From Venezuelan Guayana

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New Orthalicidae (Mollusca, Gastropoda) from Venezuelan Guayana: unravelling secrets from the Lost World

ABRAHAM S.H. BREURE National Museum of Natural History / Naturalis, P.O. Box 9517, NL-2300 RA Leiden, the Netherlands. E-mail: [email protected]

Abstract

Land snails of the family Orthalicidae from Venezuelan Guayana are revised and the following new species are described: Drymaeus (D.) rex, Plekocheilus (Eurytus) huberi, P. (E.) nebulosus, P. (E.) sophiae, and P. (E.) tepuiensis. Drymaeus (D.) griffini Haas, 1955 is now placed in the synonymy of D. (D.) extraneus (Haas, 1955). In addition, the genitalia of Plekocheilus (Eurytus) tatei Haas, 1955 are described for the first time. Plekocheilus (Eudolichotis) gibber (Oberwimmer, 1931) is now considered a member of P. (Eurytus). As a consequence, Antitragus Oberwimmer, 1931 is now regarded a junior synonym of Eurytus Albers, 1850. Of the 16 taxa treated here, 14 are endemic to the table-top mountains (‘tepuis’) of this area. A Principal Component Analysis has been used to study the biotic and abiotic factors that may influence species diversity and distributions. Habitat diversity explained 65% of the variability and was mainly influenced by plant diversity, number of forest types, elevation and slope area of the tepuis.

Key words: Mollusca, Orthalicidae, Bulimulinae, Plekocheilus, Drymaeus, systematics, new species, new synonymy, endemism, distribution, Venezuela

Introduction

Venezuelan Guayana has long been a mysterious area, their table-top mountains (‘tepuis’) considered sacred places by the indigenous Pemon communities (Huber 1995b). The area was the set of the adventure novel “The Lost World” by Arthur Conan Doyle (1912), who was inspired by the 1884 expedition of the Royal Geographical Society of London to climb Mount Roraima. From a malacological view, Venezuelan Guayana is poorly known and the goal of the present paper is to review the land snail fauna. Until now, 11 taxa have been described, all being members of the family Orthalicidae. During the preparation of this paper one new species was added, belonging to the family Clausiliidae (Thompson 2008). Due to the inaccessibility of the area, not more than about 55 specimens have been accumulated during the past 100 years. The study area (Fig. 1) was explored initially by river expeditions, like the one by Humboldt and Bonpland in 1800, the brothers Schomburgk (1835─1844), Spruce (1853─1854) and Holt and others (1929─1931). Later, several expeditions organized by major museums gathered mainly botanical and ornithological data of the tepui biota (Huber 1995b). During recent years there were several herpetological and cave expeditions to Venezuelan Guayana, mainly to the eastern part. Huber (1995a; see also McDiarmid & Donnelly 2005) gives a detailed description of the geography and physical features of Venezuelan Guayana, including climatic data. He distinguishes between highlands (> 1500 m), uplands (500─1500 m) and lowlands (< 500 m). The highlands, collectively called Guayana Highlands or Pantepui, form loosely clustered groups of isolated mountains. Many (but not all) tepui summits are connected to the surrounding lowlands by valleys and ridges (Huber 1988); groups of nearby tepuis are referred to as massifs. On botanical grounds, Venezuelan Guayana can be divided into four districts (Huber 1995a, 1995c): Eastern Pantepui District (among others the Roraima and Chimantá massifs), Western Pantepui District (e.g. Sierra de Maigualida), Central Pantepui

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District (also called Jaua-Duida district; with Cerro Guaiquimina, the Jaua-Sarisariñama massif and the Duida-Marahuaka massif) and the Southern Pantepui District (including the Cerro de la Neblina). The area is characterized by a high floristic diversity and a high ecological diversity. There is a considerable level of endemism, both in plants (Berry et al. 1995) and in different animal groups, for which data are available mainly on vertebrates and insects (Huber & Foster 2003). So far, terrestrial gastropods appear to be another group with endemisms and it seems useful to undertake a biogeographical analysis in addition to taxonomy on a family like the Orthalicidae.

FIGURE 1. A. Map of northern South America, showing the study area (white rectangle); B. Map of Venezuelan Guayana (white rectangle area of A enlarged). The localities mentioned in the text are indicated, tepuis sorted by phytogeographic Pantepui districts: Eastern District (E): Ab, Abacapá; Am, Aparamán; Ap, Apacará; Au, Auyán; Ch, Chimantá; Mu, Murey; Ro, Roraima; To, Toronó; Yu, Yuruaní. Jaua-Duida District (JD): Du, Duida; Mk, Marahuaka; RP, Río Padamo. Southern District (S): Ne, Neblina. Western District (W). Others: Gu, Guaiquinama; Ya, Yapacana. Background images courtesy by NASA/JPL.

Snail collecting was always a side-line, mainly of botanical and herpetological work. Sowerby (1890) was the first to describe an endemic member of the family Orthalicidae from this region, Bulimus fulminans linterae from Mount Roraima, now placed in the genus Plekocheilus Guilding, 1828. It was probably collected during the expedition mentioned above. Oberwimmer (1931) described two additional species belonging to this genus, collected in the western part of the area. Haas (1955) reported on the land snails collected by various people at Chimantá massif and Cerro Duida. He described eight new species, all Orthalicidae. Finally, Breure & Eskens (1981) described a new Drymaeus from Cerro Yapacana. The last expedition that yielded malacological results was one to the Cerro de la Neblina on the southern border with Brazil (Brewer-Carias 1988). The Orthalicidae collected by this expedition are reported upon here, together with a revision of the other species from this family, based upon all material available to me.

Material and methods

The following abbreviations are used to refer to depositories of material: AMNH—American Museum of Natural History, New York, USA; BMNH—Natural History Museum, London, UK; FMNH—Field Museum of Natural History, Chicago, USA; NMW—National Museum Wales, Cardiff, UK; RMNH—Nationaal Natuurhistorisch Museum/ Naturalis, Leiden, the Netherlands; SMF—Natur-Museum Senckenberg, Frankfurt am Main, Germany; UF—Florida Museum of Natural History, Gainesville, USA; ZMB—Zoologisches Museum der Humboldt-Universität, Berlin, Germany. Additionally, the following abbreviations are used throughout the text: AG—albumen gland, D—diameter of shell, EP—epiphallus, FL—flagellum, H—height of shell, HA—height of aperture, LW—height of last

26 · Zootaxa 2065 © 2009 Magnolia Press BREURE TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. whorl, M—mean, max—maximum, min—minimum, MN—mantle, N—nephridium, n—number of specimens measured, OD—ovotestis duct, P—penis, PC—pericard, PN—pneumostome, RS—receptaculum seminis, s—standard deviation, SD—spermathecal duct, SOV—spermoviduct, SP—spermatheca, U1—adrenal ureter, U2—adrectal ureter, UO—urinary opening, V—vagina, VD—vas deferens, W—number of whorls. Measurements of shells were taken with a digital caliper with sliding gauge (for methods see Breure 1974: figs 2–3). This may account for some differences to the measurements given in the original descriptions, but is consistent with those of other Orthalicidae revised by the author. Principal component analysis (PCA) was done with SPSS 16.0, using factor analysis and varimax rotation with Kaizer normalization. The geographical terminology of the area is in accordance with Huber (1995a). Localities in the Cerro de la Neblina massif are referring to the camp sites mentioned in Brewer-Carias (1988); unpublished field notes of R.W. McDiarmid and F.G. Thompson are used for data on the habitat.

Systematics

Family Orthalicidae Albers, 1860

Subfamily Bulimulinae Tryon, 1867

Genus Plekocheilus Guilding, 1828

Type species: Voluta aurissileni Born, 1780

Subgenus Plekocheilus (Plekocheilus) Guilding, 1828

Plekocheilus (Plekocheilus) fulminans linterae (Sowerby, 1890) (Figs 4A─D, 9A)

Bulimus fulminans linterae Sowerby, 1890: 582, pl. 56 fig. 12. Type locality: British Guiana, Mount Roraima; lectotype BMNH 1889.4.25.1 (Breure 1978).

