Zoologische Mededelingen, 82 (June 2008)
Redefinition of Thapsia Albers, 1860, and description of three more helicarionoid genera from western Africa (Gastropoda, Stylommatophora)
A.J. de Winter
Keywords: Cameroon; Côte d'Ivoire; Gabon; Africa; Gastropoda; taxonomy; land snails; Helicarionoidea; Thapsia; Saphtia; Pseudosaphtia; Vanmolia; Urocyclidae.
As presently used, the helicarionoid genus Thapsia Albers, 1860 embraces a large, heterogeneous assemblage of species. As a first step in the revision of this group of taxa, the genus Thapsia (type species Helix troglodytes Morelet, 1848) is redefined anatomically and conchologically. In the absence of alcohol-preserved material of T. troglodytes, Thapsia ebimimbangana spec. nov. from Cameroon and T. wieringai spec. nov. from Gabon are described to characterize the soft parts morphology of Thapsia. Three new genera are introduced, viz. Saphtia gen. nov. (type species S. granulosa spec. nov.), Pseudosaphtia gen. nov. (type species P. brunnea spec. nov.) and Vanmolia gen. nov. (type species Thapsia sjoestedti d’Ailly, 1896). A second species of Saphtia, S. lamtoensis spec. nov., is described to illustrate the large conchological variability of the genus. The identity of Helix calamechroa Jonas in Philippi, 1843 (now Saphtia calamechroa stat. nov.), Thapsia buchholzi Bourguignat, 1885, and Thapsia rosenbergi Preston, 1909 is briefly discussed.
The genus Thapsia Albers, 1860 was erected, as subgenus of Nanina Gray, 1834, non Risso, 1826, for Helix troglodytes Morelet, 1848 from Gabon based only on shell characters. Numerous African species have been attributed to the genus, which, even with the scanty anatomical data available, clearly constitutes a heterogeneous assemblage. Adam (1960) listed about 120 nominal species of Thapsia, since then only Verdcourt (1982) has added several species from East Africa. Species attributed to Thapsia have a low-spired, thin, yellowish or brownish, rather feature-less shell. These species have at least some fine spiral sculpture on the postembryonic shell, but the sculpture of some large species is decussate or even beaded. The smallest taxa (well under 10 mm) listed by Adam (1960) have since been assigned to genera of other families like the Euconulidae (e.g. De Winter & Van Bruggen, 1992). Gudeella Preston, 1913 (type Thapsia masukuensis E.A. Smith, 1899) is often used as generic or subgeneric heading for species with shells up to about 14 mm diameter, but is also considered a junior synonym of Thapsia (e.g. by Herbert & Kilburn, 2004: 259). The latter opinion is certainly incorrect, preliminary dissections indicate that Gudeella is a heterogeneous assemblage of taxa, none of which is closely related to Thapsia as defined below (De Winter, unpublished). For the species with shell diameters ranging from about 15 to 30 mm, two supra-specific names are presently available: Thapsia [type Helix troglodytes Morelet, 1848] and the monotypic taxon Megathapsia Raemaekers, 1959 [type Thapsia (Megathapsia) dartevellei Raemaekers, 1959, from the DR Congo (former Belgian Congo)]. Adam (1960) severely criticized the introduction of Megathapsia, the taxon being based solely on insufficient conchological characters of a single specimen, supposedly differing from Gudeella in having a larger shell with a comparatively wide umbilicus, and from Thapsia by the sculpture of spiral lines only. However, the taxon name Megathapsia was validly introduced and might have to be used once the anatomy of the type species is known.
Due to convergence in shell characters, conchological delimitation of most species attributed to Thapsia s.l. is very difficult, and only a handful of papers provide anatomical data, rendering the recognition of nominal species among the numerous undescribed ones virtually impossible.
The present paper is part of a project dealing with the larger-shelled species (about 15-30 mm diameter) from tropical western Africa (Senegal to Gabon) formerly attributed to Thapsia. Study of the anatomy of some tens of populations from a geographically wide range in western Africa indicated that at least four genera are needed to accomodate the species studied, some of which are conchologically very similar. As a first step in the revision of this extensive material, the genus Thapsia is defined both anatomically and conchologically, and is differentiated from three newly erected genera, in addition to which five new species are described.
Material and methods
Shell measurements were made by vernier callipers. Methodology for counting whorls follows Kerney & Cameron (1979: 13). Measurements of anatomical structures were made from camera lucida drawings of material preserved in ethanol 70%. Estimates of the extent of the pallial cavity (expressed as the approximate proportion of the last whorl occupied) are crude and likely to be influenced by the degree of contraction of the animal upon fixation. Linear measurements of the pallial organs were obtained from drawings of the pallial roof stretched out after a number of lateral incisions.
In the descriptions, the genital atrium is considered to be distally oriented relative to the proximally positioned ovotestis. Descriptions of internal soft parts focus on the distal genitalia. Organs located in the earlier whorls were studied only occasionally, because of difficulties to extract the proximal soft parts without severely damaging the fragile shell.
Genital organs of some specimens were longitudinally or transversely sectioned at various positions and drawn to provide some understanding of their gross internal organization; denominations of the tissues are to be viewed as tentative, and need confirmation by histological study.
Repositories and their abbreviations
The Natural History Museum, formerly British Museum (Natural History), London, U.K.
Musée Royal d’Afrique Centrale, Tervuren, Belgium.
Nationaal Natuurhistorisch Museum Naturalis, formerly Rijksmuseum van Natuurlijke Historie, Leiden, The Netherlands.
Swedish Museum of Natural History, Stockholm, Sweden.
left shell-lap of mantle
right shell-lap of mantle
bursa copulatrix (gameolitic gland)
duct of bursal copulatrix
maximum shell diameter
penis retractor muscle
shell height/shell width ratio
number of whorls
Class Gastropoda Cuvier, 1797
Superfamily Helicarionoidea Bourguignat, 1877
Thapsia Albers, 1860
Nanina (Thapsia) Albers, 1860: 56.
Type species.— Helix troglodytes Morelet, 1848 (by original designation).
Diagnosis.— Large-shelled helicarionoid with decussate shell sculpture above the periphery. Foot with long caudal horn. Penis consisting of two morphologically distinct parts, with a papilla-like structure at the transition of distal to proximal penis. Distal penis wider than proximal portion. Vagina greatly swollen at junction with bursa copulatrix and free oviduct. Ampulla of spermatophore elongate-oval, not convoluted. Tail of spermatophore with complex spiny ornamentation comprising a collar of coarse thorns and various longitudinal rows of short and longer spines, those of one row particularly long and asymmetrically branched.
Description.— Shell diameter of adult specimens about 25 mm at 5½-6½ whorls. Shell pale yellowish-brown, thin and fragile, partly translucent. Periphery of adult shell more or less angular except for the rounded last quarter whorl. Embryonic whorls smooth, later whorls with fine decussate sculpture that becomes gradually coarser on younger whorls; in adult specimens sculpture on last whorl often equally prominent or even less pronounced than on penultimate one. Decussate sculpture not extending below the periphery on the shell base, where only wavy spiral lines are present. Cephalopodium completely retractable into shell. Tail region about as long as anterior portion but less wide, dorsum rounded. Frontal area of head between ommatophores evenly covered by tubercles. Genital opening slightly posterior to right lower tentacle. Furrows between tubercles on tail unite into larger, obliquely oriented grooves, which unite to a more or less straight median furrow along dorsum. Pedal grooves aulacopod. Sole tripartite, central field slightly narrower than outer fields, more strongly so in tail region. Hind end of foot in preserved specimens vertically truncate, with distinct caudal horn above caudal foss; caudal horn length in preserved specimens variable, it may be partly retracted. Male distal genitalia comprise of a bi-partitioned penis, a roundish epiphallic caecum on which penis retractor muscle inserts, and a well-developed epiphallus and flagellum. Flagellum contains axial thread. Vagina strongly swollen at junction with duct of bursa copulatrix and proximal free oviduct. Proximal free oviduct partly enlarged and thick-walled (capsular gland). Spermatophore large, rigid-horny (chitinous), with a large, elongate-oval, not convoluted, sperm-containing head (ampulla), followed by a long convoluted tail with a narrow central canal and complex spiny ornamentation. This ornamentation consists of two longitudinal, parallel rows of long spines, those of one row particularly long and asymmetrically branched, and three longitudinal rows of simple short spinules on last part of tail in addition; a collar of coarse thorns is present directly behind the ampulla, the thorus point towards the tail canal opening, all other spines point in opposite direction towards the ampulla. Tail canal of exchanged (i.e. not self-produced but received from partner) spermatophore with simple terminal opening, through which the sperm is released.
