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Journal of ConChology (2011), Vol.40, no.6 583
IntroductIon
The archipelagos located in the eastern Atlantic
Ocean, known as the Macaronesian region, con-
tain a rich and diverse native malacofauna that
has undergone extensive speciation and adap-
tive radiation. However, many snail taxa are still
poorly known, including the family Discidae.
Recent checklists of the non-marine Mollusca
of Macaronesia (Bank, Groh & Ripken, 2002;
Seddon, 2008; Fauna Europaea database project,
2011), together with the data in Thiele (1931)
recognise about 14 endemic species of Discidae
from Macaronesia, which were grouped into the
genera Discus Fitzinger 1833 and Keraea Gude
1911. Two species were cited for Madeira, nine
in the Canary Islands and several in the Cape
Verde Islands (Thiele, 1931), probably the three
listed by Wollaston (1878) in Patula (Iulus). More
recently, two new species from the Canary Islands
grouped in the subgenus Canaridiscus, provision-
ally as Atlantica (Canaridiscus), were added to
these checklists (Yanes et al., 2011) as well as a
third species designated as Discus (Canaridiscus)
by Rähle & Allgaier (2011).
Despite the remarkable diversity of Discidae
in these islands, representative specimens pre-
served and available in most collections of
Mollusca are rather rare. Moreover, although
intensive fieldwork has been performed in
Madeira and the Canary Islands over the last few
decades, Discidae taxa are infrequently encoun-
tered in field surveys. Indeed, four of the species
were included in the list of European globally
extinct taxa by Fontaine et al. (2007), namely
Discus engonatus (Shuttleworth 1852), D. retex-
tus (Shuttleworth 1852), D. textilis (Shuttleworth
1852) and Keraea garachicoensis (Wollaston 1878).
In contrast with the anatomical data known for
European and some North American Discidae
(Fig. 1A–C), there has hitherto been no informa-
tion published on the internal anatomy of the
Canary Islands and Madeiran species (with the
exception of the three species recently named
by Yanes et al., 2011 and Rähle & Allgaier, 2011),
so they have been known only by their shell
characters. Hence their affinities have remained
mysterious.
TAXONOMIC REVISION, HABITATS AND BIOGEOGRAPHY
OF THE LAND SNAIL FAMILY DISCIDAE (GASTROPODA:
PULMONATA) IN THE CANARY ISLANDS
DaViD t. holyoak1, geralDine a. holyoak1, yurena yanes2, Maria r. alonso3 & Miguel iBáñeZ3
1Quinta da Cachopa, Barcoila, 6100–014 Cabeçudo, Portugal.
2Instituto Andaluz de Ciencias de la Tierra (CSIC-Universidad de Granada), Camino del Jueves s/n, 18100, Armilla,
Granada, Spain.
3Departamento de Biologia Animal, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Islas Canarias, Spain.
Abstract The endemic Macaronesian Canaridiscus, provisionally placed in the Discidae genus Atlantica, are closely linked
to the peculiar laurel forest habitat of these islands. Knowledge of Atlantica (Canaridiscus) is increased here with the descrip-
tion, for the first time, of the genital system of three more of its species. The epiphallus is apparently lacking and the penis
is much longer than that known from any of the Discidae of Europe and North America; generally it is too large to be more
than partly accommodated in the distal female genital tract. Keraea has been regarded as an endemic Macaronesian genus
of Discidae known only from a few shells, but its Madeiran species has been identified as a Trochulus (Hygromiidae) and its
type species (from Tenerife) also matches Hygromiidae, not Discidae.
The origin and relationships of the Macaronesian Discidae are discussed. The simplest explanatory model is apparently that
they represent the last living relicts of a more diverse fauna of Discidae that lived in Europe during the Tertiary; Atlantica
(Canaridiscus) was probably isolated early on from the remaining Discidae. Recent literature reports multiple patterns of
colonisation of Madeira and the Canaries that have varied between different groups of plants and animals. Hence, it is argued
that it is unwarranted to expect to find only the single pattern of colonisation among the land snails of each of these archi-
pelagos that was advocated by Waldén (1984).
Key words Africa, Atlantica, Canaridiscus, genital anatomy, Laurasia, laurisilva, Macaronesia, Madeira,
North America, paleobiogeography, penis length, Tertiary relict
Contact author : holyoak9187@hotmail.com
Dt holyoak et al
584
In this paper we revise the systematics of the
Canary Islands species assigned to the Discidae.
The genital system of three species is described
for the first time, confirming their allocation to
the subgenus Canaridiscus. The relationships of
the Macaronesian Discidae with those of Eurasia
Figure 1 Genital anatomy of some Europaean (A, B), North American (C) and Canarian (D) Discidae species:
A Discus (Discus) ruderatus (Hartmann 1821) (from Riedel & Wiktor, 1974: fig. 117); B D. (Gonyodiscus) rotundatus
(O.F. Müller 1774) (from Uminski, 1962: fig. 1); C Anguispira kochi (L. Pfeiffer 1845) (from Pilsbry, 1948: fig. 304);
D Atlantica (Canaridiscus) saproxylophaga Alonso, G. Holyoak & Yanes in Yanes et al. 2011 (drawn from Yanes et al.,
2011: fig. 3C). Parts: ag albumen gland; bc bursa copulatrix; go genital orifice; hd hermaphroditic duct; p penis; pr
penis retractor; vd vas deferens. The scale bar corresponds only to A, B and D (C was drawn originally without
a scale bar).
DisCiDae of the Canary islanDs
585
and North America are discussed, leading to a
consideration of their likely origins and history.
Conservation status of the Macaronesian forms is
also reassessed.
Methods
Snail specimens were drowned by immersion
in water, then fixed in 80% ethanol. Maps of
geographical distribution (Fig. 2) were pro-
duced using MapViewer software (Golden
Software Inc.). The photographic methodology
was described by Ibáñez et al. (2006). Drawings
of shell outlines (Fig. 3) were obtained semi-
automatically, adopting the methods used by
Yanes et al. (2009b). Standardised measurements
of the shells (Table 1, Fig. 3) were made following
Yanes et al. (2009a), using the software analySIS®
(Soft Imaging System GmbH). Abbreviations for
shell characters and measurements are shown in
Fig. 3. The number of shell whorls was counted
using the methodology described by Kerney et
al. (1979: 13). “Proximal” and “distal” refer to the
position in relation to the ovotestis. Comparisons
have been made with photographs of a syntype
of Patula (Iulus) garachicoensis Wollaston 1878
(Fig. 4A), a possible syntype of H. gueriniana
R.T. Lowe 1852 (Fig. 4B), a shell of H. calathoides
R.T. Lowe 1863 (Fig. 4C), a syntype of H. retexta
Shuttleworth 1852 (Fig. 4D), a syntype of H.
engonata Shuttleworth 1852 (Fig. 4E), a syntype
of H. putrescens R.T. Lowe 1861 (Fig. 4F), a syn-
type of H. scutula Shuttleworth 1852 (Neubert
& Gosteli, 2003: pl. 14, fig. 2), a syntype of H.
textilis Shuttleworth 1852 (Neubert & Gosteli,
2003: pl. 14, fig. 3), the shell drawings of the
holotype of Discus gomerensis Rähle 1994 (Rähle,
1994: figs 1–3), as well as a paratype of Atlantica
(Canaridiscus) saproxylophaga Alonso, G. Holyoak
& Yanes in Yanes et al. 2011 (Fig. 5A) and the hol-
otypes of A. (C.) anagaensis Ibáñez & D. Holyoak
in Yanes et al. 2011 (Fig. 5B) and D. (C.) rupivagus
Rähle & Allgaier, 2011 (Fig. 4H).
Institutional and other abbreviations
BDUNM Biology Department, University of
New Mexico, Albuquerque, U.S.A.
DBUA Departamento de Biologia,
Universidade dos Açores, Portugal
CMNH Carnegie Museum of Natural
History, Pittsburgh, U.S.A.
FMNH Field Museum of Natural History,
Chicago, U.S.A.
GBIF Global Biodiversity Information
Facility, Switzerland
Figure 2 Geographical distribution of some Atlantica (Canaridiscus) species (only those species with precise recent
data have been included). The arrows show the symbols of the only one-kilometre squares of the UTM grid with
records located outside the laurel forest. Note: In the four one-kilometre UTM grid squares with A. (C.) saproxy-
lofaga (on La Gomera Island), the species A. (C.) ganoda was also found.
Dt holyoak et al
586
IZUC Institute for Zoology, University of
Cologne, Germany
ICZN International Commission on
Zoological Nomenclature
JSGC
J. Santana private collection, Las
Palmas de Gran Canaria, Spain
Kya thousands of years ago
Mya millions of years ago
NHMUK The Natural History Museum,
London, U.K.
NHMV Natural History Museum Vienna,
Austria
NMBE Naturhistorisches Museum, Bern,
Switzerland
PAS Polish Academy of Sciences, Poland
UMA Universidade da Madeira, Funchal,
Madeira, Portugal
UTM Universal Transverse Mercator
cartographic projection system
revIew of systeMatIcs of DIscIdae
The generic names Discus and Gonyodiscus were
introduced by Fitzinger (1833) for European
Discidae. The widespread (apparently) Holarctic
species Helix ruderata Hartmann 1821 became the
type species of Discus by subsequent designa-
tion of Gray (1847), and the central and south-
eastern European Helix perspectiva Megerle von
Mühlfeld 1816 the type species of Gonyodiscus by
monotypy. Adams & Adams (1858) united these
genera into Discus.
The family Discidae Thiele 1931 of current
lists comprises species from various parts of the
Holarctic that were all placed by Thiele (1931)
in the family Endodontidae, subfamily Discinae,
genus Discus. Adoption of the name Discidae
in preference to Patulidae (based on Patulinae
Tryon 1866) follows Bouchet & Rocroi (2005).
Thiele grouped the Discinae species in several
Figure 3 Drawings of the shell of Atlantica (Canaridiscus) anagaensis Ibáñez & D. Holyoak in Yanes et al. 2011,
showing the placement of the measurements obtained (plane view, in mm or mm2). Measurements: AB aperture
breadth; AH aperture height; AP aperture perimeter; AS aperture surface area; BH body whorl height; BP body
whorl frontal perimeter; BS body whorl frontal surface area; D1 maximum shell diameter; D2 shell diameter per-
pendicular to D1; D3 maximum first whorls diameter; FH first whorls height; FP first whorls frontal perimeter;
FS first whorls frontal surface area; SFP shell frontal perimeter; SFS shell frontal surface area; SH shell height; SP
shell dorsal perimeter; SS shell dorsal surface area; UD umbilicus diameter.
