Siciliaria

Siciliaria

Revisory remarks on the species of Siciliaria Vest from N. W. Sicily

Hartmut Nordsieck (VI.2013, supplemented VII.2021)

I. History

A. Schmidt (1868: 40-43) was the first who proposed a systematic arrangement of the seven Clausilia species from N. W. Sicily known so far. He classified the species with two groups („Formenkreise“) which mainly differ by the formation of the clausilium plate. Other characters which he regarded as important were sculpture, development of lamellae (inserta, inferior lamella) and palatal plicae. His system was the following:
Formenkreis of septemplicataClausilia grohmanniana Rossmässler, Cseptemplicata  Philippi, Ccalcarae Philippi, Cconfinata = scarificata L. Pfeiffer, Ctiberii A. Schmidt; Formenkreis of crassicostataCcrassicostata L. Pfeiffer, Cnobilis L. Pfeiffer.
O. Boettger (1877: 33-34) named the groups of Schmidt (F. of septemplicata = Siciliaria Vest sensu stricto, F. of crassicostata = Trinacria O. Boettger). Later on, he (1879: 85-91) gave descriptions of several species taxa and listed eight species (Cleucophryne L. Pfeiffer added to those of Schmidt). His distribution data were in part based on wrong localities on the labels from Benoit and others.
Benoit (1882: 101-120) who had distributed most of the material in the collections of his contemporaries listed 13 species, several of them regarded as varieties or synonyms by Boettger. Like those of Boettger, his distribution data were partially wrong.
Westerlund (1892: 47-48) published three of the numerous taxa names of (Allery di) Monterosato and gave a determination key for the species.
A. J. Wagner (1913, 1925) figured the genital organs of three Siciliaria species from N. W. Sicily (Sseptemplicata: 1913: pl. 572, fig. 14; Sgrohmanniana: 1925: pl. 1, fig. 8, Scalcarae: pl. 3, fig. 25). He (1924: 123-125) gave a list of the species which is nearly identical with that of Boettger.
Brandt, after his collection trip in Sicily in 1949, prepared a manuscript with the description of 24 new taxa based on „species“ of Monterosato or collected by himself. This manuscript remained unpublished; later on, only five of the species taxa were regarded by Brandt (1961: 6-9) as different enough to be described as new (among them two species: Sferrox, with figure of genitalia fig. 1, Salcamoensis). Besides, he (: 8) united Sleucophryne and Stiberii (and Seminens which later on was recognized as species) to one species under the name Sleucophryne, with which he also affiliated the newly described Sriberothi as subspecies. Many localities given by him cannot be identified or are obviously wrong.
Alzona (1971: 90-92) listed the same species as Boettger. Brandt’s new taxa were not considered, although his paper was cited.
Nordsieck (1979: 259-260) listed also the same species as Boettger and (: 269) united his species groups (Siciliaria s. str., Trinacria (preoccupied) = Sicania Tomlin). Later on, he (1984: 202) described the new species Sspezialensis based on material collected by K. L. Pfeiffer.
Manganelli et al. (1995: 25, 47-48), in the checklist of Italian pulmonate gastropods, enumerated 10 species taxa, proposed as such by Nordsieck (in litteris, Sferrox and Sspezialensis added to those of Nordsieck 1979). At the same time, Giusti et al. (1995: 327-330) evaded a distinction of species within the group which they gave the oldest name Sseptemplicata. Therefore, they determined Scalcarae from Quaternary deposits of Malta as S. cf. septemplicata.
Nordsieck (2002: 30, 34) recognized Cleucophryna and Ceminens as different species. He (29, 34) listed 12 species of Charpentieria (Siciliaria) and classified them with three species groups, based on some shell characters regarded as informative: 1 nobiliscalcarae group, 1a nobilis subgroup (CnobilisCspezialensisCcrassicostataCeminens), 1b calcarae subgroup (CcalcaraeCtiberiiCleucophryna), 2 grohmanniana group (CgrohmannianaCseptemplicataCscarificata). Because of their ambiguous character combinations, Cferrox and Criberothi were not included in one of these groups. Several forms assumed to have originated by interspecies hybridization (: 34) were added.
Beckmann (2004: 188, maps 1 and 2) published detailed informations on the distribution of the species and described (: 188-190) two new subspecies, both assumed to be hybrid forms.
Reitano et al. (2007: 326-328) gave further informations on the distribution of Sferrox.
Liberto et al. (2015) published a detailed description of S. scarificata.
Liberto et al. (2016) gave further informations on morphology and distribution of  S. calcarae and (: 371) described a new subspecies of that species, S. c. orlandoi.

