Zoosyst. Evol. 91 (1) 2015, 45–58 | DOI 10.3897/zse.91.8536
museum für naturkunde
The shallow-water chitons (Mollusca, Polyplacophora) of Caldera,
Region of Atacama, northern Chile
Juan Francisco Araya1,2, Marta Esther Araya3
1 Programa de Doctorado en Sistemática y Biodiversidad, Departamento de Zoología, Universidad de Concepción. Casilla 160-C, Concepción, Chile
2 Laboratorio de Invertebrados Acuáticos, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras
3425, Ñuñoa CP 780-0024, Santiago, Chile
3 Los Gladiolos 520, Caldera. Chile
http://zoobank.org/6D9539C2-76A3-4803-95F6-8347908EA835
Corresponding author: Juan Francisco Araya (jfaraya@u.uchile.cl)
Abstract
Received 2 September 2014
Accepted 16 February 2015
Published 5 March 2015
Academic editor:
Matthias Glaubrecht
Key Words
Chile
Calloplax
Callistochiton
Chaetopleura
Enoplochiton
Radsia
Tonicia
Southeastern Pacific
intertidal
The Molluscan species of the northern littoral of Chile have been sparsely studied. This
work reviews for the first time the diversity of polyplacophoran molluscs around the
port of Caldera, in the Region of Atacama (26°45’49”S; 70°45’17”W to 27°20’23”S;
70°56’46”W), northern Chile. Eleven species were found in this study: Acanthopleura echinata (Barnes, 1824); Callistochiton pulchellus (Gray, 1828); Calloplax vivipara (Plate, 1899), Chaetopleura peruviana (Lamarck, 1819); Chiton cumingsii Frembly,
1827; Chiton granosus Frembly, 1827; Chiton magnificus Deshayes, 1827; Enoplochiton
niger (Barnes, 1824), Radsia barnesii (Gray, 1828), Tonicia atrata (G. B. Sowerby II,
1840) and Tonicia chilensis (Frembly, 1827). All of the species occurring in the area have
distributions in the southeastern Pacific Ocean, from Ecuador to central Chile, and three
of them are species endemic to the Chilean coasts (Calloplax vivipara, Radsia barnesii,
and Tonicia atrata). This diversity of species is comparable to that of better surveyed
faunas of central and southern Chile or Patagonia. Of the eleven species recorded, the
geographic distribution records for Callistochiton pulchellus, Radsia barnesii and Tonicia atrata are extended, and Calloplax vivipara is found alive again after 40 years, filling
a gap in its known distribution. Illustrations of living specimens in their habitat, distribution records and a taxonomic key for all the studied taxa are also provided.
Introduction
Research on marine molluscs of northern Chile began with
the descriptions of some species by Sowerby (1832),
d’Orbigny (1847), Hupé (1854) and Philippi (1860) in
the late 19th century. Further works include the studies
done by Dall (1909), mostly in deep water areas along the
Chilean and Peruvian coasts; Gigoux (1934), which listed
the species found in the Region of Atacama, Marincovich
(1973), describing the intertidal molluscs of Iquique;
Acuña (1977), Bretos (1980), Bretos et al. (1983) and
McLean (1984) dealing with fissurellid limpets and, more
recently, the works of Guzmán et al. (1998) which studied
the molluscan fauna of Antofagasta; Véliz and Vásquez
(2000) reviewing the Trochidae species from northern
Chile, and a few works, among others, describing new
Calyptraeidae (Brown and Olivares 1996, Véliz et al.
2012), Limidae (Campusano et al. 2012) or Buccinidae
species (Araya 2013).
Regarding the Chilean Polyplacophora — apart from
the early works of Frembly (1827), Rochebrune and Mabille (1885), Rochebrune (1889), Pilsbry (1893), Plate
(1901, 1902), Thiele (1906, 1911) or Melvill and Standen (1912) among others — it was the work of Leloup
(1956) which produced the most detailed study dealing
with this molluscan class in the country; encompassing
Copyright J. F. Araya, M. E. Araya. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which
permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Araya, J. F. & Araya, M. E.: The shallow-water chitons (Mollusca, Polyplacophora) of Caldera...
material from between Iquique (20°S) in northern Chile
to Punta Arenas (53°S) in the extreme south of the country. Most of the subsequent works dealing with chitons
have been focused on species from central and southern
Chile (Castellanos 1948, 1951, Stuardo 1959, Osorio and
Reid 2004, Schwabe and Sellanes 2004, 2010, Sirenko
2006), with a few works including shallow water species (Schwabe et al. 2006, Sirenko 2007). Further recent
works including species from the Region of Atacama or
northern Chile in particular only include the Kaas and
Van Belle monograph series (Kaas and Van Belle 1985a,
1985b, 1987, 1990, 1994) which studied the worldwide
chitons and, among them, Chilean species.
