Another paper just published in the ‘end-of-the-year-stream’ is by Harasewych & Tenorio.
Their abstract reads: “Morphometric analyses of shell shape of living specimens of Cerion inhabiting San Salvador Island segregate samples into two primary phenotypes, one inhabiting the western and southern coasts of the island, the other the eastern and much of the northern coast. These are concordant with phenotypes identified in prior morphometric studies. Lectotypes are designated for Cerion watlingense Dall, 1905; C. inconspicuum Dall, 1905; C. inconspicuum lacunorum Dall, 1905; and C. coloni Bartsch, 1924. The lectotype of Cerion watlingense Dall, 1905 falls within the western and southern phenotype, and is the oldest name available for this taxon. The lectotype of Cerion coloni Bartsch, 1924, a validly introduced, but previously unrecognized taxon, and the holotype of Cerion rodrigoi Gould, 1997 both fall within the group containing the east coast populations, with Cerion coloni Bartsch, 1924 being the oldest available name for this phenotype. A third, previously unrecognized phenotype, represented by a single inland population, is morphologically similar to the lectotype of Cerion inconspicuum Dall, 1905, which is the oldest available name for this phenotype. The geographical distribution and chronological succession of these phenotypes since the late Pleistocene is reviewed in the context of both the single and multiple colonization models for the arrival of Cerion on San Salvador, and the evolutionary and taxonomic corollaries of each model are discussed”.
An interesting paper which shows that morphometric analysis may be needed when the morphology and distribution are seemingly entwined. The study of Cerion, which has intrigued many authors, has been elucidated with a thorough discussion of both the morphological and distributional aspects of the species of this island.
Harasewych, M.G. & Tenorio, M.J., 2018. The genus Cerion (Gastropoda: Pulmonata: Cerionidae) on San Salvador [Watling Island], Bahamas: a geometric morphometric analysis of shell morphology. – The Nautilus, 132 (3-4): 71-82.