Abstract
The new genusJagoraof the family Pachychilidae Troschel, 1857 is described for the type speciesMelania asperataLamarck, 1822 from the Philippines. In addition toJ. asperata, a second endemic species of the new genus,J. dactylus(I. Lea & H.C. Lea, 1850), is recognized on the basis of shell morphometry and molecular genetic data (cytochrome C oxidase I and 16S rRNA). The taxonomic history ofJ. asperataandJ. dactylusis revised and the recent distribution documented on basis of available museum material and the authors’ own field collections.J. asperataoccurs on Luzon and its satellite islands Leyte and Samar, whileJ. dactylusis restricted to the Visayan islands Bohol, Cebu, and Guimeras. The morphology of the two species is presented and illustrated in detail, and compared to taxa of the closely related genusBrotiaH. Adams, 1866 to which they were previously assigned. Among the South‐east Asian freshwater Cerithioidea of the family Pachychilidae, which were previously subsumed underBrotiafor their more or less similar shell morphology and operculum, three distinct lineages can be distinguished, in particular by means of distinct reproductive anatomy: (1) the species ofBrotia sensu strictofrom mainland South‐east Asia, Sumatra, Borneo and Java, which all exhibit a subhaemocoelic brood pouch; (2) the pachychilid species endemic to Sulawesi, currently assigned to the generaBrotiaandTylomelania, as well as both species ofPseudopotamisendemic to the Torres Strait Islands, which possess a uterine brood pouch; (3) the females of the PhilippineJagora,which carry egg capsules, embryos and advanced juvenile stages within the mantle cavity — a unique reproductive feature. Associated with this mode of ovoviviparity,Jagorais characterized by additional unique properties of the reproductive system including a deeply incised and long sperm gutter in the medial lamina, a very short and posteriorly positioned spermatophore bursa formed by the medial lamina, and a prominent lateral ridge functioning as a seminal receptacle. These characteristics are exclusive toJagoraand are consequently considered to represent autapomorphies of this clade which is endemic only to the Philippines. The zoogeographical implications are discussed in connection with a recently developed palaeogeographical reconstruction.
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