II. System

The material on which the following system is based comprises about 230 samples of Siciliaria (S.) species from the collection of the Forschungsinstitut Senckenberg (abbreviation: SMF), containing the types of several species taxa, and 80 samples of my own collection, deposited in the Staatliches Museum für Naturkunde Stuttgart (abbreviation: SMNS) and the Forschungsinstitut Senckenberg. In the Senckenberg collection material collected by Kobelt, K. L. Pfeiffer, Brandt and Beckmann is kept, in my own collection an important part of the Brandt collection (SMNS) and material collected by C. and J. Hemmen in 2009 (SMF). 80 samples of all taxa have been subjected to a more thorough morphological examination.
In collections from the nineteenth century the localities given on the labels have often turned out to be wrong. In this article only locality data given by collectors, who in my opinion are reliable, are used. In any case, I had to rely on those data, because until now I had not the opportunity to collect in this region.
Siciliaria Vest and Charpentieria Stabile are separated as genera; for the arguments see Nordsieck (2013). The DNA analyses of Uit de Weerd & Gittenberger (2013: tree fig. 3) and Hausdorf (unpubl.: tree based on 16S mtDNA analysis) confirm this separation; in both trees Charpentieria appears as sister group of a clade including Siciliaria and Delima Hartmann. For a recent DNA analysis of Siciliaria species and its discussion see website article on DNA studies.
The examination of the genital morphology of several Siciliaria species (see website article on Genital studies) had the result that the genitalia of all species are similar.

1. Diagnoses and distribution

In the following the diagnoses of the species of Siciliaria from N. W. Sicily and their distribution, as far as known from the examined material, are given. In notes, geographic forms which could have subspecific rank are characterized. Among them, there are several forms which have probably originated by interspecies hybridization (see chapter 2.).
The following shell characters have turned out to be informative for species diagnoses (see figs. 1-7):
1. Decollation: Shell entire / decollated.
2. Sculpture: Whorls rib-striated, with sutural papillae / weakly ribbed, papillae still recognizable / strongly ribbed.
3. Cervix of body whorl: Only with basal keel, without dorsal keel / with more or less pronounced dorsal keel.
4. Inferior lamella: Lamella more or less protruding into the lumen of the body whorl, described as: lamella high / moderately high / low.
5. Anterior upper palatal plica: Only one plica present / two plicae present, upper and lower one / plica missing.
6. Clausilium plate: Palatal edge of plate distally receding, thus distal part narrowed, forming a gutter (figs. 1-2) / not receding, palatal and columellar edges of plate nearly parallel (figs. 3-7). Palatal edge distally much bent up (figs. 3-4) / bent up (figs. 1-2) / somewhat or not bent up (figs. 5-7).
The distribution of the species concerned is restricted to N. W. Sicily: Egadi islands, Sicilian mainland from Trapani in the west to the western boundary of Madonie in the east, in the south delimited by the imaginary line Trapani–Calatafimi–San Cipirello–Ficuzza–Monte San Calogero.
In a larger part of N. W. Sicily two species pairs with identical clausilium plate, but different appearance (shell entire, nearly smooth and papillate / shell decollated, ribbed) occur (figs. 1-4). The smooth papillate species is adapted to more shady habitats, while the ribbed one lives in more open rock habitats. Decollation is possibly an adaptation to a life under stones. One of these species pairs, Sseptemplicata / Sgrohmanniana (figs. 1-2), is distributed in the east, the other one, Scalcarae / Stiberii (figs. 3-4), in a larger part of the region, Scalcarae in the whole region, Stiberii only in the central and eastern part. The range restriction of the latter is probably caused by the occurrence of other rock-dwelling species, those of Sicania, in the west.
On the San Vito peninsula, there is a species pair of Sicania, which lives in open rock habitats, Snobilis / Sspezialensis. Both are adapted to this habitat by a well-developed white surface layer of the shell (fig. 5), looking like Albinaria species, both are decollated. Sspezialensis exhibits a special closing apparatus (clausilium plate fit into a frame of palatal plicae, anterior palatal plicae missing), which may better protect it from desiccation. On one mountain of this peninsula, Monte Cofano, a species with percostate shell, Scrassicostata (fig. 6), occurs. This sculpture, which is found also in certain Albinaria species and other rock-dwelling clausiliids of meridional Europe, may be another adaptation to a life in open rock habitats.
The occurrences of Siciliaria species on the Egadi islands are of special interest. On Marettimo, only Sscarificata occurs. On Favignana, originally only Scalcarae occurred. S. crassicostata, which has been collected by several authors on the island (e. g., by Brandt on garden walls, fig. 6) has obviously been introduced (by man?) from Monte Cofano nearby.

