Cornu (Erctella) cretense, Hausdorf & Bamberger & Walther, 2021

Hausdorf, Bernhard, Bamberger, Sonja & Walther, Frank, 2021, A Sicilian-Cretan biogeographical disjunction in the land snail genus Cornu (Gastropoda: Helicidae), Zoological Journal of the Linnean Society 192, pp. 59-74 : 65-69

CORNU (ERCTELLA) CRETENSE SP. NOV.

Z o o b a n k r e g i s t r a t i o n: l s i d: z o o b a n k. o r g: a c t: 3E86F066-5D7C-47F9-A267-378739E79B41.

Type material: Holotype: Greece, Crete, Chania: Agia Roumeli , rocks NW of the village, 90 m a.s.l., 35°13’53”N 23°57’24”E ( ZMH 148150 ; measurements: diameter, D = 25.7 mm, height, H = 24.0 mm) . Paratypes: Greece, Crete, Chania: Agia Roumeli , rocks NW of the village, 90 m a.s.l., 35°13’53”N 23°57’24”E ( FW 13138 /5; MN/1 ; NHMC 50.48871 /1; ZMH 146084 /8); Agia Roumeli, rocks across the river at end of Samaria gorge, 20 m a.s.l., 35°13’49”N 23°57’58”E (Paratypes FW 13139 /11; ZMH 146445 /1) .

Other material: Greece, Crete, Chania: Vlithias 300 m toward Kandanos , 210 m a.s.l., 35°17’04”N 23°41’30”E (subfossil, FW 13137 /1); Agia Roumeli, rocks NW of the village, 90 m a.s.l., 35°13’53”N 23°57’24”E (subfossil, ZMH 148149 /7); Agia Roumeli, E of village, rocks at coastal path, 10 m a.s.l., 35°13’51”N 23°58’26”E (subfossil, ZMH 146090 /1) .

Diagnosis: Cornu (Erctella) cretense is characterized by a medium-sized, conical-globose shell with 3.0–3.5 whorls with coarse, irregular, sometimes reticulated wrinkles and, usually, a closed umbilicus, a flagellum shorter than the combined length of penis and epiphallus and a diverticulum more than 1.5 times as long as the proximal part of the pedunculus plus bursa.

Shell ( Fig. 3A–E; Table 1): Conical-globose, with 3.0– 3.5 convex whorls; protoconch smooth; teleoconch with coarse, irregular, sometimes anastomosing wrinkles, in places with short, incised, spiral lines; creamcoloured or light brownish, unicolor or with up to five interrupted brown bands; body whorl rounded; aperture slightly oval; upper insertion of peristome distinctly descending, connected with the columellar margin of the peristome by a thin, transparent callus; peristome expanded, slightly reflexed and thickened; umbilicus closed or rarely a narrow slit.

Genitalia ( Figs 4A, 6; Table 2): Atrium short; penis long, distal part narrow, proximal part wider, surrounded by a penial tunica that fuses proximally with the epiphallus; penial lumen distal with a small, crest-like structure, otherwise smooth, distal papilla large, with an asymmetrical perforation, proximal papilla small, lateral, separated from the epiphallial pore by a pad; distal epiphallial lumen with corrugated ridges; the insertion of the penial retractor divides the epiphallus into a short distal part and a proximal part about three times longer; flagellum longer than epiphallus; dart apparatus consisting of a large dart sac and two glandulae mucosae inserting at the short vagina directly proximal of the dart;

)

; div

epiphallus sac dart of pedp) / 0.58 0.63 0.71 0.78 0.58

,

distal insertion + epd epp

epd

of (p+

; / f 0.9 0.9 0.9 2.1 2.0 epiphallus (proximal diverticulum f /v

ep,

;

vagina / v p

1.85

0.73

2.72

1.06

3.09

1.13 0.80

5.17

0.80

4.70

penis div,

,

p

: proximal

, vp

;

bursa

pedp div 27.8 16.0 20.0 32.0 22.5 16.0 19.5 25.0 17.5 30.0

Abbreviations

vagina; plus

).

mm

distal pedunculus pedd fod 4.0 6.0 7.0 4.0 4.2 2.5 6.4 5.0 5.0 9.0

in

(

aspersum vd,; vagina proximal vp vd 5.2 5.4 4.1 4.1 2.0 3.5 4.2 4.5 4.5 5.5);, v pedp,

f 19.6 22.3 17.0 45.0 47.0

Cornu

(

Cornu f;), flagellum) diverticulum; epp epd 10.5 3.5 4.0 12.7 3.7 9.2 5.2 9.5 4.0 11.0

and retractor of p 7.7 8.7 6.2 7.0 8.0 cretense

)

Erctella

penial

of

insertion

of 148150

))

146084 of

)

146067

)

146067 distal

Cornu

(

of insertion of (pedunculus ZMH holotype paratype

ZMH

river at

end ZMH

(Chania

ZMH

(Chania measurements proximal (distal ((across the) 13139 toward toward epiphallus;, pedd cretense ) Agia Roumeli Agia Roumeli rocks, FW () aspersum km 1.5 km 1.5 Genital

2

.

