Fastosarion Iredale, 1933

Hyman, Isabel T. & Köhler, Frank, 2019, Phylogeny and systematic revision of the helicarionid semislugs of eastern Queensland (Stylommatophora, Helicarionidae), Contributions to Zoology 88 (4), pp. 351-451 : 397-398

Fastosarion Iredale, 1933

Fastosarion Iredale, 1933: 37 .

Type species Vitrina superba Cox, 1871 (by original designation); masculine.

Vercularion Iredale, 1933: 38 (name unavailable, no description). Intended type species Helicarion bullaceus Odhner, 1917 (by original designation); masculine.

Eungarion Stanisic, 1993: 27 .

Type species Eungarion mcdonaldi Stanisic, 1993 (by original designation); masculine.

Dimidarion Stanisic, 2010 in Stanisic et al., 2010: 314.

Type species Dimidarion alyssa Stanisic, 2010 (by original designation); masculine.

Hymanarion Stanisic, 2010 in Stanisic et al., 2010: 318.

Type species Hymanarion hannianus Stanisic, 2010 (by original designation); masculine.

Remarks

The gender of none of the genus names treated herein has been explicitly specified in the relevant original descriptions. However, all these names are compound words ending with the noun ‘- arion ’, which determines the gender of these names to be masculine in correspondence with the gender of the name Arion Férussac, 1819. Accordingly, we here correct any previously incorrect gender assignment of species names.

The genus Fastosarion was originally described as a monotypic subgenus of Helicarion by Iredale (1933), who later elevated it to full genus rank ( Iredale, 1937). The name is of masculine gender as evident from Iredale’s (1937) use of the species name F. superbus . Iredale (1933) also proposed the name Vercularion for the type species V.bullaceus ;however this name is unavailable because it was intro - duced without a description. It has not been made available subsequently by Iredale (1937: 8) nor Iredale (1941: 6) (no description). The simultaneously published name Fastosarion was later given precedence over Vercularion by First Reviewer’s choice by Smith (1992: 231).

Smith (1992) listed eight species in the genus.

Scott (1995) revised Fastosarion , redescribing F. superbus and describing two new species, F.helenkingae Scott, 1995 and F. aquavitae Scott, 1995 . Hyman & Ponder (2010) moved two species to the new genus Stanisicarion and Stanisic et al. (2010) moved an additional species to Macularion while also describing six new species and placing two in synonymy. Subsequently, a single species was synonymized with Mysticarion hyalinus (Pfeiffer, 1855) by Hyman et al. (2017), bringing the total number of accepted species in the genus to ten.

In the current study we uphold Fastosarion as an accepted genus, but treat the genus names Eungarion , Dimidarion and Hymanarion as its subjective junior synonyms.

Eungarion was described as a monotypic genus for new species E. mcdonaldi , a small semislug with a very thin, flattened, reduced shell with degenerate lower whorls ( Stanisic, 1993a). Dimidarion was originally introduced for four new species of small to very small semislugs from southeastern to mideastern Qld, while the monotypic Hymanarion was described for a small semislug found in northeastern Qld ( Stanisic et al., 2010). Five of these six species were described based only on their shell and external appearance. These genera all have small, thin, low-spired shells of 7.5–

12 mm, but range in shape from flattened to globose. They share some anatomical characters, including a relatively short vagina, equal length arms of the epiphallus and a penis with longitudinal pilasters that often contains a proximal rounded pilaster, but other aspects of their genital anatomy differ considerably. However, all share the diagnostic morpho-anatomical characters seen in Fastosarion , Stanisicarion and Macularion (distinct vagina, elongate capsular gland, slender flagellum, distinct epiphallic caecum with a medial attachment of the penial retractor muscle, simple spermatophore with at most short teeth or spines) and hence we synonymise these three genera with Fastosarion .