Figs. 1-7. Siciliaria spp.
Frontal view and body whorl dorsal view. Actual shell height = H (mm). Phot. S. Hof.

Fig. 1. Sseptemplicata, Passo di Rosetto near Palermo, ex SMF 67942, H = 19.5, shell with clausilium plate H = 19.0.
Fig. 2. Sgrohmanniana, Monte Pellegrino near Palermo, ex SMF 67528, H = 19.3, shell with clausilium plate H = 18.1.
Fig. 3. Scalcarae, Sferracavallo, ex SMF 67925, H = 19.0.
Fig. 4. Stiberii, Monte della Fiera, ex SMF 333547, H = 17.1.

 

Fig. 5. Snobilis, Capo San Vito, ex SMF 96476, H = 20.9.
Fig. 6. Scrassicostata, Island of Favignana, ex SMF 265742, H = 18.9.
Fig. 7. Sriberothi, „Monte della Terrazza“, ex SMF 232084, H = 20.2.

Siciliaria Vest 1867

For the subdivision of Siciliaria from N. W. Sicily see website art. on DNA studies.

S. (Siciliaria)

Nomenclatural note: Clausilia decollata and Cdeshayesii Potiez & Michaud 1838 are unidentified species. The first may be Sgrohmanniana, the second Sseptemplicata or Scalcarae. Three „species“ of Benoit (1882) are also unidentified: Ctrinaclina (misprint for trinacrina) (= Scalcarae?), Crubra (= Sseptemplicata?) and Csubdiaphana (= Sgrohmanniana?). The variety names published by Monterosato, in fact infrasubspecific, are not considered in this article.

Sgrohmanniana (Rossmässler 1836)
Fig. 2

Diagnosis: Shell mostly decollated; whorls ribbed; dorsal keel indistinct or missing; inferior lamella very high; two anterior upper palatal plicae present, upper one mostly separated from upper palatal plica; palatal edge of clausilium plate distally receding, plate gutter-like narrowed, palatal edge against distal end bent up and more or less pointed.

Distribution: Monte Pellegrino, Monte Gallo.

Synonyms: Cgrohmanniana var. minor A. Schmidt 1868 [non Rossmässler], Cgrohmanniana var. panormitana Paulucci 1878.

Intraspecific forms:
Priola form, Priola near Palermo: Shell not decollated; whorls more weakly ribbed.

Sseptemplicata (Philippi 1836)
Fig. 1

Diagnosis: Shell mostly not decollated; whorls rib-striated, with sutural papillae; dorsal keel indistinct or missing; inferior lamella very high; two anterior upper palatal plicae present, upper one mostly separated from upper palatal plica; palatal edge of clausilium plate distally receding, plate gutter-like narrowed, palatal edge against distal end bent up and more or less pointed.

Distribution: From Cinisi in the west and Monte Gallo in the north to Piana degli Albanesi in the south and Monte Catalfano in the east.

Synonyms: Csericina Rossmässler 1836, Cseptemplicata var. prasina A. Schmidt 1868. The name Cprasina is a copying-mistake of Cproxima, caused by illegible labels of Benoit.

