Theodoxus fluviatilis Nerita fluviatilis Theodoxus anatolicus Nerita anatolica A revision of the extant species of Theodoxus (Gastropoda, Neritidae) in Asia, with the description of three new species Sands, Arthur F Gloeer, Peter Guerlek, Mustafa E Albrecht, Christian Neubauer, Thomas A Zoosystematics and Evolution 2020 96 1 25 66 55E91AC2-8D08-57A6-9BA9-32BD100648AE Sands & Glöer Sands & Gloeer 2020 Gastropoda Neritidae Theodoxus CoL Animalia Theodoxus wesselinghi Cycloneritida 0 25 Mollusca species wesselinghi sp. nov.   Theodoxus fluviatilis:  Odabasiand Arslan 2015: 330-331 ( non Nerita fluviatilisLinnaeus, 1758).  Theodoxus anatolicus:  Yildirimet al. 2018: 118 ( non Nerita anatolica Recluz, 1841).   Typelocality. Sakarya River, Caykoey, Bilecik, Turkey; 40.0439°N, 30.452°E(Figs 3D, 23A, B).    Holotype. RMNH. MOL.342200 (Sakarya River, Caykoey, Bilecik, Turkey; 40.0439°N, 30.452°E) stored in NMNL: Shell height 6.0 mm, width 6.0 mm (Fig. 24A-D).    Paratypes.Twenty-four specimens from Sakarya River, Caykoey, Bilecik, Turkey; 40.0439°N, 30.452°E(Fig. 23A, B): 11 in NMNL( RMNH. MOL.342201, RMNH. MOL.342202; Fig. 24E-G) and 13 in UGSB( UGSB20688, UGSB20743, UGSB20744; Fig. 25A, B, D). Twenty-four specimens from an unnamed roadside spring in Fele, Ispartaprovince, Turkey; 38.00358°N, 31.47217°E(Fig. 23C, D): 11 in NMNL( RMNH. MOL.342203, RMNH. MOL.342204; Fig. 24H-J) and 13 in UGSB( UGSB20684, UGSB20735, UGSB20736). Twenty-five specimens from Eflatun Pinari, near Sadikhaci, Konya, Turkey; 37.8256°N, 31.6748°E(Fig. 23E, F): 11 in NMNL( RMNH. MOL.342205, RMNH. MOL.342206; Fig. 24K-M) and 14 in UGSB( UGSB20685, UGSB20737, UGSB20738; Fig. 25F). Thirty specimens from BalikdamiWetland spring, Eskisehir, Turkey; 39.15277°N, 31.61562°E(Fig. 23G, H): 13 in NMNL( RMNH. MOL.342207) and 17 in UGSB( UGSB20686, UGSB20739, UGSB20740; Fig. 25C, E).   Figure 23. Typelocality of  Theodoxus wesselinghiSands & Gloeersp. nov. A, B. Sakarya River, Caykoey, Bilecik, Turkey, 40.0439°N, 30.452°E. Further paratypelocalities: C, D. Unnamed roadside spring in Fele, Ispartaprovince, Turkey, 38.00358°N, 31.47217°E; E, F. Eflatun Pinari, near Sadikhaci, Konya, Turkey, 37.8256°N, 31.6748°E; G, H. BalikdamiWetland spring, Eskisehir, Turkey, 39.15277°N, 31.61562°E.   Figure 24.  Theodoxus wesselinghiSands & Gloeersp. nov. A- D. Holotypecollected in the Sakarya River, Caykoey, Bilecik, Turkey ( RMNH. MOL.342200); E- G. Paratypefrom the same location as the holotype( RMNH. MOL.342202); H- J. Paratypefrom Fele, Ispartaprovince, Turkey ( RMNH. MOL.342204); K- M. Paratypefrom Eflatun Pinari, Konya province, Turkey ( RMNH. MOL.342206). All photographed material (A-M) is stored in NMNL. Scale bars: 1 mm.   Figure 25.Radula of  Theodoxus wesselinghiSands & Gloeersp. nov. paratypes. A. Portion of the radula showing full sets of teeth ( UGSB20688); B. Magnified view of the central teeth ( UGSB20688); C. Magnified view of the lateral and marginal teeth ( UGSB20686); D. Magnified view of the first and second rows of marginal teeth ( UGSB20688); E. Magnified view of the first row of marginal teeth ( UGSB20686); F. Magnified view of the faces of inner marginal teeth belonging to the first row ( UGSB20685). Scale bars: 100 μm(A-E), 20 μm(F).  Etymology. The species is named in honour of the molluscan palaeontologist Frank P. Wesselingh (Naturalis Biodiversity Center, Leiden, The Netherlands) for his contributions to malacology.  Description. Shell (Fig. 24A-C, E, F, H-M): Hemispherical, transversely elongate, consisting of typically three whorls that rapidly grow. Spire well defined, moderate height for  Theodoxus; often corroded along with other parts of shell. Shell height ranges from 4.0- 6.8 mm, width from 3.8-7.1 mm. Juveniles appear more globular. Periostracum is uniformly ivory or solid black, intermediate forms with broad brown-black smudged diagonal stripes also exist; surface glossy, finely striated with growth lines. Aperture semicircular, no serrations on inner lip. Columellar plate smooth, flat to slightly concave, inclined towards aperture; colouration blue-grey in darker shelled individuals to white in lighter forms. Operculum (Fig. 24D, G): Operculum plate made of two parts, calcareous base and conchioline lamella; operculum base light, mostly ivory to white, white lamella with distinct orange edge on border with operculum base. Operculum base left adductor can be blunt and rounded, weak callus on top right edge. Apophysis follows same colour scheme as operculum calcareous base, broader at top and narrower and attenuated at bottom. Very narrow rib-shield, deep rib-pouch present on operculum. Operculum lacks a pseudo-apophysis. Radula (Fig. 25A-F): R-central tooth flanked by A-central, B-central, C-central, E-lateral on each side. Additionally, two interconnected layers of marginal teeth encase central and lateral teeth. R-central shows some variation among populations, slightly spherical or more squared face with slightly concave anterior edge. A-central large and flat with thin ridge that becomes broad and folded right at end of cusp. B-central diminished, forms irregular "S"shape. C-central equally diminished, hidden below lower edge of E-lateral. E-lateral simple with smooth upper edge. First layer of marginal teeth consists of 37-44 teeth that decrease in size away from E-lateral but increase in size and bear serrations on edges of small faces; semidetached from second layer, which is fused and forms outer wall.  