The Genus Obelus Hartmann, 1842 (Gastropoda, Pulmonata, Helicoidea) and its Phylogenetic Relationships

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The Genus Obelus Hartmann, 1842 (Gastropoda, Pulmonata,Helicoidea) and its Phylogenetic Relationships

Miguel IBAÑEZ1, María R. ALONSO1, Klaus GROH2 and Rainer HUTTERER3

1Department of Animal Biology, La Laguna University, La Laguna, Tenerife, Canary Islands, Spain2Hackenheim, Germany3Zoologisches Forschungsinstitut und Museum Alexander Koenig, Bonn, Germany

Abstract. The genus Obelus, so far known from shells only, is re-described on the basis of the anatomy of its geni-tal system. Its range is here restricted to north-western Africa and the Canary Islands. Four species are traditionallylisted for the Canary Islands: Obelus despreauxii, O. moderatus, O. mirandae and O. cyclodon. The presence of thelast species on the Canary Islands is doubtful, whereas the fossil/subfossil presence of O. pumilio is documented.The species Helix morata also belongs to the genus, as well as a new species, O. discogranulatus sp. nov. The geni-tal systems of all confirmed extant Canarian species are shown. Obelus has a peculiar vaginal stimulator appendix(„appendicula“) which is homologous to the penial appendix of the Orthurethra and to the stimulatory organ ofother Stylommatophora, with the exception that the A3 portion is missing. The genus is diagnosed by characters ofthe vaginal stimulator appendix, such as a curved, finger-like A2 portion of the appendicula ending proximally in ablind, well-developed muscular sac, and by the slender tubular A4 portion arising laterally from the muscular sacduct. We conclude that Obelus belongs to the Cochlicella group because it shares an appendicula with the othergenera of the group. However, it differs in anatomical details of this structure. The Cochlicella group should be rec-ognized as a separate family Cochlicellidae Schileyko, 1972, with close relationships to the Helicellidae and theHygromiidae. A new diagnosis for Cochlicellidae is proposed and its phylogenetic relationships are discussed.This is: Notes on the Malacofauna of the Canary Islands, No. 46.

Key words. Taxonomy, Obelus, Cochlicellidae, relationships.

1. INTRODUCTION

When HARTMANN (1842, pls. 52, 57, 58) named Obelusas a new subgenus of Helix, he included five taxa:“Obelus Preauxii” from the Canary Islands (pl. 52), and “O. duplicatus” (pl. 52), “O. Michaudii, O.cheiranticola” (pl. 57) and “O. polymorphus” (pl. 58)from Madeira. The last four nominal taxa are synonymsof Hystricella bicarinata (G. B. Sowerby I, 1824),Lemniscia michaudi (Deshayes, 1831), Discula (Discu-la) cheiranticola (R. T. Lowe, 1831) and Discula (D.)polymorpha (R. T. Lowe, 1831), respectively. In hisplate-captions HARTMANN (1842) neither indicatedauthorships nor mentioned the size of the specimensfigured. The name “Helix Preauxi, d’Orb.”, used in thecombination “Obelus Preauxii” by HARTMANN (1842),appeared first in D’ORBIGNY (1842, pl. 3 figs. 21–23),apparently due to a printer’s error. This lapsus name is ajunior synonym of Helix despreauxii d’Orbigny, 1839.

The species had been described three years before onthe basis of material collected by Despréaux anddeposited in the Webb & Berthelot collection (D’OR-BIGNY 1839, 65). The epithets “preauxii” and “preauxi”should therefore be considered incorrect spellings ofdespreauxii, not referring to new nominal taxa.HARTMANN (1843, 159) stated that the five taxa he hadincluded 1842 in Obelus belonged to a peculiar groupnamed earlier by MOUSSON (in litt.) Anomalina; he alsoadded “thumulorum [sic! pro tumulorum] von Webb”and “conus von Pfeiffer” to Obelus and stated thatObelus had previously been established by him for“Helix turritella [sic! pro turrita], conica, sulculata,elegans, etc” as well. However, we found no trace of adescription of Obelus in the earlier works of HART-MANN (1821a, b). Only the name was published beforeas a nomen nudum in the folded table, “SystematischeÜbersicht der europäischen Gattungen” (HARTMANN

1840 [cf. HEPPELL 1966, 87]).