Material. Guyana, Mount Roraima (BMNH 1889.4.25.1/lectotype, 1889.4.25.2/1 paralectotype, SMF 90007/ 1 paralectotype); Ibidem, T. Pain leg., 1938 (NMW.Z 1981.118.00303/3); Ibidem, 8000 ft [2438 m], T. Pain leg., 1938 (NMW.Z 1981.118.04142/1). British Guiana [= Guyana] (ex Melvill Tomlin, NMW 1955.158.16700/1; ex Preston, RMNH/1). Remarks. The lectotype and paralectotype from the BMNH collection are figured here for the first time (Figs 4A─D). Although we do not precisely know where the type specimens were collected, we may infer from the locality given by Sowerby that it was on the slopes or base at the northeastern side of Roraima-tepui (R.W. McDiarmid, personal communication). Nonetheless, the material collected by T. Pain reveals that this is a highland species. The material also shows that there is some variation in expression of the columellar fold (in two specimens it is hardly noticeable) and in the colour of the lip (in three specimens dark liver coloured, in two other specimens whitish like in the type material).

Plekocheilus (Plekocheilus) fulminans alticola Haas, 1955 (Figs 4E─G, 9B)

Plecocheilus (Plecocheilus) fulminans alticola Haas 1955: 381, fig. 81. Type locality: Venezuela, State of Bolívar, Chimantá massif, Torono tepui, on slopes bordering Caño Mojado, 2250 m; holotype FMNH 52442.

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FIGURE 2. Genitalia in Plekocheilus (Eurytus). A. P. (E.) tate i Haas, 1955, FMNH 50346; B─D. P. (E.) huberi spec.nov., UF 284746; E─F. P. (E.) nebulosus spec.nov., UF 284723. Scale bar—5 mm.

Material. Venezuela, Estado Bolívar, Chimantá massif, Toronó-tepui, slope bordering Caño Mojado, 2250 m, J.A. Steyermark leg., 21.ii.1955 (FMNH 52442/holotype, 52443/1 paratype). Remarks. The oblique streaks on the ventral side of the last whorl make this form resemble Plekocheilus (Eurytus) juliani Haas, 1955, but the different sculpture (malleation, Fig. 24B) and the darker colour of the peristome characterize this species. The colour pattern and the darker lip also distinguish this taxon from P. (E.) fulminans linterae.

FIGURE 3. Plekocheilus (Eurytus) nebulosus spec.nov., extended penis UF 284717. A. Dorsal view; B. ventral view.

Plekocheilus (Plekocheilus) spec.

A juvenile specimen, of which the cuticula is nearly completely eroded, was found by O. Huber on 16.i.1980 at 25 km SW of Santa Elena de Uairén, 800 m (RMNH 112030/1).

Subgenus Plekocheilus (Eurytus) Albers, 1850

Type species: Helix pentadina Orbigny, 1835

Plekocheilus (Eurytus) sophiae spec.nov. (Figs 5A─C, 9C)

Plekocheilus (Plekocheilus) blainvilleanus linterae, Breure 1978: fig. 2. Genitalia.

Diagnosis. Shell sculptured on the last whorl with horizontal threads of various length, often anastomosing; colour uniform reddish-brown; aperture ovate, slightly descending in front, peristome somewhat thickened and reflexed. Description. Shell 44 mm (further dimension given in Table 1), 1.9 times longer than wide, imperforate, sides slightly convex, thin. Colour reddish-brown, with indistinct spots and tent shaped markings of darker brown; a golden hue on the ventral side of the last whorl and a line of the same colour behind the reflexed lip; upper whorls lighter, purplish, eroded. Surface shining, upper whorls with spirally incised lines, faintly crossed by vertical incisions; on the last whorl this sculpture is more conspicuous, resulting in horizontal threads of various length, often anastomosing; axial growth wrinkles at irregular spaces. Protoconch smooth (eroded). Whorls 4.8, the upper whorls hardly convex, the last whorl much more convex; suture well impressed, somewhat crenulated, slightly descending in front. Aperture elongate-ovate, hardly pointed above, 1.8 times longer than wide, 0.53 times the total length; peristome somewhat thickened and reflexed, whitish. Columellar margin straight, entering the aperture with a hardly noticeable fold. Parietal wall with a thin, translucent callus.

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FIGURE 4. Shells in Plekocheilus. A─D. P. (P.) fulminans linterae (Sowerby, 1890). A─C. Lectotype, BMNH 1889.4.25.1; D. Paralectotype BMNH 1889.4.25.2. Photos P. Crabb. E─G. P. (P.) fulminans alticola Haas, 1955, holotype FMNH 52442. H─L. P. (Eurytus) fusitorsus (Oberwimmer, 1931). H─J. Holotype SMF 5142; K─L. FMNH 198500. M─O. P. (E.) gibber (Oberwimmer, 1931), holotype SMF 5143. Scale bar—1 cm.

FIGURE 5. Shells in Plekocheilus (Eurytus). A─C. P. ( E .) sop hia e spec.nov., holotype UF 24413. Photos R. Lasley. D─F. P. (E.) juliani Haas, 1955, holotype FMNH 49737. G─I. P. (E.) nebulosus spec.nov., holotype UF 284723. J─M. P. (E.) huberi spec.nov. J─L. Holotype UF 284764; M. Paratype RMNH 112027. Scale bar—1 cm.

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Type material. Venezuela, Estado Bolívar, Yuruaní-tepui, 2300 m, R.W. McDiarmid leg., 11.i.1977, amoungst the leaves of a Heliamphora species. Holotype UF 24413. Comparison with other taxa. This species may be compared to Plekocheilus (Eurytus) mundiperditi Haas, 1955, from which it differs in (1) being stouter; (2) the different sculpture on the last whorl; (3) having the aperture more ovate, less pointed above. It also resembles closely P. (E.) nebulosus spec. nov., from which it differs in (1) having the last whorl more inflated; (2) the aperture more ovate; (3) the less descending last whorl. Remarks. This specimen appeared to be misidentified in the UF-collection as Plekocheilus (P.) blainvilleanus linterae. When Breure (1978) dissected the animal he had not received the shell and the misidentification remained unnoticed. Only the penial complex could be studied and shows the same characteristics as other P. (Eurytus) species from this area, viz. contortions and a vas deferens shorter than the length of penis and epiphallus. The sculpture of the last whorl (Fig. 9C) is the same as in P. (E.) nebulosus spec.nov. Ethymology. This attractive species is named after my wife Sophie, as a token of my gratitude for her continued support of my research.

Plekocheilus (Eurytus) juliani Haas, 1955 (Figs 5D─F, 9F)

Plecocheilus (Eurytus) juliani Haas, 1955: 375, fig. 78. Type locality: Venezuela, State of Bolívar, northwest part of Chimantá massif, summit of Apacará-tepui, ca. 2100 m; holotype FMNH 49737.

Material. Venezuela, Estado Bolívar, Chimantá massif, summit of Apacará-tepui, 2100 m, 20─22.vi.1953, J.A. Steyermark leg. (FMNH 49737/holotype, 49738/2 paratypes); Ibidem, northwest part of summit of Abácapa-tepui, J.A. Steyermark leg., 13.iv.1953, in Bonnetia forest (FMNH 49739/1 paratype); Ibidem, Auyán-tepui, 1970 m, R.W. McDiarmid leg., 26.ii.1978 (FMNH 22949/1 juv.). Remarks. The intraspecific variation within the type material has been adequately described by Haas. The species is characterized by the oblique streaks and the sculpture of the shell (Haas 1955: fig. 78; Fig. 9F. A juvenile and broken specimen preserved in ethanol 70% was collected on Auyán-tepui, on the same massif as the type locality.

Plekocheilus (Eurytus) mundiperditi Haas, 1955 (Figs 6A─C, 9E)

Plecocheilus (Eurytus) mundi-perditi Haas, 1955: 378, fig. 80. Type locality: Venezuela, State of Bolívar, Chimantá massif near Río Tirica, 2100 m; holotype FMNH 52436.