Intraspecific forms:
Parco form, Parco near Palermo: Inferior lamella in part lower; lower anterior upper palatal plica missing; palatal edge of clausilium plate less or not bent up.
salcamoensis Brandt 1961, „Alcamo“: Cervix more strongly sculptured; dorsal keel more pronounced; inferior lamella in part lower; lower anterior upper palatal plica more or less reduced; clausilium plate distally less narrowed, palatal edge less upbent. shemmeni (Beckmann 2004), Piano Margi near Cinisi, is considered as synonym.

Sleucophryna (L. Pfeiffer 1862)

Diagnosis: Shell decollated; whorls ribbed; dorsal keel mostly indistinct or missing; inferior lamella moderately high; anterior upper palatal plica present, separated from or connected with upper palatal plica; palatal edge of clausilium plate distally slightly or not receding, palatal edge distally somewhat or not bent up.

Distribution: Isola delle Femmine and Grotta Conza to Monte Gallo.

Synonyms: Cleucophryne var. laudabilis O. Boettger 1879, Cconfinata var. merens Westerlund 1892.

Intraspecific forms:
Sferracavallo form, Sferracavallo: Inferior lamella lower; palatal edge of clausilium plate more strongy bent up.

Scalcarae (Philippi 1844)
Fig. 3

Diagnosis: Shell not decollated; whorls rib-striated, with sutural papillae; dorsal keel indistinct or missing; inferior lamella moderately high or low; anterior upper palatal plica present, mostly separated from upper palatal plica, rarely lower anterior upper palatal plica present; palatal edge of clausilium plate distally not receding, palatal edge distally more or less strongly bent up.

Distribution: Island of Favignana, whole mainland of N. W. Sicily from Erice in the west to Montagna Grande in the east; in the south to Calatafimi and Ficuzza region.

Synonyms: Cadelinae Küster 1860, Cbrugnoneana Pini 1884, Ccalcarae var. nodosa Westerlund 1892.

Intraspecific forms:
cbelliemii Brandt 1961, Monte Belliemi near Partinico: Whorls ribbed.
Sagana form, Sagana near Montelepre: Inferior lamella higher; lower anterior upper palatal plica more or less developed; palatal edge of clausilium plate less strongly bent up.
c. orlandoi Liberto, Reitano, Giglio, Colomba & Sparacio 2016, region of Ficuzza: Dark brown; no further anterior upper palatal plica present; clausilium plate like in Sseptemplicata, but distally less narrowed.

Stiberii (A. Schmidt 1868)
Figs. 4, 7, 10

Diagnosis: Shell not decollated or decollated; whorls ribbed; dorsal keel of different prominence; inferior lamella moderately high or low; anterior upper palatal plica present, mostly separated from upper palatal plica, rarely lower anterior upper palatal plica present; palatal edge of clausilium plate distally not receding, palatal edge distally more or less strongly bent up.

Distribution: From north of Cinisi in the north to San Cipirello in the south, Monte San Calogero?

Synonyms: Ctiberiana Paulucci 1878.

Intraspecific forms:
Southern form from Monte Iato and Monte Kumeta = type form, Monte San Calogero?: Shell not or only in part decollated; dorsal keel less strong.
There is no doubt that Clausilia tiberii A. Schmidt (1868: 42-43) belongs to the southern form. Originals from Benoit (SMF 67544, 96458, see also Benoit 1859: pl. 6, fig.7) do not differ from the form from Monte Kumeta (fig. 10).
Northern form from Monte Palmeto and Monte della Fiera: Shell decollated; dorsal keel strong.
Sriberothi Brandt (fig. 7) is similar to that form (see chapter 3.), differing mainly by the clausilium plate with palatal edge distally not bent up.
Armetta form, Grotta Armetta near Carini: Shell decollated; more densely ribbed; dorsal keel weak; inferior lamella higher.
tscalettensis (Beckmann 2004), Port la Scaletti near Cinisi: Whorls rib-striated; inferior lamella higher; palatal edge of clausilium plate somewhat or not bent up.

S. ferrox Brandt 1961

Diagnosis: Shell mostly not decollated; whorls ribbed, sutural papillae recognizable; dorsal keel distinct or indistinct; inferior lamella moderately high or high; two anterior upper palatal plicae present, upper one mostly separated from upper palatal plica; palatal edge of clausilium plate distally less or not receding, palatal edge distally not bent up.