Zool. Anz. 242 (2003): 157–167© by Urban & Fischer Verlaghttp://www.urbanfischer.de/journals/zoolanz

Later on, HERRMANNSEN (1847) and PILSBRY (1895,76) selected H. despreauxii and H. preauxii, respec-tively, as type species of Obelus. Even though theincorrect spelling “preauxii” was used by HARTMANN

(1842, as a citation of the misspelled name in theexplanations of D’ORBIGNY’s plate of 1842, not as anew nominal taxon), the nominal taxon “Hel.Despreauxii” used by HERRMANNSEN was included inObelus [ICZN, art. 67.2.1. and 67.6.]. Therefore weaccept the selection of the type species by HERR-MANNSEN (1847). The subsequent selection of a typespecies by PILSBRY (1895) was based on a supposedtaxon “H. preauxii Hartmann, 1842” which in fact is acitation of the misspelling “preauxi“ in D’ORBIGNY

(1842) of H. despreauxii d’Orbigny, 1839.The anatomy of the genital system of Obelus wasunknown and therefore species were grouped into dif-ferent taxa on the basis of conchological charactersonly. MOUSSON (1872) and WOLLASTON (1878)assigned six Canarian nominal taxa (representing fourspecies) of Obelus with a conical, conspicuously orna-mented shell, to Helix (Turricula), with two specieswhich do not belong to Obelus. The six nominal taxaare Helix despreauxii d’Orbigny, 1839, and H.despreauxii immodica Mousson, 1872, from GranCanaria, H. moderata Mousson, 1857, from Fuerte-ventura (first named Helix despreauxii moderataMousson, 1857), H. cyclodon d’Orbigny, 1836, from“Canaries”, and H. mirandae R. T. Lowe, 1861, and H.nodosostriata Mousson, 1872, from La Gomera. Thetwo further taxa assigned to Helix (Turricula) byMOUSSON (1872) are H. melolontha Shuttleworth,1852 (SHUTTLEWORTH 1975, pl. 6 fig. 12), which mostprobably is not a Canarian taxon (WOLLASTON 1878),and H. inops Mousson, 1872, which belongs toMonilearia Mousson, 1872. The anatomy of the geni-tal system of Monilearia inops was described and fig-ured by SCHILEYKO & MENKHORST (1997, fig. 1) whoincorrectly determined their material as Monileariaphalerata (Webb & Berthelot, 1833).Confusion also accompanied the taxonomic history ofHelix cyclodon and allies. MOUSSON (1872) regardedH. cyclodon as a junior synonym of H. pumilio “Chem-nitz, 1795”, described from Mogador (Morocco) [aninvalid name, I.C.Z.N. Opinion 184 (1944) and Direc-tion I (1954); valid name: Trochus pumilio Dillwyn,1817], and expressed doubt on its occurrence in theCanary Islands. WOLLASTON (1878) disagreed withMOUSSON (1872) in considering H. cyclodon and T.pumilio two different species, and also regarded H.nodosostriata as a junior synonym of H. mirandae.GUDE (1896) grouped H. despreauxii, H. moderata, H.mirandae and H. cyclodon in Helicella (Obelus) andPILSBRY (1895) in Helicella (Helicella) sectionObelus, respectively. ODHNER (1931) placed the same

species in the genus Xeroptycha Monterosato, 1892,and ZILCH (1960), BACKHUYS (1975), RICHARDSON

(1980) and VAUGHT (1989) finally included Obelusin Trochoidea Brown, 1827.The shells of these Canarian and Moroccan species aresimilar to those of other species occurring from Lybiato Syria and Palestine, such as Helix tuberculosa Con-rad, 1825. Due to this similarity, PILSBRY (1895) andGERMAIN (1921) incorrectly included several of themin Obelus, under Helicella (Helicella) section Obelusor Helix (Obelus), respectively. However, FORCART

(1976) described the genital system of H. tuberculosa -PILSBRY’s (1895, pl. 69 fig. 12) drawing of this speciesrepresents a juvenile specimen- and other Palestinianspecies, which all belong to Trochoidea (Xerocrassa).The conchological similarity between these taxa andObelus is probably due to convergence.The aim of the present paper is to define the genusObelus, to indicate its geographic distribution, and todiscuss its phylogeny. The genital systems of the extantCanarian Obelus species are figured, suggesting thatObelus belongs to the family Cochlicellidae, the rela-tionships of which are discussed.