Material. Venezuela, Estado Bolívar, Chimantá massif, 2100 m, J.A. Steyermark leg., 4.ii.1955 (FMNH 52436/holotype, 52437/1 paratype); Ibidem, central part of Chimantá massif, slopes bordering tributary of east branch of headwaters of Río Tirica, 2450 m, J.A. Steyermark & J.J. Wurdack leg., 27.iii.1955, in Bonnetia forest (FMNH 52440/1 paratype); Ibidem, Aparamán-tepui above Río Tirica, 2120 m, J.A. Steyermark & J.J. Wurdack leg., 26.ii.1955 (FMNH 52438/1 paratype); Ibidem, Toronó-tepui, bordering valley of Caño Mojado, 2250 m, J.A. Steyermark leg., 21.ii.1955 (FMNH 52439/1 paratype); Ibidem, along trail between Río Tirica and lower summit camp, 1800 m, J.A. Steyermark & J.J. Wurdack leg., 26.ii.1955 (FMNH 52441/1 paratype); Ibidem, Eruado-tepui [= Murey-tepui], 2300 m, R.W. McDiarmid leg., 24.ii.1978 (UF 22945/1 + 5 juv., 22946/2); Ibidem, summit of Apacará-tepui, ca. 2150 m, 5° 19’ N 62° 12’ W, S. Gorzula & O. Huber leg., 11─14.iii.1986, in herbaceous vegetation (RMNH 112030/1). Shell dimensions are given Table 1.

Remarks. This species is widespread on the Chimantá massif and is characterized by its dark brown colour and its sculpture of puckered spiral bands (Fig. 9E).

TABLE 1. Dimensions in selected species of Plekocheilus and Drymaeus in mm. Abbreviations: D, shell diameter; H, shell height; HA, height of aperture; LW, height of last whorl; M, mean; max, maximum; min, minimum; n, number of specimens measured; s, standard deviation; W, number of whorls; WA, width of aperture. For depositories of material, see section on material and methods. H D HA WA LW W Plekocheilus (Eurytus) mundiperditi (Haas. 1955) (n=5) M 47.3 26.1 26.2 15.2 40.7 4.4 s 3.3 1.6 1.5 1.1 2.3 0.1 max 52.3 28.4 28.4 16.9 43.9 4.6 min 44.0 24.5 24.9 14.3 38.3 4.3 Plekocheilus (Eurytus) fusitorsus (Oberwimmer., 1931) (n=2) SMF 63.3 36.8 35.7 20.1 53.8 5.0 FMNH 47.8 28.4 28.6 17.4 40.8 4.7 Plekocheilus (Eurytus) huberi spec.nov. (n=3) UF 284746 45.5 23.6 25.4 15.1 39.6 NA UF 284746 42.9 20.7 25.8 14.7 36.0 4.2 holotype 47.9 22.8 25.5 16.1 40.7 4.5 Plekocheilus (Eurytus) nebulosus spec.nov.(n=15) M 51.9 25.9 26.6 15.3 43.5 4.6 s 6.5 3.4 2.9 2.2 5.1 0.2 max 62.5 30.9 30.9 19.3 51.8 4.8 min 41.6 20.1 21.6 11.3 35.3 4.2 holotype 59.5 30.9 30.9 19.3 49.7 4.5 Plekocheilus (Eurytus) sophiae spec.nov. (n=1) holotype 44.4 23.2 23.7 13.1 38.0 4.8 Plekocheilus (Eurytus) tepuiensis spec.nov. (n=1) holotype 35.5 20.4 23.0 13.5 30.3 4.5 Plekocheilus (Eudolichotis) sinuatus (Albers. 1854) (n=2) RMNH 53.0 23.1 28.0 9.7 47.9 5.2 RMNH 48.9 22.4 27.6 8.9 38.8 4.9 Drymaeus (D.) extraneus (Haas. 1955)(n=3) FMNH 49736 32.1 14.1 14.6 8.0 22.0 6.3 FMNH 52444 19.2 10.1 9.7 6.9 14.9 5.4 FMNH 49734 20.7 10.6 9.3 6.4 14.5 5.7 Drymaeus (D.) rex spec.nov. (n=19) M 35.0 15.6 18.1 10.3 26.5 5.2 s 3.2 1.0 1.4 0.8 2.2 0.3 max 40.7 17.7 20.9 11.8 31.0 5.7 min 28.6 13.3 15.8 8.7 21.1 4.6 holotype 39.2 15.4 18.1 9.8 26.7 5.4

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FIGURE 6. Shells in Plekocheilus. A─C. P. (Eurytus) mundiperditi Haas, 1955, RMNH 112030. Photos J. Goud. D─G. P. ( E .) ta te i Haas, 1955. D─F. Paratype FMNH 50346. G. Holotype AMNH 73455. H─J. P. (E.) tepuiensis spec.nov., holotype RMNH 112031. Photos J. Goud. K. P. (Eudolichotis) sinuatus (Albers, 1854), RMNH 112032. Scale bar—1 cm.

FIGURE 7. Drymaeus (Drymaeus) rex spec.nov. A. Genitalia UF 284722; B. Longitudinal section penis; C. Spermatophore; D. Pallial organs. Scale bar—5 mm.

Plekocheilus (Eurytus) fusitorsus (Oberwimmer, 1931) (Figs 4H─L, 9I)

Eurytus fusitorsus Oberwimmer, 1931: 190, figs 1, 4. Type locality: Venezuela, Territorium Amazonas, Río Padamo; holotype SMF 5142.

Material. Venezuela, Estado Bolívar, Cerro Guaiquinima, along Río Paragua, 1500 m, J.A. Steyermark leg., 1978, in wooded portion of moist dwarf forest (FMNH 198500/1); Estado Amazonas, Río Padamo (SMF 5142/holotype). Shell dimensions are given Table 1. Remarks. This species is characterized by dark, undulating stripes on the last whorl bordered by a yellowish ‘shadow’ and a fine granulation of dotted granules (Fig. 9I). A subadult specimen from Cerro Guaiquinima (FMNH 198500) is tentatively referred to this species. It is characterized by the same colour pattern as observed in the holotype, but has oblong granules on the upper part of the last whorl, giving an impression of spiral incisions in between. The type locality is a river basin that covers 10.280 square km and drains the northwestern slopes of the Sierra Parima on the east-central border of Estado Amazonas in Venezuela and Estado Roraima in Brazil (Huber 1995a). Río Padamo is slightly east of Cerro Duida [type locality of Plekocheilus (Eurytus) tatei Haas, 1955] and Cerro Marahuaka [type locality of P. (E.) gibber (Oberwimmer, 1931)]. The headwaters of Río Padamo are on Cerro Kikirisha, slightly over 1000 m, but along its course elevations of 500 m or less prevail. Since the exact type locality is unknown, it cannot be excluded a priori that P. (E.) fusitorsus also occurs in the lowland. This species might also be expected at intermediate localities in between the two occurrences, e.g. in the Jaua-Sarisariñama massif.

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Plekocheilus (Eurytus) tatei Haas, 1955 (Figs 2A, 6D─G)

Plecocheilus (Eurytus) tatei Haas, 1955: 385, fig. 84. Type locality: Venezuela, Territory of Amazon, Cerro Duida, “ledge 23B”; holotype AMNH 73455.

Material. Venezuela, Estado Amazonas, Cerro Duida, G.H.H. Tate leg. (FMNH 50346/3 paratypes). Genitalia. Penis proximally somewhat swollen, thereafter more slender and distally subcylindrical, passing without external transition into the epiphallus, which is partly contorted and tapering towards the transition to the flagellum. The flagellum is somewhat tapering, relatively shorter than in Plekocheilus (Eurytus) juliani and P. (E.) mundiperditi (Breure 1978: figs 6─7). The vas deferens is shorter than the length of the penis and epiphallus. Vagina rather short; proximal part of spermathecal duct subcylindrical, its intermediate part widened before distally tapering towards the globose spermatheca. Spermoviduct very contorted; albumen gland relatively long. Remarks. According to Haas (1955) the type material was preserved first in formalin and later in ethanol. The conservation measures taken by Haas, viz. lacquer on the conchinic layer that began to peel off, have only been partly successful. Of the three paratypes studied, only one has retained the conchinic layer preserved as intended. But as a consequence of the lacquer application, the fine granular sculpture on the last whorl has become almost invisible. The preservation status of the two soft bodies included in the paratype material was rather poor, allowing only studying the genitalia.

