Nodilittorina von Martens, 1897

Reid, DG & Williams, ST, 2004, The Subfamily Littorininae (Gastropoda: Littorinidae) in the Temperate Southern Hemisphere: The Genera Nodilittorina, Austrolittorina and Afrolittorina, Records of the Australian Museum 56, pp. 75-122 : 78-81

Nodilittorina von Martens, 1897

Littorina (Nodilittorina) von Martens, 1897: 204 (type Littorina pyramidalis Quoy & Gaimard, 1833 , by subsequent designation, Abbott, 1954: 451).

Taxonomic history. The name Nodilittorina was introduced by von Martens (1897) as a subgenus for those Littorina species with nodulose shell sculpture, but lacking the manywhorled circular operculum and apertural tooth characteristic of Tectus (now Tectarius , see Reid & Geller, 1997). In the influential classification of Thiele (1929; followed by Wenz, 1938; Clench & Abbott, 1942), Nodilittorina appeared as a subgenus of Tectarius , because of the narrow rachidian tooth. It was first used as a full genus by Abbott (1954), on the basis of comparisons of penes, radulae and egg capsules of Nodilittorina tuberculata (Menke, 1828) (now Echinolittorina tuberculata ) with those of other littorinids. He did also note the Nodilittorina -like” penes of Littorina (Melarhaphe) mauritiana ( Lamarck, 1822) (a misidentification of Austrolittorina unifasciata , see synonymy of that species below) and L. (M.) ziczac ( Gmelin, 1791) (now Echinolittorina ziczac ), in the first indication that Nodilittorina might include species without nodulose shells. Nevertheless, in his monograph of Indo-Pacific species, Rosewater (1970) still emphasized shell sculpture above anatomical characters, and included only species with nodulose or granulose sculpture in Nodilittorina . Smoothshelled species with penes resembling those of Nodilittorina (i.e. with single mamilliform gland and adjacent glandular disc, in terminology of Reid, 1989) were placed in a new subgenus, Littorina (Austrolittorina) . The first attempt to revise the classification of littorinids taking into account all available anatomical evidence was by Bandel & Kadolsky (1982). The main features of their diagnosis of Nodilittorina were: spirally striate, nodulose or granulose shell; pale basal band in aperture; narrow rachidian tooth; pelagic egg capsule sculptured with spiral ridges; penis variable, but often with single mamilliform gland and glandular disc. This definition greatly increased the number of species, because it included the smooth, striate forms formerly classified as Littorina (Austrolittorina) . It was essentially supported, with some modifications, by new anatomical information on paraspermatozoa and pallial oviducts ( Reid, 1986, 1989). This broad definition has persisted in the taxonomic literature ( Reid, 2001, 2002 a) and the most recent review listed 60 species of Nodilittorina ( Reid, 2002 b) .

However, a rigorous phylogenetic definition of the genus has proved elusive, suggesting that this large group is not a monophyletic one. The first attempt at a parsimony analysis of morphological characters of the Littorinidae included four exemplars of Nodilittorina , and only a single, nonunique synapomorphy was discovered for the genus, the banding pattern of the cephalic tentacles ( Reid, 1989). A recent analysis of the morphological characters of all 60 species then included in Nodilittorina produced a poorly resolved tree, in which all but two Nodilittorina species formed a paraphyletic group within a clade that also included the genus Littorina sensu stricto ( Reid, 2002 b). This Nodilittorina plus Littorina clade was defined by the one unique and unequivocal synapomorphy of the form of the outer marginal radular teeth (with a flange on either side of the base), although this character state was reconstructed as lost within Littorina . According to this interpretation, all other features previously used to characterize Nodilittorina were plesiomorphic similarities and without phylogenetic significance. Analysis of DNA sequence data has now shown unequivocally that Nodilittorina in the broad sense is not a monophyletic group, and has supported the integrity of three distinct clades: a large clade of 50 tropical species (for which the name Echinolittorina is available), a clade of five species from Australia, New Zealand and South America (a restricted use of Rosewater’s genus Austrolittorina ), and a clade of four species from southern Africa and Australia (for which the new name Afrolittorina was established) ( Williams et al., 2003). There was no strong support for the inclusion of the remaining species, Nodilittorina pyramidalis , in these or other generic-level clades. This is the type species of the genus ( Abbott, 1954) and it is therefore appropriate to treat Nodilittorina as monotypic.