2. MATERIALAND METHODS

2.1. Material

2.1.1. Dissected specimensThe material used for the dissections is in the Department ofAnimal Biology, La Laguna University, La Laguna, Tenerife,Canary Islands, Spain.

2.1.2. Museum material studied (shells)Obelus despreauxii (d’Orbigny, 1839): 3 syntypes of Helixdespreauxii (BMNH 1854.9.28.33, collection d’Orbigny)and 3 syntypes of Helix despreauxii immodica (ZMZS505047, leg. Fritsch, 1863).Obelus moderatus (Mousson, 1857): 4 syntypes of Helixmoderata (ZMZS 505023/4, leg. Hartung, 1856).Obelus pumilio (Dillwyn, 1817): 44 shells (SMFD 97293/4,288741/14, 288743/9 and 288745/17), from betweenMogador and Agadir (Morocco).Obelus cyclodon (d’Orbigny, 1836): A syntype of Helixcyclodon (BMNH 1854.9.28.38; collection d’Orbigny).Obelus mirandae (R. T. Lowe, 1861): Holotype of Helixnodosostriata (ZMZS 505019, leg. Fritsch, 1868).Obelus moratus (Mousson, 1872): A syntype of Helix morata(ZMZS 505016, leg. Fritsch, 1863).

2.2. MethodsSeven conchological and nine genital system measurementswere taken and four indices were calculated (Tabs. 1, 2). Theterms ‘shell’ and ‘specimen’ in the list of the material studiedrefer to empty shells and live specimens, respectively, and

158 M. IBAÑEZ et al.

The genus Obelus and its relationships 159

Tab. 1. Dimensions (in mm) and indices of the Obelus shell. A: shell height; B: shell diameter; C: body whorl height; D: aper-ture length; E: aperture width; F: umbilicus diameter; Gº: aperture inclination angle (in degrees); n: number of measured spec-imens. Values: M, maximum; m, minimum; X, average; CV: Pearson’s variation coefficient (in %).

A B C D E F Gº B/A C/A D/E B/F n

O. despreauxiiM 6.50 8.20 4.50 3.40 4.40 1.10 48.59 1.56 0.72 0.79 17.50m 4.60 7.00 3.30 2.50 3.50 0.40 34.85 1.25 0.66 0.67 7.18X 5.47 7.67 3.82 2.97 3.98 0.60 42.71 1.41 0.70 0.74 13.60 16CV 6.06 4.78 6.06 7.50 6.72 22.92 7.16 4.54 1.96 2.99 18.38

O. moderatusM 6.90 10.00 4.50 3.50 5.20 1.50 64.99 2.02 0.74 0.77 14.60m 4.20 7.80 3.10 2.90 4.00 0.60 28.94 1.22 0.56 0.62 5.57X 5.54 8.55 3.80 3.10 4.49 1.09 40.67 1.57 0.69 0.69 8.26 15CV 9.24 6.67 7.72 4.30 8.26 15.78 15.26 12.64 5.27 5.84 18.26

O. pumilio (Gran Canaria Island)M 8.20 8.30 4.65 3.00 4.10 0.70 66.44 1.09 0.57 0.79 15.61m 6.40 6.70 3.30 2.40 3.50 0.50 43.60 0.95 0.50 0.64 10.50X 7.30 7.45 3.88 2.75 3.84 0.58 53.50 1.02 0.53 0.72 12.92 10CV 5.84 4.92 6.06 6.91 3.60 9.31 11.90 3.21 3.55 4.98 7.21