We demonstrate in the current study that many Fastosarion species have larger ranges than previously thought, resulting in the synonymy of several existing species. In particular, we synonymise F.schelli with F.helenkingae , F. ameyi with F. aquavitae , F.virens with F. freycineti , and F. slatyeri and F. peterbrocki with F. alyssa . We also introduce eight new species, bringing the total number of accepted species in this genus to 21.

The genus as delineated herein comprises Clades A and B in the mtDNA phylogeny ( figs. 1–3 ).

Differential diagnosis

External appearance: Shell small to large (6–25 mm), amber, glossy, ear-shaped, 2.6–4.1 whorls, globose to flattened with an expanded last whorl, whorls rounded. Protoconch and teleoconch with very fine spiral grooves, sometimes becoming obsolete on the teleoconch. Body colour ranging from cream to dark reddish grey or brown, dark green or black, sometimes speckled or spotted, sole often contrasting in colour and sometimes with vertical stripes. Mantle lobes and shell lappets well-developed, completely covering shell when extended, often speckled, spotted or mottled, either smooth or sculptured with pustules or ridges, sometimes with rows of larger warts on shell lappets; median and left lobes always fused to form a cephalic shield. Slime network well developed; tail sometimes keeled. Caudal horn small to prominent.

Genital anatomy: Spermoviduct of 2–6 lobes, embedded in digestive gland. Talon and carrefour embedded in albumen gland. Spermoviduct folded several times in zig-zag fashion. Free oviduct with a large, oval, orange capsular gland medially; free oviduct internally smooth or sculptured with longitudinal pilasters or very fine transverse ridges. Vagina short to moderately long, sometimes swollen, internally smooth or with longitudinal pilasters. Bursa copulatrix short to moderately long, with slender duct and oval to elongate sac, inserted on the vagina, base of duct sometimes swollen. Penis long, cylindrical or proximally swollen, with variable internal sculpture of pustules or ridges (transverse, longitudinal or diagonal); longitudinal and/or rounded pilasters sometimes present. Penis tunica attached by muscle fibres to middle of epiphallus; epiphallus enters penis through simple pore or verge, verge never fused to penial wall; epiphallus 2 longer than or equal in length to epiphallus 1; epiphallic caecum present, penial retractor muscle attached to middle of caecum (near base). Long, slender epiphallic flagellum with axial filaxment present; internal cryptae minor and not visible externally. Spermatophore a soft-walled capsule with hard tail-pipe; tail-pipe mostly smooth, towards terminal end sometimes sculptured a single ridge with or without small teeth; spermatophore tip simple, or with hair-like spines, or expanded into a bell.

Figures

FIGURE 1 Best maximum likelihood tree based on analysis of the concatenated data set of fragments of the mitochondrial genes 16S and COI using IQ-TREE.Ambiguous alignment sites in 16S removed using MAFFT.Numbers on branches indicate nodal support based on 10,000 ultra-fast bootstrap repeats as well as by employing Shimodaira-Hasegawa’s (1999) approximate Likelihood Ratio Test (‘SH-aLRT’). Scale bar indicating 10% of modelled sequence divergence. Shells shown to scale.

FIGURE 2 Majority-rule consensus tree based on Bayesian analysis of the concatenated data set of fragments of the mitochondrial genes 16S and COI. Ambiguous alignment sites in 16S removed using MAFFT. Numbers on branches indicate posterior probabilities. Scale bar indicating 40% of modelled sequence divergence. Shells shown to scale.

FIGURE 3 Best maximum likelihood tree based on analysis of the concatenated data set of fragments of the mitochondrial genes 16S and COI using IQ-TREE,with reduced taxon sampling (including only the ingroup). Ambiguous alignment sites in 16S removed using Guidance2. Numbers on branches indicate nodal support based on 10,000 ultra-fast bootstrap repeats as well as by employing Shimodaira-Hasegawa’s (1999) approximate Likelihood Ratio Test (‘SH-aLRT’).Scale bar indicating 10% of modelled sequence divergence. Shells shown to scale.