Distribution: From Altavilla Milicia to Termini Imerese.

Synonyms: C. confinata var. commeata Westerlund 1892 could be an older synonym, but the description is too poor (lower anterior upper palatal plica not mentioned) and types are not available (Reitano et al. 2007: 328).

S. (Sicania) Tomlin

Snobilis (L. Pfeiffer 1848)
Fig. 5

Diagnosis: Shell decollated; with well-developed white surface layer; whorls mostly weakly rib-striated, with sutural papillae; dorsal keel missing; inferior lamella moderately high or high; anterior upper palatal plica present, mostly separated from upper palatal plica, or missing, basalis tending to be shortened, posterior lower palatal plica more or less reduced; palatal edge of clausilium plate distally not receding, palatal edge distally somewhat or not bent up.

Distribution: San Vito peninsula from Monte Monaco and Monte Acci, Monte Cofano.

Synonyms: Ccantrainei Deshayes 1851, Csicula Rossmässler 1856 (validated by Paulucci 1878).

Intraspecific forms:
Type form from „Ridicofano“ = probably San Vito: Anterior upper palatal plica mostly present.
Form from remaining species range: Anterior upper palatal plica mostly missing.
nepisoma Brandt 1961, coast near S. Vito: Shell smaller; whorls more distinctly rib-striated; anterior upper palatal plica missing.

Sspezialensis H. Nordsieck 1984

Diagnosis: Shell decollated; with well-developed white surface layer; whorls ribbed or weakly rib-striated, with sutural papillae; dorsal keel missing; inferior lamella mostly high; anterior upper palatal plica missing, basalis missing, posterior lower palatal plica connected with lunella; clausilium plate fit in the frame of lunella and posterior lower palatal plica; palatal edge distally not bent up.

Distribution: San Vito peninsula from Macari and Castelluzzo to Monte Acci and Monte Speziale.

Intraspecific forms:
Type form is ribbed.
Form from remaining species range: Whorls weakly rib-striated.

Seminens (A. Schmidt 1868)

Diagnosis: Shell decollated; whorls ribbed; dorsal keel indistinct or missing; inferior lamella mostly high; anterior upper palatal plica present, mostly separated from upper palatal plica, basalis tending to be shortened; palatal edge of clausilium plate distally not receding, palatal edge distally somewhat or not bent up.

Distribution: From Custonaci in the west to Castellammare in the east, environs of Calatafimi, M. Bonifato near Alcamo.

Intraspecific forms:
Custonaci form: Whorls more widely ribbed, transitional to S. crassicostata.

Scrassicostata (L. Pfeiffer 1856)
Fig. 6

Diagnosis: Shell decollated; whorls ribbed, in part percostate; dorsal keel distinct or indistinct; inferior lamella moderately high or high; anterior upper palatal plica present, separated from upper palatal plica, in part missing, basalis tending to be shortened; palatal edge of clausilium plate distally not receding, palatal edge distally somewhat or not bent up.

Distribution:: Monte Cofano, (probably introduced on) island of Favignana.

Siciliaria (?)

Sscarificata (L. Pfeiffer 1856)

Diagnosis: Shell mostly decollated; whorls ribbed, sutural papillae recognizable; dorsal keel indistinct ore missing; inferior lamella high; anterior upper palatal plica present, separated from or connected with upper palatal plica; palatal edge of clausilium plate distally receding, palatal edge distally somewhat or not bent up.

Distribution: Island of Marettimo.

Synonyms: The names Cscarificata and Csacrificata are copying-mistakes of Cconfinata, caused by illegible labels of Benoit.