DisCiDae of the Canary islanDs
587
Table 1 Data on the shell characters measured (minimum – maximum, in mm or mm2): AB aperture breadth; AH aperture height; AP aperture
perimeter; AS aperture surface area; BH body whorl height; BP body whorl frontal perimeter; BS body whorl frontal surface area; D1 maximum shell
diameter; D2 shell diameter perpendicular to D1; D3 maximum first whorls diameter; FH first whorls height; FP first whorls frontal perimeter; FS first
whorls frontal surface area; SFP shell frontal perimeter; SFS shell frontal surface area; SH shell height; SP shell dorsal perimeter; SS shell dorsal surface
area; UD umbilicus diameter; n number of specimens measured.
A. (A.)
gueriniana
A. (C.)
saproxylophaga
A. (C.)
anagaensis
A. (C.)
textilis
A. (C.)
ganoda
A. (C.)
kompsa
A. (C.)
scutula
A. (C.)
putrescens
A. (C.)
gomerensis
A. (C.)
retexta
A. (C.)
engonata
A. (C.)
rupivaga
D1 5.5–6.1 12.1–15.8 7.1–7.5 7.1–8.0 8.4–8.8 7.8–7.9 7.1–8.0 8.9–9.5 7.8 6.7 6.7 11,8
D2 5.2–5.8 10.9–14.5 6.6–6.8 6.5–7.7 7.9–8.3 7.3–7.4 6.7–7.6 8.2–8.7 7.6 6.5 6.7 10,8
SS 21.3–26.8 96.3–169.0 34.7–37.4 34.5–44.9 49.5–54.7 42.5–43.9 35.8–45.3 54.0–61.2 45.5 32.5 34.1 94,1
SP 16.9–18.9 35.8–49.5 21.6–22.7 21.3–24.9 25.6–27.2 23.7–24.2 21.8–25.6 27.3–29.8 25.4 21.5 22.1 35,5
SH 2.4 5.4–6.9 3.3–3.6 3.6–4.5 4.4–5.6 4.3–4.6 2.7–3.0 4.2–4.5 3.5 3.1 3.7 3,1
SFS 8.9–9.5 43.1–72.2 17.9–19.4 17.7–23.8 26.5–33.2 24.2–25.6 13.0–16.1 24.2–27.3 18.2 13.7 15.2 24,6
SFP 12.8–14.0 27.4–36.7 17.4–18.4 17.4–20.1 20.7–22.7 19.6–20.0 16.3–19.0 20.9–22.6 18.7 16.6 17.3 25,2
FH 0.7–0.8 1.2–1.7 0.5–0.7 0.8–1.1 0.7–1.1 0.9–1.0 0.6–0.8 0.9 1.2 0.9 1.1 0,5
D3 3.6–4.0 7.2–9.9 4.2–4.3 4.6–5.4 5.1–5.7 5.2–5.3 5.0–5.6 4.9–5.1 5.7 4.4 4.6 6,4
FS 1.8–2.0 5.3–11.0 1.5–2.0 2.5–3.9 2.4–4.1 2.9–3.6 2.2–3.0 2.7–3.0 4.0 2.9 3.1 2,3
FP 7.6–8.4 15.1–20.7 8.8–9.1 10.0–11.6 10.6–12.5 11.1–11.5 10.5–11.9 10.3–10.8 12.2 9.7 10.1 12,8
BH 1.5–1.7 4.2–5.3 2.7–2.9 2.6–3.4 3.7–4.4 3.3–3.7 2.0–2.2 3.3–3.6 2.4 2.1 2.6 2,6
BS 6.9–7.6 37.8–61.3 16.3–17.4 14.5–19.9 24.0–29.1 20.6–22.7 10.8–13.2 21.3–24.6 14.2 10.8 12.1 22,3
BP 12.5–13.8 26.8–35.8 17.2–18.0 16.7–19.2 20.2–21.8 18.7–19.5 15.9–18.4 20.9–22.3 18.0 15.7 16.4 25,1
UD 2.4–2.9 3.4–4.5 2.1–2.4 1.9–2.5 2.4–2.6 2.1–2.5 4.3–5.0 2.5–2.8 2.1 3.1 3.3 3,8
AH 1.4 3.2–4.0 2.2–2.4 1.9–2.4 2.6–2.9 2.4–2.5 1.5–1.9 2.2–2.4 1.7 1.5 1.9 2,1
AB 1.6–2.0 4.7–6.0 2.6–2.8 2.6–3.0 3.1–3.4 2.9–3.2 1.3–1.8 3.2–3.3 2.8 2.0 1.9 4,5
AS 1.2–1.4 9.0–13.0 3.5–3.7 3.2–4.6 4.9–6.1 3.9–4.6 1.2–2.0 4.5–5.1 3.1 2.1 2.2 5,7
AP 4.8–5.3 12.8–15.6 7.9–8.0 7.3–8.8 9.1–10.1 8.3–8.9 4.3–5.5 8.5–9.0 7.1 5.6 5.7 10,4
n 2 4 3 4 4 2 4 3 1 1 1 1
Dt holyoak et al
588
Figure 4 Shells of: A Keraea garachicoensis, a syntype of Patula (Iulus) garachicoensis Wollaston 1878 (NHMUK
1985.2.2 73–75; photo by J. Ablett) from Tenerife; B possible syntype of Helix gueriniana R.T. Lowe 1852 (NHMUK
1875.12.31.219; photo by J. Ablett) from Madeira; C specimen of Helix calathoides R.T. Lowe 1863 (photo by Dinarte
Teixeira, UMA), from Deserta Grande Islet, Madeiran Archipelago, currently considered as a subspecies of A.
gueriniana (Bank et al., 2002) – the arrows mark the location of two pairs of palatal tooth-shaped lamellae, visible
by transparency on the outer wall of the body whorl; D syntype of Helix retexta Shuttleworth 1852 (NMBE 18783;
© 2006 GBIF Switzerland/Eike Neubert), from La Palma (firstly published by Neubert & Gosteli, 2003: pl. 14
fig. 4); E syntype of Helix engonata Shuttleworth 1852 (NMBE 18790; © 2006 GBIF Switzerland/Eike Neubert),
from Tenerife (firstly published by Neubert & Gosteli, 2003: pl. 14, fig. 1); F syntype of Helix putrescens (NHMUK
1875–12–31–299; photo by J. Ablett), from La Palma; G specimen of Discus gomerensis Rähle 1994, from drift debris
of a stream in Las Rosas ravine, La Gomera; H holotype of Discus (Canaridiscus) rupivagus Rähle & Allgaier 2011
(from Rähle & Allgaier, 2011: fig. 1A).
DisCiDae of the Canary islanDs
589
sections mainly on the basis of shell characters.
His Nearctic sections comprise Anguispira Morse
1864, Mexicodiscus Pilsbry 1926 and Planogyra
Morse 1864. The Palearctic sections were Discus
s. str., Gonyodiscus, Atlantica Ancey 1887 and
Keraea. Section Atlantica of Thiele included only
the Madeiran species Helix gueriniana R.T. Lowe
1852, as D. (A.) semiplicatus (L. Pfeiffer 1852),
which has 2–3 pairs of tooth-shaped lamellae on
the interior of the outer wall of the shell body-
whorl (see Fig. 4C). Section Keraea of Thiele
included Patula (Iulus) garachicoensis Wollaston
Figure 5 Shells of Atlantica (Canaridiscus) species: A paratype of A. (C.) saproxylophaga Alonso, G. Holyoak &
Yanes in Yanes et al. 2011 (JSGC), from La Gomera (first published by Yanes et al., 2011: fig. 2A); B holotype of A.
(C.) anagaensis Ibáñez & D. Holyoak in Yanes et al. 2011, from Tenerife (first published by Yanes et al., 2011: fig. 2B);
C specimen of A. (C.) textilis, from La Palma (first published by Yanes et al., 2011: fig. 2C); D specimen of A. (C.)
scutula, from Montaña Grande, Tenerife; E specimen of A. (C.) ganoda, from Mériga, La Gomera; F specimen of A.
(C.) kompsa, from Los Corchos, El Hierro.
Dt holyoak et al
590
1878 from Tenerife and some species from the
Cape Verde Islands, without providing their
names.
Pilsbry (1948) raised Anguispira to the rank
of genus in the Discidae, added a new Nearctic
subgenus Discus (Nematodiscus) based on shell
characters and described the pallial complex in
Anguispira and Discus, which have the lung long
and narrow without large or noticeable branches
on the pulmonary vein, kidney triangular, a little
longer than the pericardium and the secondary
ureter closed. Pilsbry also presented drawings of
the jaw and radula of Discus patulus (Deshayes
1830) as well as those of the genital system and
some details of Anguispira alternata (Say 1816)
and A. kochi (Fig. 1C). Uminski (1963) reported
on the taxonomy of D. marmorensis H.B. Baker
1932, and Solem (1976) made a detailed ana-
tomical study of the distal genitalia and radula of
three Anguispira species, A. alternata, A. cumber-
landiana cumberlandiana (I. Lea 1840) and A. picta
(G.H. Clapp 1920). Contrary to earlier literature,
Solem found that the vas deferens enters the
penis directly through a simple pore (without an
epiphallus) and the penial retractor muscle arises
from the diaphragm, not the columellar muscle.
He also noted that the marginal radular teeth
of Anguispira are not multicuspid, maintaining
a basically bicuspid condition, the outermost
marginals showing splitting of side cusps. On
some individual outer marginal teeth there is a
weak endocone. Schileyko (2002) raised Discus
(Gonyodiscus) section Antediscus Baker in Pilsbry
1948 to the rank of a subgenus of Discus and
gave detailed drawings of the genital systems
of Anguispira alternata, A. (Zonodiscus) kochi and
Discus (Discus) ruderatus.