Table,

proximal

epp,

oviduct

fod

free

( Erctella

Cornu

of

rocks

NW

rocks

of NW

Agia

Roumeli Samaria gorge Cornu Cornu (Sfakion Chora Chora Sfakion

sac; each glandulae mucosae divided into five to ten thin, terminal branches that are slightly longer than their broader stem; opening of the dart sac into the vagina surrounded by a v-shaped lip that continues distally into a large pilaster that slightly extends into the distal penial lumen; proximal part of vagina internally with four longitudinal folds; short oviduct opens into the vagina with a papilla-like protuberance; proximal part of pedunculus (proximal of insertion of diverticulum), including the elongated bursa, almost three times as long as distal part; diverticulum broad, more than 1.5 times as long as the narrower proximal part of pedunculus plus bursa.

Remarks: With regard to anatomical characters, Cornu (Erctella) cretense is most similar to Cornu (Erctella) cephalaeditanum (Giannuzzi-Savelli et al., 1986) . The diverticulum of the bursa copulatrix of C. cretense is more than 1.5 times as long as the proximal part of the pedunculus plus bursa, whereas it is 1.2–1.5 times as long in C. cephalaeditanum ; two times as long in C. mazzullii (De Cristofori & Jan, 1832) and approximately as long as the proximal part of the pedunculus in C. insolidum (Monterosato, 1892) ( Colomba et al., 2011) . Whereas each glandula mucosa is divided into five to ten terminal branches in C. cretense , each is divided into 11–18 branches in C. cephalaeditanum , into 20–35 in C. mazzullii and into 23–45 in C. insolidum . Cornu cretense agrees with regard to the number of longitudinal folds in the proximal part of the vagina (four) with C. cephalaeditanum (four to five folds), but both differ from C. mazzullii (five to six folds) and C. insolidum (seven to eight folds). Both recent C. cretense (shell diameter 21.0– 28.9 mm) and C. cephalaeditanum (21–28 mm) are usually smaller than C. insolidum (29–35 mm) and C. mazzullii (25–36 mm), but the shell diameter range of the subfossil shells of C. cretense from the type locality (25.5–37.5 mm; Fig. 3C, D; Table 1) even exceeds the size range of these species. The shell sculpture of C. cretense is similar to some forms of C. mazzullii , but coarser than in C. insolidum and weaker than in C. cephalaeditanum .

Cornu (Erctella) cretense differs from the widespread Cornu (Cornu) aspersum (Müller, 1774) , which also occurs in Crete, in the usually smaller, more conical, lighter shell with a coarser sculpture and fewer whorls. However, both species show a wide range of variation in shell characters (see Fig. 3A–E vs. 3F–G; Table 1) so that an anatomical or genetic investigation may be necessary for a definite identification. The flagellum of C. cretense is shorter than the penis and epiphallus together, whereas it is, on average, 2.4 times as long as the penis plus epiphallus in C. aspersum [based on measurement data of 2078 C. aspersum specimens from Sherpa et al. (2018); S. Sherpa, pers. comm.]. However, there is a large variation of the relative length of the flagellum in C. aspersum from 0.8 to 5.0 times the penis plus epiphallus length. The flagellum was shorter than, or as long as, penis plus epiphallus in 0.7% of the measured C. aspersum specimens. In none of the measured 137 C. aspersum populations was the average flagellum length smaller than 1.4 times the penis plus epiphallus length. Whereas the flagellum is shorter than, or as long as, penis plus epiphallus in C. (Erctella) cretense and all other Erctella species; individuals with such a short flagellum are outliers in C. (Cornu) aspersum .

Distribution: Living populations of Cornu (Erctella) cretense were found only in the surroundings of Agia Roumeli at the south coast of western Crete. The animals hide under rocks at the base of limestone cliffs ( Fig. 7A). A subfossil shell ( Fig. 3E) was also found in rock crevices in Vlithias 300 m toward Kandanos, indicating that the range of C. cretense was larger in the past. However, it is possible that there are still additional relict populations of this species.

The type locality of C. cretense ( Fig. 7A) is almost identical with the type locality of Albinaria sublamellosa schultesi ( Wiese, 1987) , which has been visited by several malacologists. Thus, it is likely that C. cretense has been found previously. Apparently, the distinctness and importance of this taxon has been overlooked.

Conservation: Cornu (Erctella) cretense is assessed as Endangered [EN B1ab(i,ii) + 2ab(i,ii)] according to the IUCN criteria ( IUCN, 2012). This is based on the species occurring at two locations separated by a river. The localities in the direct vicinity of Agia Roumeli are outside the Samaria National Park. The expansion of the settlement due to the construction of tourist facilities and recreational activities in the area pose a major threat. The finding in the clay of rock crevices at Vlithias indicates that the species was more widespread and has experienced a considerable range reduction. Although we do not know the age of the shell from Vlithias, one might speculate that the range reduction might have been the result of anthropogenic land use, and/or of competition and introgression with the invasive C. aspersum .

Etymology: This species is named after its occurrence in Crete (cretensis used as an adjective).