This molluscan class is often overlooked in Chile, as
their species are mostly small and hard to collect and to
preserve, however, three of the large species of Chilean
chitons (Acanthopleura echinata (Barnes, 1824), Chiton
(Chiton) magnificus Deshayes, 1827 and Chiton (Chiton)
granosus (Frembly, 1827)) are collected with gastronomic purposes (Osorio 2002), and some species are used in
traditional medicine in northern Chile. Chitons play a
role in controlling the green algal cover in mid-intertidal
exposed rocky-shores of central Chile (Aguilera and Navarrete 2007) eating encrusting corallines (Camus et al.
2012), newly settled barnacles (Aguilera 2005) and other
sessile and mobile invertebrates (Camus et al. 2008), and
thus they have a direct impact on the intertidal ecosystem.
The coast of the Region of Atacama consists of rocky
formations of volcanic origin with a few sandy beaches.
The intertidal area of most of the coast, with the exception of a few scattered bays, is narrow (up to 20 m) and
presents a diverse geography including cliffs, rocky plat-
Table 1. Sampling sites, arranged from north to south.
Locality
Habitat type/Macroalgae
Rocky coast with tidal pools, crustose
Obispito
coralline algae.
Rocky coast with tidal pools, large
Aguas Verdes
phaeophyta algae (Lessonia sp).
Playa Granito Orbicular Pebble beach, minor algae covering.
Playa Rodillo
Species present
26°45’49”S; 70°45’17”W Calloplax vivipara, Chiton cumingsii.
Chiton cumingsii, Chiton magnificus,
Tonicia chilensis.
26°58’22”S; 70°47’43”W Chiton cumingsii.
26°52’20”S; 70°49’25”W
26°59’48”S; 70°47’27”W Enoplochiton niger.
Callistochiton pulchellus, Calloplax
Rocky coast with tidal pools and rock
vivipara, Chaetopleura peruviana,
Sur de Playa Ramada
intrusions in sandy beach. Great diversity 27°00’37”S; 70°48’04”W
Chiton cumingsii, Chiton magnificus,
of algae.
Radsia barnesii, Tonicia chilensis.
Rocky coast, big boulders. Holdfasts of
Chaetopleura peruviana, Chiton
Islote Playa Ramada
27°00’41”S; 70°48’23”W
Lessonia nigrescens.
cumingsii, Enoplochiton niger.
Chaetopleura peruviana, Callistochiton
Pebble beach, rock formation. Several
Playa El Pulpito
27°01’22”S; 70°48’30”W pulchellus, Chiton cumingsii,
algae.
Enoplochiton niger.
Chaetopleura peruviana, Callistochiton
Rocky coast with protected sandy beach.
Playa El Pulpo
27°01’37”S; 70°48’39”W pulchellus, Chiton cumingsii,
Great diversity of algae.
Chiton granosus, Radsia barnesii.
Acanthopleura echinata,
Rocky coast, rock slabs and pockets of
Norte Bahía de Caldera
27°03’01”S; 70°48’30”W Chaetopleura peruviana,
sand. Encrusting algae, Ulva lactuca, etc.
Chiton granosus, Enoplochiton niger.
Sandy beach with rock formation. Minor
Chaetopleura peruviana, Chiton
Sur de Playa Negra
27°03’38”S; 70°48’51”W
algal covering.
cumingsii.
Rock formation among sandy beaches,
Chaetopleura peruviana, Chiton
Sur de Playa Brava
27°03’50”S; 70°49’13”W
Ulva lactuca and red algae.
cumingsii.
Acanthopleura echinata,
Limestone slabs on sandy beach. Small
Chaetopleura peruviana,
Playa Mansa
27°03’58”S; 70°49’36”W
algae covering, encrusting algae.
