Saturday, August 19, 2017

[Gastropoda • 2017] Attenborougharion gen. nov. (Mollusca: Pulmonata: Helicarionidae): A Likely Case of Convergent Evolution in southeastern Tasmania

Attenborougharion rubicundus (Dartnall & Kershaw, 1978)

Hyman & Köhler, 2017  

Helicarion Férussac, 1821 from southeastern Australia currently comprises five species of endemic semislugs. Analyses of comparative morphological data and partial sequences of the mitochondrial genes cytochrome c oxidase subunit I (COI) and 16S rRNA (16S) reveal that one of these species, Helicarion rubicundus Dartnall & Kershaw, 1978, which is restricted to southeastern Tasmania, is not closely related to the other known species of this genus. This species is distinguished from Helicarion in several key morphological characters, such as the bright two-toned red and green colouration of its larger body with a flattened tail that is keeled only at the tip, the triangular shape of the pneumostome, the degree and type of folding present in the spermoviduct and free oviduct, the presence of a longer, more slender bursa copulatrix, the presence of a small epiphallic caecum and a hooked flagellum, and the presence of irregular longitudinal pilasters in the penial interior in contrast to the v-shaped rows of papillose lamellae seen in Helicarion. Moreover, the mitochondrial phylogeny provides evidence that this species is phylogenetically distinct from Helicarion as well as any other currently described genus from southeastern Australia. Based on these findings, we here describe a new genusAttenborougharion, for this species.

Keywords: Helicarionoidea; morphology; mitochondrial DNA; land snail; taxonomy.

Figure 1. Living animal of Attenborougharion rubicundus from Forestier Peninsula (QVM 9:15514).
photo: Simon Grove, TMAG. 


Attenborougharion gen. nov.
 Type species. Helicarion rubicundus Dartnall & Kershaw, 1978.

Etymology. Named for Sir David Attenborough, Lifetime Patron of the Australian Museum, in recognition of his lifetime’s contribution to the fields of natural science and conservation. The Latin noun arion refers to a “kind of snail or slug”; masculine.

A new genus of snail has been named Attenborougharion in honour of Sir David Attenborough.
Photographer: James Morgan / 

Diagnosis External appearance. Large, shell ear-shaped, flattened, thin, golden, glossy, whorls rounded, base membraneous. Protoconch with radial wrinkles near suture; otherwise sculptured with very faint beading and indistinct to absent spiral grooves; teleoconch with very fine, indistinct spiral grooves and more prominent radial growth lines. Body colour green and burgundy. Mantle lobes and shell lappets of moderate size, none fused; shell lappets elongate, lacking pigmented warts; slime network prominent; caudal horn well-developed. Keel confined to very tip of tail; most of tail dorsally

Attenborougharion rubicundus (Dartnall & Kershaw, 1978) comb. nov. 
Helicarion rubicundus Dartnall & Kershaw, 1978: 2; Kershaw, 1980: 213.

Distribution and conservation status: Attenborougharion rubicundus is found only on the Tasman and Forestier Peninsulas in Tasmania (Taylor, 1991; Otley et al., 1999). The total known extent of occurrence of this species is 85, leading to its listing as Vulnerable on the IUCN Red List of Threatened Species. In addition to its restricted range, within this area Attenborougharion rubicundus inhabits only closed wet forests and is not found in dry forests or damp sclerophyll forests (Otley eal., 1999), making it vulnerable to habitat loss through the effects of climate change as well as habitat destruction through changed land use.

  Isabel T. Hyman and Frank Köhler. 2017. Attenborougharion gen. nov. (Mollusca: Pulmonata: Helicarionidae): A Likely Case of Convergent Evolution in southeastern Tasmania. Records of the Australian Museum. 69(2): 65–72.  DOI: 10.3853/j.2201-4349.69.2017.1676

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