Plekocheilus (Eurytus) gibber (Oberwimmer, 1931) comb.nov. (Figs 4M─O, 9H)

Auris (Antitragus) gibber Oberwimmer, 1931: 192, figs 2, 5. Type locality: Venezuela, Staat Orinocco, Sierra Maraguaca [= Cerro Marahuaka], 2170 m; holotype SMF 5143.

Material. Venezuela, Estado Amazonas, Cerro Marahuaka, 2170 m (SMF 5143/holotype). Remarks. Only the type material is known, making it difficult to judge any intraspecific variation. The taxonomic placement of this species has thus been somewhat enigmatic, the shape of the aperture and the conspicuous but weak fold setting it apart from other members in the genus. Breure (1978) placed it in the subgenus Eudolichotis because of these characteristics. After restudying the holotype in the context of this revision, it is clear that the granulation on the last whorl is very similar to that of Plekocheilus (Eurytus) tatei. The material of P. (E.) mundiperditi contains a specimen with a similarly shaped aperture that is immature (FMNH 52440). The type of P. (E.) gibber, however, has an expanded lip and a convex fold in the columella, both characteristics of maturity. This species is here placed in the Plekocheilus (Eurytus) juliani-group, awaiting further anatomical or DNA studies; see also the discussion part below. Because of this new combination, Antitragus Oberwimmer, 1931—which was erected solely for this species—should now be considered a junior subjective synonym of Eurytus Albers, 1860.

Plekocheilus (Eurytus) tepuiensis spec.nov. (Figs 6H─J, 9J)

Diagnosis. A species characterized by the obliquely descending zig-zag streaks; surface hardly shining, with spiral lines of dot-like granules on the last whorl. Description. Shell 35 mm (further dimension given in Table 1), 1.7 times longer than wide, imperforate, ovate, sides hardly convex, rather thin. Colour pale yellowish brown, with descending, somewhat oblique stripes of reddish-brown, broken up into separate stripes of different length; upper whorls lighter, corneous,

36 · Zootaxa 2065 © 2009 Magnolia Press BREURE TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. eroded. Surface hardly shining, upper whorls with growth striae, on the penultimate and ultimate whorls transferring into spiral lines of dot-like granulation, more oblong towards the aperture. Protoconch smooth (eroded). Whorls 4.5, rather flat, the last whorl somewhat swollen, suture somewhat impressed, hardly descending in front. Aperture ovate, somewhat skewed, the colour pattern from the outside shining through, 1.7 times longer than wide, 0.65 times the total length; peristome thin and hardly reflexed, whitish with a hue of pink. Columellar margin straight, entering the aperture with a weak fold, hardly dilated and somewhat receding. Parietal wall with a thin, translucent callus. Type material. Venezuela, Estado Amazonas, Cerro Yapacana, 800 m, J. Cerda leg., 21.ii.1978. Holotype RMNH 112031. Comparison with other taxa. Differs from P. (E.) huberi spec.nov. by (1) the less descending last whorl; (2) by the different granulation on the last whorl; (3) being less slender. It may also be compared to P. (E . ) gibber, from which differs in (1) having the last whorl less descending in front; (2) having the suture less impressed; (3) the different shape of the aperture. Remarks. Only a subadult specimen is known. The colouration and especially the sculpture of the last whorl (Fig. 24J) sets it apart, but it seems most closely allied to the species with which it is compared above. Etymology. The name refers to the type locality, Cerro Yapacana, an isolated tepui.

Plekocheilus (Eurytus) huberi spec.nov. (Figs 2B─D, 5J─M, 9G)

Diagnosis. Characterized by a slender, thin shell, light chestnut-brown with descending, narrow reddish- brown “lightning” stripes; an almost lustreless surface, very finely granulated on the last whorl. Description. Shell up to 47.9 mm (further dimension given in Table 1), 2.0 times longer than wide, imperforate, slenderly ovate, sides hardly convex, (rather) thin. Colour yellowish- to light chestnut-brown, with descending oblique stripes of reddish-brown, on the penultimate whorl with a tendency to be continuous, on the last whorl waved, broken up into separate stripes or dissolved into an irregular pattern of reddish-brown spots and some lines; upper whorls lighter, whitish, eroded. Surface hardly shining, upper whorls with growth striae, on the penultimate and last whorl also with spiral series of finely incised lines of almost equal strength, its visibility depending on the angle of view. Protoconch smooth (eroded). Whorls 4.3, rather flat, the last whorl slightly swollen; suture impressed, somewhat descending in front. Aperture elongate-ovate, somewhat pointed above, the stripes or spots from the outside shining through, in some specimens whitish inside, 1.7 times longer than wide, 0.56 times the total length; peristome thin and hardly reflexed, whitish. Columellar margin slightly curved, with a very weak fold above, hardly and narrowly dilated above. Parietal wall with a thin, whitish callus. Genitalia. Penis subcylindrical, distally with a somewhat swollen appendix, passing subdistally into the long epiphallus, which is partly contorted and tapering towards the transition to the flagellum. The flagellum is somewhat tapering, ca. 1/8 the total length of the penial complex. The vas deferens is free, shorter than the length of the penis and epiphallus. Vagina rather short; proximal part of spermathecal duct subcylindrical, its intermediate part widened before distally tapering towards the globose spermatheca. Spermoviduct very contorted; albumen gland moderately long. Type material. Venezuela, Estado Amazonas, Cerro de la Neblina massif, ridge at Brazil-Venezuelan border divide [00° 53’ N 65° 56’ W], 2000 m, T. Plowman & W. Thomas leg., 16.iv.1984, on south slope in a cloud forest in terrestrial bromeliads. Holotype UF 284764, paratypes: Ibidem, 5.3 km NE Pico Phelps at the base of the escarpment 1 km NE Pico Maguire, Camp VII [00° 50’ 40” N 65° 58’ 10” W], ca. 1800 m, R.W. McDiarmid leg., 31.i─10.ii.1985 (RMNH 112027/1, UF 284746/1 + 1 juv.). Comparison with other taxa. This novelty seems closely related to Plekocheilus (Eurytus) juliani Haas, 1955, but differs in (1) the weaker sculpture on the last whorl; (2) being somewhat smaller (47.9 vs. 54.2 mm); (3) the less shining surface. It may also be compared to P. (E.) tatei Haas, 1955, from which it differs in (1)

ORTHALICIDAE FROM VENEZUELAN GUAYANA Zootaxa 2065 © 2009 Magnolia Press · 37 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. being more slender; (2) the less conspicuous sculpture on the last whorl; (3) the slightly less shining surface. Etymology. Named in honour of Otto Huber (Merano, Italy), who has devoted his career to augment our knowledge of the Guayana region and the conservation of its biodiversity.

Plekocheilus (Eurytus) nebulosus spec.nov. (Figs 2E─F, 3, 5G─I, 9D)