Chiton cumingsii, Chiton granosus,
Tonicia atrata, Tonicia chilensis.
Chaetopleura peruviana,
Rock slabs, pebble beach. Encrusting
Sur Bahía de Caldera
27°03’33”S; 70°49’55”W Chiton cumingsii, Chiton granosus,
algae.
Tonicia chilensis.
Loose boulders on sandy beach, Gracilaria
Chaetopleura peruviana, Chiton
Calderilla
27°05’30”S; 70°50’56”W
algae.
cumingsii, Tonicia chilensis.
Calloplax vivipara, Chaetopleura
Rocky coast with small pebble beach,
Peninsula Calderilla
27°05’15”S; 70°51’27”W peruviana, Chiton cumingsii,
Ulva lactuca and red algae.
Radsia barnesii.
Chaetopleura peruviana,
Norte Bahía Inglesa
Rocky beach, scattered sandy pockets.
27°05’14”S; 70°51’49”W
Chiton cumingsii.
Rocky formation on sandy beach.
Chaetopleura peruviana,
Sur Playa Rocas Negras
27°07’39”S; 70°54’53”W
Encrusting corallines.
Chiton cumingsii.
Rocky coast with scattered pebble
Chaetopleura peruviana,
Playa Chorrillos
beaches. Large algae holdfasts (Lessonia 27°12’44”S; 70°57’05”W
Chiton cumingsii, Chiton magnificus.
nigrescens, Lessonia trabeculata)
Sandy beach with rock platforms.
Bahia Cisne
27°14’57”S; 70°57’42”W Chiton cumingsii.
Filamentous algae.
Sandy beach with limestone rocks
Puerto Viejo
27°20’23”S; 70°56’46”W Chiton cumingsii.
intrusions. Minor algae communities.
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Exposed rocky coast and pebble beach.
Coordinates
Zoosyst. Evol. 91 (1) 2015, 45–58
forms, intertidal pools, and boulder fields. The exposed
side of rocks and boulders are exposed to strong surf,
with just a few sheltered areas, particularly in the area
of the Bay of Caldera, Obispito and Calderilla (Table 1).
This work presents an overview, with distributions and
illustrations, of all the species of Polyplacophora found in
the Region of Atacama, northern Chile. The distribution
range and a taxonomic key to all the studied species is
also provided. The aim of this preliminary paper is thus
to contribute on the knowledge of the molluscan fauna, in
particular of northern Chile.
Material and methods
The material considered in this study was mostly obtained by sampling in the rocky coastal areas around
the port of Caldera (27°04’S; 70°50’W), between Caleta Obispito (26°45’49”S; 70°45’17”W) and Puerto Viejo (27°20’23”S; 70°56’46”W), and in specific localities
along the coasts of the Region of Atacama, northern
Chile, during the summers of 2011 to 2012 and in August–December 2012. A synopsis of all the stations is
given in Table 1. The surveys used a similar approach to
the work of García-Ríos et al. (2011). The terminology of
shell morphology is based upon Schwabe (2010). Original descriptions of all species were carefully reviewed
and voucher specimens, unless indicated, are deposited
under accession number 3072014 in the collections of the
Museo Paleontológico de Caldera, Caldera, Chile (MPCCL). Abbreviations used are: LACM, Natural History
Museum of Los Angeles County, Los Angeles, USA;
SBMNH, Santa Barbara Museum of Natural History,
Santa Barbara, USA; NHMUK, National History Museum, London, United Kingdom.
Systematic taxonomy
Class Polyplacophora Gray, 1821
Subclass Neoloricata Bergenhayn, 1955
Order Chitonida Thiele, 1909
Suborder Chitonina Thiele, 1909
Superfamily Chitonoidea Rafinesque, 1815
Family Callistoplacidae Pilsbry, 1893
Genus Callistochiton Carpenter MS, Dall, 1879
Type species. Callistochiton palmulatus Carpenter MS,
Dall, 1879, by monotypy.
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3f–g (non Callistochiton shuttleworthianus Pilsbry,
1893). Callistochiton carmenae Smith & Ferreira, 1977:
87, figs 10–11. Callistochiton pulchellus: Ferreira 1979:
460, figs 25–26; Aguilera 2005a: 207, fig. 1. Detailed
bibliography and synonymy in Kaas and Van Belle
(1994: 161).
