First systematic study using the variability of the residual colour patterns: the case of the Paleogene Seraphsidae (Mollusca, Gastropoda, Stromboidea)

This work presents for the first time the application of the residual colour patterns revelead under UV light for the systematic study on Caenozoic seraphsids. The seraphsids species have been previously distinguished on the basis of the shell shape, but this generally bear few diagnostic characters. This study concerns 14 European Palaeogene species belonging, in the previous classification, to the following taxa Seraphs (s.s.) Montfort, 1810, S. (Diameza) Deshayes, 1865, S. (Miniseraphs) Jung, 1974 and Paraseraphs Jung, 1974. The observation of 1400 specimens under UV light allows integrating intraspecific variability. Except for P. praecedens n. sp. (Thanetian, oldest occurrence of the genus) and S. subconvolutus (d’Orbigny, 1852) (Rupelian), all species show colour patterns. The bauplan of the fossil colour patterns is very similar to that of the single extant Terebellum terebellum (Linnaeus, 1758), except for Diameza Deshayes, 1865. Taking into account their peculiar pattern and shell shape, Diameza and Miniseraphs are here excluded from Seraphs and raised to genus level, and Miniseraphs is regarded as a subgenus of Diameza. At specific level, the similarity of the colour patterns of S. volutatus (Solander in Brander, 1766), S. olivaceus (Cossmann, 1889) and S. sopitus (Solander in Brander, 1766), do not justify their distinction based on close shell shapes. Considering the colour patterns, we demonstrate that several shell characters, previously used to distinguish Paraseraphs species, are no longer useful for diagnose. Seraphs peterjungi n. sp. (Lutetian, Paris Basin) is distinguished on the basis of the colour pattern and two Seraphs species are in open nomenclature. As for T. terebellum, the colour patterns of S. chilophorus (Cossmann, 1889) and P. tetanus Jung, 1974 are highly variable. Thus, taking into account intraspecific variability, the residual colour patterns represent an important taxonomic tool in addition to the traditional study of the shell shape.