2. Interspecies hybridization

The forms of Siciliaria, which are possibly hybrid ones, are enumerated in the following. They are forms of well-defined species restricted to certain localities or regions differing from the nominotypical forms by showing characters of another species. This other species is clearly different from that species and is distributed in the same region. The possible hybrid forms occur in the neighbourhood of or are even surrounded by populations of the nominotypical form of the species to which they belong. They could be the products of gene flow from the other species restricted to a limited locality or region.
These forms are the following:
1. S. grohmanniana, Priola form (fig. 8), with characters of Sseptemplicata, occurring in the environs of Palermo, where both species are distributed.
2. Sseptemplicata, Parco form, with characters of Scalcarae, from a locality near Palermo in a region, where both species have been traced in localities nearby.
3. Sseptemplicata alcamoensis (fig. 9) = Sshemmeni, with characters of Stiberii, the latter occurring near Cinisi in a region, where both species are distributed. The locality Alcamo for Ssalcamoensis is probably wrong, also because neither Sseptemplicata nor Stiberii have been found in that region.
4. Scalcarae belliemii from Monte Belliemi, with the ribbing of Stiberii, which occurs in the Monte della Fiera nearby.
5. St. tiberii, type form from Monte Kumeta (fig. 10), with characters of Scalcarae, occurring nearby.
6. Sleucophryna, Sferracavallo form, with characters of Scalcarae, from Sferracavallo where both species have been found.
7. S. eminens with widely ribbed shell from near Monte Cofano, transitional to S. crassicostata, occurring nearby.

3. The riberothi problem

The taxon which has been described by Brandt (1961: 8) as Sleucophryne riberothi is a special problem within the systematics of Siciliaria (S.). The locality of the type form „valley north of Ribera“ given by Monterosato, who provided it as Clausilia riberothi, is probably wrong. The species cannot be found in the environs of Ribera (Agrigento province) (Beckmann 2004: 188); besides, this locality is outside the range of Siciliaria (S.). Another form (fig. 7), also coming from Monterosato and named Cremota (this name, however, has been used by him also for the northern form of Stiberii, Brandt 1961: 8), is said to come from the mountains „della Terrazza“ (or „Torrazza“) (two samples, already mentioned by Beckmann: 188). This locality could not be traced until now.
Sriberothi differs from Sleucophryna by the prominent dorsal keel, which is like that of the northern form of Stiberii, and from both by the clausilium plate (fig. 7). In all probability, it belongs to S. tiberii next to the northern form.

Figs. 8-10. Siciliaria spp., hybrid forms (numbers see list in the text).
Frontal view and body whorl dorsal view. Actual shell height = H (mm). Phot. S. Hof.

Fig. 8. Sgrohmanniana, Priola form = 1., ex N 10022, H = 19.8.
Fig. 9. Sseptemplicata alcamoensis = 3., N 10018, H = 21.1.
Fig. 10. St. tiberii, form from „M. della Scala“ = Monte Kumeta = 6., N 10008, H = 24.2.

References

Alzona, C. (1971): Malacofauna Italica. Catalogo e bibliografia dei molluschi viventi, terrestri e d’acqua dolce. – Atti della Società italiana di Scienze naturali e del Museo civico di Storia naturale di Milano, 111: 1-433.

Beckmann, K.-H. (2004): Zur Verbreitung der endemischen nordwestsizilianischen Clausiliidae der Untergattung Charpentieria (Siciliaria) mit Beschreibung von zwei neuen Unterarten (Gastropoda: Stylommatophora: Clausiliidae). – Archiv für Molluskenkunde, 133 (1/2): 185-191.

Benoit, L. (1857-1862): Illustrazione sistematica critica iconografica de‘ testacei estramarini della Sicilia Ulteriore e delle isole circostanti. – I-XVI, 1-52, pls. 1-2 (1857); 53-116, pls. 3-4 (1857); 117-180, pls. 5-6 (1859); 181-248, pls. 7-8 (1862); pls. 9, 11, 12 (without date); Napoli.

Benoit, L. (1882): Nuovo catalogo delle conchiglie terrestri e fluviatili della Sicilia. – Atti della Reale Accademia Peloritana, 3: 43-216 (Sep.: I-VI, 7-176).

Boettger, O. (1877): Clausilienstudien. – Palaeontographica, (N. F.) Suppl., 3: 1-122, 4 pls. Cassel.

Boettger, O. (1879): Gattung Clausilia Drap. – In: Rossmässler, Icon. Land- und Süsswasser-Mollusken, (1) 6 (4/6): 52-153, pls. 167-178. Wiesbaden.