Bank et al. (2002) grouped eight Canary Islands
species in “Discus (Gonyodiscus?)” and included
Patula garachicoensis in Keraea. Their allocation to
Discus (Gonyodiscus) and Keraea has since been
adopted by the Fauna Europaea database project
(2011), which also included Helix deflorata R.T.
Lowe 1854 from Madeira in Keraea, a species
previously classified in Iulus by Wollaston (1878).
Yanes et al. (2011) raised Atlantica to the rank
of a genus of Discidae and described a new
subgenus, Canaridiscus, provisionally allocated
as Atlantica (Canaridiscus), and two new species
from the Canarian Islands. Rähle & Allgaier (2011)
described a new Canaridiscus species, retaining
the genus Discus with subgenera Atlantica and
Canaridiscus. Hence, current understanding of
the Discidae species from the Canary Islands can
be summarised in Table 2, which also presents
data on distribution for each island and refers to
the figures of their shells in this paper.
The entire genital systems of some of the
European Discus species were figured by
Uminski (1962) and Riedel & Wiktor (1974) (Fig.
1A, B), these being similar to those of the North
American Discus and the Anguispira species fig-
ured by Pilsbry (1948) (Fig. 1C). Uminski (1962)
showed differences in the structure of the genital
organs of Discus ruderatus, D. perspectivus and D.
rotundatus, justifying their taxonomic arrange-
ment in the subgenera Discus s. str. (the first-
named species) and Gonyodiscus (the other two
species). The penis of D. (Discus) (Fig. 1A) is
an elongated cone with the narrow distal end
communicating with the genital atrium and the
penial retractor inserted on the wider proximal
end of the penis and arising from the diaphragm.
The vas deferens joins the penis laterally, at one
side of the wide proximal end and the pros-
tate is distinctly elongated. In D. (Gonyodiscus)
(Fig. 1B) the penis is cylindrical and elongated,
the penial retractor is attached to the penis lat-
erally and the vas deferens connects with the
penis terminally. The prostate is triangular or
semicircular in shape. Schileyko (2002) described
some additional characters of the Discus genital
system, mainly related to the internal anatomy
of the penis (without penial papilla) and free
oviduct (with several pilasters, folds and plicae).
He also showed (Schileyko, 2002: fig. 1384B) the
presence of a markedly swollen distal zone of the
bursa duct and a small stimulator in the proximal
end of the penis in Anguispira (Zonodiscus) kochi.
Finally, the two Atlantica (Canaridiscus) species
as well as the new species recently described
by Rähle & Allgaier (2011) differ from the other
Discidae mainly by their remarkably long penis,
ca. eight times the maximum shell diameter in
A. (C.) saproxylophaga (Fig. 1D). It is much longer
than that known from any of the Discidae of
Europe and North America and too large to be
more than partly accommodated in the distal
female genital tract.
The absence of the epiphallus was noted by
Uminski (1962) in the subgenera Discus (Discus)
and D. (Gonyodiscus) and by Solem (1976) in
Anguispira. The connection between the vas defe-
rens and the penis in A. (C.) saproxylophaga (Yanes
DisCiDae of the Canary islanDs
591
Table 2 Current understanding of the Discidae species from the Canary Islands.
Original name Usual name
(bibliography) Current name
(this paper) Island Figure (this
paper)
Patula (Iulus) garachicoensis Wollaston 1878 Keraea garachicoensis Microxeromagna?
Xerotricha?
garachicoensis
Tenerife 4A
Helix retexta Shuttleworth 1852 Discus (Gonyodiscus) retextus Atlantica (Canaridiscus)
retexta
La Palma 4D
Helix engonata Shuttleworth 1852 D. (G.) engonatus A. (C.) engonata Tenerife 4E
Helix (Lucilla) putrescens R.T. Lowe 1861 D. (G.) putrescens A. (C.) putrescens La Palma 4F
Discus gomerensis Rähle 1994 D. (G.) gomerensis A. (C.) gomerensis La Gomera 4G
Discus (Canaridiscus) rupivagus Rähle & Allgaier 2011 D. (C.) rupivagus A. (C.) rupivaga La Gomera 4H
Atlantica (C.) saproxylophaga Alonso, G. Holyoak & Yanes in
Yanes et al. 2011
A. (C.) saproxylophaga A. (C.) saproxylophaga La Gomera 5A
Atlantica (C.) anagaensis Ibáñez & D. Holyoak in Yanes et al. 2011 A. (C.) anagaensis A. (C.) anagaensis Tenerife 5B
Helix textilis Shuttleworth 1852 D. (G.) textilis A. (C.) textilis La Palma 5C
Helix scutula Shuttleworth 1852 D. (G.) scutulus A. (C.) scutula Tenerife 5D
Helix ganoda J. Mabille 1882 D. (G.) ganodus A. (C.) ganoda La Gomera 5E
Helix kompsa J. Mabille 1883 D. (G.) kompsus A. (C.) kompsa El Hierro 5F
Dt holyoak et al
592
et al., 2011: fig. 3F) is similar to that described
by Solem (1976) in Anguispira, so an epiphal-
lus is apparently also absent in the subgenus
Canaridiscus.
observatIons
Family Hygromiidae Tryon 1866
Genus Keraea Gude 1911
Type species by original designation: Patula
(Iulus) garachicoensis Wollaston 1878 (Gude, 1911:
271). [syn: Iulus Wollaston 1878, non Linnaeus
1758].
We studied photographs of a syntype of
Patula garachicoensis (Fig. 4A), which apparently
belongs to a species of the Hygromiidae, not to
the Discidae. The shell is somewhat immature,
with nearly 4½ whorls and maximum diam-
eter of 6.7 mm. It shows irregular ribs above,
apparently with some hair-pits and perhaps faint
hints of a blotched colour pattern, and looks
like an old shell of a hygromiid of the genera
Microxeromagna Ortiz de Zárate López 1950 or
Xerotricha Monterosato 1892.
Patula garachicoensis and Helix deflorata share
similar shell characters, differing in dimensions.
Wollaston (1878) indicated that the shell diam-
eter of the only specimen of H. deflorata (a single
adult shell with a large umbilicus and the basal
whorl conspicuously – though not very greatly
– deflexed at the aperture) is about “5½ lines”
(11.6 mm) and that of P. garachicoensis, with 5–5½
whorls, is “3½ lines” (7.4 mm). Seddon (1996a)
considered H. deflorata to be a junior synonym
of the European species now known as Trochulus
striolatus (C. Pfeiffer 1828) following comments
from the late H. W. Waldén, who had seen the
specimen and commented that it is a shell of
that species (in lit. to Wells & Chatfield, 1992).
Whereas Bank et al. (2002) listed H. deflorata as
a valid taxon, Bank (2009) does not include H.
deflorata or Trochulus striolatus in a list of recent
terrestrial gastropods of the Madeiran archipel-
ago.
Besides P. garachicoensis and H. deflorata, three
species from the Cape Verde Islands were grouped
by Wollaston (1878) in Patula (Iulus): Helix gorgo-
narum Dohrn 1869; H. bertholdiana (M. Pfeiffer
1852); and H. bouvieri (A. Morelet 1873). These are
also likely to be species of Hygromiidae rather
than of Discidae.
Family Discidae Thiele 1931 (1866)
[syn: Patulidae, see Bouchet & Rocroi, 2005: 11,
268; ICZN, 1999: Art. 40.2].
Type genus: Discus Fitzinger 1833.
Genus Atlantica Ancey 1887
Type species by monotypy: Helix gueriniana R.T.
Lowe 1852, from Madeira Island.
Subgenus Atlantica (Canaridiscus) Alonso &
Ibáñez in Yanes et al. 2011
Type species by original designation: Atlantica
(Canaridiscus) saproxylophaga Alonso, G. Holyoak
& Yanes in Yanes et al. 2011, from La Gomera
Island.
In addition to A. (C.) saproxylophaga, A. (C.)
anagaensis and A. (C.) rupivaga, we were able to
study the genital systems of three other Discidae
species from the Canary Islands: A. (C.) ganoda
(Fig. 6A) from La Gomera, A. (C.) kompsa (Fig.
6B) from El Hierro and A. (C.) scutula (Fig. 6D,
E) from Tenerife. These last three species have
the basic structure and arrangement of the geni-
talia similar to those of the three former species,
although there are differences mainly in the penis
length. Hence they can be shown to belong in the
subgenus Canaridiscus. The remaining Discidae
species from the Canary Islands for which the
genital anatomy remains unknown are also likely,
therefore, to be species of this subgenus.
The longest penis is that of A. (C.) saproxylo-
phaga, followed in turn by A. (C.) ganoda, A. (C.)
rupivaga, A. (C.) anagaensis, A. (C.) kompsa and A.
(C.) scutula. The shortness of the penis of A. (C.)
scutula is perhaps related to the thinness of the
soft part body (Fig. 6C, its maximum diameter
being 1.1–1.2 mm), but it is proportionally longer
than those of the genera Discus and Anguispira.
The “ampulla” of the hermaphroditic duct has
been found only in Atlantica saproxylophaga and
A. (C.) ganoda. The talons of A. (C.) saproxylo-
phaga, A. (C.) anagaensis, A. (C.) ganoda and A.
(C.) kompsa are similar to, but seemingly less
developed, than those of Anguispira alternata and
A. kochi drawn by Pilsbry (1948: figs 304D, E), as
well as that of A. cumberlandiana cumberlandiana
drawn by Solem (1976).
Affinities of the Discidae genera: Discus, Anguispira
and Atlantica (Canaridiscus) share many shell
DisCiDae of the Canary islanDs
593
and anatomical character-states, as follows: a
shell moderately to strongly depressed, radi-
ally ribbed, with the base having a widely open
umbilicus that reveals all the whorls including
the nucleus; lung long and narrow, without large
or noticeable branches on the pulmonary vein;
Figure 6 A, B, D, E, genital systems; C, body of the animal extracted from the shell. A Atlantica (Canaridiscus)
ganoda; B A. (C.) kompsa; C–E A. (C.) scutula. Parts: a atrium; ag albumen gland; au auricle; bc bursa copulatrix;
bcd bursa copulatrix duct; e egg; f foot; go genital orifice; hd hermaphroditic duct; o oviduct; p penis; pr penis
retractor; t talon; v vagina; vd vas deferens; ve ventricle.