Differentiating features. Based on conchological features of periostracum colouration and patterning and shell shape, it is difficult to differentiate  T. wesselinghisp. nov. from most Asian  Theodoxusspp. given the variety in colour and patterns among the typematerial (Fig. 24A-M). However, in some instances it can be distinguished from Anatolian morphotypes of  T. baeticus, which typically displays ivory blotches on a brown background (Fig. 7A-D);  T. altenaiwith clear ivory checks on a dark brown-black background (Fig. 4A-G) and  T. gloerilacking shell pigmentation and bearing strong axial ribs on the shell (Fig. 11A-C). The light ivory-coloured operculum calcareous base makes this species distinct from  T. gurursp. nov. (light to dark brown; Figs 13D, 24D, G) and  T. wilkeisp. nov. (bright orange; Figs 24D, G, 27D). More differentiating features occur in the operculum structure (Fig. 24D, G). The presence of an attenuated apophysis distinguishes  T. wesselinghisp. nov. from  T. altenaiand  T. jordani, which have non-attenuated apophyses (Figs 4, 15, 17). A rib-pouch and rib-shield are either totally lacking or extremely diminished in  T. altenai,  T. anatolicus,  T. jordani, and  T. macri(Figs 4, 5, 15, 17, 18), while they are more pronounced in  T. wesselinghisp. nov. (Fig. 24). The rib-shield in  T. wesselinghisp. nov. is however less broad than that typically observed in  T. fluviatilisand  T. baeticus(Figs 6- 10). Furthermore, the lack of a pseudo-apophysis differentiates the new species from  T. altenai,  T. anatolicus,  T. baeticus,  T. gurursp. nov.,  T. jordani, and  T. macri(Figs 4- 8, 13, 15, 17, 18). Additionally, the presence of a weak callus on the top right edge of the operculum base in  T. wesselinghisp. nov. helps to differentiate this species from  T. gurursp. nov. and  T. jordani, which lack a callus (Figs 13, 15, 17, 18, 24), as well as from  T. anatolicus,  T. fluviatilis,  T. major,  T. pallidus, and  T. wilkeisp. nov., which have stronger calluses (Figs 5, 9, 10, 19, 20, 24, 27). Based on the available data for  Theodoxusralulae,  T. wesselinghisp. nov. can be distinguished by a more globular R-central face from  T. gurursp. nov.,  T. wilkeisp. nov.,  T. fluviatilis, and  T. jordani, where it is more rectangular or triangulate (see Baker 1923; Zettler 2008; Figs 14B, 25B, 28B). Furthermore, the smooth upper edge of the E-lateral can be used to distinguish this species from  T. wilkeisp. nov. and  T. major, which generally have E-laterals with serrated edges (see Anistratenko et al. 2017; Figs 25C, 28C, D).  Remarks.   Theodoxus wesselinghisp. nov. forms part of a larger clade that includes  T. syriacusand  T. wilkeisp. nov., where it shares a closer sister-species relationship with  T. wilkeisp. nov. ( Sands et al. 2019a; Fig. 2). The three species likely diverged from one another in quick succession over the Pliocene-Pleistocene transition (Fig. 2).  Distribution. Known so far only from the four localities in central-west Anatolia (Figs 3D, 23A-H).  Ecology.   Theodoxus wesselinghisp. nov. can be found in both springs ( BalikdamiWetland, Eflatun Pinari, Fele; Fig. 23C-H) and streams (Sakarya River, Caykoey; Fig. 23A, B) with clear water. The occurrence of macrophytes appears negligible to the species as it occurs in localities both with (Fig. 23E-H) and without (Fig. 23A-D) aquatic plant growth. The floors of all localities are made up of coarse grained sand and large and small rocks and stones that  T. wesselinghisp. nov. is often attached to (personal observation M.E.G.; Fig. 23H).  Theodoxus wesselinghisp. nov. co-occurs with  Potamopyrgus antipodarum(Gray, 1843) and  Isparta felei Yildirim, Koca, Guerlek& Gloeer, 2018 inFele spring,  Falsipyrgulasp. in Eflatun Pinari, and  Pseudamnicola natolica( Kuester, 1852) (and possibly also  T. gloeri;  Odabasiand Arslan 2015) in the BalikdamiWetland spring (personal observation M.E.G.). RMNH Turkey 40.0439 30.452 Nmnl Holotype A Turkey 40.0439 30.452 Paratypes C Turkey 38.00358 31.47217 E Turkey 37.8256 31.6748 G Turkey 39.15277 31.61562