Brandt, R. (1961): Diagnosen neuer Clausiliiden. – Archiv für Molluskenkunde, 90 (1/3): 1-20, 2 pls.

Giusti, F., Manganelli, G. & Schembri, P. J. (1995): The non-marine molluscs of the Maltese Islands. – Museo Regionale di Scienze Naturali Torino, Monografie XV: 607 pp.

Liberto, F., Colomba, M., Reitano, A., Giglio, S.  & Sparacio, I. (2015): The endemic door snail of Marettimo (Egadi Islands, Sicily, Italy): Siciliaria (Siciliaria) scarificata (L. Pfeiffer, 1856) (Pulmonata Clausiliidae). – Biodiversity Journal, 6 (1): 483-492.

Liberto, F., Reitano, A., Giglio, S., Colomba, M. & Sparacio, I. (2016): Two new Clausiliidae (Gastropoda Pulmonata) of Sicily (Italy) . – Biodiversity Journal, 7 (3): 365-384.

Manganelli, G., Bodon, M., Favilli, L. & Giusti, F. (1995): Gastropoda Pulmonata. – In: Minelli, A., Ruffo, S. & La Posta, S. (Eds.): Checklist delle specie della fauna italiana, 16: 1-60. Bologna.

Nordsieck, H. (1979): Zur Anatomie und Systematik der Clausilien, XXI. Das System der Clausilien, II: Die rezenten europäischen Clausilien. – Archiv für Molluskenkunde, 109 (4/6): 249-275.

Nordsieck, H. (1984): Neue Taxa rezenter europäischer Clausilien, mit Bemerkungen zur Bastardierung bei Clausilien (Gastropoda: Clausiliidae). – Archiv für Molluskenkunde, 114 (4/6): 189-211, 2 pls.

Nordsieck, H. (2002): Contributions to the knowledge of the Delimini (Gastropoda: Stylommatophora: Clausiliidae). – Mitteilungen der deutschen malakozoologischen Gesellschaft, 67: 27-39.

Nordsieck, H. (2007): Worldwide Door Snails (Clausiliidae), recent and fossil. – 214 pp., 20 pls. Hackenheim (ConchBooks).

Nordsieck, H. (2013): Delimini (Gastropoda, Pulmonata, Clausiliidae) from Apennine Italy, with the description of three new subspecies from Calabria. – Conchylia, 44 (1/2): 3-14.

Reitano, A., Liberto, F. & Sparacio, I. (2007): Nuovi dati su molluschi terrestri e dulciacquicoli di Sicilia. 1° Contributo (Gastropoda Prosobranchia Neotaenioglossa; Gastropoda Pulmonata Basommatophora, Stylommatophora). – Naturalista siciliano, 31 (3-4): 311-330.

Schmidt, A. (1868): System der europäischen Clausilien und ihrer nächsten Verwandten: 175 pp., 1 tab. Cassel.

Uit de Weerd, D. R. & Gittenberger, E. (2013): Phylogeny of the land snail family Clausiliidae (Gastropoda: Pulmonata). – Molecular Phylogenetics and Evolution, 67: 201-216.

Wagner, A. J. (1913-1915): Familie Clausiliidae. – In: Rossmässler, Iconogr. Land- und Süßwassermollusken, (2) 21: 1/2 (1913): 1-20, pls. 571-580; 3/4 (1914): 21-44, pls. 581-590; 5/6 (1915): 45-65, pls. 591-600. Wiesbaden.

Wagner, A. J. (1924): Systematisches Verzeichnis der mir heute bekannten Arten und Formen der Clausiliidae. III. – Annales Zoologici Musei Polonici Historiae Naturalis, 3 (3/4): 99-126.

Wagner, A. J. (1925): Studien über die Systematik, Stammesgeschichte und geographische Verbreitung des Genus Delima (Hartmann) A. J. Wagner. – Annales Zoologici Musei Polonici Historiae Naturalis, 4 (1): 1-73, 16 pls.

Westerlund, C. A. (1892): Spicilegium Malacologicum. Neue Binnen-Conchylien in der paläarktischen Region. – Verhandlungen der k. k. zoologisch-botanischen Gesellschaft in Wien, 42: 25-48.