Dt holyoak et al
594
kidney triangular, a little longer than the peri-
cardium; secondary ureter closed; male genital
system lacking flagellum and epiphallus; penis
without penial papilla; bursa copulatrix small;
bursa duct long and very thin, without diver-
ticulum.
The genera Discus and Anguispira share similar
characters of the genital system, notably a short
penis (Fig. 1A–C), whereas Atlantica (Canaridiscus)
clearly differs from both of them because it has a
much longer penis (Fig. 1D). Therefore the rela-
tionship of Atlantica (Canaridiscus) with Discus
and Anguispira is apparently more distant than
that between the last two genera.
generIc classIfIcatIon
Due to the unknown anatomical and genetic
characteristics of Atlantica gueriniana from
Madeira (the type-species of the genus Atlantica),
the existence of close relationships between the
Madeiran and Canary Islands Discidae can only
be surmised. Nevertheless, they have generally
similar shell characters as described above and
both are related to the peculiar laurel forest
vegetation type (laurisilva) of these archipela-
gos in northern Macaronesia (Wollaston, 1878),
although the Madeiran species was recently
found outside the laurisilva, in drier but well
vegetated regions (Cameron & Cook, 1999) and
A. gueriniana calathoides occurs in dry habitats of
the Desertas (which have their maximum alti-
tude at 442 m). Thus, we provisionally group
Canaridiscus in Atlantica, raising the latter to
generic rank in the Discidae, because Canaridiscus
is not closely related to the genera Discus and
Anguispira. Future study of the genital system of
the Discidae species from Madeira is needed to
either confirm the position of Canaridiscus as a
subgenus of Atlantica or raise it to generic rank.
However, future studies of the Discidae combin-
ing anatomical and molecular techniques may
modify our understanding of the systematics of
the whole family.
habItats
The Canarian Discidae species have a narrow
range of habitats. The Canary Islands species
mostly live in the laurisilva, a forest found in
subtropical or warm-temperate areas with high
humidity and relatively stable temperatures. The
older literature indicates that they were gener-
ally found on the ground beneath the trunks
of decaying trees, pieces of rotten wood, dead
leaves, or sometimes beneath stones (Mousson,
1872; Wollaston, 1878). Recent finds were mostly
in undisturbed, humid laurel forest, closely
associated with rotting wood. The two recently
described species, A. (C.) saproxylophaga and A.
(C.) anagaensis, were found inside the humid
trunks of decaying trees, beneath them, or in
both types of site.
Exceptional finds in other habitats include the
holotype of A. (C.) gomerensis (an empty white
shell) and the species A. (C.) rupivaga. A. (C.)
gomerensis was found in a ravine outside the lau-
risilva, near the Macizo de Teselinde (La Gomera
Island), but about 2 km to the north-east of the
Epina mountain, which has laurel forest (Fig. 2,
the arrow on La Gomera map). Some specimens
of this species were also collected by J. Santana
(JSGC; Fig. 4G) in Las Rosas ravine (UTM:
28RBS8420, 250 m altitude), about 8 km east of
the type locality; the latter locality is not included
on the map because the shells were from stream
deposits. A. (C.) rupivaga was found hidden in
narrow crevices of shattered, northeast-exposed
volcanic rocks, as well as between stones at the
base of these rocks, at an altitude of 600 m; it is
the only A. (Canaridiscus) species known to live in
narrow rock crevices.
The main vegetation type at the A. (C.) rupivaga
locality nowadays is pine forest (Rähle & Allgaier,
2011: fig. 1C) but this forest results from re-
afforestation begun between 1960 and 1970 (Del
Arco et al., 1990, 2006) on an area where the ancient
vegetation was mainly laurisilva. Although the
species has evidently survived this change from
laurisilva to pine forest, its survival was probably
due to the adaptation to living in rock crevices.
In addition, some specimens of A. (C.) scu-
tula from Tenerife (localities outside the Anaga
mountains, between 1000 and 1250 m altitude)
and A. (C.) textilis from La Palma (to 1500 m
altitude), were found outside the laurisilva, in
pine forest (Fig. 2, see arrows on Tenerife and
La Palma maps). In the case of A. (C.) scutula, it
is possible that these few occurrences are from
areas where laurel forest occurred formerly but
regressed mainly as a consequence of human
impacts much as in the A. (C.) rupivaga locality;
DisCiDae of the Canary islanDs
595
there is abundant evidence of historic reduction
in extent of the laurel forests (Parsons, 1981; de
Nascimento et al., 2009; Fernández-Palacios et al.,
2011). In the case of A. (C.) textilis, it is more likely
that a natural regression of the higher-altitude
laurel forests has occurred due to changes in
the moist trade winds, which are essential for
the presence and development of the laurisilva,
since there is currently no laurisilva in the Canary
Islands above 1200 m altitude (Yanes et al., 2009c:
Fig. 2). Survival of A. (C.) scutula and A. (C.)
textilis could perhaps be related to the pres-
ence of trunks of decaying trees and pieces of
rotten wood in the pine forest that has replaced
laurisilva.
dIscussIon
Evolution and biogeographical history of Discidae
The occurrence of endemic Discidae in the
Canary Islands, which differ widely in anatomy
from the living European and North American
species, is described above. All of the Canary
Islands they inhabit have ages of less than 12
Mya, so we are confronted with a problem in
explaining the occurrence there of taxa more
distinctive than any of those on the geologi-
cally much older European and North American
continents. This is addressed in the following
sections of the Discussion, through consideration
of: time-scales for evolution of Stylommatophora
and of Discidae in particular, based on fossil
records and “molecular-clock” studies; timing
of separation of the European and American
continents and the European-African connec-
tion, as deduced from geochronological, geo-
magnetic and other geological data; evidence of
the volcanic origins and ages of the Canary and
Madeiran archipelagos; origins of the land snails
and other biota of Madeira and the Canaries,
including evidence that Canaries Discidae were
mainly restricted to relict laurel forests; the his-
tory of laurisilva in the western Palearctic; and
the most parsimonious model to explain distri-
butional history of Discidae in the Canaries and
other regions. Terminology for divisions of the
geological record and the ages assigned to them
here follow Gradstein et al. (2005) and Ogg et al.
(2008).
Time-scales for evolution of Stylommatophora and
of Discidae Records of fossil terrestrial pulmo-
nates from the Carboniferous coal forests (ca 300
Mya) were regarded as representing the earliest
Stylommatophora by Solem & Yochelson (1979),
but some of these have been reidentified as non-
stylommatophoran eupulmonates by Bandel
(1991, 1997) and attribution of Carboniferous fos-
sils to several Recent stylommatophoran families
is now regarded as highly controversial (Mordan
& Wade, 2008). The suggestion has been made
that no land snails survived the mass extinc-
tion event at the end of the Permian (250 Mya)
with a loss of up to 95% of all species (Wade
et al., 2006). However, not all animal taxa were
equally affected by this event and terrestrial
invertebrates appear to have survived the crisis
better than marine animals or terrestrial tetra-
pods (Stworzewicz et al., 2009); for example,
only eight of the 27 orders of Paleozoic insects
became extinct, and nearly half of the remaining
ones survived to the present day (Labandeira &
Sepkoski, 1993).
Solem & Yochelson (1979), in their detailed
study of North American Upper Paleozoic land-
snail fossils, placed Protodiscus priscus (Carpenter
1867) within the Discidae based on its shell sculp-
ture. Subsequent workers have regarded it as
belonging to an uncertain family but possible the
Pleurodiscidae (Nordsieck, 1986), or perhaps the
Valloniidae (Stworzewicz et al., 2009). This species
has also been found in Early Permian (250–260
Mya) sediments of the Upper Silesian-Cracow
Upland (Karniowice, S. Poland), indicating it
occurred not only in proto-N. America, but also in
the European part of the Pangea supercontinent
(Stworzewicz et al., 2009). There are additional
records of fossil pulmonates from the Middle
Jurassic (Planorbidae representing the Hygrophila
from the Doggerian Epoch, 188–163 Mya) and
Late Jurassic (Ellobiidae and Siphonariidae from
the Malm Epoch, 163–144 Mya), but no undis-
puted fossil Stylommatophora from before the
Cretaceous (130 Mya: Bandel, 1991, 1997; Zilch,
1959). Fossils of species assigned to the Discidae
have been recognised from the Upper Cretaceous
(65–100 Mya), Eocene, Oligocene and Miocene in
America (Henderson, 1935; Pilsbry, 1948; Pierce &
Constenius, 2001), and there were many Tertiary
species reported from Europe (Wenz, 1923; Zilch,
1959; Harzhauser & Binder, 2004; Harzhauser et
al., 2008).
On the basis of a “molecular-clock” approach,
Tillier et al. (1996) suggested that divergence and
Dt holyoak et al
596
rapid early diversification of the Stylommatophora
occurred around 90–60 Mya (Late Cretaceous to
Paleocene), which is at least roughly congru-
ent with the 130 Mya demonstrated by fossils.
Wade et al. (2001) and Wade et al. (2006) pre-
sented the fullest molecular studies currently
available of the Pulmonata. They revealed an
early separation into an “achatinoid clade” and a
“non-achatinoid” lineage, both of which contain
families originating in the Mesozoic southern
supercontinent of Gondwanaland. Some of these
had a wide distribution in Gondwanaland before
its fragmentation in the Late Jurassic (around 150
Mya), from which it is reasonably assumed that
the initial diversification of Stylommatophora
took place even earlier. Wade et al. (2001) showed
that the Discidae are not closely related to
Punctidae, Charopidae or Otoconchidae as sug-
gested by previous studies. Instead, the Discidae
appears as an early offshoot of a very large clade
that later gave rise successively to Cerionidae,
Haplotrematidae, Spiraxidae and eventually to
all Helicoidea. In addition, it is clear that the
Discidae are not only known exclusively from
the Holarctic (living or as fossils), but that they
show no close affinity with any group originating
in Gondwanaland, strengthening the likelihood
that they originated in the northern superconti-
nent Laurasia.
Timing of separation of the European and American
continents and the European-African connection
Prior to the separation of Gondwanaland and
Laurasia (Triassic, 248–213 Mya) the single large
land mass (Pangea II) comprised Laurasia in the
north (with proto-North America as its south-
ern part, proto-Europe as its northern part) and
Gondwanaland in the south (with its northern
part comprised of proto-South America in the
west, proto-Africa in the east) (Scotese, 2001).