O. cyclodon BMNH syntype6.48 6.72 3.62 – 3.50 – – 1.04 0.56 – – 1

O. moratusM 4.80 8.00 4.00 3.20 4.10 1.10 64.59 1.88 0.87 0.89 11.80m 3.95 6.90 3.30 3.00 3.50 0.60 40.18 1.58 0.80 0.78 7.18X 4.36 7.42 3.63 3.11 3.74 0.79 48.95 1.71 0.83 0.83 9.66 9CV 5.07 5.06 5.62 1.90 4.88 16.74 11.50 4.97 2.00 3.72 12.00

O. discogranulatus sp. nov.5.10 10.50 4.35 4.20 5.40 1.50 43.67 (holotype)

M 6.80 11.15 5.50 4.70 5.90 1.50 62.00 2.14 0.90 0.96 8.64m 4.30 8.30 3.20 3.05 4.00 1.10 35.38 1.58 0.74 0.73 6.33X 5.11 9.71 4.20 3.98 4.95 1.30 47.17 1.91 0.82 0.81 7.51 26CV 6.54 6.06 6.36 7.97 9.23 9.93 9.53 6.10 3.40 5.32 6.44

Tab. 2. Dimensions (in mm) of the adult genital system of Obelus. A: atrium – penis retractor muscle; B: atrium – epiphallusend; C: flagellum; D: duct of bursa copulatrix; E: distal (A1) portion of appendicula; F: A2 portion of appendicula; G: A4 por-tion of appendicula; H: A5 portion of appendicula; I: branchs number of H; n: number of measured specimens. Values: M,maximum; m, minimum.

A B C D E F G H I n

O. despreauxii M 2.5 10.0 0.8 5.8 2.5 1.8 2.1 2.3 4 3m 2.2 9.0 0.7 5.1 1.2 1.3 1.7 2.1 3

O. moderatus M 2.1 10.0 1.2 5.8 5.0 2.0 2.8 3.1 4 3m 1.7 8.5 0.9 4.0 2.0 1.2 2.0 2.0 3

O. moratus M 2.5 12.7 1.3 7.0 2.3 1.8 4.3 5.9 3 2m 1.7 10.2 1.2 5.4 2.2 1.3 3.5 5.4 3

O. discogranulatus sp.nov. M 2.0 13.5 1.1 6.0 1.8 2.3 3.8 6.5 3 2m 2.0 12.0 1.0 5.8 1.2 1.5 2.5 4.9 3


Fig. 1. Shell (scale bar: 5 mm); a) dorsal view; b) frontal view; c) ventral view. A) Obelus despreauxii (D’Orbigny, 1839), ElCharco de Maspalomas (Gran Canaria, UTM: 28RDR4168). B) Obelus moderatus (Mousson, 1857), Llano de La Angostura(Fuerteventura, UTM: 28RES5008). C–F)Obelus pumilio (Dillwyn, 1817), showing its conchological variability. C) 75 km NAgadir (Morocco; SMFD 288741; leg. H. Kaltenbach). D) Arinaga (Gran Canaria, UTM: 28RDR6182). E) Ojos de Garza(Gran Canaria, UTM: 28RDR6291). F) 4 km E El Aaiun port, 500 km SW Agadir.


Fig. 2. Shell (scale bar: 5 mm); a) dorsal view; b) frontal view; c) ventral view. A) Obelus cyclodon (D’Orbigny, 1836), syn-type (BMNH 1854.9.28.38). B)Obelus mirandae (R. T. Lowe, 1861), Degollada de Peraza (La Gomera, UTM: 28RBS8609).C) Obelus moratus (Mousson, 1872), Morro del Cavadero (Fuerteventura, UTM: 28RES6207). D) Obelus discogranulatusAlonso & Groh sp. nov., holotype (TFMC MT 0379).

‘proximal’ and ‘distal’ refer to the position in relation to thegonad. The calculation of the number of shell whorls followsKERNEY & CAMERON (1979, 13).The species Obelus despreauxii (Fig. 1A), O. moderatus (Fig.1B), O. pumilio (Figs. 1C–F), O. cyclodon (Fig. 2A), O.mirandae (Fig. 2B), and O. moratus (Fig. 2C), are concholog-ically well described in the literature (D’ORBIGNY 1836, 1839,1842; HARTMANN 1842, 1843; LOWE 1861; MOUSSON 1857,1872; L. PFEIFFER 1848-1877, 1870-1876; WOLLASTON 1878;PILSBRY 1895; SHUTTLEWORTH 1975). Therefore we includehere only photographs of their shells and measurements fortaxonomical comparisons with O. discogranulatus sp. nov.