This description of the anatomy is based on characters shared by the two species described in this paper and confirmed by observations on specimens from various other populations from Gabon and Cameroon (De Winter, unpublished), the anatomy of the type species of Thapsia being unknown (see below).
Remarks.— Thapsia species can strongly resemble large members of Saphtia gen. nov. by their shells, but differ, among others, by the possession of a distinct caudal horn, in many aspects of the morphology of the distal genitalia, and by the very different spermatophore morphology. Pseudosaphtia gen. nov. and Vanmolia gen. nov. have distinctly smaller and differently sculptured shells, as well as different soft parts morphologies.
The shell of Thapsia species can continue to grow for at least half a whorl more after the animal has reached sexual maturity. Therefore adult shell size per se is not a very good character for species recognition without taking the number of whorls into account.
Hardly any information of the soft anatomy of true Thapsia species has been published. Pfeffer’s (1883) brief account of “Thapsia troglodytes” from Bonjongo, Cameroon, apparently constitutes the only – rather incomplete – anatomical description of a true Thapsia species in the existing literature. Watson’s (1934) observations of “Thapsia troglodytes” from the Gold Coast (Ghana), Verdcourt’s (1982) description and illustration of the genital anatomy of an unnamed species from Togo, and Schileyko’s (2002) account of “Thapsia pellucida Gould, 1843” from Côte d’Ivoire relate to a genus that is described below as Saphtia gen. nov. Schileyko’s (2002) notes were intended as a kind of definition of the genus Thapsia, but the anatomical data provided do not refer to the same genus as the depicted shell of “Thapsia troglodites” [sic!] from Fernando Poo, which is a species of true Thapsia indeed. Baker’s (1941: 212) observations on “Thapsia troglodytes (Morelet), approaching T. pellucida (Gould), from near Tringa, Lake Nyassa”, refer to a different genus not dealt with in the present paper.
Schileyko (2002) incorrectly attributed the authorship of Thapsia to Von Martens, who was editor of the second edition of Albers’ book. Von Martens (1860: iv) clearly indicated that the authorship of most new taxa in the book is attributable to Albers, these being described in the manuscript he received from Albers’ widow. To these new (sub)genera the name of Albers was added as author in the heading, in agreement with article 50.1 of the ICZN (1999).
Thapsia troglodytes (Morelet, 1848)
Helix troglodytes Morelet, 1848: 351 “in Guinea provincia Gabon”. Morelet, 1858: 11, pl. 1 fig. 1 (shell). 3 syntypes BMNH Reg. No. 1822.214.171.1243-5.
?Helix troglodites [sic!], Petit de la Saussaye, 1852: 67, pl. 1 figs 14-16 (shell). “La côte du Gabon”.
Remarks.— The syntype series of T. troglodytes in the BMNH consist of three shells, the largest of which is marked as “potential lectotype”, probably by Connolly, but a type designation appears not to have been published. The type locality is rather imprecise (Morelet, 1848: “in Guinea provincia Gabon”; Morelet, 1858: “... Gabon, à quelque distance du littoral...”), so that it is not possible to collect fresh specimens at the type locality. This is especially unfortunate since anatomical and conchological variation among the Gabonese populations studied strongly suggests the presence of various species, of which two will be described below. The exact provenance of the type shells is unlikely to be far from the coast, where the French had settlements/fortifications as early as 1846, when M. de Folin collected the type specimens (Morelet, 1858). The type series could even belong to two different species, given differences in shell characters (table 1). The largest of the three syntypes has fewer whorls, a more depressed spire (and consequently a wider aperture), and a more strongly angulate periphery than the other two, which are more similar in these respects. Still, size, outline and sculpture of all three shells fall within the range of variation known for other Thapsia populations, and I was unable to match shells of recently collected Gabonese specimens unequivocally with any of the type shells.
Table 1. Dimensions of syntypes of Helix troglodytes Morelet, 1848 in The Natural History Museum, London (18126.96.36.1993-5).
The anatomy of the type species of Thapsia thus remains unknown. However, there appears to be no urgent need to know the anatomy of the type species for defining the genus. None of the dissected specimens with large shells and decussate sculpture from various localities in northern, central and southern Gabon anatomically resemble species of Saphtia gen. nov. (see below) or other helicarionoid Thapsia-like genera described from outside the area under study. Species conchologically similar to Thapsia, but belonging to Saphtia were not found among dozens of such specimens and populations examined from Cameroon either. In fact, Saphtia species with large, Thapsia-like shells with decussate sculpture (unlike smaller-shelled Saphtia species) have so far not been found east of Togo, whilst specimens anatomically confirming to true Thapsia have not yet been found west of Cameroon (De Winter, unpublished observations). It seems therefore most likely that the soft parts of the type specimens of Thapsia resembled those described below for two species from Cameroon and Gabon. Should a species conchologically similar to, but anatomically distinct from, Thapsia as taken here, be discovered in the coastal regions of Gabon, a neotype for T. troglodytes may need to be designated, in which case the ICZN should be requested to invalidate the syntype series. The diversity of Thapsia will be further explored in later papers (De Winter, in prep.).
Thapsia ebimimbangana spec. nov.
Material.— Holotype: [sta. CAM.132] Cameroon, Sud Province, Chromolaena odorata-covered fallow land close to the village of Ebimimbang, 3°02.8’N, 10°26.1’ E, alt. ~ 70 m, 30.v.1996, A.J. de Winter & E.-J. Semengue leg. (RMNH.MOL.110333, shell dry, soft parts in alcohol). Paratypes (all paratypes were collected less than 2 km to the south of the type locality by A.J. de Winter & E.-J. Semengue): [sta CAM.046] Locus typicus, 12.x.1995 (RMNH.MOL.110334/ 1 adult, shell dry, soft parts in alcohol; MRAC/ 1 specimen in alcohol). [sta. CAM.50a] Undisturbed high forest on slope ~ 1 km WSW of Saa, 3°03’N, 10°26’E, alt. ~ 70 m, 17.x.1995, crawling on tree trunk (RMNH.MOL.110335/ 1 juv. specimen in alcohol). [sta. CAM.130a] Undisturbed swamp forest near Ebimimbang, 3°02.8’N, 10°26.1’E, alt. ~ 70 m, 30.v.1996, in understorey vegetation (RMNH.MOL.110336/1 adult, shell dry, soft parts in alcohol). [sta. CAM.113a] Young secondary forest on south bank of the Lokoundjé River, close to Ebimimbang, on palm 1.5 m above forest floor, 3°02.1’N, 10°28.1’E, alt. ~ 70 m, 23.v.1996 (RMNH.MOL.110337/ 1 adult, shell dry, soft parts in alcohol, 1 juv. in alcohol). [sta. CAM.040] Patch of young secondary forest among Chromolaena odorata-covered fallow land close to the village of Ebimimbang, 3°02.8’N, 10°26.1’E, alt. ~ 70 m, 10.x.1995 (RMNH.MOL.110338/ 1 adult, shell dry, soft parts in alcohol. [sta CAM.43a] Undisturbed high forest on flat terrain ~ 1 km WSW of Saa, 3°03’N, 10°26’E, alt. ~ 70 m; 11.x.1995, in understorey vegetation (RMNH.MOL.110339/ 1 (semi)adult specimen in alcohol). [no station number] Chromolaena odorata-covered fallow land close to the village of Ebimimbang, 3°02.8’N, 10°26.1’E, alt. ~ 70 m, 25.v.1996; pair in copula (RMNH.MOL.110340/ 1 specimen, shell dry, soft parts in alcohol; second specimen intact in alcohol).