Diagnosis. Shell sculptured on the last whorl with horizontal threads of various length, often anastomosing; colour pattern with darker spots on the uniform brownish ground colour; aperture decidedly descending in front, peristome somewhat thickened and reflexed. Description. Shell up to 62.5 mm (further dimension given in Table 1), 2.0 times longer than wide, imperforate, sides slightly convex, thin to rather solid. Colour golden- to chestnut-brown, with irregularly placed dark-brown spots; upper whorls lighter, purplish, usually eroded. Surface (rather) shining, upper whorls with spirally incised lines, faintly crossed by vertical incisions; on the last whorl this sculpture is more conspicuous, resulting in horizontal threads of various lengths, often anastomosing; in some specimens, the vertical incisions are relatively stronger, breaking the threads into coarse granules; axial growth wrinkles at irregular spaces. Protoconch smooth (eroded). Whorls 4.6, the upper whorls hardly convex, the last whorl much more convex; suture well impressed, somewhat crenulated, deeply descending in front. Aperture elongate-ovate, pointed above, with dark-brown spots visible at the inside, 1.8 times longer than wide, 0.51 times the total length; peristome somewhat thickened and reflexed, whitish. Columellar margin hardly curved, entering the aperture with a slight fold. Parietal wall with a thin, whitish callus. Genitalia. Penis subcylindrical, slightly swollen distally and somewhat constricted at the transition to the epiphallus, which is relatively long and contorted at the junction of the vas deferens that is adhered to and as long as penis and epiphallus. Flagellum thin and slightly tapering, a very thin retractor muscle distally attached. Vagina slightly swollen, short, spermoviduct distally contorted. Spermathecal duct subcylindrical, its intermediate part hardly dilated, tapering towards the elongate-globose spermatheca, which is pigmented. One specimen (UF 284717) was found with fully extended penis (Figs 3A─B), showing the slightly swollen base of the penis and the sculpture of the epiphallus and around the genital pore. Ecology. Living specimens have been collected in bromeliad scrub forest. This “Neblinaria scrub” is composed primarily of one species, Bonnetia maguiereorum (Clusiaceae), which forms dense stands of plants 2─3 m tall. The plants have terminal rosettes of leathery leaves that can hold considerable water. Type material. Venezuela, Estado Amazonas, Cerro de la Neblina massif, 3 km NE Pico Phelps, Camp II [00° 49’ 40” N 65° 59’ 00” W], 2085─2100 m, R.W. McDiarmid leg., 28─31.ii.1985, in Brocchinia plants. Holotype UF 284723, paratypes: Ibidem (RMNH 112028/2, UF 284716/2, 284717/2, 284718/1, 284724/1); Ibidem, 5.3 km NE Pico Phelps at the base of the escarpment 1 km NE Pico Maguire, Camp VII [00° 50’ 40” N 65° 58’ 10” W], ca. 1800 m, R.W. McDiarmid leg., 31.i─10.ii.1985 (UF 284731/1, 284732/1, 284737/1); Ibidem, ridge on E slope of Pico Maguire, 2000 m, F.G. Thompson leg., 17.iv.1984, in and under bromeliads (UF 284766/1, 284767/1); Ibidem, ridge at Brazil-Venezuelan border divide [00° 53’ N 65° 56’ W], 2000 m, T. Plowman & W. Thomas leg., 16.iv.1984, on north slope in bromeliad shrub forest (UF 284762/1, 284765/ 1). Comparison with other taxa. This novelty seems closely related to Plekocheilus (Eurytus) sophiae spec. nov., from which it differs in (1) being more slender; (2) the aperture more descending in front; (3) the darker spots in the colour pattern. It differs from P. (E . ) mundiperditi Haas, 1955 in (1) the sculpture of the last whorl being more thread-like; (2) the aperture deeply descending in front. It has also been compared to the lectotype of P. (E.) superstriatus (Sowerby, 1890), from which it differs in (1) being smaller (51.9 vs. 64.5 mm); (2) lacking the whitish spots in the colour pattern; (3) having the aperture regularly rounded. Remarks. The sculpture of the last whorl (Fig. 9D) is similar to that of P. (E.) sophiae, suggesting it to be a sibling species.

Etymology. Latin nebula, cloud; referring to the type locality, where misty weather prevails most of the year.

Plekocheilus (Eurytus) coloratus (Nyst, 1845)

Bulimus coloratus Nyst, 1845: 228, figs 2a─b. Type locality: la province de Cumana, dans la Colombie [sic, Venezuela, Estado Monagas].

Material. Venezuela, Estado Amazonas, Río Negro, A.A. Olsson leg., 1945 (UF 184700/1). Remarks. The label “Venezuela, Rio Negro” is not very conclusive about the precise locality where this specimen was found. It could refer either to the District Río Negro or to the borders of the river with the same name, both in the southwestern part of Estado Amazonas. In the latter case it would imply that the locality is at ca. 100 m elevation. In the former case it covers an area of 37.903 km2, which partly consists of uplands and highlands (including the Cerro de la Neblina massif). Pilsbry (1895: 75) quotes “La Esperanza estate, near Rio Negro” on the authority of Bland, suggesting a lowland occurrence; I do, however, not know if Bland ever collected in the Colombian-Venezuelan border region near the Río Negro. This is the southernmost record for this species, which is widely distributed in Colombia (Borrero, personal communication) and has been reported from north-western Venezuela by Arias (1953).

Subgenus Plekocheilus (Eudolichotis) Pilsbry, 1896

Type species: Bulimus distortus Bruguière, 1789

Plekocheilus (Eudolichotis) sinuatus (Albers, 1854) (Fig. 6K)

Bulimus sinuatus Albers, 1854: 32. Type locality: Venezuela; lectotype ZMB 101794 (Köhler 2007).

Material. Venezuela, Estado Amazonas, 10 km S Río Autana, 4° 44’ N 67° 33’ W, 100 m, O. Huber leg., 2.vii.1979 (RMNH 112032/2). Shell dimensions are given Table 1. Remarks. This species is reported here for the first time from the Venezuelan Guayana area. Hitherto it was only known from the Cordillera de la Costa in northern Venezuela (Baker 1926, Thompson 1957, Breure 1976). There it was found in cloud forest at 1000 m elevation and the current finding in the lowland was unexpected. It is closely allied to the somewhat smaller P. (E.) euryomphalus (Jonas, 1844), which has been reported from the Roraima savannah in Guyana (Solem 1964).

Genus Drymaeus Albers, 1850

Type species: Helix hygrohylaea Orbigny, 1835

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Subgenus Drymaeus (Drymaeus) Albers, 1850

Drymaeus (Drymaeus) steyermarki (Haas, 1955) (Fig. 8D─F)

Plecocheilus (Eurytus) steyermarki Haas, 1955: 377, fig. 79. Type locality: Venezuela, State of Bolívar, northwest part of Chimantá massif, plateau below the summit of Apacara tepui, 1800 m; holotype FMNH 49735.

Material. Venezuela, Estado Bolívar, northwest part of Chimantá massif, plateau below the summit of Apacará-tepui, 1800 m (FMNH 49735/holotype). Remarks. This species has the same white line bordering the suture as Drymaeus (D.) rex spec.nov., but is decidedly smaller. The very faint pinkish border lining the inside of the aperture behind the white lip clearly links both species. The thread-like fold of the columella mentioned by Haas is, however, much weaker than those in the aberrant specimens of D. (D.) rex mentioned below. It is, just as most specimens of D. (D.) extraneus Haas, 1955, without distinct colour pattern and occurs on the same massif. However, it is smaller and more pointed, having straight sides and some incomplete, dark brown axial streaks on the pale ground colour.

Drymaeus (Drymaeus) extraneus (Haas, 1955) (Fig. 8A─C)

Bulimulus (Lissoacme) extraneus Haas, 1955: 382, fig. 82. Type locality: Venezuela, State of Bolívar, northwest part of Chimantá massif, summit of Apacara tepui, ca. 2100 m; holotype FMNH 49736. Drymaeus (Drymaeus) griffini Haas, 1955: 383, fig. 83. Type locality: Venezuela, State of Bolívar, Chimantá massif, western side of Abacapa tepui, drainage of Río Abacapa, ca. 1300 m; holotype FMNH 49734. New synonymy.

Material. Venezuela, Estado Bolívar, northwest part of Chimantá massif, summit of Apacará-tepui, 2100 m, J.A. Steyermark leg., 20─22.vi.1953 (FMNH 49736/holotype); Ibidem, along trail between Río Tirica and lower summit camp, 1800 m, J.A. Steyermark & J.J. Wurdack leg., 26.ii.1955 (FMNH 52444/1 juv. paratype); Idem, west side of Abacapá-tepui, 1189 m, J.A. Steyermark & C. Griffin leg., 13.iv.1953 (FMNH 49734/1). Shell dimensions are given Table 1. Remarks. Upon restudying the type material, also in the context of the material from Cerro de la Neblina, I have come to the conclusion that this species belongs to what I would like to call the Drymaeus (D.) steyermarki-group; see discussion below. D. (D.) extraneus resembles in shell shape most closely D. (D.) rex, but it is smaller, with the aperture less broad. The type specimens are unicoloured. D. griffini—occurring on the same massif—proves to be synonymous; the name extraneus has page priority. The holotype of griffini is immature, but shows that also a banded colour pattern is possible in this taxon. The original label of D. griffini reads “Venezuela Botanical Expedition, 1953, Camp 33900, drainage of Rio Abacapá, western side Abacapá- tepui”. I have been unable to obtain more information from field notes made during the expedition.

Drymaeus (Drymaeus) yapacanensis Breure & Eskens, 1981 (Fig. 8G─H)

Drymaeus (Drymaeus) yapacanensis Breure & Eskens, 1981: 47, fig. 159, 343; pl. 3 figs 5─6, pl. 5 fig. 9. Type locality: Venezuela, Territoria Amazonas, Cerro Yapacaná, ca. 700 m; holotype RMNH 55331. Genitalia, mandibula, radula.

