Grossuana thasia Georgiev & Glöer, 2020, n. sp.
Creators: name: Georgiev, Dilian
name: Glöer, Peter
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Hydrobiidae
Grossuana
Grossuana thasia

description: Grossuana thasia n. sp. (Figs. 2, 4, 9-10)   
https://zoobank.org/ urn:lsid:zoobank.org:act: 019E5D1D-E033-4913-896D-4C779ACA9198  
 Material studied:   
 Holotype: shell height 1.7 mm, width 1.1 mm, from type locality (ZMH 140793).   
 Paratypes: 5 specimens in ethanol (ZMH 140794), 5 specimens in coll. Glöer, 11 specimens in coll. Georgiev.   
 Type locality: Greece, Thassos Island, North Aegean, a spring (water source) south of Kinira near the round road of the island, N40 38 07.5 E24 45 52.2, 144 m a.s.l. (Fig. 3).   
 Etymology: Named after Thassos Island on which the species lives.   
 Description: Shell: The corneous shell is elongate ovate with a prolonged body whorl (Fig. 2). The apex is rounded and often eroded. The 4-4.5 whorls are slightly convex with a weak suture, with rough irregular growth lines. The aperture is ovate slightly angled at the top with a sharp periostome thickened at the columella. The umbilicus is closed. The operculum is dark red. Animal: The animal is mostly black colored. The mantle is black with a thin white border. The snout and tentacles are black with white or grayish tips. Penis: The penis is nearly regularly broad with a long tapered penis-tip. There is a dark spot at the near the penis-tip.   
 Differentiating features: The new species is most similar to Grossuana angeltsekovi Glöer & Georgiev, 2009 which is known to be widely distributed in Bulgaria and North Greece (Georgiev 2013, Georgiev et al., 2015, Falniowski et al. 2015, Glöer et al., 2018). From this species Grossuana thasia n. sp. differs by its more elongated and slender shell with flatter whorls, which have rough surface with irregular growth lines, and by its more rounded, often eroded apex. The whorls of the shell of the new species are 4-4.5 while in G. angeltsekovi they are 5-5.5 and the later is larger (height of the holotype = 2.1 mm). In addition G. thasia has a well visible bifurcated penis lobe, while in G. angeltsekovi it is very small and hardly visible (Glöer & Georgiev, 2009).   
 Grossuana thasia n. sp. is similar by its shell morphology to Grossuana stenaensis Glöer, Reuselaars & Papavasileiou, 2018 described from the nearby mainland of Greece (Glöer et al., 2018) but this species has a penis with broader base and shorter and thicker tip.   
 Previously all Grossuana of Thassos were assigned to G. hohenackeri (Küster, 1853) (Reischütz, 1983). It was later re-described and split into two species: Radomaniola tritonum (Bourguignat, 1852) and Grossuana tembii Boeters, Glöer & Falniowski (2018) (Boeters et al., 2018). G. thasia n. sp. differs from G. tembii by its higher whorl number (3.25-3.5 in G. tembii) and longer penis tip.   
 Distribution: Known only from the type locality.   
 Habitat: Karst spring in a mixed broad leaf forest (mainly Platanus orientalis and Quercus spp.). Found on moss, dry leaves, sand and stones.
description: Published as part of Georgiev, Dilian & Glöer, Peter, 2020, Three new hydrobiid species from Thassos Island (Greece) with a re-description of Amnicola charpentieri Roth, 1855, pp. 129-137 in Ecologica Montenegrina 35 on page 133, DOI: 10.37828/em.2020.35.10, http://zenodo.org/record/13232490