Diagnosis.— Distal portion of penis rather short, about one fifth of length of proximal penis, with 2 or 3 strong pilasters on inner wall. Spermatophore large, tail with about 13 long, asymmetrically (unilaterally) branched spines, individual spines split in up to 5 minor (second order) spines.
Shell (fig. 1).— Thin and fragile, partly translucent, yellowish-brown, periphery weakly angulate, whorls moderately convex, spire low-conical. Aperture roundish-oval, height/width ratio ~ 0.8. Sculpture as described for genus. Size: D = 24-27 mm, H = 14-17 mm, H/D = 0.55-0.64, W = 6-6½ (n = 14).
Fig. 1. Thapsia ebimimbangana spec. nov.; A-C, different views of holotype shell (RMNH). Actual shell width 24.5 mm.
Fig. 2. Thapsia ebimimbangana spec. nov., pair in copula on Araceae leaf. Cameroon, Ebimimbang (paratypes in RMNH).
Pallial region (fig. 7).— Both right and left shell laps well developed, left shell lap slender and more elongate than right one. Pallial cavity takes up about 0.8 whorls. Pallial roof well vascularized, densely pigmented by small and larger blackish spots not coalescing into a band. Kidney about 20 mm long, slender, hardly flaring posteriorly, less than half the length of pallial cavity. Pericardium about one third of kidney length.
Jaw (fig. 8).— Oxygnathous, pale brown, about 2.5 mm wide, with a short median projection.
Radula (fig. 9).— Teeth rather elongate. Formula (half a row) R - ~ 26 - ? Due to folding of radula marginal teeth were not countable, but well exceeding number of laterals. Central tooth little smaller than flanking laterals, mesocone of central tooth moderately elongate, clearly longer than basal plate. Ectocones of marginal teeth much larger than endocones. Transition of laterals into marginals gradual, endocone disappearing at about the 26th lateral.
Reproductive organs (fig. 10).— Atrium longer than wide, internally with 3-4 coarse longitudinal pilasters below the distal penis and many more fine plicae extending from the vagina; this bipartite atrium division is already discernable without further dissection. Upper atrium attached to (internal) body wall by strong, muscular strands of tissue. Penis (between atrium and epiphallic caecum) about 20 mm long, bipartite, portions very unequal in length. Distal penis rather short, thin-walled, internal lumen spacious, with few and prominent vertical pilasters and a short, papilla-like structure at transition to proximal penis. Proximal penis rather long, about five times longer than distal portion, thick-walled and muscular, gradually tapering towards the epiphallic caecum, internal wall around narrow lumen with about 6 somewhat irregularly fringed longitudinal ridges. Epiphallic caecum small, ovate, diameter not exceeding width of epiphallus, thin-walled. Penial retractor muscle long and slender, inserting on caecum and originating from columellar muscle complex. Epiphallus much shorter than proximal penis. Flagellum slightly shorter than epiphallus, little convoluted, thick-walled and muscular. Internal glandular wall of flagellum surrounded by thick outer layer of muscular tissue. Vas deferens little convoluted along its entire course, last portion before entering epiphallus somewhat widening. Upper penis connected to epiphallus and part of vas deferens by tissue fibres (not shown in drawing). Vagina close to atrium thin-walled and slender, internal wall with few stronger longitudinal ridges and finer ones in between. More proximally, at junction of bursal duct, vagina strongly swollen, thick-walled and muscular, attached to internal body wall by strong muscles. Lumen of swollen portion of vagina narrow, with deep crypts on one side; the thick inner stratum may be glandular. Free oviduct branches off at about widest portion of vagina, and more proximally becomes wide and seemingly glandular (capsular gland). Duct of bursa copulatrix thick-walled and muscular close to vagina, wall thickness becoming much less towards bursal sac. Bursal sac very voluminous in specimens containing a spermatophore.
Spermatophore (fig. 11).— Ampulla about 16 mm long and at most 2.0 mm wide. Tail length about 25 mm. Transition of ampulla into tail marked by a sharp curve, a collar of about 10 coarse thorns pointing away from the ampulla and a single small denticle just anterior of thorn collar. A longitudinal row of simple, initially erect, spines follows a short, spineless section posterior of collar. After four spines, there is a second parallel row of 13 much longer spines. First and smallest of these spines with one or two incisions, the following increasing in length to about 2.5 mm, asymmetrically branched into up to 5 minor (second order) spines; last two spines in this row shorter and simpler than preceding ones. One long spine in one spermatophore (out of three spermatophores examined) has an extra, dichotomous split resulting in 7 minor spines; this is probably an aberration. Simple spine row extends farther posterior on tail than branched spines, these spines gradually change in aspect from erect or slightly bent to distinctly curved. Last portion of tail with three parallel longitudinal rows of simple, tiny spinules, arranged spirally around tail axis towards hind tip.
Fig. 11. Thapsia ebimimbangana spec. nov., different views of spermatophore from bursa copulatrix of paratype (RMNH).
Ecology.— This species occupies a wide range of habitats: from undisturbed high forest to fields (established by slash and burn practices) and fallow land overgrown by the non-native bush Chromolaena odorata. In forests, adults and large juveniles were nearly always found rather sparsely on the forest floor or crawling a few meters high on the bark of tree trunks after rain; live small juveniles were collected in larger numbers exclusively on both green and dead leaves in the understorey vegetation 1-3 m above the floor.
Etymology.— The name is derived from the village of Ebimimbang, close to the type locality. The epithet ebimimbangana is to be used as a noun in apposition.
Remarks.— Thapsia ebimimbangana differs from T. wieringai spec. nov. by a higher, larger and less strongly angulate shell, a much shorter distal penis, and by a larger spermatophore with more numerous, longer and more strongly branched spines. These two species are described as new since their provenance is sufficiently far from the surmised coastal Gabonese origin of the type shells of T. troglodytes (see above).
The description of the anatomy of “T. troglodytes” by Pfeffer (1883) is too imperfect to be of much use. Pfeffer (1883) dissected material from Bonjongo, Cameroon that he had received from the Berlin museum. Von Martens (1876) reported and described as “Nanina troglodytes Morelet” material from the same locality, and all this material was probably part of the same lot, collected by Buchholz. Pfeffer possibly dissected the same specimen of which Von Martens (1876) illustrated the tail (von Martens, 1876, pl. 1 figs 9b, 9c). Unfortunately no alcohol-preserved material could be found in Berlin. When distinct, this species should bear the name Thapsia buchholzi Bourguignat, 1885, Bourguignat’s description being based on the illustration of the shell in Von Martens (1876, pl. 1, fig. 9). Bourguignat (1885) erroneously located the type locality in Mozambique.
No other true Thapsia species appear to have been formally described so far.
Thapsia wieringai spec. nov.