Description. Animal of small size, up to 11.5 mm in examined specimens, elongate oval, moderately elevated,
color of tegmentum creamy white or bright white. Head
valve semicircular, sculpture with 10–15 low rounded,
equally spaced, nodulose, annulate, radial ribs, becoming
obsolete towards the apex, the posterior ribs being strongest and more nodulose. Intermediate valves rectangular,
lateral areas well defined, sculptured with two strong radial ribs. Central area with two series of equally spaced,
diagonal lirae, forming rounded depressions in the interspaces. Tail valve semi-oval, slightly less wide than
head valve, sculptured like head valve, with 8–11 weaker
radial ribs. Girdle rather wide, yellowish white, dorsally
covered with small, oval, imbricating scales (After Kaas
and Van Belle 1994).
Material examined. Specimens found under sunken
rocks in tidal pools in Playa El Pulpito (SBMNH 452240,
1 specimen), Sur de Playa Ramada and Playa El Pulpo
(Table 1).
Distribution. This species has records from Islay
(17°03’S; 72°06’W), Peru to Chanavayita cove, 54 km
south of Iquique, Chile (20°42’S; 70°09’W), with records
also in the Galápagos Islands (01°40’N; 92°01 W), Ecuador (Aguilera 2005a). The present record (at 27°S) is now
the southernmost record for this species.
Remarks. This is a small (under 12 mm) chiton, easily
overlooked but for its bright whitish color. It is a fairly
rare species; they were not abundant and were found
only in two of the studied locations (Table 1), under
rocks sunken in tidal pools, associated to small communities of Acar pusilla Sowerby, 1832, Liotia cancellata
Gray, 1842, Rissoina inca Sowerby, 1832, encrusting
algae and sponges. It has been reported that this species feeds on sponges, bryozoa and diatoms (Aguilera
2005). This species can be mistaken for Calloplax vivipara (Plate, 1902), differing from this species in having a less elongate body shape, with a much finer and
subtle sculpture (especially noticeable on the terminal
valves), it differs from C. vivipara in having rounded
depressions in the central-lateral areas of the valves, especially in the middle valves.
Callistochiton pulchellus (Gray, 1828)
Plate 1, Fig. 2; Table 2
Genus Calloplax Thiele, 1909
Chiton pulchellus Gray, 1828: 6, pl. 3, fig. 9. Chiton bicostatus d’Orbigny, 1847: 486, pl. 81, figs 7–9. Callistochiton shuttleworthianus: Bergenhayn 1937: 284, figs
Type species. Chiton janeirensis Gray, 1828, by monotypy.
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Araya, J. F. & Araya, M. E.: The shallow-water chitons (Mollusca, Polyplacophora) of Caldera...
Calloplax vivipara (Plate, 1899)
Plate 1, Fig. 3; Table 2
Callistochiton viviparus Plate, 1899: 154, pl. 9, figs 267–
281; Dall 1909: 246; Gigoux 1934: 281; Boudet 1945:
134; Leloup 1956: 46; Stuardo 1959: 144: Smith 1966:
436, 437, 441, 442. Chiton janeirensis, Var.?: Gray 1828:
5; Sowerby 1840: 6, sp. no. 78 (spelled janierensis). Calloplax viviparus: Ferreira 1978: 60, figs 2 & 5.
Description. Animal of small size, up to 12 mm in examined specimens, elongate oval, moderately elevated, color
of tegmentum tan or creamy white. Head valve semicircular, sculpture with about nine equally spaced, nodulose,
annulate and well defined radial ribs. Intermediate valves
rectangular, lateral areas well defined, sculptured with
two strong radial ribs. Central area with about eight longitudinal riblets per side, well-marked in the pleural areas
but becoming obsolete at the jugum. The riblets tend to
converge anteriorly and are not latticed. Posterior valve
semi-oval, elevated at the central mucro, with nine well
defined radial ribs. Girdle yellowish white, dorsally covered with small scales (After Ferreira 1978).
Material examined. Specimens found under rocks in a tidal pool at Obispito (MPCCL 3072014B, 1 specimen), Sur
de Playa Ramada and under rock slabs sunken under boulders in Peninsula Calderilla (SBMNH 452241, 1 specimen).