From the perspective of stability of taxonomic usage of the generic name Nodilittorina , the identity of its type species is unfortunate. The designation of N. pyramidalis as the type species has a confused history. Under his original description of Littorina (Nodilittorina) von Martens (1897) listed the names nodulosa Pfeiffer , dilatata d’Orbigny , trochiformis Dillwyn, antonii Philippi and granosa Philippi, he gave a detailed description of L. vilis Menke , and gave notes on L. pyramidalis Quoy & Gaimard , L. natalensis Krauss in Philippi and L. subnodosa Philippi. The first designation of a type species was by Wenz (1938) who, without discussion, gave the type as T. (N.) nodulosus (Gmelin) [ Turbo ]”. Abbott (1954) rejected this designation as invalid, on the grounds that Turbo nodulosus Gmelin, 1791 was not among the species included by von Martens (1897) and because it is a turbinid species. (In fact it is an Angaria ; the littorinid species that Wenz presumably intended was Trochus nodulosus Gmelin, 1791 .) Abbott (1954, following Clench & Abbott, 1942) interpreted nodulosa Pfeiffer ”, as listed by von Martens (1897), as the species now classified as Tectarius (Tectininus) antonii (Philippi, 1846) , whereas he believed Trochus nodulosus Gmelin to be based on both N. dilatata and N. pyramidalis . However, as pointed out by Kadolsky (1971; Bandel & Kadolsky, 1982), Pfeiffer was not in fact the author of the name nodulosa as listed by von Martens (1897), but only of the new combination Litorina nodulosa (Gmelin) . A case might therefore be made that Wenz’s (1938) designation was valid, although this could be dismissed on the technicality of his mistaken use of the original genus Turbo . Gmelin’s species Trochus nodulosus is based on figures by Chemnitz (1781) that are here interpreted to represent the species currently classified as Echinolittorina trochoides (Gray, 1839) (see Taxonomic History of N. pyramidalis below). Rejecting Wenz’s designation of this species, Abbott (1954) instead proposed Littorina pyramidalis as the type of Nodilittorina . Abbott himself believed this to be the earliest valid name for a species that included the two taxa now recognized as N. pyramidalis and E. trochoides ( Trochus nodulosus Gmelin is unavailable, as it is a junior homonym of T. nodulosus Solander, 1766 ). He therefore probably aimed to fulfil the intention of Wenz. Although to allow Wenz’s (1938) designation would preserve Nodilittorina more nearly in its accustomed usage, it seems preferable to accept the designation by Abbott (1954). This avoids the doubt surrounding the identity of Gmelin’s species. Furthermore, N. pyramidalis has been accepted as the type species for nearly 50 years, even if it has been frequently misidentified during that time.

Further details of the history of the usage of Nodilittorina , including subgeneric divisions and inclusion of species now assigned to other genera, are available elsewhere (Reid & Geller, 1997; Reid, 2002 a,b).

Diagnosis. Shell nodulose; nodules not axially aligned; eroded parietal area; no pseudoumbilicus; unpatterned. Cephalic tentacles with 2 broad black longitudinal stripes. Penis with swollen filament bearing numerous minute papillae; base bifurcate; single mamilliform gland surrounded by subepithelial glandular tissue (not separated as distinct glandular disc or flap); penial vas deferens an open groove. Paraspermatozoa with small rod bodies. In pallial oviduct egg groove makes a simple loop through albumen gland, circular loop through capsule gland, no loop in jelly gland; copulatory bursa opens in anterior position near anterior end of pallial oviduct. (After Williams et al., 2003.)