Skeneimorph but not skeneid: systematics and anatomy of Lodderena Iredale, 1924 (Vetigastropoda: Trochoidea)

Abstract

ABSTRACTThe genus Lodderena Iredale, 1924 has been classified in the Skeneidae by most recent authors. However, this family, originally characterized by their minute size, lack of nacre in the teleoconch and a rhipidoglossate radula, is currently considered to be polyphyletic assemblage, and preliminary molecular systematic data suggest exclusion of Lodderena from Skeneidae. In order to shed light on the systematic position of this genus, we provide a detailed description of the anatomy and histology of the type species, Lodderena minima (Tenison-Woods, 1878), and of L. ornata (Olsson & McGinty, 1958). The anatomical data confirm the vetigastropod-trochoid nature of Lodderena but exclude the genus from Skeneidae. Skeneidae are mainly characterized by a propodial penis, a hermaphroditic condition with separated testis and ovary, and a large receptaculum in the mantle roof. In contrast, Lodderena species lack both a copulatory organ and receptaculum, and have a true ovotestis. We also provide a critical review of nominal species in the genus. Based on molecular and morphological evidence, we exclude Lodderena from Skeneidae, instead treating it as a genus incertae sedis within Trochoidea. We discuss the implications of small size for functional morphology and reproduction.