Distribution. Plate (1899) described this species for Isla
Pacharos (=Pájaros), near Coquimbo, Chile (29°58’S;
71°21’W). Ferreira (1978) additionally recorded this species from the intertidal of Pozo Toyo, South of Iquique,
Tarapacá Province (20°25’S; 70°10.5’W) and mainland
East of Isla Santa María, North of Antofagasta, Antofagasta Province (23°25’S; 70°36’W) from specimens
housed at the LACM. A specimen labelled Chiton janeirensis (NHMUK 197742) identified by Ferreira (1978)
as C. viviparus extended the southern distribution of this
species at Valparaiso (33°02’S; 71°38’W). This is the first
time this species is recorded, in the field, since its description and the present record fills a gap in the distribution in
Chile of this rare species.
Remarks. This is a rare species, found in only two of
the locations under study; in both places this species was
found under rocks sunken in tidal pools, associated to encrusting sponges and to communities of the small mussel Brachidontes granulata (Hanley, 1843). According
to Plate (1899) this species is ovoviviparous; that cited
author found about 15 embryos, some with seven shell
valves, in the ovary of a single specimen. In fact, this is
the only chiton species ever reported to be ovoviviparous
(Pearse 1979). This species is somewhat similar to Callistochiton pulchellus (Gray, 1828), differing in the coarse
sculpture (especially in the anterior valve, with fewer and
stronger ribs), the presence of longitudinal riblets in the
central areas, and the more yellowish body color.
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Family Chaetopleuridae Plate, 1899
Subfamily Chaetopleurinae Plate, 1899
Genus Chaetopleura Shuttleworth, 1853
Type species. Chiton peruvianus Lamarck, 1819, by subsequent designation.
Chaetopleura (Chaetopleura) peruviana (Lamarck,
1819)
Plate 1, Fig. 4; Table 2
Chiton peruvianus Lamarck, 1819: 321; Barnes 1824: 70,
pl. 3, fig. 2. Chaetopleura peruviana: Plate 1902: 182,
pl. 2, figs 141–142, pl. 10, figs 294–301, pl. 11, figs 302–
303; Dall 1909: 244; Marincovich 1973: 44, fig. 101;
Aldea and Valdovinos 2005: 383, fig. 5C. Chaetopleura
(Chaetopleura) peruviana: Kaas and Van Belle 1987:
62, fig. 27; Reid and Osorio 2000: 113, fig. 2A.
Description. Animal of medium to large size, up to 45
mm long in examined specimens. Oval to elongate oval,
slightly depressed, color of tegmentum greenish-brown
to dark brown. Head valve semicircular, front slope
straight, posterior margin V-shaped. Intermediate valves
broadly rectangular. Tail valve less than semicircular, almost as wide as head valve. Girdle profusely beset with
very long (up to 10 mm) thick, coarse, corneous hairs, not
only interspersed throughout girdle but in girdle bridges,
protruding at sutures and extending over valves. Tegmentum pustulose sculptured with minute and neatly separated pustules, on the end valves the pustules are arranged
in radiating rows. Body width/length, mean 0.66; height/
length, mean 0.22 (After Ferreira 1983).
Material examined. Specimens found in almost all locations, with the exception of Bahia Cisne, Puerto Viejo and
Playa Rodillo up to Obispito (Table 1). Calderilla (MPCCL 3072014C, 1 specimen).
Distribution. Kaas and Van Belle (1987) cited this species along the western coast of South America, between
Cape San Lorenzo (1°4’0”S; 80°55’60”W), Ecuador to
the Chonos Archipelago (45°0’0”S; 74°0’0”W), southern
Chile. This species lives in the intertidal zone down to a
depth of 40 m (Kaas and Van Belle 1987).
Remarks. This species is easily distinguished from all
other chitons in the region by the presence of hairs covering
the valves and sutures. A similar species, Chaetopleura
(Chaetopleura) benaventei Plate, 1899 is slightly smaller
in size and differs in the overall coloration and in the
absence of the corneous bristles. Chaetopleura hennahi
(Gray, 1828) found between El Callao, Peru and Arica,
Chile (Kaas and Van Belle 1987) has a wine-red to reddish
brown tegmentum and lacks the blackish corneous hairs
which protrude at the sutures in Chaetopleura peruviana.
