Phylogeny and systematic revision of the helicarionid semislugs of eastern Queensland (Stylommatophora, Helicarionidae)

Abstract

The helicarionid fauna of southeastern to mid-eastern Queensland is dominated by a group of semislugs with moderately reduced shells belonging to genera Fastosarion, Eungarion, Stanisicarion, Dimidarion, Macularion and Hymanarion. We comprehensively revise their systematic classification using comparative morpho-anatomy and mitochondrial phylogenetics, and demonstrate that these genera combined form a well-differentiated and monophyletic radiation. In our mitochondrial phylogeny, this radiation is divided into three main clades that are statistically well supported. One clade is also well defined in terms of diagnostic morpho-anatomical characters, but we could not identify diagnostic characters for the other two clades due to considerable levels of morpho-anatomical variation. We propose accepting only two genera, Fastosarion (with junior synonyms Eungarion, Dimidarion, and Hymanarion) and Stanisicarion (with junior synonym Macularion). Both genera represent mutually monophleytic sister taxa that can consistently be distinguished by the presence or absence of a penial verge that is fused to the penial wall and by egg shape. We also synonymise Fastosarion ameyi with F. aquavitae, F. schelli with F. helenkingae, Dimidarion peterbrocki and D. slatyeri with F. alyssa, Stanisicarion virens with S. freycineti. Revised species descriptions are presented for Fastosarion alyssa, F. aquavitae, F. brazieri, F. comerfordae, F. griseolus, F. hannianus, F. helenkingae, F. mcdonaldi, F. minerva, F. paluma, F. papillosus, F. pustulosus, F. superbus, Stanisicarion aquila and S. freycineti. Nine new species, Fastosarion deensis, F. ephelis, F. insularis, F. katatonos, F. longimentula, F. rowani, F. sarina, F. tuljun and Stanisicarion wolvi are described, bringing the total number of accepted species to 24.