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found in some taxa of Mollusca (Pinceel et al. 2005 and references therein) but not in others (Murray et al. 1991;
Douris et al. 1998; Guiller et al. 2001; Pfenninger & Posada 2002), does not occur in this case. Therefore, in our
opinion, the mtDNA genetic differences assessed between groups (6–10% for 16S rDNA; 7–17% for 12S rDNA)
can be considered a good value for species delimitation in Stylommatophora, suggesting strong isolation and strong
divergence, i.e., the very low dispersal ability of these animals is likely to have drastically reduced gene flow. This
justifies to consider the taxa under investigation as different phylogenetic species. Moreover, taking into account
that in molluscs for the ITS region interspecific divergences rise up to 3.4% and divergences between different gen-
era are up to 10% (e.g., Wade et al. 2001; Van Riel et al. 2005), ITS-2 distances between the mazzulli group and C.
aspersum and C. apertus (7.6% and 6%, respectively) seem not only to substantiate our hypothesis that the mazzul-
lii group comprises three species but also to strongly support the concept that these species belong to a distinct
genus.

The morphological data demonstrate that the three taxa within the mazzullii group differ in many features
including shell size, shape and sculpture, the ratio of the bursa copulatrix diverticulum (BCD) and duct (DBC)
lengths, the number of digit-like appendices of the digitiform glands and the number of vaginal longitudinal pleats.

When compared to Cornu aspersum, Cantareus apertus and Eobania vermiculata, the genitalia of the three
species of the mazzullii complex differ significantly in many morphological characters, although the general geni-
talic architecture is similar (see Giusti et al. 1995). Thus, genital morphology likewise indicates that the mazzullii
complex may deserve to be treated as a separate genus.

To further investigate this point, twenty species, representing sixteen currently recognized Helicidae genera,
together with the thirty-seven specimens analysed in this study, were used to construct a Maximum Likelihood
molecular phylogeny. Partial DNA sequences of the mitochondrial 16S rDNA for the twenty species were retrieved
from GenBank. Most genera are represented by a single species. Helicella itala (Hygromiidae) was used as an out-
group. As shown in Figure 42, the ML consensus tree clearly indicates that (i) all genera are well separated from
one another; (ii) 16S rDNA sequences of C. aspersum and C. apertus reported in the present paper are absolutely in
line with those deposited in GenBank by other authors (i.e., all specimens of a given genus are in the same clade);
(iii) the mazzullii complex, Cantareus and Cornu form a monophyletic group which is distinct from other related
genera (e.g., Eobania, Helix); and (iv) the mazzullii group is supported by a high BP value (97%). The results of
this “meta-analysis”, combined with the fact that the exclusive ecological features and very limited distribution
area of mazzullii group make it very peculiar among Mediterranean Helicidae, once again support the idea that the
complex might be attributed to a distinct genus.

More than a century ago, Monterosato (1894) introduced Erctella (from Ercta, the ancient name of Monte Pel-
legrino, near Palermo) as a new section in the subgenus Helix (Pomatia). He included two species group taxa of the
mazzullii group, H. mazzullii and H. costae, in the new section. Monterosato didn’t publish any other papers on
these land snails, but in one of his manuscripts he wrote: “…Tutte queste quattro principali forme: luparellensis
(estinta); retirugis, mazzulli, insolida (attuali); sono appartenenti al sottogenere Erctella…” (“…All four main
types: luparellensis [extinct]; retirugis, mazzulli, insolida [extant]; belong to the subgenus Erctella…” [translation
by the authors]) (see http://www.sim-online.it/area.php?idarea=26, under”Manoscritti”, file name:”su alcune helix/
gs003-4 su alcune helix.jpg”) . In an autographic note (Fig. 43) (Gigli collection, Natural History Museum of
Milan) commenting on several mazzullii specimens caught on Monte Pellegrino in 1912, Monterosato says: “…It
belongs to the genus Erctella Monts., introduced by me and adopted by Pilsbry. Because of its anatomical charac-
ters it firmly differs from Cryptomphalus (aspersa)”.

The differences among H. mazzullii s.l., Cantareus apertus and Cornu aspersum were confirmed by Varga’s
(1989) detailed work on the digestive and other organ systems of these taxa (all included in the genus Helix by
Varga) from Sicily. In addition, Varga (1989) recognized a distinct species within the mazzullii complex (as Helix
sp.), collected between Palermo and Trapani.

The name Erctella has been mostly ignored or considered as synonym of related genera (Alzona 1971; Bank et
al. 2001; Bank 2009) despite the rather high number of species included in this supraspecific taxon by Pilsbry
(1895). Recently, Liberto et al. (2010) proposed to re-introduce the genus Erctella for this group of endemic Sicil-
ian taxa with their peculiar rupicolous and saxicavous biology. Results discussed in this paper not only support the
suggestion to re-introduce the genus Erctella including E. mazzullii, E. cephalaeditana and E. insolida, but also
complement and support Monterosato’s opinion (1894; Ryolo & Palazzi 2009) that Erctella shows a high variabil-
ity and is to be kept quite distinct from the closely related genera Cantareus and Cornu.

FROM HELIX MAZZULLII COMPLEX TO ERCTELLA Zootaxa 3134 © 2011 Magnolia Press · 15