Material.— Holotype: Gabon, Région Woleu-Ntem, Monts de Cristal, 1 km SE. of Tchimbélé, 0°36.9’N 10°23.8’E, ca. 600 m alt., J.J. Wieringa leg., 17.ix.1994 (RMNH.MOL.110341/ shell dry, soft parts in alcohol). Paratypes (all material collected by J.J. Wieringa): same data as holotype (RMNH.MOL.110342/ 1 juv. specimen in alcohol). 0.5 km SW. of Tchimbélé, 0°37’N 10°24’E, primary rainforest, 16.v.1990 (RMNH.MOL.110343/ 1 specimen in alcohol). Tchimbélé, 0°37’N 10°24’E, 18.v.1990 (RMNH.MOL.110344/ 1 dry shell). Tchimbélé, 0°37’N 10°24’E, 28.ii.1990 (RMNH.MOL.110345/ 1 dry shell). Around Tchimbélé, collected between 14.xii.1989 and 26.i.1990 (RMNH.MOL.110346/ 2 subadult specimens in alcohol, 1 shell dry collection, soft parts and specimen with damaged shell in alcohol (ex colln. De Winter 8142); (RMNH.MOL.110347/ 1 adult, shell dry, soft parts in alcohol (ex colln. De Winter 8815). Tchimbélé, primary rainforest, 27.i.1990 (RMNH.MOL.110348/ 1 adult, shell dry, soft parts in alcohol (ex colln. De Winter 8140). 1 km ESE. of Tchimbélé, 0°37’N 10°25’E, ca. 600 m alt., primary rainforest, 15.v.1990 (RMNH.MOL.110349/ 1 adult, shell dry, soft parts in alcohol (ex colln. De Winter 8813). Tchimbélé, Pinus plantation, 0°37’N 10°24’E, alt. 570 m, 26.iv.1990 (RMNH 97613, 1 adult specimen, shell dry, soft parts in alcohol) (ex colln. De Winter 8141). 0.5 km SW. of Tchimbélé, 0°37’N 10°24’E, alt. 600 m, primary rainforest, 24.iv.1990, pair in copula (RMNH.MOL.97611/ 1 specimen shell dry, soft parts in alcohol, other specimen with damaged shell in alcohol). 2 km SSW. of Tchimbélé, 0°36.5’N 10°23.8’E, alt. 440 m, 26.i.2005 (RMNH.MOL.110350/ 1 adult, shell dry, soft parts in alcohol).
Diagnosis.— Shell periphery more or less angulate in front view. Distal portion of penis about equally long as proximal portion. Spermatophore tail with comparatively few spines, only about 7 of which are long and branched into 2 - 4 minor (second order) spines.
Shell (fig. 12).— Rather thin and fragile, partly translucent, yellowish-brown but very fresh specimens often with a subtle purplish hue. Periphery of last whorl strongly angulate, except for about the last ¼ whorl which is more rounded (but often still distinctly angular, especially in smaller adult shells). Spire depressed-conical with comparatively flat whorls. Aperture oval-lunate, height/width ~ 0.7. Sculpture as described for genus. Size: D = 21.5-26.0 mm, H = 12.9-15.4, H/D = 0.54-0.62, W = 5.5-6 mm (n = 7).
Fig. 12. Thapsia wieringai spec. nov.; A-C, different views of holotype shell (RMNH). Actual shell width 23.8 mm.
Cephalopodium.— Anterior part of cephalopodium (head to mantle rim) more or less dark-grey, becoming paler towards tail. Caudal appendage rather long, darker than rest of tail.
Pallial region.— Pigmentation quite variable; either consisting of distinct, small blackish spots not coalescing into a band, or more diffuse brownish pigmentation extending over most of the pallial roof, except for the portion above the strikingly white kidney.
Jaw.— Not examined.
Radula.— Not examined.
Reproductive organs (figs 13, 14).— Atrium rather slender, internally with fine, irregular longitudinal ridges. Proximal and distal portion of penis about equally long, entire penis length (between atrium and epiphallic caecum) about 20 mm. Distal penis almost twice as wide as proximal penis, wall of distal penis with deep longitudinal invaginations (externally discernable through the penial sheath), internally resembling strong pilasters. Transition of distal to proximal penis more or less abrupt, with internally a kind of penial papilla. Proximal penis not strongly tapering towards epiphallic caecum, rather muscular and thick-walled, lumen narrowed by fine irregularly fringed longitudinal ridges and tubule-like structures. Epiphallic caecum rather small and inconspicuous. Penial retractor muscle inserts on epiphallic caecum; its point of origin appears to vary between individuals: either the diaphragm, or the columellar muscle complex. Epiphallus somewhat shorter and less wide than proximal penis. Flagellum strongly convoluted, about as long and wide as epiphallus. Vagina distinct, slender distal portion internally with 3-4 rather irregular longitudinal ridges that become more prominent further proximally, with fine irregular plicae in between. Vagina strongly swollen at junction with bursa copulatrix, both externally and on cross-section not appearing muscular, separated from the muscular distal portion of bursal duct by a shallow depression just proximally of where the proximal free oviduct continues; strong strands of musclar tissue from this constriction attach vagina and adjoining bursal duct to the internal body wall. Bursal duct distally rather wide and muscular, somewhat laterally flattened (rather than bulbous) with narrow lumen, internal wall with strong longitudinal ridges; more proximally bursal duct strongly tapering towards the wide bursal sac.
Spermatophore (fig. 15).— Ampulla elongate-oval, about 13 mm long and at most 1.5 mm wide, not convoluted. Tail collar with about 8 coarse, incised thorns, preceded by a single, small inconspicuous denticle. Tail about 24 mm long, ornamented by a row of 4 simple erect spines, followed by 7 long, branched spines, with partly parallel to these a second short longitudinal row of 5 simple, curved spines. Largest, most complex, spine about 1.4 mm long, branched into 4 minor spines. Posterior portion of tail comparatively straight with three parallel longitudinal rows of simple, tiny spinules. Terminal opening of tail canal simple.
Fig. 15. Thapsia wieringai spec. nov., A-B, different views of spermatophore from bursa copulatrix of paratype (RMNH).
Ecology.— This species was found on the forest floor as well as in the understorey, but the collector did not differentiate between adults and juveniles. The habitat was mostly primary rainforest at around 600 m elevation, but some specimens were also collected in a pine tree (Pinus sp.) plantation.
Remarks.— This species differs in various aspects from T. ebimimbangana, most conspicuously by the generally smaller, more depressed adult shell with fewer whorls, in proportions and internal morphology of distal and proximal penis, and in the much less elaborate ornamentation of the spermatophore. Many adult specimens, especially the small-shelled ones, have a strongly angulate shell periphery. This may be a paedomorphic character, juvenile Thapsia shells are invariably strongly keeled, and sexually mature specimens have not necessarily reached their maximum shell size.
Specimens from the pine tree plantation seemed to possess a shell slightly differently coloured as compared to the ones collected in rainforest (dull
brown, without purplish hue), but no significant anatomical peculiarities could be detected, and all are considered to be conspecific.
Etymology.— The species is named after Dr Jan Wieringa, who spent months in the forests around Tchimbélé studying the flora, and collected a considerable number of snails, among others this Thapsia species.
Saphtia gen. nov.
Type species.— Saphtia granulosa spec. nov.
Diagnosis.— Fully shelled helicarionoid with poorly developed caudal horn, a long verge inside the distal penis and a muscular ring on the distal vagina. Spermatophore ampulla elongate and convoluted, tail with short, unbranched spines; margin of tail canal opening reflected and incised.
Description.— Adult shell diameter between 15 and 25 mm, very thin and fragile, wider than high, periphery of adult shell rounded to distinctly keeled. Postembryonic sculpture of shell either decussate-granulose (large species) or consisting of fine spiral lines only. When present, decussate sculpture extends to shell base. Sole tripartite. Caudal horn above caudal foss poorly developed. Distal portion of penis comparatively wide, containing long verge. Epiphallic caecum globular and conspicuous, at least as wide as epiphallus diameter. Epiphallus and flagellum well developed. Flagellum contains axial thread. Penis retractor inserts on epiphallic caecum. Vagina close to atrium partly surrounded by well-demarcated, swollen muscular band. Free oviduct proximally of junction with bursa copulatrix (capsular gland) distinctly widened and thick-walled. Spermatophore rigid, pale-yellowish, with an elongate, convoluted sperm ampulla, followed by a long, narrow, convoluted tail; tail with two spirally arranged rows of simple spines that decrease in size towards posterior tip. Opening of narrow tail canal with disc-like reflected and partly incised margin, resulting in a flower-like appearance.
