Abstract
The genus Sibogasyrinx has to date included only four species of rare deep-water Conoidea, each known from few specimens. In shell characters it strongly resembles three distantly-related genera, two of which, Comitas and Leucosyrinx, belong to a different family, the Pseudomelatomidae. A molecular phylogenetic analysis of a large amount of material of Conoidea has revealed the existence of much additional undescribed diversity within Sibogasyrinx from the central Indo-Pacific and temperate Northern Pacific. Based on partial sequences of the mitochondrial cox1 gene and morphological characters of 54 specimens, 10 species hypotheses are proposed, of which six are described as new species: S. subula sp. nov., S. lolae sp. nov., S. maximei sp. nov., S. clausura sp. nov., S. pagodiformis sp. nov. and S. elbakyanae Kantor, Puillandre & Bouchet sp. nov. One of the previously described species was absent in our material. Most of the new species are very similar and are compared to Leucosyrinx spp. Species of Sibogasyrinx are unique among Conoidea on account of the high intrageneric variability in radular morphology. Three distinct radula types are found within Sibogasyrinx, two of which are confined to highly supported subclades.
Highlights
The superfamily Conoidea is well known for high levels of homoplasy in shell form
The species of Sibogasyrinx described are rather heterogeneous on one hand, while on the other, some species are very similar to each other (e.g. S. cf. pyramidalis 1 and S. cf. pyramidalis 2; S. filosa and S. lolae sp. nov.)
Species of Sibogasyrinx are superficially similar in shell shape and sculpture to species of Leucosyrinx (Fig. 13); based on shell alone, it is not possible to reliably attribute the species to either genus
Summary
The superfamily Conoidea is well known for high levels of homoplasy in shell form. Molecular studies have revealed that very similar or nearly indistinguishable shell morphologies are found in distantly related lineages (Puillandre et al 2011; Abdelkrim et al 2018), rendering the attribution of species to genus and even family questionable, when based on shell characters alone.European Journal of Taxonomy 773: 19–60 (2021) striking examples of such homoplastic shells are found in the genera Comitas Finlay, 1926, Leucosyrinx Dall, 1889, Sibogasyrinx Powell, 1969 and, to some extent, Comispira Kantor, Fedosov & Puillandre, 2018, all of which possess rather similar fusiform shells with a long siphonal canal and axial ribs or nodules on a more or less angular shoulder. Species of Sibogasyrinx are characterized by a radula typical of Cochlespiridae – with paired marginal and well-defined central teeth, in contrast to Leucosyrinx spp. which possess only marginal teeth (Bouchet et al 2011). Both radula type and phylogenetic analyses (Bouchet et al 2011; Puillandre et al 2011; Abdelkrim et al 2018) confidently placed Comitas in the Pseudomelatomidae. The recently described Comispira is clearly referable to the Cochlespiridae, both on anatomical and molecular grounds
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