2.3. AbbreviationsA1–A5 stimulator portions; terminology after SCHILEYKO

(1984, 39, fig. 18).AIT: Alonso & Ibáñez collection, Department of Animal

Biology, University of La Laguna, Tenerife, CanaryIslands, Spain.

CGH: K. Groh private collection, Hackenheim, Germany.CHB: R. Hutterer private collection, Bonn, Germany.ICZN: International code of Zoological Nomenclature

(I.C.Z.N. 1999).I.C.Z.N.: International Commission on Zoological Nomen-

clature.

3. RESULTS

3.1. Genus Obelus Hartmann, 1842

Type species: Helix despreauxii d’Orbigny, 1839, bysubsequent designation of HERRMANNSEN (1847) [dif-fering spelling: Helix preauxi in D’ORBIGNY (1842)and Helix preauxii in HARTMANN (1842)].

IUCN: International Union for Conservation of Nature andNatural Resources.

BMNH: The Natural History Museum, London, England.SMFD: Natur-Museum Senckenberg, Frankfurt/Main, Ger-

many.TFMC: Museo de Ciencias Naturales de Tenerife, Canary

Islands, Spain.ZMZS: Zoologisches Museum der Universität, Zürich,

Switzerland (Collection Mousson).


Fig. 3. Genital system and anatomical details. A) Obelus despreauxii (D’Orbigny, 1839), Arinaga (Gran Canaria, UTM:28RDR6182). B–C) Obelus moderatus (Mousson, 1857), Jorós (Fuerteventura, UTM: 28RES5804). C) detail of connectionbetween A1 and A2 appendicula portions. D) Obelus moratus (Mousson, 1872), Pico de la Zarza (Fuerteventura, UTM:28RES6308). E) Obelus mirandae (R. T. Lowe, 1861), juvenile, Topogache (La Gomera, UTM: 28RBS7508). F–H) Obelusdiscogranulatus Alonso & Groh sp. nov., paratype, Valle de Mal Nombre (Fuerteventura, UTM: 28RES6609). G) detail ofpenial papilla. H) detail of the muscular sac portion. Scale bar: A, B, D–F, 2 mm; C, G, H, 1 mm.

Fig. 5. A) Actual (full symbols)and fossil/subfossil (empty sym-bols) geographical distributionof the Canarian species ofObelus; contour lines’ equidis-tance: 400 m; symbols represent1 × 1 km UTM squares. B) Driftof a buoy showing the whirl-pools formed by a fringe of themain NE-SW ocean current(data from the MAST III Canigoproject were provided by Dr. E.D. Barton, University of Wales,Bangor).


Fig. 4. Comparison between the generalized penialappendix of the Orthurethra (A) and the appendicula of thegenera of Cochlicellidae (B–E). B) Obelus. C) Monilearia.D) Cochlicella. E) Prietocella. A, redrawn after HAUSDORF

(1998, fig. 1); C–E, based on the drawings of SCHILEYKO &MENKHORST (1997, figs. 1, 4, 3 and 6F, respectively).

3.1.1. Description

Shell small (diameter <12 mm, height <9 mm), elon-gate conical to depressed discoidal, with an angulated tokeeled periphery and an open, usually narrow umbili-cus. Kidney sigmurethric with a very small secondaryureter. Bursa copulatrix independent of diaphragm.There is a peculiar vaginal stimulator appendix („appen-dicula“) composed of four portions (Fig. 3). Wide andlong distal A1 portion arising from the distal end of thevagina, opposite to the point of entry of penis into geni-tal atrium. Curved, finger-like A2 portion attached api-cally to the former and ending proximally in a blind,well-developed, muscular sac (maybe a dartless sty-lophore, filled with mucous gland secretion), openinginto A1 portion through a small propulsatory organ witha very narrow duct. Slender tubular A4 portion, the ductof the mucous glands arising laterally from the muscularsac duct, splitting apically in 3–4 digit-like, thin, rami-fied mucous glands of the branched proximal A5 por-tion. The structure of A2 andA4 in particular are diagnos-tic for the genus. Penis with a perforated penial papillaand without calcareous envelope. With epiphallus andthin flagellum. Penis retractor muscle inserting at theepiphallus. Right ommatophoran retractor independentof penis and vagina.

