Clavatula Nathaliae (Mollusca: Gastropoda: Conoidea: Turridae) a New Species from Gabon: an Old Mystery Finally Elucidated
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Clavatula nathaliae (Mollusca: Gastropoda: Conoidea: Turridae) a new species from Gabon: an old mystery finally elucidated Frank Nolf Pr. Stefanieplein, 43/8 – B-8400 Oostende [email protected] Key words: GASTROPODA, TURRIDAE, Clavatula nathaliae, Clavatula gabonensis, Introduction: On p.242 in their ‘Compendium of Gabon, new species. Seashells’ Abbott & Dance (1982) illustrated a shell called ‘Clavatula gabonensis Melvill, 1923. Abstract: In recent literature confusion Senegal. Offshore; uncommon.’ In fact they took originated after J. Knudsen’s misidentification of over a misinterpretation by J. Knudsen (1952) in some shells belonging to the ‘Atlantide’ his report on the shells dredged by the ‘Atlantide’ Expedition material as Clavatula gabonensis. Expedition. A few years later P. Bernard (1984) The real C. gabonensis Melvill, 1923 is illustrated figured the same shell in ‘Coquillages du Gabon’ here and a new species-name is introduced for a as ‘Clavatula strebeli f.’ He described the shell as mollusc living from Ghana to Gabon. follows: ‘Turreted shell with elongated siphonal Comparison is made with the related Clavatula canal and two raised spiral cords on the keel. strebeli Knudsen, 1952. Colour pale pink with small well spaced brown blotches on the cords. Trawled in the equatorial Abbreviations: zone.’ All these authors illustrated the same FN: Private collection of Frank Nolf, Oostende, species under different names, but none of them Belgium. took the opportunity to describe it as new to PEMARCO: Pêche maritime du Congo. science. In this paper it will be demonstrated that RBINS: Royal Belgian Institute for Natural the new species is very different from the real Sciences, Brussels, Belgium. Clavatula gabonensis Melvill, 1923 as well as ZMC: Universitets Zoologisk Museum, from Clavatula strebeli Knudsen, 1952. Copenhagen, Denmark. From: Bernard, P.A., 1984. Coquillages du Gabon, pl. 48, fig. 181 From: Abbott & Dance, 1982. Compendium of Seashells, p. 242 Clavatula nathaliae sp. nov. (Plate I, figs 1-8; Plate II, figs 9-15; Plate III, figs 16-19; Plate IV, figs 20-23) Type material: depth of 50 m. 30 January 1946. ‘Atlantide’ Holotype: 30.8 mm (ZMC) - Ghana, West Africa Expedition (Station 85). (5°37’ N. 0°38’ E.). Dredged in grey mud at a Neptunea, vol.5, n°3 1 October 2006 1 Paratypes: 1. 24.4 mm (ZMC) - Ghana, West Derivation of name: The species-name is Africa (5°37’ N. 0°38’ E.). Dredged in grey mud derived from the name of my oldest daughter at a depth of 50 m. 30 January 1946. ‘Atlantide’ Nathalie. For convenience sake the last vocal ’e’ Expedition (Station 85). in ‘Nathalie’ has been omitted. 2. 27.2 mm (ZMC) - Nigeria, West Africa (5°59’ N. 4°36’ E.). Dredged in mud at a Habitat: From 15 to 90 m, in mud. depth of 17 m. 15 February 1946. ‘Atlantide’ Expedition (Station 101). Geographic range: From Ghana to Gabon 3. 32.7 mm (ZMC) - Ghana, West (West Africa). Africa (3°55’ N. 6°08’ E.). Dredged in mud at a depth of 55-88 m. 18 February 1946. ‘Atlantide’ Discussion: In the shell literature of the past fifty Expedition (Station 106). years, Clavatula nathaliae has been confused 4. 25.3 mm (FN) - off Libreville, with C. gabonensis Melvill, 1923 and C. Gabon, West Africa. Trawled at a depth of 30 m. strebeli Knudsen, 1952. As all problems started 5. 25.4 mm (FN) - off Libreville, with the misidentification of J. Knudsen in his Gabon, West Africa. Trawled at a depth of 30 m. description of the samples from the ‘Atlantide’ 6. 26.3 mm (FN) - off Libreville, Expedition, I here reproduce the original text and Gabon, West Africa. Trawled at a depth of 30 m. figure of Clavatula gabonensis by Melvill (1923): 7. 28.4 mm (FN) - off Libreville, ‘Shell pyramidate, smooth throughout, eleven Gabon, West Africa. Trawled at a depth of 30 m. whorled, the two nuclear white, plain, and 8. 29.5 mm (FN) - trawled at 20 m bulbous, the remainder concave, well exhibiting off Lagos, Nigeria. incremental lines of growth, elegantly and regularly ornamented with fluctuate brown lines, Description: Shell turreted with 11 whorls and and, on the body-whorl, longitudinal flames; the an elongated siphonal canal. The protoconch periphery is conspicuously angular and consists of one or two whorls. The following two bicarinate, mouth ovate, outer lip with median whorls have about 20 slightly developed, oblique angle, sinus wide, canal moderate, very slightly ribs on the lower part. Two raised spiral cords recurved, columellar margin straight. run on the keel, a prominent ridge is followed by Long. 25, lat. 10 mm. a lower less conspicuous one, just above the Hab. Gaboon, West Africa.’ distinct suture. The upper part of the body whorl is smooth, but on the lower part and partly on the Melvill continues: ‘To this the only allied species siphonal canal, a number (about 10-12) of spiral is C. lelieuri, Récluz. Both species agree in ridges are present. No axial sculpture, except for complete smoothness of surface, with no sign of numerous close-set growth lines, which are tubercles or spines which characterize all others flexuous across the subsutural band. The of the genus. But it differs from the species just surface of the shell is rather shiny. The colour is named in the very conspicuous bicarinate angle pale pink or white, with fluctuate brown lines or at the periphery of the body-whorl, thereby flames and small well spaced brown blotches on rendering the shell attenuate at either extremity, the cords. The brown colour is stronger on the while the character and disposition of the brown carinae than on the remaining part of the whorl. markings differ likewise.’ From: Melvill, J.C., 1923. Descriptions of twenty-one species of Turridae (Pleurotomidae) from various localities in the collection of Mr. E.R. Sykes. Proceedings of the Malacological Society of London, vol. XV, part IV, Pl. V. Fig. 11: Clavatula gabonensis Melvill, 1923. Neptunea, vol.5, n°3 1 October 2006 2 Clavatula gabonensis Melvill, 1923 Cape Fria, Namibia, SW Africa. Trawled by Belgian fishermen (PEMARCO). 19.2 mm (FN). C. gabonensis Melvill, 1923 Type – Gabon, West Africa ‘C. gabonensis’ by J. Knudsen Neptunea, vol.5, n°3 1 October 2006 3 ‘Clavatula gabonensis Melvill, 1923’ From: Knudsen, J., 1952. Marine Prosobranchs of Tropical West Africa collected by the “Atlantide” Expedition 1945-46. Vidensk. Medd. fra Dansk naturh. Foren. Bd. 114: pl. I, fig. 11. Neptunea, vol.5, n°3 1 October 2006 4 According to Knudsen the specimens dredged by present. Most of the shell is completely without the ‘Atlantide’ Expedition (three samples: station an axial sculpture, except numerous close-set 85, station 101 and station 106) ‘could easily be growth lines, which are flexuous across the identified from the description and figure of subsutural band. The colouration is as described Melvill’. That means the specimens illustrated on by Melvill except that the brown colour is p. 3 all represent the same species, but already stronger at the carinae than on the remaining at first glance it is evident this is a wrong part of the whorl.’ conception. In spite of his statement ‘could easily From the above text, we can conclude that be identified’ the Danish scientist must have Knudsen was clearly influenced by Melvill’s been in serious doubt, because in his remarks he expression ‘the very conspicuous bicarinate goes on with an enumeration of several angle at the periphery of the body whorl’, which characteristics that are different in both shells: is in fact not conspicuous at all but obtuse and ‘The present shells are, however, somewhat indistinct. Instead of completing the description more slender and have a longer canal than the by Melvill, J. Knudsen added a number of single specimen on which the original description differences, which in fact results in the is based.’ He continues: ’on the basis of the description of another species. I thus conclude present material a number of details not the shells of the ‘Atlantide’ Expedition belong to a mentioned by Melvill can be described: The species different from the real C. gabonensis protoconch consists of about 2 somewhat Melvill, 1923. C. nathaliae is a much slenderer inflated whorls. The successive whorl has about shell with the typical two spiral cords on the 20 slightly developed, oblique ribs on the lower shoulder and 10-12 spiral cords on the lower part part. The ribs are crossed by a small number (2- of the body whorl. C. gabonensis only has one 4) of very delicate spiral lines. On the remaining raised spiral cord near the suture. Anyway the part of the shell a fine spiral sculpture can be surface of C. gabonensis is mostly smooth. seen under the microscope. It consists of a number of incised spiral lines, particularly distinct Another species very close to C. nathaliae is on the middle of the whorl, but they are also Clavatula strebeli Knudsen, 1952. found on both the upper and lower carina. On the (Plate V, figs 24-31; Plate VI, figs 32-37; Plate lower part of the body whorl and partly on the VII, figs 38-49). siphon, a number (about 10) of spiral ridges are We hereby illustrate the real Clavatula strebeli compared to the figure of ‘C. gabonensis’ by Knudsen. From: Knudsen, J., 1955. Marine Prosobranchs of Tropical West Africa (Stenoglossa). In: Atlantide Report , n°3, Scientific Results of the Danish Expedition to the Coasts of Tropical West Africa 1945-1946, Copenhagen, pl. IV, fig. 18. ‘Clavatula gabonensis Melvill, 1923’ From: Knudsen, J., 1952. Marine Prosobranchs of Tropical West Africa collected by the “Atlantide” Expedition 1945-46. Vidensk. Medd. fra Dansk naturh.