Material. Venezuela, Estado Amazonas, Cerro Yapacana, 700 m, J. Cerda leg., ii.1978 (RMNH 55331/ holotype, 55332/1 paratype).

Remarks. So far, only the type material is known, which was collected on one of the slopes; the top of this isolated tepui is at 1300 m (Huber 1995a: fig. 1.22).

FIGURE 8. Shells in Drymaeus (Drymaeus). A─C. D. (D.) extraneus (Haas, 1955). A─B. Holotype FMNH 49736; C. FMNH 49734. D─F. D. (D.) steyermarki (Haas, 1955), holotype FMNH 49735. G─H. D. (D.) yapacanensis Breure & Eskens, 1981, holotype RMNH 55331. I─S. Drymaeus (Drymaeus) rex spec.nov. I─M, Q─S. Paratypes UF 284745, 284730, 284759, 284748, 284714, 284719, 284719 and 284715 respectively; N─P. Holotype UF 284726. Scale bar—1 cm.

Drymaeus (Drymaeus) rex spec.nov. (Figs 7, 8I─S)

Diagnosis. A relatively large species of Drymaeus, with a white line below the suture and typically with three interrupted spiral colour bands on the last whorl, crossing weaker axial streaks of a less intense colour. Aperture with a white, slightly expanded lip, bordered pink inside. Description. Shell up to 40.7 mm (further dimension given in Table 1), 2.2 times longer than wide, narrowly rimate with rather convex sides, rather elongated, solid. Colour very variable, whitish-yellowish to yellowish-brown, with the following patterns: a) chestnut-brown axial streaks and three, darker interrupted

ORTHALICIDAE FROM VENEZUELAN GUAYANA Zootaxa 2065 © 2009 Magnolia Press · 41 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. spiral bands; b) with axial chestnut-brown streaks of varying width, sometimes coalescing; c) axial streaks chestnut-brown and zig-zagging. The spiral bands, if present, are evenly spaced on the last whorl, one at the periphery. Upper whorls in the same ground colour as the rest of the shell or with a pinkish hue; in the latter case the apex is dark reddish-black. Surface somewhat shining, in most cases dull; the upper whorls smooth, on the remaining whorls the growth striae are slightly thickened, most noticeable on the third and fourth whorl. Protoconch with a grating sculpture of axial riblets and spiral striae, which are of equal strength. Whorls 5.2, rather convex; suture slightly impressed and bordered by a whitish to yellowish line below. Aperture elongate-ovate, 1.8 times longer than wide, 0.52 times the total length. Peristome thin, expanded, especially below, whitish with a pink or orange border inside. Columellar margin curved, reflexed, dilated above and receding. Parietal wall with a thin callus, with a pink or orange hue. Genitalia. Proximal part of the penis with a sheath (ca. 1/5 the length of the phallus), distally slightly swollen and passing without external differentiation into the epihallus. The flagellum is slightly tapering, relatively thick, ca. 1/8 the length of the phallus; the distally attached retractor muscle relatively short and thin. Internally three different zones may be distinguished in the penis: proximal part with longitudinal folds of various lengths, the median part with fewer folds bearing cross-folds, the distal part with a bulgy fold and smaller folds at right angles; epiphallus with longitudinal folds, flagellum with short longitudinal ridges. Spermathecal duct somewhat swollen proximally, subcylindrical in its lower part, thereafter constricted towards the elongate-globose spermatheca. The spermatophore is curved, cylindrical and tapering at both ends. Pallial organs. Nephridium elongate-truncated, passing into a very short adrenal (primary) ureter, which tapers into the relatively long and wide adrectal (secondary) ureter. Urinary opening at inner side of the pneumostome. Pericardium situated alongside the nephridium, triangularly shaped; ventriculum about twice the size of the aorta. Pulmonary vein ramified towards the mantle edge; a secundary vein runs parallel under the adrectal ureter, with side veins towards the main pulmonary vein, becoming stronger and ramified near the pneumostome. Type material. Venezuela, Estado Amazonas, Cerro de la Neblina massif, 5.3 km NE Pico Phelps at the base of the escarpment 1 km NE Pico Maguire, Camp VII [00° 50’ 40” N 65° 58’ 10” W], ca. 1800 m, R.W. McDiarmid leg., 31.i─10.ii.1985. Holotype UF 284726, paratypes: Ibidem, UF 284725/1, 284730/1); Ibidem, L. Cocroft leg., 10─13.ii.1985 (UF 284736/1); Ibidem, A. Paolillo leg., 10─13.ii.1985 (UF 284744/1, 284745/1); Ibidem, 3 km NE Pico Phelps, Camp II [00° 49’ 40” N 65° 59’ 00” W], 2085─2100 m, R.W. McDiarmid leg., 28.ii.1985, in Brocchinia plants (RMNH 112026/2, UF 284714/2, 284715/1, 284719/2, 284720/1, 284721/1, 284722/2 + 1 juv.); Ibidem, 2 km NNW Pico Phelps, in leaf litter, Camp V [00° 49’ 10” N 66° 00’ 02” W], ca. 1300 m, F.G. Thompson leg., 13.iv.1984 (UF 284759/1); Idem, Idem, 6.25 km NNE Pico Phelps, Camp XI [00° 52’ 00” N 65° 58’ 42” W], 1400─1500 m, R.W. McDiarmid leg., ii.1985, in forest (UF 284748/1 subadult); Ibidem, 2.0 km SW Neblina Base Camp, 200 m, R.W. McDiarmid leg., 22.ii.1985, in tree 2 m off ground (UF 284747/1). Remarks. As often seen in Drymaeus, this species shows a great deal of variation in colour and pattern. One specimen (UF 284730) is evenly coloured, the last whorl lighter than the upper whorls, the axial streaks hardly noticeable. This species is also rather variable in shape. Three specimens are somewhat aberrant and have hardly any transition between columellar and parietal margin, giving the aperture a skewed appearance. Of these, one specimen (UF 284759) has the columellar margin straight and the aperture is ear-shaped. In two other specimens (UF 284747, 284748) the aperture is also somewhat ear-shaped, but the columella shows a slight fold. The specimens have been collected at lower elevations (1450, 1300 and 200 m respectively), but it is not clear from the material at hand if there is a correlation between elevation and morphology. Comparison with other taxa. This species is closely allied to Drymaeus (D.) yapacanensis Breure & Eskens, 1981, from which it differs in (1) being stouter; (2) having a more swollen last whorl; (3) having less whorls. This new species is also very similar to Drymaeus (D.) steyermarki (Haas, 1955) from which it differs in (1) being larger; (2) missing the thread-like columellar fold. It may also be compared to D. (D.) extraneus (Haas, 1955), from which it differs in (1) having the surface less shining; (2) the less dilated columellar

42 · Zootaxa 2065 © 2009 Magnolia Press BREURE TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. margin; (3) the pink lip; (4) the different colour pattern. Drymaeus (D.) edmuelleri (Albers, 1854), of which the type material (ZMB 111.929) has been studied, resembles this new species but differs in (1) being smaller and slenderer; (2) having the last whorl less swollen and somewhat protruded at base; (3) having straight sides. Etymology. Latin rex, king. Named in honour of Roy W. McDiarmid who collected most of the type material. “Roy” is the Old French word for king, but also the Anglicized spelling of a nickname from Scottish Gaelic ruadh (red, referring to the reddish apex in some specimens). The name also refers to the majestical appearance of this species when collected alive. The epithet is used as a noun in apposition.

FIGURE 9. Shell sculpture in Plekocheilus. A. P. (P.) fulminans linterae; B. P. (P.) fulminans alticola; C. P. (Eurytus) sophiae; D. P. (E.) nebulosus; E. P. ( E . ) m u nd ip e rd it i; F. P. (E.) juliani; G. P. (E.) huberi; H. P. (E.) gibber; I. P. ( E. ) fusitorsus; J. P. (E.) tepuiensis.