3.1.2. Phylogenetic relationships

SCHILEYKO & MENKHORST (1997) placed the generaCochlicella A. Férussac, 1820, Prietocella Schileyko& Menkhorst, 1997, and Monilearia Mousson, 1872,in the Cochlicellidae, a family characterized mainly byits well-developed vaginal appendix with 1–3 apical,simple, or ramified tubular mucous glands.The phylogenetic relationships of this group were quitevague, as SCHILEYKO (1991) had indicated earlier. Thevaginal appendix has a simple structure in Cochlicellaand Prietocella. It was not known in Obelus, and insuf-ficiently known in Monilearia until SCHILEYKO &MENKHORST (1997) provided a description. Cochlicel-la and Monilearia were traditionally classified as Heli-coidea in the Helicidae, Helicellinae (THIELE 1931;ZILCH 1960; RICHARDSON 1980). SCHILEYKO (1972)placed Cochlicella in a subfamily Cochlicellinae of theHygromiidae because of its highly conical shell andpeculiarities of the reproductive apparatus. NORDSIECK

(1987, 1993) placed both genera in the hygromiid sub-family Monachinae for the presence (in Cochlicella, aswell as in Euomphalia Westerlund, 1889, andMonacha Fitzinger, 1833) of 23 chromosomes, a char-acter regarded as an apomorphy of the subfamily. Heclassified Cochlicella and Monilearia in the tribeCochlicellini because of the presence of an appendicu-la. SCHILEYKO & MENKHORST (1997) regarded theCochlicellidae as a family of Xanthonychoidea, related

to Aegistinae (Bradybaenidae), an opinion that wasmainly based on the similarity between the stimulators.WADE et al. (2001) placed Cochlicella acuta (O. F.Müller, 1774) and Cernuella virgata (Da Costa, 1778)in the Helicellidae on the basis of a large-scale molecu-lar phylogenetic analysis of the Stylommatophora;they combined Helicellidae and Bradybaenidae withHelicidae, Polygyridae, Helminthoglyptidae, Hygro-miidae and Camaenidae in the supposedly mono-phyletic Helicoidea.Several authors, such as NORDSIECK (1985), HAUSDORF

(1998), ALONSO et al. (2000) and BARKER (2001)argued that most of the different stimulator types arehomologous. HAUSDORF (1998, fig. 1) compared thegeneralized type of the Orthurethra and his ancestralstate model of the Limacoidea sensu lato. The appen-dicula of Obelus is similar to both the penial appendixof the Orthurethra (Fig. 4) as well as to the stimulatoryorgans of other Stylommatophora, except that the A3portion is not present, but according to HAUSDORF

(1998) the segment A3 was already reduced in the stemform of the Helicoidea.Obelus belongs to the Cochlicella group because itshares an appendicula with the other genera in thattaxon, differing only in its anatomy (Fig. 4). InMonilearia and Prietocella the A2 portion of theappendicula lacks the muscular sac that is present inObelus. Only Cochlicella has a very rudimentary sac,without the propulsatory organ of the A2 portion pre-sent in Obelus, Monilearia and Prietocella. Finally, theA4 portion of the appendicula is absent in Prietocella,which has a propulsatory organ (as assumed by SCHI-LEYKO & MENKHORST 1997, 54) split into three or fournodules.The stimulatory organ of the Cochlicella group is verysimilar to the hypothetical ancestral state of the stimu-lator in the Helicoidea (HAUSDORF, 1998) and differsclearly from that of the Helicellidae and Hygromiidae,with 1-2 dart-bearing stylophores, additional dartlessstylophores (= “accessory sacs”) and additional sepa-rate glands (NORDSIECK 1987). The Cochlicella groupis not closely related to the Bradybaenidae or to xan-thonychid families since the similarities of their stimu-latory organs are symplesiomorphies. Moreover, thespecies of Bradybaenidae have 28–29 chromosomes(haploid number) in contrast to 23 in Cochlicella(NORDSIECK 1987).The Cochlicella group should be recognized as a fami-ly of its own, the Cochlicellidae, closely related to theHelicellidae (sensu WADE et al. 2001) and the Hygro-miidae.