Remarks.— Large Saphtia species can conchologically be very similar to Thapsia, but in such coarse-sculptured Saphtia shells, the decussate sculpture extends to the shell base, in contrast to the Thapsia species examined so far. However, any identification to genus level should preferably be verified by soft part characters. The shell characters of helicarionoids are of such a generalized nature that they are of limited taxonomic value and only apply in a limited geographical area; in view of the poor knowledge of western African helicarionoids, the possibility of additional radiations with similar shells cannot be excluded.
Etymology.— Saphtia is an anagram of Thapsia, pointing to the conchological resemblance between both genera.
Saphtia granulosa spec. nov.
Material.— Holotype: Côte d’Ivoire, Forêt de Banco near Abidjan (no coordinates or other locality information on label), J.J. Van Mol leg., viii.1968 (MRAC 795.167, shell and dissected soft parts). Paratypes: same data as holotype (MRAC MRAC 302.305/ ca. 35 undissected paratypes; RMNH.MOL.110351/ 1 specimen, soft parts in alcohol, shell dry; RMNH.MOL.110353/ 4 damaged or juvenile shells. Côte d’Ivoire, Banco National Park, ~ 5°25’N, 4°03’W, alt. 100 m, closed forest, J.J. Wieringa leg., 1.ix.2001 (RMNH.MOL.110352/ 1 juvenile specimen in alcohol).
Other material: Secondary forest near Adiopodoume, 5°12’N, 4°04’W; T. Bongers leg (RMHN.MOL. 110354/ 1 dry shell).
Diagnosis.— Shell diameter about 22-25 mm, low-conical, with strongly angulate periphery. Postembryonic whorls with distinct, comparatively coarse, decussate-granulose sculpture that extends to shell base. Mantle and pallial roof almost without dark pigmentation. Distal penis rather bulbous. Spermatophore large with comparatively coarse spines on tail, reflected margin of tail opening with deep incisions.
Shell (figs 16, 17).— Comparatively large, pale yellowish-brown, thin, brittle, low-conical, wider than high. Whorls little convex. Periphery strongly angulate, apart from the rounded last ¼ whorl. Aperture oval-lunate. First half whorl smooth, following two whorls with fine spiral lines, thereafter sculpture finely decussate, gradually becoming coarser towards aperture, giving a somewhat granulose appearance. Decussate sculpture extends over periphery to shell base, becoming finer and less conspicuous towards the umbilicus. Sculpture noticeably finer near upper suture than near lower suture. Umbilicus narrow, but open. Size (adult specimens): D = between 22 and 25 mm, H = 12-14, H/D = 0.54-0.59, W = 5-5¼ (n = 5).
Fig. 17. SEM photographs of shell sculpture (paratype MRAC). A, sculpture on third whorl close to lower suture; B, sculpture central part last (fifth) whorl (scale bar A-B = 100 µm).
Cephalopodium (fig. 18).— Colour uniformly pale (tentacles and dorsum included), length in fully relaxed preserved specimens about 50 mm. Tail (in preserved specimens) longer than anterior portion, somewhat laterally compressed, dorsum rounded. Genital opening slightly posterior to right lower tentacle. Area between ommatophores covered by close-set tubercles. Caudal horn poorly developed. Caudal foss long vertical slit. Sole tripartite, anteriorly fields about equal in width, posteriorly central field markedly narrower than outer fields.
Pallial region.— Both right and left shell laps well developed, left shell lap more elongate than right one. Pallial cavity takes up about half a whorl. Mantle and pallial roof pigmentation limited to some brownish pigment around blood vessels and above kidney. Even in a comparatively fresh alcohol-preserved specimen there are only few, small blackish spots.
Jaw (fig. 19).— Oxygnathous, reddish brown, about 2.7 mm wide, with prominent median projection.
Radula (fig. 20).— Formula (half a row): R - ~ 20 - ~ 57. Mesocone of central tooth moderately elongate, slightly higher than basal plate. Ectocones of laterals much larger than endocones. Transition of laterals into marginals gradual; with one or two transitional teeth. At about the 20th lateral the endocone disappears. Marginal teeth narrower than laterals, bicuspid, with ectocone smaller than mesocone.
Fig. 20. Saphtia granulosa spec. nov., radula (paratype, MRAC). A, central tooth and first laterals (scale bar = 10 µm); B, Central tooth and lateral teeth (scale bar = 50 µm); C, transitional teeth of laterals into maginals (scale bar = 10 µm).
Reproductive organs (fig. 21).— Atrium elongate, internal wall with transverse pilasters over entire surface. Penis twisted, consisting of a wide distal portion, gradually passing into a more slender portion towards the epiphallic caecum. Distal portion of penis thick-walled and muscular, lumen with transverse strands of tissue holding tip of long verge. Proximal penis muscular, slender. Penial retractor muscle long and thin, inserting on spherical epiphallic caecum and originating from diaphragm. Epiphallus much shorter than penis. Epithelium of epiphallus lumen surrounded by a thick layer of muscular tissue. Flagellum muscular, stout, about as long and wide as epiphallus, lumen lined with smooth epithelium and containing axial thread attached to apical end. Vas deferens strongly convoluted between prostate and penoviducal angle, portion between penoviducal angle and epiphallus comparatively straight. Duct of bursa copulatrix with muscular sheath, lumen lined with thick papillose epithelium; lumen narrowing at opening into bursal sac. Free oviduct widening proximally of junction with bursa copulatrix, with thick inner wall (capsular gland), passing into the proximal-most, more slender part of free oviduct through a conical papilla-like structure. Clumps of acini of ovotestis, separated by liver tissue, occupying first 2.5 whorls. Hermaphrodite duct wide and convoluted. Talon hidden within albumen gland.
Spermatophore (fig. 22).— The bursa copulatrix of one paratype contained an about 23 mm long spermatophore comprising an elongate, convoluted sperm-containing sac (ampulla) and a 1.5 times longer convoluted tail. Tail with longitudinal row of comparatively large, simple, spirally arranged spines, joined at about two-thirds down the tail by a second row of spines. Size of spines decreasing towards posterior tip of tail. Tail canal opening disc-like, two-thirds of reflected margin deeply incised.
Fig. 22. Saphtia granulosa spec. nov., spermatophore from bursa copulatrix of paratype (MRAC). A-B, different views; C, tail canal opening.
Ecology.— The type locality is probably in evergreen or wet semi-decidous lowland forest; one fresh empty shell was collected from a cultivated garden with exotic plants.
Etymology.— The epithet granulosa refers to the comparatively coarse beaded shell sculpture.
Remarks.— Shells of both ’Thapsia‘ africana (L. Pfeiffer, 1850) and ’T.’ pellucida (Gould, 1843) conchologically resemble S. granulosa and, also in view of their distribution, most probably belong to Saphtia (De Winter, unpublished). The type shell of Helix africana (in BMNH) has a less sharply angulate periphery, finer sculpture, and more whorls at about the same size. Shells of ’T.’ pellucida have coarse granulose sculpture, but are higher and thereby more conical than S. granulosa, with a compressed, but less sharply angulate periphery (Johnson, 1964: pl. 37 fig. 7). The specimens reported by Petit de la Saussaye (1852: 69) from Grand Bassam (Côte d’Ivoire) as Thapsia troglodytes may be S. granulosa.
The original sample of S. granulosa (in MRAC) included specimens of a second, much smaller species of the same genus with a shell sculpture of fine spiral lines only. These specimens have juvenile genitalia, but they are sufficiently developed to secure their generic attribution, showing that different species of Saphtia can occur syntopically.