FIGURE 10. Distribution of high- and upland species in Venezuelan Guayana. A. Plekocheilus. Symbols: orange circle: P. (Eurytus) huberi; orange rhomb P. (E.) nebulosus; purple circle P. (E.) tepuiensis; lightblue square P. (E.) tatei; lightblue triangle P. (E.) gibber; green triangle P. (E.) fusitorsus; red circle P. (E.) juliani; red star P. (P.) fulminans alticola; red square P. (E.) mundiperditi; blue rhomb P. (E.) sophiae; blue star P. (P.) fulminans linterae. B. Drymaeus. Symbols: square D. (D.) rex; triangle D. (D.) yapacanensis; rhomb D. (D.) extraneus; circle D. (D.) steyermarki.

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Biogegraphical results

Analyzing the data from the systematic part, it is first of all interesting to look at the elevation ranges. Following the distinction made by Huber (1988)—viz. highlands (> 1500 m), uplands (500─1500 m) and lowlands (< 500 m)—it can be appreciated that only two species are confined to lowlands (Table 2). Surprisingly a few specimens of Drymaeus rex were encountered at lower altitudes; it has to be kept in mind, however, that Cerro de la Neblina—unlike many other tepuis—is gradually sloping into the surrounding lowlands. Geographically, the highland and upland species of Plekocheilus and Drymaeus are clearly distinguished according to the Pantepui districts based on the phytogeography (Berry et al. 1995); see Figure 10 and Table 3. An analysis of influences related to this diversity was done, using PCA (Tables 4, 5). This identified three factors with Eigenvalue greater than 1.0 (factor 1 = 6.5, explaining 65.4% of the variation; factor 2 = 1.8, 17.8%; factor 3 = 1.3, 13.0%). Factor 1 was highly loaded—in decreasing order—by the number of primitive vascular plants (both total number and endemics), elevation of the tepuis, the number of angiosperm plants (both total number and endemics), the slope area, and number of forest types (Table 5). Two variables (summit area and number of forest types) loaded heavily on factor 2. The number of tepuis in a massif was the variable that loaded heavily on factor 3, with the average nearest-neighbour distance highly negatively correlated.

TABLE 2. Altitudinal distribution of Orthalicidae, arranged according to highlands (> 1500 m), uplands (500─1500 m) and lowlands (< 500 m). Plekocheilus Drymaeus Highlands fusitorsus extraneus gibber rex huberi steyermarki juliani f. linterae, f. alticola mundiperditi nebulosus sophiae tatei Uplands ?fusitorsus extraneus tepuiensis rex yapacanensis Lowlands coloratus rex ?fusitorsus sinuatus

Discussion

Systematics

Generic level The taxonomic placement of the species of Orthalicidae from this region has been somewhat problematic. Described as Plekocheilus, Auris, Bulimulus and Drymaeus respectively, they are here condensed into two

44 · Zootaxa 2065 © 2009 Magnolia Press BREURE TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. genus groups: Plekocheilus and Drymaeus. Both genera are widespread in northern South America and adjacent areas, and their species show a considerable (intra-specific) variation. Due to the inaccessibility of the tepuis, most species are known from very few specimens, making it difficult to study their intra-specific variation.

TABLE 3. Distribution of species according to phytogeographic districts (adapted from McDiarmid & Donnelly 2005). District Subdistrict Tepui / massif Plekocheilus Drymaeus Eastern Pantepui Roraima Roraima f.linterae Yuruaní sophiae Chimantá Abacapá juliani, mundiperditi extraneus Apacará juliani, mundiperditi extraneus, steyermarki Aparamán mundiperditi Auyán juliani Chimantá mundiperditi Murey mundiperditi Toronó f.alticola, mundiperditi Central Pantepui Guaiquinima Guaiquinima fusitorsus Duida-Marahuaka Duida tatei Marahuaka gibber Yapacana tepuiensis yapacanensis Southern Pantepui Neblina-Aracamuni Neblina huberi rex nebulosus

Breure (1979: 25) already noted that the differences between the subgenera of Plekocheilus are slight and considered the division of the genus in different subgenera as tentative. In his phylogenetic analysis he found no characters corroborating the monophyly of Plekocheilus (Eurytus) and P. (Eudolichotis). The only character hypothesized for the monophyly of Plekocheilus s.str. is the presence of two glandular cell types in the penis epithelium. Schileyko (1999) seems to have omitted Eurytus at all, not even mentioning it in the synonymy of any Plekocheilus subgenus. Tentatively these subgenera are treated here separately. There are, however, different reasons to suspect that Plekocheilus (P.) and P. (Eurytus) are very closely related or, possibly, paraphyletic. First of all, when ecological niche modeling the distributions of species from the two subgenera, the same ecological variables—precipitation during the last quarter of the year and maximum temperature—have the greatest contributions to the models (Breure, unpublished data). Secondly, the sculpture of the shell surface is an important character to distinguish the two subgenera (Breure 1979), the nominate subgenus always being malleated. Malleation of the shell sculpture has been studied in other groups and has been linked to their ecology. Rensch (1932) observed a marked intraspecific difference between specimens of Cepaea nemoralis (L., 1758). Specimens from Italy were malleated, while those from northern Germany were without malleation and show finely incised spiral lines. He linked his observations to climatological circumstances, the malleated forms originating from drier regions. Given the localities for Plekocheilus (P.) species in the Eastern Pantepui District and the climatological data provided by Huber (1995a), it is highly unlikely that drought plays a role in the malleation of these species. They occur at places where average rainfall is high to very high and dry seasons do not occur. To clarify the occurrence of malleated and non-malleated species in this group, further ecological and molecular studies are needed.

Species level At the species level, it is apparent that the shell sculpture (Fig. 9) and the reproductive anatomy are

ORTHALICIDAE FROM VENEZUELAN GUAYANA Zootaxa 2065 © 2009 Magnolia Press · 45 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. important characters to distinguish the different taxa of Plekocheilus, with the shell shape and colour pattern as a second external characteristic. Within this framework it is possible to distinguish the following sets of closely related species: (1) Plekocheilus (Eurytus) juliani and P. (E.) huberi, having in common the zig-zag streaks and the shell shape; (2) P. (E.) mundiperditi, P. (E.) sophiae and P. (E . ) n e bu l os u s, having in common the shell shape, the spotted colour pattern and the relatively strong spiral sculpture; and (3) P. (E.) fusitorsus and P. (E.) tatei, having in common the shell shape with a less descending last whorl and the oblique streaks in the colour pattern. It may be noted that the first two sets each have representatives in both the Eastern and Southern Pantepui District. The last pair is confined to the Central Pantepui District. In this district also occurs P. (E.) gibber, which together with P. (E.) tepuiensis stands somewhat isolated. All these highland species are distinct from the more widespread species that have been collected in the lowland, viz. P. (Eurytus) coloratus and P. (Eudolichotis) sinuatus. The four species of Drymaeus closely resemble each other, but may be distinguished in an eastern (extraneus, steyermarki) and western group (rex, yapacanensis). The eastern group has the overall shell shape and the relatively uniform colour in common. The shell shape and anatomy of Drymaeus (D.) rex resembles those of the eastern group, but the colour pattern and the pink band inside the aperture is similar to that in D. (D.) yapacanensis; the anatomy of the latter is still unknown. It is clear from the records of D. (D.) rex that the species may disperse into the lowland.

Ecology Both Plekocheilus and Drymaeus are found in low abundance. In the rest of their distributional range, species of both genera (especially Drymaeus) are primarily arboreal. Although some species can also be found on the ground, many more utilize trees and vegetation at least most of the time. From the very few data available, it may be noted that in this area Plekocheilus was found in Bonnetia—Clusiaceae; with 75% endemic species in the area (Huber 1988)—or bromeliads. Drymaeus has been collected in this region on bromeliads, viz. Brocchinia, a genus that is native to southern Venezuela and Guyana, and is found in areas containing sandstone. The soils in the area are poor in nutrients and it has been suggested that the low availability of soil nutrients might be a limiting factor for the diversity of these plant communities (Michelangeli 2000). It has been observed elsewhere in the tropics (Indonesia, Malaysia, Vietnam, Cambodia) that in lowlands snails often occur in low abundance, due to nutrient(Calcium)-poor and acidic soils. The malacofauna that can survive under such conditions consists often of (larger) snails living on (tree-like) vegetation off the ground (J.J. Vermeulen, personal communication). However, de Winter & Gittenberger (1998) reported a high species richness, low abundance and seasonal fluctuations for land snails from a rainforest in Cameroon. A relatively high number of smaller species (< 10 mm) occurred and nearly 50% was associated with the forest floor. In Venezuelan lowlands no similar intensive sampling has been done, which possibly may explain the observation of only larger species. On the tepuis the weathering of rocks may leach more minerals and thus explain the relatively higher—but in absolute terms still low—specimens abundance.