3.1.3. Ecology and biogeographyIn the Canary Islands (Fig. 5A) the species of Obelususually live in dry areas. Only O. moratus prefers more


humid habitats, like O. mirandae and O. moderatus insome localities. Only O. moratus reaches the summitof the highest mountains in Fuerteventura. O. cyclodon(Fig. 2A) does not occur in the archipelago; our surveyyielded no evidence for its existence in the Canaries.O. pumilio was found in fossil or subfossil deposits inGran Canaria and Fuerteventura, however (Figs.1D–E). The type locality for O. moderatus (Lanzarote)and subsequent citations from Lanzarote by MOUSSON

(1872), L. PFEIFFER (1870–1876) and WOLLASTON

(1878) are most probably wrong; we found this speciesin Fuerteventura only.From a biogeographic point of view, the presence ofObelus in Fuerteventura and its absence from Lan-zarote are remarkable. Both islands are separated by anarrow strait of less than 40 m depth, and certainlywere interconnected in the past during times of lowersea level. It is possible that Obelus once colonizedLanzarote, but was subsequently exterminated by theextensive lava fields which cover large parts of theisland now. Also the presence of Obelus on La Gomeraand its absence from Tenerife are remarkable. Themain NE-SW ocean currents would make a coloniza-tion of Tenerife from the northeast more probable.Recently fringes of the main currents were found toform whirlpools (E. D. BARTON, in litt. 2001, Fig. 5B)however, which may offer an explanation. Suchwhirlpools could shift a floating vegetation raft aroundTenerife and send it to La Gomera.

3.2. Taxonomic descriptions

3.2.1. Family Cochlicellidae Schileyko, 1972Type genus: Cochlicella A. Férussac, 1820Diagnosis: Helicoidea with a long vaginal stimulatoryorgan (“appendicula”) composed of four portions. Dis-tal A1 portion arising from the distal end of the vaginaat the level of the opening of penis into the genital atri-um. A2 portion attached apically to the former, withouta dart-bearing stylophore but sometimes with a muscu-lar sac. Slender tubular A4 portion; the duct of themucous glands generally present, splitting at tip in 3–4digit-like, thin and farther ramified mucous glands ofthe branched proximal A5 portion. Flagellum alwayspresent.

3.2.2. Obelus discogranulatus Alonso & Groh, sp. nov.Type material: Holotype (TFMC MT 0379; leg. M. R.Alonso and M. Ibáñez, 17-02-94). Paratypes: 4 speci-mens and 197 shells collected between 1987 and 1994;deposited in TFMC (MT 0380/1) CGH (3 shells), CHB(3 shells) and AIT (4 specimens, and 190 shells).

Type locality: Degollada de los Canarios, JandiaPeninsula, Fuerteventura (UTM: 28RES6510, 350 m).

Etymology: The epithet discogranulatus refers to thediscoid, granulated shell.

Distribution, habitat, and conservation status: Thisspecies is endemic to the Jandia Peninsula (southernFuerteventura), occurring in a small area of about 20km2 to the southwest of the ‘Jable’ (sand dunes occupy-ing the La Pared isthmus), at altitudes between 40 and400 m. Psammophilous plants and shrubs dominate thevegetation. Conservation status proposed: “Vulnera-ble” (VU, B1, B2c), according to the IUCN (1994,1996) Red List categories.

Soft parts: Body uniform pale-brown, mantle whitish.Pallial complex occupying slightly more than 2/3 ofthe body whorl. Kidney 3.5 mm long; heart 5 mm long;lung 11 mm long.