Saphtia lamtoensis spec. nov.
Material.— Holotype: Côte d’Ivoire, Lamto “dans plantation café”, J.J. Van Mol leg., 6.viii.1968 (MRAC 795-131). Paratypes: same data as holotype (MRAC 795-131/ 35 paratypes in alcohol, shells and shell fragments of dissected specimens dry; RMNH.MOL.110335/ 1 specimen, shell dry, soft parts in alcohol; RMNH.MOL.11035x/ 2 adult and 1 juv. in alcohol). Material almost certainly stems from near the ecological research station of Lamto (about 6°13’N, 5°02’W), situated about 160 km NW. of Abidjan.
Diagnosis.— A pale brownish, comparatively small-sized species of Saphtia. Shell periphery rounded, sculpture consisting of fine spiral lines only. Reflected margin of spermatophore tail opening finely incised. Roof of pallial cavity with band of dark pigmentation.
Shell (fig. 23).— Very thin, translucent, pale brownish, low-conical, periphery of last whorl rounded. Whorls moderately convex. Embryonic whorls not demarcated from later ones, sculpture almost from nucleus onwards consisting of very fine spiral lines that continue on later whorls, thereby becoming gradually coarser; spiral lines more distant near upper suture than further down the whorl. On earliest whorls spiral sculpture visible only in very fresh shells at high magnification. Umbilicus small but open. Size (adult shells): D = 16-18 mm, H = 10-10.5 mm, H/D = 0.57-0.63, W = 4.5-5 (n = 6).
Fig. 23. Saphtia lamtoensis spec. nov., A-C, different views of holotype shell (MRAC). (actual shell width 17.8 mm).
Cephalopodium (figs 24, 25).— Basically similar to that of former species. Length of foot about 30 mm in specimens relaxed prior to fixation. After nearly 40 years in alcohol, cephalopodium greyish, without prominent pigment, only somewhat darker behind upper tentacles and on dorsum.
Figs 24-27. Saphtia lamtoensis spec. nov. paratype (MRAC). 24, tail, lateral view. 25, posterior part of sole. 26, pallial region, ventral (interior) view. 27, jaw.
Pallial region (fig. 26).— Pallial lobes unpigmented. Right and left shell lap well developed. Pallial cavity occupying about half a whorl. Roof of pallial cavity with small, elongated dark spots alongside hindgut, coalescing into diffuse band. Roof of cavity above kidney (largely above primary ureter) with a conspicuous dark band.
Jaw (fig. 27).— Reddish brown, about 1.7 mm wide, and comparatively high; median projection not prominent, cutting edge rather irregular in all three specimens examined.
Radula (fig. 28).— Formula (half a row) R - 18 - ~ 33. Mesocone of central tooth lanceolate, markedly longer than basal plate. Endocones of lateral teeth smaller than ectocones. Endocone disappears at about 18th lateral. Marginals narrower than laterals, bicuspid, ectocone smaller than mesocone.
Reproductive organs (fig. 29).— Distal penis wide and twisted, gradually passing into a more slender proximal portion. Distal penis thick-walled, lumen with strands of tissue, surrounding tip of long verge. Penial retractor muscle long and narrow, inserting on spherical epiphallic caecum and originating from diaphragm. At least in some specimens penial retractor seems branched. Epiphallus much shorter than penis. Flagellum comparatively straight, about 1.6-2 times as long as epiphallus and more slender, containing axial thread. Portion of vas deferens between prostate and penoviducal angle strongly convoluted, much less so between penoviducal angle and epiphallus. Duct of bursa copulatrix with muscular outer sheath, lumen lined with a thick papillose stratum, narrowing at opening into bursal sac. Capsular gland twice as wide as bursal duct width, longer than proximalmost portion of free oviduct.
Fig. 29. Saphtia lamtoensis spec. nov., distal genitalia of holotype (A, MRAC) and paratype (B, MRAC).
Spermatophore (fig. 30).— In several specimens the bursa copulatrix contained one fresh, intact spermatophore. Entire spermatophore about 18 mm long. Both ampulla and tail convoluted. Tail longer than ampulla, with initially a row of simple, spirally arranged spines, joined about halfway by a second row of spines. First 8 spines conical, comparatively large and prominent, remaining spines becoming flatter and smaller towards tail canal opening. About ⅔ of disc-shaped margin of tail canal opening delicately incised.
Fig. 30. Saphtia lamtoensis spec. nov., spermatophore from bursa copulatrix of paratype (MRAC); A-B, different views; C, tail canal opening.
Ecology.— Basically unknown. Specimens were collected at a coffee plantation.
Etymology.— The specific epithet refers to the type locality, Lamto, which is a long-standing research station and nature reserve at the transition of the coastal forest zone into the wooded savannah region of Côte d’Ivoire.
Remarks.— Saphtia lamtoensis is conchologically very different from S. granulosa, the type species of Saphtia, but the two species clearly belong to the same genus, given numerous shared characters of the soft part morphology and spermatophore. The shell of S. granulosa strongly resembles species of Thapsia in size, shape and sculpture, which illustrates that shells in helicarionoids are poor predictors of the phylogenetic relationships of the animals.
This species could be ‘Thapsia‘ calamechroa (Jonas, 1843), under which name specimens resembling S. lamtoensis in shell size and sculpture have been reported from much of western Africa. Helix calamechroa was described only after its shell, and the type locality (“Guinea”) is very vague. The type material seems to be hidden or lost, but the original description and illustration strongly suggests that the species should be placed in Saphtia rather than Thapsia, hence Saphtia calamechroa stat. nov. Without access to the original specimens, the specific identity of S. calamechroa remains obscure.
Pseudosaphtia gen. nov.
Type species.— Pseudosaphtia brunnea spec. nov.
Diagnosis.— Fully-shelled helicarionoid, diagnostically different from Thapsia by the comparatively small shell with fine spiral lines rather than decussate sculpture, and the simple ornamentation of the spermatophore tail, with few branched long spines and no collar of coarse thorns. Differs from smaller-shelled Saphtia species by various soft part characters shared with Thapsia, notably the distinct caudal horn, the simple posterior opening of the spermatophore tail, and the rather different morphology of the distal penis and vagina. The scattered, swollen, oval-roundish head warts appear to be a unique character for the genus.
Description.— See description of the only attributed species, P. brunnea spec. nov.
Etymology.— The name Pseudosaphtia
refers to the conchological similarity to some (smaller-shelled)
Remarks.— Pseudosaphtia is more similar in soft part characters to Thapsia than to Saphtia, e.g. the strongly swollen vagina at the junction with the bursa copulatrix, overall penis morphology and some aspects of the spermatophore; also the geographic distribution suggests the genus to be related to Thapsia rather than Saphtia.
The sample of S. brunnea (in MRAC) included specimens of two other shelled helicarionoid species, one of which is a species of true Thapsia.
The scattered, swollen, oval-roundish warts on the head appear to be a unique character for the genus.
Pseudosaphtia brunnea spec. nov.
Material.— holotype: Cameroon, Olounou (probably 2°49’N, 12°08’E, see remarks), F. Puylaert leg., 13-19-ix-1971 (MRAC 795.848, shell dry, soft parts in alcohol). Paratypes: same data as holotype (MRAC 302.306/ 14 paratypes in alcohol, shells and shell fragments of dissected specimens dry, RMNH.MOL.110356/ 2 shells dry, soft parts in alcohol; 1 entire specimen in alcohol).
Diagnosis.— Differs conchologically from the smaller Saphtia species described to date by the low-spired shell. Anatomically it is characterized by the generic characters listed above.
