1, Ponta da Canaveira, Quaternary aeolinites, 33°02'30"N / 16°23'35"W, 50 m, leg. K. Groh & J. Hemmen, Jun. 24 1983; CKG/10, between Porto dos Frades and Ferreira Grande, approx. 300 m N sand pit, 33°04'28"N / 16°17'42"W, 25 m, leg. K. Groh & J. Hemmen, Jun. 24 1983; CKG/1, Barbinha, uppermost light Quaternary aeolinite layer, 33°04'04"N / 16°17'49"W, 8 m, leg. K. & C. Groh & J. & C. Hemmen, Jun. 24 1983; ANSP H 11919/21, Barbinha, Quaternary aeolinites, 33°04'04"N / 16°17'49"W, 8 m, leg. K. & C. Groh & J. & C. Hemmen, Jul. 7 1983; ZMH 110125/34, coastal slopes at road from harbour to Porto Santo [Vila Baleira], 33°03'48"N / 16°19'17"W, c. 10-50 m, leg. E. Clauss, Sep. 22 1992; ZMH 110139/23, coastal slopes at road from harbour to Vila Baleira, 33°03'48"N / 16°19'17"W, c. 10-50 m, leg. E. Clauss, Sep. 22 1992; ZMH 110104/5, coastal slopes in the SE to E coast of Porto Santo, 33°03'46"N / 16°18'21"W, c. 10-50 m, leg. E. Clauss, Jun. 1 1996; ZMH 24295/1, Madeira archipelago, without exact locality data, ex coll. Altonaer Museum, ex coll. O. Semper, ex coll. Dohrn. Recent: CKG/1, W slope of Pico do Baixo, in a rock crack, 33°03'47"N / 16°17'58"W, approx. 125 m, leg. K. Groh & J. Hemmen, Jun. 9 1983; CKG/2, Ilhéu das Cenouras, 33°06'12"N / 16°17'20"W, 20 m, leg. K. Groh & J. Hemmen, Jul. 2 1983.

Original description.

[vermetiformis]: From Lowe 1855: T. anguste umbilicata distincte bicarinata pyramidato-conoidea solidula crassiuscula utrinque granulata; spira elevata anfractui ultimo quasi superimposita, carina inferiore suturae distinctæ superincumbente; anfr. 7 –7½ planiusculis conspicue bicarinatis, carina inf. prominente sulco infra exarata, ult. antice valde deflexo; umbil. parvo; apert. ovali-rotundata circinata, labris continuis conjunctis; perist. undique soluto relevato tenui acuto. Diam. major 8½– 9, min. 8¼–8¾, alt. 7 –8½ mill. Anfr. 7 –7½; [var. minor]: From Paiva 1867: Variet. adest α minor, testa minore.

Diagnosis.

Shell large for the genus, conical, scalariform. Whorls not rounded, vertical. Surface of the shell covered by small and relatively densely set tubercles. Second whorl and body whorl bicarinated, with upper keel weaker than the lower one. Umbilicus narrow. Last whorl descending towards the aperture. Aperture oval with continuous peristome.

Redescription of the shell.

Shell medium to large for the genus, with 6½ regularly increasing whorls, the protoconch with 2 whorls. The form of the shell is conical, the convex teleoconch whorls with two sharp keels. The last whorl measures 60%, the penultimate whorl 17% of the total shell height. The lower ⅔ of the body whorl are beneath the lower peripheral keel, which is set off by a relatively deep constriction above and below the keel; outline of body whorl below the lower constriction regularly convex in frontal view. The keels of the body whorl are placed in the upper twelfth and third, respectively, of its total height. The suture between the whorls is simple and slightly sunken. The aperture, which is inclined to the vertical axis of the shell in an angle of 40° and is descending in its last 5% in an angle of 31° to the horizontal axis, has an elliptic form; its width is 42% of the total shell width and its height 26% of the total shell height. It has a slightly reflected, narrow lip, which is completely detached from the body whorl. The eccentric umbilicus, which measures 11% of the shell's total width, is circular in the last whorls and completely closed in earlier whorls. The protoconch is smooth, the teleoconch shows a number of oblique radial ribs, 19 in the penultimate quadrant of the body-whorl and is additionally covered by numerous small, ovate and rough tubercles. The number of tubercles in the standard-quadrate of the base is estimated to approximately 70. There are no traces of colouration in subfossil shells. In recent specimens, the colour pattern of the shell is the same as in H. bicarinata . Figs 118-120.

Variation of shell.

The spire can be more or less elevated but always letting the shell appear remarkably conical and scalariform in shape. Subfossil and recent material does not show much variation.

Measurements.

D 6.3 ± 0.4 mm (range 5.6-7.0 mm); H 6.1 ± 0.6 mm (range 5.8-6.6 mm); FW 3.7 ± 0.2 mm; PA 44.0 ± 3.2°; DU 0.6 ± 0.07 mm; NT 70 ± 16; NW 6.75 ± 0.2 (n = 7). Ratio D/H 1.0; ratio FW/H 0.6.

Distribution.

Subfossil material is known, except for one location in the westernmost part of the island, exclusively from the southeastern coast of Porto Santo, i.e. the mud deposits and aeolinites along Barbinha, Zimbral da Areia and Porto dos Frades. Recent, living specimens are only known from Pico do Baixo and Ilhéu das Cenouras, collected during the 1980's. Other recent material is kept at the NMWC 80.202, acc. 55.158 (ex coll. Melvill-Tomlin, ex coll. T. V. Wollaston) and NMWC 2004.045.00055 (ex coll. Coles) (see Seddon 2008: pl. 29 fig. C), but without exact locality data (just: Porto Santo). The distribution is shown in Fig. 121.

Ecology.

Living specimens were collected in the 1980s on slopes under stones covered with lichens and in a rock crack. More field research is necessary for a better understanding of the ecology and actual distribution of this species.

Comparison and comments.

Wollastonia vermetiformis is superficially similar to H. echinoderma , W. falknerorum sp. n. and W. ripkeni sp. n. From the first two it differs in the development of the two keels on the body whorl, and from the second also in the much coarser shell sculpture, the more pronounced upper keel, and the narrower aperture. From the quite similar H. ripkeni sp. n. it differs in the lower last whorl, the oblique ovate aperture, the coarser granulation, and finer ribbing. From similar-sized W. subcarinulata and W. inexpectata sp. n. it can be separated by the coarser granulation and the presence of two keels. The last known recent specimens were collected during the 1980s. Unfortunately, this material was not stored in ethanol. Therefore, an anatomical and molecular investigation was not possible. Recent intensive field research (on the main island Porto Santo and its outlying islets, D. Teixeira pers. comm. 2016) failed to find any living specimen of W. vermetiformis on the Pico do Baixo. The species may possibly have gone extinct in the 1980s on the main island.

Status and conservation.

Only three recent specimens of the species collected in the 1980s (KG) from two isolated localities (Porto Santo, W slope of Pico do Baixo, in a rock crack and Ilhéu das Cenouras; Fig. 121) are known. Despite intensive recent field research, the species has not been refound and is probably extinct on the main island of Porto Santo. Although recent data are missing for Ilhéu das Cenouras, we cannot exclude the existence of extant living populations on that small offshore islet. We regard the species as Critically Endangered (CR B1a, b(i, ii, iv), 2a, b(i, ii, iv)) (see also Groh 2017) because the extent of occurrence and the area of occupancy of the species is less than 1 km2 and because the species is arguably extinct at one of the two known locations (Fig. 121).