Shell: Shell (Tab. 1; Fig. 2D) depressed, nearly dis-coidal, with a strongly keeled periphery and 41/2–43/4whorls. Umbilicus moderately large (approximately13% of shell diameter). Apertural margins, except forthe columellar one, straight, simple, not expanded orreflexed but with an internal strong white rib in adultspecimens. Protoconch smooth. Teleoconch with veryclose, irregularly granulated, radial ribs. Shell pale yel-lowish with numerous irregular pale brown streaks andthree darker brown interrupted spiral bands, one dor-sal, one ventral and the third along the periphery.

Genital system (2 specimens dissected): Atriumslightly shorter than distal male duct (between atriumand penis retractor muscle insertion), which measuresonly 1/5 to 1/6 of the length of the very long, spirallycoiled, proximal portion of the epiphallus. Very short,thin flagellum. Penis retractor muscle inserting at theepiphallus. Penis widened, containing a large perforat-ed papilla. Vagina very short, its diameter equal to thatof the free oviduct. Duct of bursa copulatrix long, end-ing in a peculiar, very elongated, clown-shoe-likebursa copulatrix, similar to that of Cochlicella and Pri-etocella. Branched glandular portion (A5) of appendic-ula split into 3 digit-like thin ducts.

Differentiation: O. discogranulatus sp. nov. differsfrom O. moratus in the discoidal shell form and thelarger size (Figs. 1–2; Table 1). Regarding the genitalsystem, O. discogranulatus sp. nov. differs from allother Obelus species in the shortest A1 portion of theappendicula (Fig. 3; Table 2) and the largest atrium.

3.2.3. Species groups in ObelusConchologically, two species groups can be recog-nized within Obelus. In O. despreauxii, O. moderatus,O. pumilio, O. cyclodon and O. mirandae (Figs. 1,2A–B) the shell has a conical spire and is spectacularly


ornamented with an elegant, deeply dentate keel, gen-erally accompanied in the middle of each whorl by asecond keel. The latter keel is similar to the main one,but slightly less prominent in O. despreauxii, O. mod-eratus and O. pumilio, reduced in O. mirandae, andobsolete in O. cyclodon. In a second group, with O.moratus and O. discogranulatus sp. nov. (Fig. 2C–D),the shells differ by a convex-depressed shape with anangulated periphery (O. moratus), or a depressed,nearly discoidal shape (O. discogranulatus sp. nov.).The shell sculpture is far less conspicuous here, andalso the shell aperture has an internal white rib in fullygrown specimens. Both groups could be natural enti-ties because of their shell characters, but anatomical orzoogeographical data supporting this assumption arenot known.

Acknowledgements. Our special thanks go to H. Nordsieck(Aarbergen-Rückershausen, Germany), Dr. G. Peters (Bonn)and two anonymous referees for the critical review of themanuscript and their valuable information and suggestions;to Dr. F. Naggs (BMNH), Dr. R. Janssen (SMFD) and Mrs. T.Meier (ZMZS), for the loan of type material from museumscollections under their care; to G. Falkner (Hörlkofen, Ger-many) for his kind help in searching bibliographic data; toDr. C. Castillo (La Laguna), for her distributional data of O.pumilio from the island of Fuerteventura, and to Dr. E. D.Barton (Bangor) for his MAST III Canigo project data pro-vided to us.

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Authors’ addresses: Miguel IBAÑEZ(corresponding author),María R. ALONSO, Department of Animal Biology, La Lagu-na University, E-38206 La Laguna, Tenerife, Canary Islands,Spain; e-mail: [email protected]; Klaus GROH, Mainzer Straße, 25, D-55546 Hackenheim,Germany, e-mail: [email protected]; Rainer HUTTERER, Zoologisches Forschungsinstitut undMuseum Alexander Koenig, Adenauerallee 160, D-53113Bonn, Germany, e-mail: [email protected]

Received: 19. 04. 2002Revised: 25. 01. 2003Accepted: 20. 02. 2003Corresponding Editor: E. GITTENBERGER


Documents

The Genus Obelus Hartmann, 1842 (Gastropoda, Pulmonata, Helicoidea) and its Phylogenetic Relationships