Biogeography McDiarmid & Donnelly (2005) analysed the distributions of amphibians and reptiles in Venezuelan Guayana. Comparing their analysis to the distribution of land snails is interesting as both groups, the land snails and the amphibians/reptiles, are not very vagile and both are relatively old taxa (63% of Neotropical molluscs and 96% of amphibians have a pre-Glacial origin; Rull 2008). The eastern and western tepuis have a similar fauna at the generic level but differ at the species level. This pattern is similar in both groups (herpetological data from McDiarmid & Donnelly 2005 and in addition from R.W. McDiarmid, personal communication). In their in-depth analysis, using PCA, McDiarmid & Donnelly (2005) studied the abiotic and biotic factors that may influence species diversity and distributions in the area. Their factors include: tepui size (area of summit and slope), elevation, nearest-neighbour distance between massifs, number of forest types, number of (endemic) angiosperm vascular plants, and number of (endemic) primitive vascular plants (see McDiarmid

& Donnelly 2005 for details). In the present PCA study on Orthalicidae (Table 4) days spent collecting (DC), used by McDiarmid & Donnelly as a measure of sampling effort, has been omitted since insufficient data exists for malacological collecting efforts. Also their variable to express elevational range (ER) has been omitted due to lack of data. McDiarmid & Donnelly (2005) used the variable distributional pattern (DP) to express a distributional range from highly endemic (one tepui) to widespread species (continental). Since nearly all snails in this study are highly restricted in distribution, this variable is not appropriate for Orthalicidae. When the PCA results on Orthalicidae (Table 4) are compared with those of McDiarmid & Donnelly for amphibians and reptiles, the similarities are striking. Factor 1 may be considered an index of habitat diversity, with the four variables for plant diversity, forest types, elevation and slope area of the tepuis having the most positive influence. Analogous to their conclusions for herpetological data, it can be argued that the varied and unusual growth forms of tepui plants (e.g. Brocchinia) contribute to the availability of suitable habitats for snails. The effect of an increase in elevation and number of tepuis in a massif may also add to making different habitats available. Just as McDiarmid & Donnelly (2005) have observed, in the PCA the factor scores for primitive plants are higher than for angiosperm vascular plants, but—contrary to their findings—only in the latter group the score for endemics is higher than for the total of angiosperm plants. Their factor 2 was regarded an index of “accessibility” because variables that are associated with surface area and extent of vertical cliffs were important. In the snail data the surface area also loads heavily on factor 2, but the other important variable is the number of forest types. This may be explained by the arboreal habit of the snails (see Ecology section above). Factor 3 is associated with distance between massifs, but unlike the herpetological data, the correlation is negative here. Isolation as such does not seem to contribute to snail diversity in this area. The number of tepuis in a massif is positively correlated to this factor and points to “topographical variation”. Several hypotheses have been proposed to explain speciation of faunal elements in Venezuelan Guayana (McDiarmid & Donnelly 2005; see also Pérez-Hernández & Lew 2001, Rull 2004, 2005, 2006, Noonan & Gaucher 2006). Rull (in press) summarizes the hypotheses and shows the significance of Venezuelan Guayana for biological sciences. Without further phylogenetic studies, a discussion of these hypotheses remains rather speculative. However, once undertaken, they could certainly help understanding evolutionary and biogeographical processes in this fascinating area.

TABLE 4. Variables used in Principal Component Analysis (columns 2--12). Column headings are abbreviated as follows: LOC, massif or tepui; TOT, number of Orthalicid species known from each massif; TEP, number of tepuis in each massif known to have orthalicids; ELE, maximum elevation (m); SUM, summit area (m2); SL, slope area (m2); NN, average nearest-neighbour distance between each massif (km); FT, number of forest/vegetation types from each massif; VPT, number of vascular plants known from each massif; VPE, number of endemic vascular plants known from each massif; PPT, total number of primitive plants known from each massif; PPE, number of endemic primitive plants known from each massif. Massif or tepuis are abbreviated as follows: ETC, Eastern Tepui Chain; AUY, Auyán; CHI, Chimantá; GUQ, Cerro Guaiquinima; YAP, Cerro Yapacana; DUI, Duida-Marahuaka; NEB, Neblina-Aracamuni. LOC TOT TEP ELE SUM SL NN FT VPT VPE PPT PPE ETC 2 2 2810 70 320 383 1 135 56 112 19 AUY 1 1 2450 667.7 715 272 4 54 165 76 83 CHI 5 6 2650 615 915 268 4 242 129 156 28 GUQ 1 1 1650 1096 410 260 3 111 40 41 4 YAP 2 1 1300 10.5 38 421 1 28 13 5 0 DUI 2 2 2800 1219 1100 346 7 220 135 187 28 NEB 3 1 3014 473 1515 538 5 199 118 180 23

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TABLE 5. Factor loadings scores (varimax normalized) for variables used in the PCA. Original variable Factor 1 Factor 2 Factor 3 Number of tepuis with snails 0.438 -0.148 0.848 Maximum elevation (m) 0.947 -0.052 -0.045 Summit area (m2) 0.166 0.966 0.175 Slope area (m2) 0.868 0.345 -0.237 Nearest-neighbour distance (km) 0.279 -0.386 -0.862 Number of forest types 0.663 0.715 -0.087 Number of angiosperm vascular plant species 0.905 0.297 0.292 Number of angiosperm vascular plant endemics 0.928 0.321 0.147 Number of primitive vascular plant species 0.977 0.189 -0.007 Number of primitive vascular endemics 0.960 0.087 0.212

Conclusions

In biogeographical terms the tepuis can be seen as islands: highlands as “islands in the air”, for which the surrounding lowlands form the only means of connection. Most tepuis rise steeply above the surrounding plains. Thus the tepuis may be considered ‘ecological islands’ of which the biota to some extent have co- evolved. The Orthalicidae of Venezuelan Guayana appear to be a highly endemic group at the species level (87.5% endemicity). Although the speciation processes remain unclear, the hypothesis of Rull (2005) on speciation that enhances intra-tepuian biodiversity and promotes endemism atop them is a good candidate for further elucidation. The presence of closely related species in different Pantepui Districts points to a joint evolution of snails and plants (see also Rull & Nogué 2007). The additional data presented in this paper may give a better understanding of the orthalicid land snails and their distribution in Venezuelan Guayana, but this picture is far from complete. Additional sampling of tepuis (and/or making available hitherto unknown collections, also of non-orthalicid snails) will be necessary to further our knowledge of the tepuian malacofauna. Phylogenetic research is needed to obtain insights in the speciation processes that have led to the current distribution patterns. The secrets of the Lost World are not yet unravelled.

Acknowledgements

First of all, I am much indebted to R.W. McDiarmid (Washington) and F.G. Thompson (Gainesville) for supplying me with information on their field work in Venezuelan Guayana and especially to the former for his stimulating discussions. The multidisciplinary expedition to Cerro de la Neblina 1983─1987 was funded by FUDECI and directed by C. Brewer-Carias. I am grateful to the following persons for providing photographs or lending me material from the collections in their charge: J. Ablett (London), J. Gerber (Chicago), M. Glaubrecht (Berlin), R. Janssen (Frankfurt am Main), M. Siddall (New York) and J. Slapcinsky (Gainesville). L. Simone (Sao Paulo) kindly sent me data on the occurrences of several genera in northern Brazil, F.J. Borrero (Cincinnati) provided data on occurrences in Colombia. I thank J. Slapcinsky (Gainesville) and J.W. Arntzen (Leiden) for various help during preparation of the manuscript. C. van Achterberg and J. Goud (Leiden) kindly provided expert assistance with taking some of the photographs. Finally I am grateful to F.J. Borrero, A.C. van Bruggen and V. Rull for their reviews of an earlier draft and to J. Miller for his invaluable help in the preparation of the figures.

References

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