Shell (fig. 31).— Shell warm brown, fragile, partly translucent, rather low-spired, periphery rounded. Umbilicus narrow but open. Earliest whorls smooth, not well demarcated from later ones. Postembryonic sculpture consists of fine spiral striae over entire whorl, at some spots sculpture extremely finely decussate where spiral lines are crossed by fine radial lines. Size (adult specimens): D = 18.1-19.1 mm, H = 9.0-11.1 mm, H/D ~ 0.50, W = 5¼-5½ (n = 6).
Fig. 31. Pseudosaphtia brunnea spec. nov., A-C, different views of holotype shell (MRAC) (actual shell width 18.1 mm).
Cephalopodium (figs 32, 33).— Area on head between ommatophores and lower tentacles with scattered, oval-roundish tubercles (warts). Animal rather dark, anterior cephalopodium (apart from contrasting paler ommatophores and head warts) dark grey, followed by a cream-coloured central portion, posterior portion including caudal horn dark grey. Tail with vertical caudal foss and long, distinct caudal horn.
Figs 32-35. Pseudosaphtia brunnea spec. nov., paratype (MRAC). 32, lateral view of tail. 33, head in frontal view. 34, ventral (interior) view pallial region. 35, jaw.
Pallial region (fig. 34).— Occupying about half a whorl. Pallial roof very dark, almost black in the median sector, becoming paler laterally. Mantle lobes dark grey. Right and left shell laps well developed, more or less elongate triangular. Kidney about 8 mm long, less than half the stretched pallial cavity length.
Jaw (fig. 35).— 1.7 mm wide, with prominent median projection.
Radula (figs 36).— Formula (half a row) R - 16 - ~ 64. Mesocone of central tooth elongate, longer than basal plate. Endocone of lateral teeth smaller than ectocone, endocone disappears at about 16th lateral. Marginal teeth very long and narrow, bicuspid, ectocone smaller than mesocone, tip of both ectocone and mesocone very fine.
Reproductive organs (figs 37, 38).— Atrium rather long, internally with a strong vertical pilaster in between outlet of male and female tubes. Penis rather long, but length varies among individuals. Distal portion of penis contorted within penial tunica, wider than proximal penis. Inner wall of distal penis with vertical pilasters. Transition of proximal to distal penis marked by presence of small papilla. Proximal penis muscular, with about 9 longitudinal ridges on inner wall narrowing lumen. Penis retractor muscle narrow, inserting on smallish epiphallic caecum and originating from columellar muscle complex. Epiphallus elongate and little convoluted except at the point of entry of the vas deferens, about as long as flagellum. Epiphallus lumen narrowed by longitudinal ridges, on cross-section appearing as high papillae. Flagellum about half as wide as epiphallus, not strongly convoluted, containing axial thread. Branched spines of spermatophore tail (see below) are moulded in distal, widest portion of flagellum where crypts can be observed either protruding or by transparency. Vagina comparatively stout and muscular, with bulbous widening at junction with proximal free oviduct and bursal duct. Lumen of swollen vaginal portion narrow, at one side strongly branched. Proximal free oviduct with distinct capsular gland. Bursal duct not very long, distal portion wide and muscular with a conspicuous retractor muscle, rapidly narrowing more proximally; inner wall of bursal duct irregular-papillose. Bursal sac not very voluminous, not even when containing a spermatophore.
Fig. 37. Pseudosaphtia brunnea spec. nov., holotype (MRAC). A-B, different views of distal genitalia; C, cross-section proximal free oviduct (capsular gland); D, cross-section swollen portion vagina. Arrow indicates place where cross section is made.
Spermatophore (fig. 39).— One complete but empty (ampulla flattened) spermatophore and fragments of at least one more were found in the bursa copulatrix of three specimens each. Ampulla elongate-oval. Tail ornamented with comparatively few long spines, 5-6 of which branched, most complex spine divided in four minor spines. Last portion of tail with two rows of sharp, short spinules that disappear shortly before opening of central canal. Opening of tail canal a simple hole.
Fig. 39. Pseudosaphtia brunnea spec. nov., different views of spermatophore from bursa copulatrix of paratype (MRAC).
Etymology.— The specific epithet brunnea refers to the dark brown colour of the animal, due to the brown shell colour reinforced by the darkly pigmented soft parts.
Remarks.— There could be some confusion as to the exact location of the type locality. There are at least two, rather distant, localities with the name Olounou in Cameroon, and no coordinates or other details are provided on the label. However, the collector also collected some fish species on the same date at the locality, which are mapped to 2°49’N, 12°08’E (see http://www.fishbase.com).
Conchologically, Pseudosaphtia brunnea somewhat resembles Thapsia rosenbergi Preston, 1909, described from “Bitze” (misspelling for Bitye, 3°01’N, 12°22’E) near the Ja River in Cameroon, especially one paratype shell on which Preston (1909) noticed: “one specimen is of a much darker colour than the others..., and the margin of the suture, instead of being whitish, is of even a deeper shade of reddish brown than the rest of the shell...”. However, the holotype shell (BMNH) is rather different (shape, smaller size, paler in colour etc.) from P. brunnea, so these species are unlikely to be conspecific. In the absence of anatomical data, the generic attribution of T. rosenbergi remains unclear, but the species is unlikely to remain in the genus Thapsia in view of its shell size and sculpture.
Vanmolia gen. nov.
Type species.— Thapsia sjoestedti d’Ailly, 1896.
Diagnosis.— Shell medium-sized, very thin and brittle, capable of covering entire visceral mass and foot, differing from smaller species of Saphtia by inconspicuous but regular and close-set growth ridges below the suture and on the shell base. Free oviduct, penis and bursa copulatrix open simultaneously into atrium. Flagellum absent. Spermatophore without spiny ornamentation. Caudal appendage well-developed, overhanging strongly indented caudal foss.
Description.— See the description of the only attributed species, V. sjoestedti.
Etymology.— Vanmolia is named after the malacologist Prof. Jean-Jacques Van Mol, whose publications significantly contributed to the knowledge of African helicarionoids.
Vanmolia sjoestedti (d’Ailly, 1896)
Thapsia Sjöstedti d’ Ailly, 1896: 39, pl. 2 figs 15-20.
Material.— Cameroon, between Mundemba and Mattamani (Mundemba: 4°57’N, 8°52’E), Y. Sjöstedt leg., vi.1891. Various syntypes in alcohol (3 dissected) (SMNH), and 3 dry syntype shells (SMNH 1585A), marked as “type” on label, probably including shell illustrated by d’Ailly, 1896, pl. 2 figs 15-18. Syntype shells also present in MRAC and in Göteborg museum.
Diagnosis.— See genus diagnosis.
Shell (fig. 40).— Very thin, umbilicus narrow, partly covered by the sinuously reflected columella; periphery rounded, colour hyaline-milky, translucent. Earliest whorls smooth, the later ones with very fine, somewhat wavy, spiral striae. The later whorls are finely but regularly plicate, which is particularly visible below the suture and on the shell base. Size: D = 18.1-19.0 mm, H = 10-10.8 mm, H/D = 0.56-0.57, W = ~ 4 ¾ (n = 2).
Fig. 40. Vanmolia sjoestedti (d’Ailly, 1896), A-C, different views of syntype shell (SMNH) (actual shell width 19.0 mm).
Cephalopodium (fig. 41).— Typically helicarionoid, with tripartite sole. Tail with indented caudal foss and long, prominent caudal horn. Genital opening immediately behind right lower tentacle. All specimens examined are strongly contracted.
Figs 41-43. Vanmolia sjoestedti (d’Ailly, 1896) (syntypes, SMNH). 41, lateral view of tail. 42, pallial region. 43, jaw.
Pallial region (fig. 42).— Pallial cavity occupying about half a whorl. Pallial roof well vascularized. Mantle pigmentation of syntypes a pale reddish-brown band above the primary ureter. According to d’Ailly (1896: 40, pl. 2 fig. 19), this pigmentation band is strikingly black and branched in fresh material; the flanking white band in the original description probably represents the kidney. Heart comparatively small, occupying only about 2/7 of the kidney length. Kidney rather narrow, about half as long as stretched-out pallial cavity. Consistency of primary ureter solid, macroscopically similar to that of kidney, secondary ureter thin-walled and transparent, but becomes strongly dilated and much thicker shortly before reaching mantle edge (particularly striking in dorsal view). Pallial lobes well developed; especially right and left shell laps large and wide, rounded.