During the Jurassic, Gondwanaland and Laurasia
separated and the developing Atlantic Ocean
separated Laurasia into proto-North America
and proto-Europe. By the Late Jurassic (152 Mya)
the Atlantic Ocean was still much narrower than
at the present day and seas of approximately
similar width separated North America from
South America and Europe from Africa (Smith et
al., 1973). Geological and paleobiogeographical
data show that Africa was isolated from the Mid-
Cretaceous to Early Miocene, i.e. for ca. 75 Mya,
but also that this isolation was broken intermit-
tently by discontinuous filter routes that linked it
mainly to Laurasia until the Early Miocene (ca. 23
Mya), when a definitive connection with Eurasia
was established (Gheerbrant & Rage, 2006). This
connection was interrupted on its western side
at the start of the Pliocene (ca. 5 Mya), when the
Straits of Gibraltar were formed.
Volcanic origins and ages of the Canaries and Madeira
The Canarian and Madeiran archipelagos are
comprised exclusively of volcanic islands that
rose above sea-level in the Tertiary, after the
Atlantic had almost reached its present-day
width. The oldest dated rocks known to still
exist on land that is subaerially exposed are in
the eastern Canaries (15.5–20.6 Mya), but these
islands lack laurel forests and also Discidae. This
is no doubt because the moist trade winds ascend
to altitudes higher than those of both islands
(with the exception of a small peak on each
of them). Although Fuerteventura now has a
maximum altitude of 806 m (La Zarza Peak), it
is estimated to have reached about 3000 m high
in the Miocene (Stillman, 1999). The western
Canaries range from 1.1 Mya (El Hierro) and
1.7 Mya (La Palma) to 7.5 Mya (Tenerife) and 12
Mya (La Gomera) (Carracedo et al., 2005). The
small island of Porto Santo is the oldest of the
Madeiran islands (10 Mya) and it lacks Discidae;
the larger Madeira island is up to 5 Mya but has
suffered renewed vulcanism as recently as 2.5
Mya. However, Fernández-Palacios et al. (2011)
have recently argued from geological evidence
that large and high islands may have been con-
tinuously available in northern Macaronesia for
very much longer than is indicated by the surface
of the oldest current island of the region, possibly
for as long as 60 Mya.
Origins of the land snails and other biota of Madeira
and the Canaries Currently, because of the
unknown anatomical and genetic characteristics
of Atlantica gueriniana from Madeira, the exist-
ence of close relationships between the Madeiran
and Canarian Discidae can only can be sur-
mised. Nevertheless, as discussed above, we
provisionally group all of these taxa in Atlantica
based on the similarities in shell shape and main
habitats.
Waldén (1984) indicated that “the most con-
spicuous difference between the land-mollusc
faunas of Madeira and the Canary Islands is the
DisCiDae of the Canary islanDs
597
complete absence of taxa with north-west African
affinities on Madeira, despite the fact that they
hold a similar position relative to the African
continent”. Indeed, Porto Santo, the oldest island
of the Madeiran archipelago, was susceptible to
colonisation for over 10 Mya without major vol-
canic activity and colonists are thought to have
arrived by island-hopping from Europe (i.e. the
south-west Iberian Peninsula) through a former
island chain now remaining as seamounts (Cook,
2008). It has been suggested that the Canary
Islands were colonised by land-snails from neigh-
bouring north-west Africa, possibly on floating
vegetation rafts (Alonso et al., 2000; Arnedo et al.,
2001; Yanes et al., 2009b). An Afrotropical origin
seems likely for the endemic Canary Islands
genus Gibbulinella (Rowson et al., 2011). However,
the Canarian Discidae have close ecological ties
to the laurel forest, as do several other genera
of land snails present in both the Canaries and
Madeira (Craspedopoma L. Pfeiffer 1847, Lauria
J.E. Gray 1840, Leiostyla R.T. Lowe 1852, Columella
Westerlund 1878). Hence greater similarity of
the land-snail faunas of these archipelagos is
evident than was implied by Waldén’s (1984)
analysis.
Different groups of plants show differing pat-
terns of phytogeographical affinity between the
archipelagos in northern Macaronesia. There are
relatively few endemic genera of angiosperms
compared to older island archipelagos or conti-
nental fragments: ca 15 of them being found only
in the Canaries, 4 only in the Madeiran archipel-
ago (Chamaemeles, Monizia, Musschia, Parafestuca),
none only in the Azores, three in both the
Canaries and Madeira, one in the Canaries and
the Azores (Lytanthus), one in Madeira and the
Azores (Melanoselinum) and one in all three archi-
pelagos (Aichryson) (Good, 1964; Press & Short,
1994). Analyses of floristic data sets for liverworts
(Hepaticophyta) and Pteridophyta support (or
cannot reject) existence of an Azorean-Madeiran-
Canarian clade, whereas a similar analysis of the
mosses (Bryophyta) resolves the Canary Islands
as sister to North Africa (Vanderpoorten et al.,
2007). Even within the liverworts, Plagiochila
stricta (Dickson) Dumortier from the Canaries
has been demonstrated to have close Neotropical
affinities and origin by a wealth of molecular,
phytochemical and morphological data (Rycroft
et al., 2002); its microscopic spores might of course
have been wind-blown across the Atlantic. In con-
trast, the liverwort Radula lindenbergiana Gottsche
ex C. Hartmann may have had a refugium in the
Macaronesian archipelagos during Quaternary
glaciations, from which it subsequently recol-
onised the European continent (Laenen et al.,
2011). Among angiosperms, the four genera of
Lauraceae that characterise the Macaronesian
laurisilva all occur in both the Canaries and
Madeira, with Apollonia and Ocotonia absent from
both the Azores and neighbouring continental
regions, whilst Persea and Laurus also occur in
the Azores and the latter is present addition-
ally in southern Europe and north-west Africa
(Hohenester & Weiss, 1993; Fernández-Palacios
et al., 2011). All of these trees have large fleshy
fruits that are likely to be dispersed primarily
by frugivorous birds, principally pigeons, so it
is surely no coincidence that endemic frugivo-
rous pigeons occur in the laurisilva of Madeira
(Columba trocaz Heineken 1829) and the Canaries
(C. bollii Godman 1872, C. junoniae Hartert 1916).
All three of these birds specialise in Lauraceae
fruits and all are thought to have derived from
the European and North African continental spe-
cies C. palumbus Linnaeus 1758 (Goodwin, 1977;
Cramp et al., 1985; Emmerson, 1985; Oliveira et
al., 2002; Marrero et al., 2004).
In contrast to the vast Tertiary colonisation
of northern Macaronesian islands deduced for
many of the plants discussed above, a molecu-
lar study of Erica arborea Linnaeus (Ericaceae)
demonstrates colonisation of both Madeira
and the Canaries during the Pleistocene via the
Mediterranean basin, from refugia in East Africa
(Désamoré et al., 2011). Erica arborea has very
small dry seeds and it may be surmised that
these are readily dispersed over long distances.
Overall, it is probably unsurprising to find mul-
tiple patterns of colonisation of Madeira and
the Canaries that have varied between different
groups of organisms, partly no doubt due to their
differing propagules and dispersal agents, partly
due to differing climatic or ecological tolerances,
but perhaps also sometimes due only to chance.
Consequently, it is unwarranted to expect to find
only a single pattern of colonisation among the
land snails of each of these archipelagos.
History of laurisilva in the western Palearctic In
the western Palearctic the laurel forest veg-
etation type is now restricted to middle lev-
els (600–1200 m a.s.l.) in the mountains of the
Dt holyoak et al
598
Azores, Madeira and the western Canary Islands.
A varied evergreen forest vegetation of similar
subtropical affinities, but richer in plant gen-
era, was widespread in Europe (northwards to
the London basin: Reid & Chandler, 1933) dur-
ing the Early and Middle Tertiary, 65–24.6 Mya.
Thereafter, the forest became progressively less
diverse and apparently retreated southwards by
the Miocene (24.6–5.1 Mya) and especially the
Pliocene (5.1–2.0 Mya) (e.g. Krutzsch, 1967; West,
1968; Flenley, 1979; Nilsson, 1983; Fernández-
Palacios et al., 2011).
By the Early Pleistocene, the subtropical ever-
green forest had disappeared from the mainland
of Europe and north-west Africa. However, some
of its characteristic plants persisted as relicts char-
acterising the laurisilva on the Azores, Madeira
and Canaries (Fernández-Palacios et al., 2011).
Four Late Pleistocene marine pollen records from
offshore of Portugal and Morocco representing
the period 250–5 Kya demonstrate that in the
presumed mild (interglacial) stages (respectively
240–190, 125–70, 10–5 Kya) a Mediterranean oak
forest was widespread in the continental areas to
the east, whereas during colder (glacial) stages
a steppe-like vegetation (Artemisia rich, partly
wooded with Pinus) formed a transition zone
between the Sahara to the south and the tree-less
tundras of western Europe (Hooghiemstra et al.,
1992). Roucoux et al. (2001) have subsequently
demonstrated that the changes in the marine pol-
len record offshore of continental Portugal from
65–9 Kya closely tracked temperature changes
deduced from marine oxygen-isotope data, with
Mediterranean oak forest occurring only during
the warm stages. Neither study showed paly-
nological evidence for anything resembling lau-
risilva on the European and north-west African
mainland during the past 240 Kya and it seems
highly unlikely that most of its characteristic
plants could have survived there during the
cold stages (a few exceptions probably included
Laurus nobilis Linnaeus and Prunus lusitanica
Linnaeus, both of which still grow in the Iberian
Peninsula).
Iberia and the Maghreb are of course rich
in endemic biota and the region has repeat-
edly been demonstrated as a likely “Atlantic-
Mediterranean refugial area” allowing survival
of species through the Late Pleistocene cold
stages (e.g. Schmitt, 2007), but these are animals
and plants of varied open or aquatic habitats or
deciduous woodlands, not stenophiles requir-
ing floristically-rich, broadleaved, evergreen for-
ests. Colonisation of the Canaries by Discidae
was apparently restricted to laurisilva habitats
so that it almost certainly followed the arrival of
this vegetation type, while persistence of their
Discidae to the present day was doubtless related
to continuing presence of the laurisilva through-
out the Late Tertiary and Pleistocene.
