MALACOLOGIA, 1992, 34(1-2): 107-128
A NEW PROBLEMATICAL HYGROMIIDAE FROM THE AEOLIAN ISLANDS
(ITALY) (PULMONATA: HELICOIDEA) 1
Folco Giusti 2 , Giuseppe Manganelli 2 & Jorge V. Crisci 3
ABSTRACT
Helicotricha n. gen. is proposed for a very small hygromiid from the Aeolian Islands, Italy: H.
carusoi n. sp. The new species has a shell with persistent postembhonal hairs and is charac-
terized anatomically by: a right ommatophore retractor independent of the genitalia; a penial
nerve originating from the right cerebral ganglion; a vaginal complex with digitiform glands and
dart-sac complex consisting of two couples of stylophores disposed on opposite sides of the
vagina (each couple is formed by a larger dart-bearing outer stylophore and a smaller dartless
inner stylophore); and a penial complex with a very peculiar penial papilla. Direct anatomical
comparison of the new genus with other genera of the Hygromiidae suggested that it may be
very closely related to Microxeromagna. This hypothesis was subsequently found to be sup-
ported by the results of cladistic analysis. New evidence is thus provided to confirm that the
distinction between the Hygromiinae and the Trichiinae is artificial. A neotype is designated for
Helix aetnea Benoit, 1 857, a junior synonym of Xerotricha conspurcata (Draparnaud, 1 801 ), and
the presence of Helicopsis (s. str.) in western North Africa is confirmed.
Key words: Hygromiidae, Aeolian Islands, Italy, western Mediterranean, Helicella, Xerotricha,
Helicopsis, systematics.
INTRODUCTION
Recent insular equilibrium theory studies
based on analytical comparison of the mala-
cofaunas of the Tuscan and Aeolian archipel-
agos, Italy (Piantelli et al., 1990), have moti-
vated new field research and study of the
material collected from the various islands. As
happened for the islands of the Tuscan Archi-
pelago (Giusti & Manganelli, 1989, 1990),
new data emerged for the Aeolians. A new
species of the Hygromiidae was identified
amongst material of Xerotricha conspurcata
(Draparnaud, 1801) collected in all the Aeo-
lian Islands. The Hygromiidae are a group of
helicoids of western Palaearctic distribution
recently separated from the Helicidae as a
distinct family and characterized by a bursa
copulatrix duct free from the diaphragm wall
and a variable number of stylophores.
The peculiar structure of the genitalia made
it difficult to establish relationships and ge-
neric status of the new species. Although the
2 + 2 structure of the dart-sac complex as-
sociated with the vagina, and the right om-
matophore retractor free of penis and vagina,
at first glance suggested a relationship with
the genus Helicopsis, details of the penial
complex suggested other possibilities. In par-
ticular, as in the case of Helicella (one large,
evident and one vestigial, externally invisible,
stylophore on opposite sides of the vagina)
and Xerolenta (one normal and one modified
stylophore on opposite sides of the vagina)
which appear to form monophyletic groups re-
spectively with Candidula (one large, evident
and one vestigial, externally invisible, stylo-
phore on one side of the vagina) and Xero-
munda (one normal and one modified stylo-
phore on one side of the vagina) respectively
(Hausdorf, 1988, 1990a; Giusti & Manganelli,
1989; Manganelli & Giusti, 1989), it seems
highly probable that the new genus (one
larger outer stylophore and one smaller dart-
less inner stylophore on opposite sides of the
vagina) is a member of the monophyletic
group to which also Microxeromagna (one
larger outer stylophore and one smaller dart-
less inner stylophore on one side of the va-
gina) belongs. Accordingly, in view of the fact
that Helicella, Xerolenta, Candidula, Xero-
munda are unanimously regarded as distinct
generic taxa and in view also of our consid-
erations on character weighting in establish-
1 Notulae Malacologicae, LI.
2 Dipartimento di Biológica Evolutiva, Università degli Studi di Siena, Via Mattioli 4, 1-53100 Siena, Italy
laboratorio de Sistemática y Biología Evolutiva, Museo de La Plata, Paseo del Bosque 1900, La Plata, Argentina
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