Jaw (fig. 43).— Oxygnathous, yellowish, about 1.7 mm wide, with prominent median projection.
Radula (fig. 44).— Formula (half a row,): R - 18 - >25. Teeth subequal to basal plate. Central tooth distinctly smaller than laterals, with comparatively short, rounded mesocone. Endocone of laterals smaller than ectocone, endocone absent after 18th lateral. Marginals more elongate than laterals, bicuspid with ectocone remaining smaller than mesocone.
Reproductive organs (fig. 45).— Atrium short. Oviduct, penis and bursa copulatrix open together into atrium, a vagina thus being absent or obsolete. Penis consists of three portions: a distal, thin-walled and slender portion with fine longitudinal pilasters on inner wall, abruptly widening into much more voluminous central portion which contains a long, convoluted verge; most proximal portion globular-spherical, its interior wall covered by coarse, high papillae. Penis retractor inserted on proximal penis. Vas deferens (or epiphallus, see below) opens into proximal penis through an elongate, narrow, tongue-like structure with a slit-like opening. Vas deferens very short, thick-walled, widening at about one third of its length before entering proximal penis. Flagellum or lime sac absent. Bursa copulatrix comprise of a rather wide, thick-walled duct and an elongate, thin-walled sac. Inner wall of bursal duct with coarse ridges on one side and finer papillae on the other, surrounded by layer of muscular tissue. Free oviduct long and slender, attached to inner body wall by muscle tissue.
Fig. 44. Vanmolia sjoestedti (d’Ailly, 1896), radula (syntype, SMNH). A, central tooth and first laterals (scale bar = 10 µm); B-C, central tooth and lateral teeth); D, transition of laterals into early maginals; E, marginals (scale bars B-E = 20 µm).
Spermatophore (fig. 45H).— Bursal sac of the depicted specimen contained a brownish, partly dissolved and possibly incomplete spermatophore, with no indication of a well-defined tail with spines or other ornamentation.
Fig. 45. Vanmolia sjoestedti (d’Ailly, 1896), distal genitalia (syntype, SMNH). A, external view, vas deferens cut; B, internal view distal penis; C, proximal penis longitudinally opened; D, cross-section proximal penis (other syntype);
Ecology.— According to field notes by the collector (quoted by d’Ailly, 1896: 40), the species was found in thick, humid, low forest (“Bushwald”, probably secondary vegetation), on the forest floor among rotting leaves. The species may locally occur in large numbers: Sjöstedt remarked that at one occasion he could collect a handful at a single spot.
Remarks.— Upon examination of the anatomy of syntypes, the morphology of the genitalia proved to be very different from that of Thapsia or any other fully-shelled taxon of Urocyclidae known. The systematic relationships of Vanmolia are obscure (see general discussion below).
The terminology of the various parts of the male genitalia of Vanmolia is tentative, especially since a well-defined epiphallus and flagellum are absent. The globular-spherical proximal penis externally resembles the epiphallic caecum of Thapsia, Pseudosaphtia and Saphtia species, and, like in these taxa, the penial retractor inserts on it. Its internal morphology strongly differs from the rest of the penis as well as from the wider portion of the vas deferens, and either of these parts, wholly or in part, may represent the epiphallus. The wider portion of the vas deferens on cross-section seems to differ macroscopically only by a thicker outer layer of muscular tissue from the narrower portion. The establishment of the homologies of the various organs require detailed histological studies.
General discussion: Phylogenetic relationships of Thapsia, Saphtia, Pseudosaphtia and Vanmolia
Notwithstanding their conchological similarity, Thapsia, Saphtia, and Vanmolia do not appear to be closely related. Several anatomical features suggest that Pseudosaphtia is phylogenetically closer to Thapsia than to Saphtia. It may be that some genera have closer relationships to certain slug-like taxa than to any shelled helicarionoid in the region under consideration. However, none of the (semi)slug genera dealt with by Van Mol (1970) and Van Goethem (1977) are obvious candidates at this point, though it should be realized that too little comparative data are as yet available; few helicarionoids have been dissected and many taxa probably remain to be discovered in Africa.
Vanmolia is clearly the most deviating taxon dealt with here. It shares several characters with species of the subfamily Gymnarioninae Van Mol, 1970, sometimes considered a distinct family of its own (see e.g. Schileyko, 2002), like the absence of a flagellum-like structure and the spermatophore formation taking place in the penis proper (Binder, 1976). However, there are also conspicuous differences between Gymnarion and Vanmolia: absence in Vanmolia of what Pilsbry (1919: 277-278) termed a dart sac or dart gland (glandular atrial diverticulum sensu Van Mol, 1970); a much longer caudal horn in Vanmolia than in Gymnarion; mantle lobes large and conspicuous in Vanmolia, rather small or absent in Gymnarion; distinct verge in penis of Vanmolia, penis in Gymnarion only with pilasters on inner wall (Pilsbry, 1919; Watson,1920; Degner, 1934; Binder, 1976). Binder’s (1969, 1976) work on the genus Gymnarion focused on the frontal organ (not observed in V. sjoestedti) and the internal structure of the penis, and a detailed comparison of other parts of the genital organs in a greater number of species is still outstanding.
Another option could be to assign Vanmolia to the family Rhysotinidae Schileyko, 2002, recently erected for two species of the genus Rhysotina, both endemic to Sao Tomé Island, which, like Gymnarion species, lack a flagellum and vagina.
It is even unclear whether the four genera treated in this paper and other shelled African taxa belong the same branch of the Helicarionoidea (sensu Bouchet & Rocroi, 2005). The African shelled and slug-like helicarionoids are often treated as a single family, Urocyclidae, endemic to Africa (including the Arabian peninsula). However, the African taxa seem to be quite heterogeneous and are probably polyphyletic (Bouchet & Rocroi, 2005). Some taxa may be closer to branches of the helicarionoid-ariophantoid radiation recognized outside Africa (south and southeast Asia, Australia, the Pacific islands, and Madagascar). For instance, in several anatomical characters Vanmolia superficially resembles the South Asian taxon Cryptaustenia (sensu Solem, 1966). True Urocyclidae (e.g. members of the slug genus Urocyclus
Gray, 1864, see Van Goethem, 1977) have a very different genital morphology from any of the taxa dealt with in this paper. For this reason, the name Urocyclidae for the entire African helicarionoid radiation is avoided here. Clearly, the helicarionoid group (sensu Bouchet & Rocroi, 2005) is in need of a phylogenetic analysis using both morphological and molecular data.
I thank F. Naggs (Natural History Museum London), A. Warén (Swedish Museum of Natural History, Stockholm), F. Puylaert and R. Jocqué (Musée Royal d’Afrique Centrale, Tervuren) for enabling the study of specimens from the collections under their care. J.J. Wieringa and T. Bongers (Wageningen University) kindly provided specimens. Part of the material was collected in Cameroon during a project funded by the Netherlands Foundation for the Advancement of Tropical Research (NWO-WOTRO), for which the Tropenbos Cameroon Programme provided facilities. Eric-Joel Semengue (Ebom, Came-roon) is thanked for his enthusiastic field assistance. Staff of the National Museum of Natural History, Leiden kindly assisted with the illustrations: (SEM)photographs (except fig. 2) were taken by Jeroen Goud, spermatophores were drawn by Inge van Noortwijk, and Niko Korenhof assisted with the layout of the illustrations. The manuscript benefited from the comments by Isabel Hyman, and two anonymous referees.
Edited: A.C. van Bruggen
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