A model of distributional history of the Discidae
Much of the information that would allow a
detailed understanding of the evolution and
biogeographical history of Discidae is lacking.
The fossil record of the family is probably very
incomplete, the known fossils (shells) cannot
provide the data on genital anatomy that would
allow better assessment of their generic affinities,
and there has been no molecular study of the
phylogeny of the extant taxa. Attempts at recon-
structing the history of the family must there-
fore be generalised and somewhat speculative,
accompanied by recognition that the simplest
explanation may not be the correct one.
The earliest radiation of taxa in the Discidae
was probably no older than Upper Cretaceous
(ca. 100–65 Mya), as established by fossils from
America (Henderson, 1935; Pilsbry, 1948; Pierce
& Constenius, 2001), but it could be much older
than this. Numerous fossil taxa (Wenz, 1923)
also confirm that the range extended to Europe
through much of the Tertiary (65–5 Mya). By
the Late Cretaceous the widening north Atlantic
Ocean was still much narrower than at the
present day, with relatively narrow sea gaps
separating the British Isles from Newfoundland,
Labrador and southern Greenland (e.g. Smith et
al., 1973). By the Eocene (54.9–38 Mya) the sea
gaps involved were wider, but considerably nar-
rower than they are today. Throughout the Late
Cretaceous and Early Tertiary the vegetation at
the palaeo-latitude of 30o-40o N was essentially
subtropical broad-leaved forest. The Eocene flora
of the London Clay (Reid & Chandler, 1933)
gives detailed evidence of this, and Pearson
(1964) provided data suggesting this flora had
clear tropical affinities. However, Steenis (1962)
has argued that much of this flora may con-
sist of material drifted across the Tethys; Muller
(1970) found that European Eocene pollen and
spore micro-floras are very different to the few
known Indo-Malayan ones; likewise, Krutzsch
DisCiDae of the Canary islanDs
599
(1967) found that there is evidence of only a few
Indo-Malayan taxa penetrating Europe in warm
phases. Thus, Daley (1972) was led to suggest
that the London Clay climate of the Eocene was
seasonal but frostless, with higher rainfall than
today (for the palaeo-latitude that was then 40º
N.), warmer than now, but not as warm as in
tropical rainforest regions. Occurrence of Eocene
coral reefs in the London basin nevertheless
strengthens the evidence for at least a moderately
warm climate. The early Discidae could therefore
have had ample opportunity to cross the narrow
north Atlantic Ocean of the Late Cretaceous and
Early Tertiary and find suitable habitats on both
sides. The much later overseas colonisation of the
Canaries and Madeira demonstrates that repre-
sentatives of the family have the ability to cross
substantial sea gaps.
It might seem simpler to imagine early Discidae
occurring in the Triassic (248–213 Mya) or Early
Jurassic, when proto-Europe and proto-North
America were a single land mass. However, this
is much earlier than any fossils assignable to
Discidae. An additional objection to the hypoth-
esis of such ancient existence and spread of
Discidae is that their broad-leaved forest habitat
did not exist until much later, when a diverse flora
of angiosperms evolved during the Cretaceous
and gradually replaced vegetation dominated
by cycads, conifers and ferns (e.g. Axelrod, 1959,
1963; Muller, 1970; Wolfe et al., 1975; Hughes,
1976).
The following hypothetical outline of bioge-
ographical history of Discidae in Europe and
northern Macaronesia since the Early Tertiary
can therefore be suggested as the simplest sce-
nario accounting for the evidence available. (1)
The numerous species of the family present in
the Tertiary of Europe (Wenz, 1923; Zilch, 1959),
included lineages allied to those still extant in
North America. (2) The emergent Madeiran
islands and Canaries were colonised in the
Tertiary from Europe, North Africa, or both, by
Discidae of a lineage no longer present in these
continental areas. (3) On the European continent
Discidae were reduced to three surviving spe-
cies (one of them also in NW. Africa) by the Late
Pleistocene (250–0 Kya), none of which is closely
related to the relict taxa present in the Canaries
and, probably, also in Madeira. These extinctions
resulted from climatic and vegetational changes
(cf. discussion above). (4) Subsequent evolution
probably accounts for some of the characters of
each of the Madeiran and Canaries species, all of
which are distinctive single-island endemics.
Conservation of Macaronesian Discidae The
morphological and taxonomic uniqueness of
the Discidae of the Canary Islands, their relict
nature and restriction predominantly to the lau-
risilva habitats, emphasise the importance of their
conservation.
Fontaine et al. (2007) showed that most of the
recent extinctions in Europe have affected taxa
with small geographical ranges, along with others
having strict ecological requirements. Similarly,
most European species listed as threatened in
the IUCN Red List have small ranges. Most
Canarian Discidae have small ranges and D.
engonatus, D. retextus, D. textilis and Keraea gara-
chicoensis were included in the list of European
globally extinct taxa by Fontaine et al. (2007),
as was Janulus pompylius (Shuttleworth 1852) of
the Gastrodontidae, but without details being
given of the reasons for them being regarded as
extinct.
Fortunately, among the Discidae species listed
by Fontaine et al. (2007) as globally extinct, at
least Atlantica (Canaridiscus) textilis is known
to still survive since we collected several fresh
shells at two localities on La Palma Island (e.g.
Fig. 5C). Similarly, the Madeiran A. gueriniana
was originally listed as possibly extinct (Wells
& Chatfield, 1992; Groombridge, 1994; Seddon,
1996b), then reassessed as extinct (E) in the
1996 Red List (Baillie & Groombridge, 1996)
because it had not been recorded since the 1860s
despite intensive searching since 1983. However,
Cameron & Cook (1999) rediscovered it at the
western end of Madeira island at two close, but
separate locations. It was found there outside
the laurisilva, in drier but well vegetated regions,
on highly disturbed precipitous hillsides facing
the ocean, differing from the habitats described
in Wollaston (1878). Apparently only shells have
been recorded recently, but these are sufficiently
fresh to assume the species is living at these
sites (Seddon, 2000). A. gueriniana calathoides
might possibly also survive in the Desertas and
it remains possible that several of the other spe-
cies currently listed as extinct will be refound
living because all of them were from locations
which have remained undisturbed, or relatively
undisturbed.
Dt holyoak et al
600
acknowledgeMents
Special thanks go to Dr. Eike Neubert (NMBE) and
GBIF Switzerland for their permission to publish
photographs of the syntypes of the four Atlantica
(Canaridiscus) species described by Shuttleworth
(© 2006 GBIF Switzerland/Eike Neubert); to
Mr. Jonathan Ablett (NHMUK) for the photo-
graphs of syntypes of Patula (Iulus) garachicoensis
and Helix putrescens, and those of a possible
syntype of Helix gueriniana; to Dr. Cristina Abreu
and Dr. Dinarte Teixeira (UMA) for data and
photographs of a specimen of Atlantica gueriniana
calathoides; to Mr. Jesús Santana (JSGC) for the loan
of paratype shells of A. (C.) saproxylophaga and
some specimens of A. (C.) gomerensis; to Dr. Heike
Kappes (IZUC), Dr. Ewa Stworzewicz (PAS), Dr.
Mathias Harzhauser (NHMV), Dr. Jochen Gerber
(FMNH), Dr. Jeff Nekola (BDUNM) and Dr.
Aydin Örstan (CMNH), for information about
Eurasian and North American Discidae species;
and to Dr. António Frias Martins (DBUA), for his
insightful comments that greatly improved the
quality of this manuscript.
references
ADAMS H & ADAMS A 1858 The genera of recent Mollusca,
2. J van Voorst, London. 661 pp.
ALONSO MR, VALIDO MJ, GROH K & IBÁÑEZ M 2000
Plutonia (Canarivitrina), new subgenus, from the
Canary Islands, and the phylogenetic relation-
ships of the subfamily Plutoniinae (Gastropoda:
Limacoidea: Vitrinidae). Malacologia 42: 39–62.
ARNEDO MA, OROMÍ P & IBERA C 2001 Radiation of
the spider genus Dysdera (Araneae, Dysderidae) in
the Canary Islands: cladistic assessment based on
multiple data sets. Cladistics 17: 313–353.
AXELROD DI 1959 Poleward migration of early
angiosperm flora. Science 130: 203–207.
AXELROD DI 1963 Fossil floras suggest stable, not
drifting continents. Journal of Geophysical Research
68: 3257–3263.
BAILLIE J & GROOMBRIDGE B (eds) 1996 1996 IUCN red
list of threatened animals. IUCN, Gland. 378 pp.
BANDEL K 1991 Gastropods from brackish and fresh
water of the Jurassic-Cretaceous transition (a sys-
tematic evaluation). Berliner geowissenschaftliche
Abhandlungen A 134: 9–55.
BANDEL K 1997 Higher classification and pattern of evo-
lution of the Gastropoda. Courier Forschungsinstitut
Senckenberg 201: 57–81.
BANK RA 2009 Systematic list of the Recent terrestrial
gastropods of the Madeiran archipelago. Conchylia
40: 61–64.
BANK RA, GROH K & RIPKEN TEJ 2002 Catalogue
and bibliography of the non-marine Mollusca of
Macaronesia. In FALKNER M, GROH K & SPEIGHT
MCD (eds) Collectanea Malacologica—Festschrift für
Gerhard Falkner: 89–235, pls 14–26. ConchBooks,
Hackenheim.
BOUCHET P & ROCROI JP 2005 Classification and nomen-
clature of gastropod families. Malacologia 47: 1–397.
CAMERON RAD & COOK LM 1999 Island land snail
relocated. Journal of Molluscan Studies 65: 273–274.
CARRACEDO JC, PÉREZ FJ, MECO J 2005 La Gea: Análisis
de una isla en estado post-erosivo de desarrollo.
In RODRÍGUEZ O (ed.) Patrimonio natural de la isla
de Fuerteventura: 27–44. Cabildo de Fuerteventura,
Consejería de Medio Ambiente y Ordenación
Territorial del Gobierno de Canarias, y Centro de la
Cultura Popular Canaria, Tenerife.
