Theodoxus wesselinghi Sands & Gloeer, Sands & Gloeer, 2020

Sands, Arthur F, Gloeer, Peter, Guerlek, Mustafa E, Albrecht, Christian & Neubauer, Thomas A, 2020, A revision of the extant species of Theodoxus (Gastropoda, Neritidae) in Asia, with the description of three new species, Zoosystematics and Evolution 96 (1), pp. 25-66: 25

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Theodoxus wesselinghi Sands & Gloeer

sp. nov.

Theodoxus wesselinghi Sands & Gloeer   sp. nov. Figures 23A-H View Figure 23 , 24A-M View Figure 24 , 25A-F View Figure 25

Theodoxus fluviatilis   : Odabaşı and Arslan 2015: 330-331 (non Nerita fluviatilis   Linnaeus, 1758).

Theodoxus anatolicus   : Yıldırım et al. 2018: 118 (non Nerita anatolica   Récluz, 1841).

Type locality.

Sakarya River, Çayköy, Bilecik, Turkey; 40.0439°N, 30.452°E (Figs 3D View Figure 3 , 23A, B View Figure 23 ).

Holotype. RMNH. MOL.342200 (Sakarya River, Çayköy, Bilecik, Turkey; 40.0439°N, 30.452°E) stored in NMNL: Shell height 6.0 mm, width 6.0 mm (Fig. 24A-D View Figure 24 ) GoogleMaps   .

Paratypes. Twenty-four specimens from Sakarya River, Çayköy, Bilecik, Turkey; 40.0439°N, 30.452°E (Fig. 23A, B View Figure 23 ): 11 in NMNL ( RMNH. MOL.342201, RMNH. MOL.342202; Fig. 24E-G View Figure 24 ) and 13 in UGSB ( UGSB 20688, UGSB 20743, UGSB 20744; Fig. 25A, B, D View Figure 25 ) GoogleMaps   . Twenty-four specimens from an unnamed roadside spring in Fele, İsparta province, Turkey; 38.00358°N, 31.47217°E (Fig. 23C, D View Figure 23 ): 11 in NMNL ( RMNH. MOL.342203, RMNH. MOL.342204; Fig. 24H-J View Figure 24 ) and 13 in UGSB ( UGSB 20684, UGSB 20735, UGSB 20736) GoogleMaps   . Twenty-five specimens from Eflatun Pınarı, near Sadıkhacı, Konya, Turkey; 37.8256°N, 31.6748°E (Fig. 23E, F View Figure 23 ): 11 in NMNL ( RMNH. MOL.342205, RMNH. MOL.342206; Fig. 24K-M View Figure 24 ) and 14 in UGSB ( UGSB 20685, UGSB 20737, UGSB 20738; Fig. 25F View Figure 25 ) GoogleMaps   . Thirty specimens from Balıkdamı Wetland spring, Eskişehir, Turkey; 39.15277°N, 31.61562°E (Fig. 23G, H View Figure 23 ): 13 in NMNL ( RMNH. MOL.342207) and 17 in UGSB ( UGSB 20686, UGSB 20739, UGSB 20740; Fig. 25C, E View Figure 25 ) GoogleMaps   .


The species is named in honour of the molluscan palaeontologist Frank P. Wesselingh (Naturalis Biodiversity Center, Leiden, The Netherlands) for his contributions to malacology.


Shell (Fig. 24A-C, E, F, H-M View Figure 24 ): 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 View Figure 24 ): 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 View Figure 25 ): 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. wesselinghi   sp. nov. from most Asian Theodoxus   spp. given the variety in colour and patterns among the type material (Fig. 24A-M View Figure 24 ). 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 View Figure 7 ); T. altenai   with clear ivory checks on a dark brown-black background (Fig. 4A-G View Figure 4 ) and T. gloeri   lacking shell pigmentation and bearing strong axial ribs on the shell (Fig. 11A-C View Figure 11 ). The light ivory-coloured operculum calcareous base makes this species distinct from T. gurur   sp. nov. (light to dark brown; Figs 13D View Figure 13 , 24D, G View Figure 24 ) and T. wilkei   sp. nov. (bright orange; Figs 24D, G View Figure 24 , 27D View Figure 27 ).

