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494 N. MAIO, A. PETRACCIOLI, P. CROVATO, N. AMOR & G. ODIERNA

tionships with T. caroni. The morpho-biometric these species as a single species complex (“ciclo di
criterion used to date does not enable clear discrim- forme”). Giusti et al. (1995), too, suggest that these
ination between the various populations. T. trochlea species probably all belong to a hypothetical “su-
should have an h/d between 1.14 and 0.70 or lower, perspecies” or “species group”, the validity of
T. caroni between 1.30 or higher and 0.88 and T. which has yet to be confirmed.
elegans between 0.82 and 0.62 or lower. Thus the According to Liggia (2013), T. trochlea Pfeiffer
h/d ratios of the three forms overlap and the same 1846 is synonymous with T. elegans (Gmelin
is true of their distributions. 1791), but the site does not provide sources or other
Studies of anatomical characters do not solve references for this conclusion.
the problem. Interestingly, in their times, von
Ihering (1892) and Hesse (1934) already observed Conservation status
that the anatomy of specimens of T. caroni from
Capri was indistinguishable from that of Sicilian In the Red List of the International Union for the
specimens. Moreover, Caziot (1908) and Sacchi Conservation of Nature (IUCN), version 2013.1.
(1956a) considered that the anatomy of H. elegans (Falkner et al., 2011), the status of T. caroni is clas-
from Tunisia was identical to that of Sicilian H. ca- sified as “LC” (Least Concern) or “lowest risk, not
roni-elata. Giusti et al. (1995) observed an evident endangered or low risk”. In the Red List of the 27
similarity of genital systems between T. caroni from countries of the European Union it is classified as
Sicily and T. elegans from Tuscany and Algeria, “LC” and is considered a “European endemic
sustaining that anatomically, all species of the “ele- species” (Cuttelod et al., 2011). T. elegans is also
gans group” (T. elegans, T. caroni, T. spratti and T. classified as “LC” by the IUCN (Gargominy, 2011)
cumiae) were indistinguishable. and in the European Red List it is considered a “Eu-
Sacchi (1955a; 1956b) considers Helix caroni- ropean endemic species” (Cuttelod et al., 2011). In
elata and H. trochlea valid species, distinct from H. view of the extreme localisation of currently known
elegans by virtue of “their particular geographic dis- populations of these species, we think they are near
tribution” and the “remarkable morphological char- threatened and worthy of protection at regional and
acterisation” of their shells, even if he views all national level.

Figure 33. Sites of finding of Trochoidea caroni in the Western Mediterranean.