COOK LM 2008 Species richness in Madeiran land
snails, and its causes. Journal of Biogeography 35:
647–653.
CRAMP S (ed.) 1985 Handbook of the birds of Europe, the
Middle East and North Africa. The birds of the Western
Palearctic. 4: Terns to Woodpeckers. Oxford University
Press, Oxford. 960 pp.
DALEY B 1972 Some problems concerning the Early
Tertiary climate of southern Britain. Palaeogeography,
Palaeoclimatology, Palaeoecology 11: 177–190.
DEL ARCO M, PÉREZ DE PAZ PL, WILDPRET W, LUCÍA
VL & SALAS M 1990 Atlas cartográfico de los pinares
canarios: La Gomera y El Hierro. Viceconsejería de
Medio Ambiente y Conservación de la Naturaleza.
Consejería de Política Territorial, Gobierno de
Canarias, S/C de Tenerife. 90 pp + 17 map.
DEL ARCO M, WILDPRET W, PÉREZ DE PAZ PL, LUCÍA
VL, RODRÍGUEZ O, ACEBES JR, GARCÍA A, MARTÍN VE,
REYES A, SALAS M, DÍAZ MA, BERMEJO JA, GONZÁLEZ
R, CABRERA MV & GARCÍA S 2006 Mapa de Vegetación
de Canarias. Grafcan, Santa Cruz de Tenerife. 550 pp
+ 7 map + CD.
DÉSAMORÉ A, LAENEN B, DEVOS N, POPP M, GONZÁLEZ-
MANCEBO JM, CARINE MA & VANDERPOORTEN A
2011 Out of Africa: north-westwards Pleistocene
expansion of the heather Erica arborea. Journal of
Biogeography 38: 164–176.
EMMERSON KW 1985 Estudio de la biología y ecología de
la Paloma Turqué (Columba bollii) y la Paloma Rabiche
(C. junoniae) con vistas a su conservación. Vol. 2.
Ornistudio SL, Tenerife. 355 pp.
FAUNA EUROPAEA DATABASE PROJECT 2011 Version 2.4,
last update, 27 January 2011. (Online at http://
www.faunaeur.org/, accessed June 2011)
FERNÁNDEZ-PALACIOS JM, DE NASCIMENTO L, OTTO
R, DELGADO JD, GARCÍA-DEL-REY E, ARÉVALO JM
& WHITTAKER RJ 2011 A reconstruction of Palaeo-
Macaronesia, with particular reference to the long-
term biogeography of the Atlantic island laurel
forests. Journal of Biogeography 38: 226–246.
FITZINGER LJ 1833 Systematisches Verzeichniss der
im Erzherzogthume Oesterreich vorkommenden
Weichthiere als Prodrom einer Fauna derselben.
Beiträge zur Landeskunde Oesterreich’s unter der Enns
DisCiDae of the Canary islanDs
601
(Herausgegeben von einem Vereine für vaterländische
Geschichte, Statistik und Topographie) 3: 88–122.
FLENLEY JR 1979 The equatorial rain forest: a geological
history. Butterworths, London & Boston. 162 pp.
FONTAINE B, BOUCHET P, VAN ACHTERBERG K, ALONSO-
ZARZAGA MA, ARAUJO R, ASCHE M, ASPÖCK U,
AUDISIO P, AUKEMA B, BAILLY N, BALSAMO M, BANK
RA, BARNARD P, BELFIORE C, BOGDANOWICZ W,
BONGERS T, BOXHSHALL G, BURCKHARDT D, CAMICAS
JL, CHYLARECKI P, CRUCITTI P, DEHARVENG L, DUBOIS
A, ENGHOFF H, FAUBEL A, FOCHETTI R, GARGOMINY
O, GIBSON D, GIBSON R, GÓMEZ MS, GOUJET D,
HARVEY MS, HELLER KG, VAN HELSDINGEN P, HOCH
H, DE JONG Y, KARSHOLT O, LOS W, LUNDQVIST L,
MAGOWSKI W, MANCONI R, MARTENS J, MASSARD JA,
MASSARD-GEIMER G, MCINNES SJ, MENDES LF, MEY E,
MICHELSEN V, MINELLI A, NIELSEN C, NIETO JM, VAN
NIEKERKEN EJ, NOYES J, PAPE T, POHL H, DE PRINS W,
RAMOS M, RICCI C, ROSELAAR C, ROTA E, SCHMIDT-
RHAESA A, SEGERS H, ZUR STRASSEN R, SZEPTYCKI
A, THIBAUD JM, THOMAS A, TIMM T, VAN TOL J,
VERVOORT W & WILLMANN R 2007 The European
Union’s 2010 target: putting rare species in focus.
Biological Conservation 139: 167–185.
GHEERBRANT E & RAGE JC 2006 Paleobiogeography of
Africa: how distinct from Gondwana and Laurasia?
Paleogeography, Paleoclimatology, Paleoecology 241:
224–246.
GOOD R 1964 The geography of the flowering plants. 3rd
ed. Wiley, New York. Xvi + 518 pp.
GOODWIN D 1977 Pigeons and doves of the world. 2nd ed.
Comstock Publiaction Associates, Ithaca, New York.
GRADSTEIN FM, OGG JG, SMITH AG EDS 2005 A geo-
logic time scale 2004. Cambridge University Press,
Cambridge, UK.
GRAY JE 1847 A list of the genera of recent mol-
lusca, their synonyms and types. Proceedings of the
Zoological Society 15: 129–219.
GROOMBRIDGE B (ed.) 1994 The IUCN Red List of threat-
ened animals. WCMC Chapman et al., Cambridge,
UK. 286 pp.
GUDE GK 1911 Note on some preoccupied molluscan
generic names and proposed new genera of the
family Zonitidae. Proceedings of the Malacological
Society of London 9: 269–273.
HARZHAUSER M & BINDER H 2004 Synopsis of the
Late Miocene mollusc fauna of the classical sec-
tions Richardhof and Eichkogel in the Vienna Basin
(Austria, Pannonian, MN 9-MN11). Archiv für
Molluskenkunde 133: 1–57.
HARZHAUSER M, GROSS M & BINDER H 2008
Biostratigraphy of Middle Miocene (Sarmatian)
wetland systems in an Eastern Alpine intramon-
tane basin (Gratkorn Basin, Austria): the terrestrial
gastropod approach. Geologica Carpathica 59: 45–58.
HENDERSON J 1935 Fossil non-marine Mollusca of
North America. Geological Society of America, Special
Paper 3: 1–313.
HOHENESTER A, WEISS W 1993 Exkursionflora für
die Kanarischen Inseln mit Ausblicken auf ganz
Makaronesien. Verlag Eugen Ulmer, Stuttgart.
HOOGHIEMSTRA H, STALLING H, AGWU COC, DUPONT
M 1992 Vegetational and climatic changes at the
northern fringe of the Sahara 250,000–5000 years
BP: evidence from 4 marine pollen records located
between Portugal and the Canary Islands. Review of
Palaeobotany and Palynology 74: 1–17.
HUGHES NF 1976 Palaeobiology of angiosperm origins.
Cambridge University Press, Cambridge, UK. 251
pp.
INTERNATIONAL COMMISSION ON ZOOLOGICAL NOMEN-
CLATURE 1999 International code of zoological nomen-
clature, ed. 4. The International Trust for Zoological
Nomenclature, London. 306 pp.
IBÁÑEZ M, SIVERIO F, ALONSO MR & PONTE-LIRA CE 2006
Two Canariella species (Gastropoda: Helicoidea:
Hygromiidae) endemic to the northwest Tenerife
(Canary Islands). Zootaxa 1258: 33–45.
KERNEY MP, CAMERON RAD & JUNGBLUTH JH 1979 A
field guide to the land snails of Britain and north-west
Europe. Collins, London. 288 pp.
KRUTZSCH W 1967 Atlas der mittel und jungtertiaren
dispersen Sporen und Pollen-sowie der Mikroplankton-
former des nordlichen Mitteleuropas. Publ. VEB
Deutscher Verlag der Wissenschaften (vols. 1–3) &
Gustav Fischer Verlag, Berlin (vols. 4–7).
LABANDEIRA CC & SEPKOSKI JJ JR 1993 Insect diversity
in the fossil record. Science 261: 310–315.
LAENEN B, DÉSAMORÉ A, DEVOS N, SHAW AJ, GONZÁLEZ-
MANCEBO JM, CARINE MA & VANDERPOORTEN A 2011
Macaronesia: a source of hidden genetic diversity
for post-glacial recolonization of western Europe in
the leafy liverwort Radula lindenbergiana. Journal of
Biogeography 38: 631–639.
MARRERO P, OLIVEIRA P & NOGALES M 2004 Diet of
the endemic Madeira Laurel Pigeon Columba tro-
caz in agricultural and forest areas: implications
for conservation. Bird Conservation International 14:
165–172.
MORDAN P & WADE C 2008 Heterobranchia II. In
PONDER WF & LINDBERG DR (eds). Phylogeny and
evolution of the Mollusca. University of California
Press, Berkeley: 409–426.
MOUSSON A 1872 Révision de la faune malacologique
des Canaries. Neue Denkschriften der allgemeinen
schweizerischen Gesellschaft für die gesammten
Naturwissenschaften 25 (1): 1–176, pls 1–6.
MULLER J 1970 Palynological evidence on early dif-
ferentiation of angiosperms. Biological Reviews 45:
417–450.
DE NASCIMENTO L, WILLIS KJ, FERNÁNDEZ-PALACIOS JM,
CRIADO C & WHITTAKER RJ 2009 The long-term
ecology of the lost forests of La Laguna, Tenerife
(Canary Islands). Journal of Biogeography 36: 499–
514.
NEUBERT E & GOSTELI M 2003 The molluscan spe-
cies described by Robert James Shuttleworth. I
Gastropoda: Pulmonata. Contributions to Natural
History 1: 1–123.
NILSSON T 1983 The Pleistocene. Geology and life in the
Quaternary Ice Age. D Reidel Publishing, Dordrecht,
Boston & London. 651 pp.
Dt holyoak et al
602
NORDSIECK H 1986 The system of the Stylommatophora
(Gastropoda), with special regard to the systematic
position of the Clausiliidae, II. Importance of the
shell and distribution. Archiv für Molluskenkunde
117: 93–116.