More differentiating features occur in the operculum structure (Fig. 24D, G View Figure 24 ). The presence of an attenuated apophysis distinguishes T. wesselinghi   sp. nov. from T. altenai   and T. jordani   , which have non-attenuated apophyses (Figs 4 View Figure 4 , 15 View Figure 15 , 17 View Figure 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 View Figure 4 , 5 View Figure 5 , 15 View Figure 15 , 17 View Figure 17 , 18 View Figure 18 ), while they are more pronounced in T. wesselinghi   sp. nov. (Fig. 24 View Figure 24 ). The rib-shield in T. wesselinghi   sp. nov. is however less broad than that typically observed in T. fluviatilis   and T. baeticus   (Figs 6 View Figure 6 - 10 View Figure 10 ). Furthermore, the lack of a pseudo-apophysis differentiates the new species from T. altenai   , T. anatolicus   , T. baeticus   , T. gurur   sp. nov., T. jordani   , and T. macri   (Figs 4 View Figure 4 - 8 View Figure 8 , 13 View Figure 13 , 15 View Figure 15 , 17 View Figure 17 , 18 View Figure 18 ). Additionally, the presence of a weak callus on the top right edge of the operculum base in T. wesselinghi   sp. nov. helps to differentiate this species from T. gurur   sp. nov. and T. jordani   , which lack a callus (Figs 13 View Figure 13 , 15 View Figure 15 , 17 View Figure 17 , 18 View Figure 18 , 24 View Figure 24 ), as well as from T. anatolicus   , T. fluviatilis   , T. major   , T. pallidus   , and T. wilkei   sp. nov., which have stronger calluses (Figs 5 View Figure 5 , 9 View Figure 9 , 10 View Figure 10 , 19 View Figure 19 , 20 View Figure 20 , 24 View Figure 24 , 27 View Figure 27 ).

Based on the available data for Theodoxus   ralulae, T. wesselinghi   sp. nov. can be distinguished by a more globular R-central face from T. gurur   sp. nov., T. wilkei   sp. nov., T. fluviatilis   , and T. jordani   , where it is more rectangular or triangulate (see Baker 1923; Zettler 2008; Figs 14B View Figure 14 , 25B View Figure 25 , 28B View Figure 28 ). Furthermore, the smooth upper edge of the E-lateral can be used to distinguish this species from T. wilkei   sp. nov. and T. major   , which generally have E-laterals with serrated edges (see Anistratenko et al. 2017; Figs 25C View Figure 25 , 28C, D View Figure 28 ).


Theodoxus wesselinghi   sp. nov. forms part of a larger clade that includes T. syriacus   and T. wilkei   sp. nov., where it shares a closer sister-species relationship with T. wilkei   sp. nov. ( Sands et al. 2019a; Fig. 2 View Figure 2 ). The three species likely diverged from one another in quick succession over the Pliocene-Pleistocene transition (Fig. 2 View Figure 2 ).


Known so far only from the four localities in central-west Anatolia (Figs 3D View Figure 3 , 23A-H View Figure 23 ).


Theodoxus wesselinghi   sp. nov. can be found in both springs ( Balıkdamı Wetland, Eflatun Pınarı, Fele; Fig. 23C-H View Figure 23 ) and streams (Sakarya River, Çayköy; Fig. 23A, B View Figure 23 ) with clear water. The occurrence of macrophytes appears negligible to the species as it occurs in localities both with (Fig. 23E-H View Figure 23 ) and without (Fig. 23A-D View Figure 23 ) aquatic plant growth. The floors of all localities are made up of coarse grained sand and large and small rocks and stones that T. wesselinghi   sp. nov. is often attached to (personal observation M.E.G.; Fig. 23H View Figure 23 ). Theodoxus wesselinghi   sp. nov. co-occurs with Potamopyrgus antipodarum   (Gray, 1843) and Isparta felei   Yıldırım, Koca, Gürlek & Glöer, 2018 in Fele spring, Falsipyrgula   sp. in Eflatun Pınarı, and Pseudamnicola natolica   ( Küster, 1852) (and possibly also T. gloeri   ; Odabaşı and Arslan 2015) in the Balıkdamı Wetland spring (personal observation M.E.G.).


Netherlands, Leiden, Nationaal Natuurhistorische Museum ("Naturalis") [formerly Rijksmuseum van Natuurlijke Historie]








National Museum of Natural History, Naturalis


Universidad Nacional Agraria La Molina


Natuurmuseum Nijmegen e.o.














Theodoxus wesselinghi Sands & Gloeer

Sands, Arthur F, Gloeer, Peter, Guerlek, Mustafa E, Albrecht, Christian & Neubauer, Thomas A 2020

Nerita anatolica

Recluz 1841

Nerita fluviatilis

Linnaeus 1758