OGG JG, OGG G & GRADSTEIN FM 2008 The concise
geologic time scale. Cambridge University Press,
Cambridge, UK.
OLIVEIRA P, MARRERO P & NOGALES M 2002 Diet of the
endemic Madeira Laurel Pigeon and fruit resource
availability: A study using microhistological analy-
ses. Condor 104: 811–822.
PARSONS JJ 1981 Human influence in the pine and
laurel forests of the Canary Islands. Geographical
Review 71: 253–271.
PEARSON R 1964 Animals and plants of the Cenozoic Era.
Butterworths, London.
PIERCE HG & CONSTENIUS KN 2001 Late Eocene-
Oligocene nonmarine mollusks of the Northern
Kishenehn Basin, Montana and British Columbia.
Annals of Carnegie Museum 70: 1–112.
PILSBRY HA 1948 Land Mollusca of North America
(north of Mexico). Academy of Natural Sciences of
Philadelphia, Philadelphia, Monograph 3, vol. II (2):
i-xlvii, 521–1113.
PRESS JR & SHORT MJ 1994 Flora of Madeira. HMSO,
London. 192 pp.
RÄHLE W 1994 Über eine neue Discus-Art von
La Gomera (Kanarische Inseln) (Gastropoda
Pulmonata: Endodontidae). Basteria 58: 11–14.
RÄHLE W & ALLGAIER C 2011 Discus (Canaridiscus)
rupivagus sp. nov., a rock-dwelling species from La
Gomera, Canary Islands (Gastropoda: Pulmonata:
Discidae). Zootaxa 3098: 55–58.
REID EM & CHANDLER MEJ 1933 The flora of the London
Clay. British Museum (Natural History), London.
RIEDEL A & WIKTOR A 1974 Arionacea. Slimaki krazalko-
wate i slinikowate (Gastropoda: Stylommatophora).
Fauna Polski 2: 1–140.
ROUCOUX KH, SHACKLETON NJ & DE ABREU L 2001
Combined marine proxy and pollen analyses reveal
rapid Iberian vegetation reponse to north Atlantic
millennial-scale climate oscillations. Quaternary
Research 56: 128–132.
ROWSON B, TATTERSFIELD P & SYMONDSON WOC 2011
Phylogeny and biogeography of tropical carnivo-
rous land-snails (Pulmonata: Streptaxoidea) with
particular reference to East Africa and the Indian
Ocean. Zoologica Scripta 40: 85–98.
RYCROFT DS, COLE WJ, HEINRICHS J, GROTH H, RENKER
C & PRÖSCHOLD T 2002 Phytochemical, morphologi-
cal, and molecular evidence for the occurrence of
the neotropical liverwort Plagiochila stricta in the
Canary Islands, new to Macaronesia. The Bryologist
105: 363–372.
SCHILEYKO AA 2002 Treatise on recent terrestrial pul-
monate molluscs. Part 8. Punctidae, Helicodiscidae,
Discidae, Cystopeltidae, Euconulidae, Trochomor-
phidae. Ruthenica, Supplement 2: 1035–1166.
SCHMITT T 2007 Molecular biogeography of Europe:
Pleistocene cycles and postglacial trends. Frontiers
in Zoology 4, 11 (13 pp.).
SCOTESE CR 2001 Atlas of Earth History, 1,
Paleogeography. PALEOMAP Project, Arlington,
Texas. (PALEOMAP online at http://www.scotese.
com, accessed June 2011)
SEDDON MB 1996a Discus defloratus (Lowe, 1854). In
VAN HELSDINGEN PJ, WILLEMSE L & SPEIGHT MCD
(eds) Background information on invertebrates of
the Habitats Directive and the Bern Convention.
Part 3: Mollusca and Echinodermata. Nature and
environment 81: 424. Council of Europe, Strasbourg.
SEDDON MB 1996b Discus guerinianus Lowe, 1852. In
VAN HELSDINGEN PJ, WILLEMSE L & SPEIGHT MCD
(eds) Background information on invertebrates of
the Habitats Directive and the Bern Convention. Part
3: Mollusca and Echinodermata. Nature and environ-
ment 81: 425–427. Council of Europe, Strasbourg.
SEDDON MB 2000 Discus guerinianus. In IUCN 2010.
IUCN Red List of Threatened Species. Version
2010.4. (Online at www.iucnredlist.org/apps/
redlist/details /6735/0, accessed June 2011)
SEDDON MB 2008 The landsnails of Madeira. An illus-
trated compendium of the landsnails and slugs of
the Madeiran archipelago. Studies in Biodiversity and
Systematics of Terrestrial Organisms from the National
Museum of Wales, Biotir Reports 2: 1–204.
SMITH AG, BRIDEN JC & DREWRY GE 1973 Phanerozoic
World Maps. In HUGHES NF (ed.) Organisms and con-
tinents through time. Special Papers in Palaeontology
12: 1–42.
SOLEM A 1976 Species criteria in Anguispira (Anguispira)
(Pulmonata: Discidae). The Nautilus 90: 15–23.
SOLEM A & YOCHELSON EL 1979 North American
Paleozoic land snails, with a summary of other
Paleozoic nonmarine snails. United States Geological
Survey Professional Papers 1072: 1–42, pls 1–10.
STEENIS CGGJ VAN 1962 The distribution of mangrove
plant genera and its significance for palaeogeog-
raphy. Proceedings of the Koninklijke Nederlandse
Akademie van Wetenschappen, Ser. C 65: 164–169.
STILLMAN CJ 1999 Giant Miocene landslides and evo-
lution of Fuerteventura, Canary Islands. Journal of
Volcanology and Geothermal Research 94: 89–104.
STWORZEWICZ E, SZULC J & POKRYSZKO BM 2009 Late
Paleozoic continental gastropods from Poland: sys-
tematic, evolutionary and paleoecological approach.
Journal of Paleontology 83: 938–945.
THIELE J 1931 Handbuch der systematischen Weichtierkunde.
Gastropoda: Opisthobranchia und Pulmonata. Zweiter
Teil: 377–778. Gustav Fischer, Stuttgart.
TILLIER S, MASSELOT M & TILLIER A 1996 Phylogenetic
relationships of the pulmonate gastropods from
rRNA sequences, and tempo and age of the stylom-
matophoran radiation. In TAYLOR JD (ed.) Origin
and evolutionary radiation of the Mollusca: 267–284.
Oxford University Press, Oxford.
UMINSKI T 1962 Revision of the Palearctic forms of
the genus Discus Fitzinger, 1833 (Gastropoda,
Endodontidae). Annales Zoologici Musei Polonici
Historiae Naturalis 20: 299–333.
UMINSKI T 1963 Taxonomy of Anguispira (?) marmoren-
sis (H.B. Baker, 1932) and notes on the taxonomy of
DisCiDae of the Canary islanDs
603
the genera Anguispira Morse and Discus Fitzinger
(Gastropoda, Endodontidae). Annales Zoologici
Musei Polonici Historiae Naturalis 21: 81–91.
VANDERPOPORTEN A, RUMSEY FJ & CARINE MA 2007
Does Macaronesia exist? Conflicting signal in the
bryophyte and pteridophyte floras. American Journal
of Botany 94: 625–639.
WADE CM, MORDAN PB & CLARKE B 2001 A phylog-
eny of the land snails (Gastropoda: Pulmonata).
Proceedings of the Royal Society of LondonB 268: 413–
422.
WADE CM, MORDAN PB & NAGGS F 2006 Evolutionary
relationships among the pulmonate land snails and
slugs (Pulmonata, Stylommatophora). Biological
Journal of the Linnean Society 87: 593–610.
WALDÉN HW 1984 On the origin, affinities, and evo-
lution of the land Mollusca of the mid-Atlantic
islands, with special reference to Madeira. Boletim
do Museu municipal do Funchal 36: 51–82.
WELLS SM & CHATFIELD JE 1992 Threatened non–
marine Mollusca of Europe. Nature and environment
Report 64: 1–163. Council of Europe, Strasbourg.
WENZ W 1923 Gastropoda extramarina tertiaria. 1. In
DIENER C (ed.), Fossilium Catalogus I: Animalia 17:
1–352. W Junk, Berlin.
WEST RG 1968 Pleistocene geology and biology, with
especial reference to the British Isles. Longman
Group, London. 377 pp.
WOLFE JA, DOYLE JA & PAGE VM 1975 The bases of
angiosperm phylogeny: palaeobotany. Annals of the
Missouri Botanical Garden 62: 801–824.
WOLLASTON TV 1878 Testacea Atlantica or the land and
freshwater shells of the Azores, Madeiras, Salvages,
Canaries, Cape Verdes and Saint Helena. L Reeve,
London. Xi + 588 pp.
YANES Y, MARTÍN J, ARTILES M, MORO L, ALONSO MR &
IBÁÑEZ M 2009 A rediscovery and redescription of
an almost unknown Hemicycla species (Gastropoda,
Pulmonata, Helicidae): H eurythyra O Boettger 1908
from Tenerife, Canary Islands. Journal of Conchology
40: 31–35.
YANES Y, MARTÍN J, MORO L, ALONSO MR & IBÁÑEZ M
2009B On the relationships of the genus Napaeus
(Gastropoda: Pulmonata: Enidae), with the descrip-
tion of four new species from the Canary Islands.
Journal of Natural History 43: 2179–2207.
YANES Y, ROMANEK CS, DELGADO A, BRANT HA, NOAKES
JE, ALONSO MR & IBÁÑEZ M 2009C Oxygen and
carbon stable isotopes of modern land snail shells
as environmental indicators from a low latitude
oceanic island. Geochimica et Cosmochimica Acta 73:
4077–4099.
YANES Y, HOLYOAK GA, HOLYOAK DT, ALONSO MR
& IBÁÑEZ M 2011 A new Discidae subgenus and
two new species (Gastropoda: Pulmonata) from
the Canary Islands. Zootaxa 2911: 43–49. (Online
at http://www.mapress.com /zootaxa/ 2011/f/
zt02911p049.pdf, accessed June 2011)
ZILCH A 1959 Euthyneura. In SCHINDEWOLF OH (ed.)
Handbuch der Paläozoologie, 6. Gastropoda. Lieferung
2: 201–400. Gebr. Borntraeger, Berlin.