Zoosyst. Evol. 91 (1) 2015, 45–58
49
Plate 1. Chiton species photographed in situ; 1. Acanthopleura echinata, Playa Mansa; 2. Callistochiton pulchellus, Playa El Pulpo;
3. Calloplax vivipara, Peninsula Calderilla; 4. Chaetopleura peruviana, Sur Playa Ramada; 5. Chiton cumingsii, Playa El Pulpo;
6. Chiton granosus, Playa Mansa. Scale bars are: 2 cm for 1, 2, 3 and 1 cm for 4, 5, 6.
Family Chitonidae Rafinesque, 1815
Subfamily Acanthopleurinae Dall, 1889
Acanthopleura echinata (Barnes, 1824)
Plate 1, Fig. 1; Table 2
Genus Acanthopleura Guilding, 1829
Type species. Chiton spinosus Bruguière, 1792, by subsequent designation.
Chiton echinatus Barnes, 1824: 71, pl. 3, figs 4a, b. Chiton
spiniferus Frembly, 1827: 196, suppl. pl. 16, fig. 6; Sowerby 1833, pl. 1, fig. 47. Acanthopleura echinata: Dall
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Table 2. Distribution range of taxa considered in this work.
Species
Distribution
References
Talara, Peru (04°34’S; 81°16’W) to Punta Tumbes, Bahía de
Acanthopleura echinata (Barnes, 1824)
Concepción, Chile (36°49’S; 73°03’W).
Islay (17°03’S; 72°06’W), Peru to Ramada Beach, Caldera
Callistochiton pulchellus (Gray, 1828)
(26°56’S; 70°47’W).
Pozo Toyo, South of Iquique (20°25’S; 70°10.5’W) to
Calloplax vivipara (Plate, 1902)
Valparaiso (33°02’S; 71°38’W), Chile.
Cape San Lorenzo, Ecuador (01°04’S; 80°55’60”W) to the
Chaetopleura (Chaetopleura) peruviana
Chonos Archipelago, Chile (45°00’S; 74°00’W).
(Lamarck, 1819)
Paita, Peru (05°05’34”S; 81°06’07”W) to Puerto Montt
Chiton (Chiton) cumingsii Frembly, 1827
(41°28’S; 72°56’W), Chile.
Paita, Peru (05°05’34”S; 81°06’07”W) to Boca de Guafo
Chiton (Chiton) granosus Frembly, 1827
(43°39’S; 74°00’W), Region of Aysén, Chile.
San Lorenzo Island, Peru (12°05’23”S; 77°13’26”W) south
Chiton (Chiton) magnificus Deshayes, 1827 to Bahía Tictoc, Chiloé Province, Chile. (43°36’40”S;
72°57’15”W).
Talara, Peru (04°34’S; 81°16’W) to Coquimbo Bay, Chile
Enoplochiton niger (Barnes, 1824)
(29°58’S; 71°21’W).
Ramada Beach, Caldera (26°56’S; 70°47’W) to the Chonos
Radsia barnesii (Gray, 1828)
Archipelago (45°0’0”S; 74°0’0”W), Chile.
Playa Mansa, Caldera (27°03’58”S; 70°49’36”W) to Tierra del
Tonicia atrata (Sowerby II, 1840)
Fuego (54°S), Chile.
Tonicia chilensis (Frembly, 1827)
Peru (12°S) to Chile (54°S).
1909: 180, 248, pl. 23, fig. 6; Marincovich 1973: 44, fig.
100; Osorio 2002: 52.
Description. Animal of very large size, up to 158 mm in
examined specimens. Tegmentum smooth to shiny (but
often eroded), dark reddish-brown, with occasional small
blue spots. Lateral areas hardly raised, smooth except for
two radial rows, one of 5–9 round granules indenting sutural edge. Anterior valve with some 10 radial rows of
round granules; space between rows smooth. Central areas
with raised, well-defined, smooth jugal band bordered by
shallow, longitudinal grooves with short, wavy, longitudinally oriented riblets on pleural areas. Girdle upper surface with erect, strong, spike-like spines, round in cross
section, up to 8 mm long in large specimens (longer if not
broken), often encrusted. Girdle bridges empty (After Ferreira 1986). According to Osorio (2002) this is a dioecious
species, which can reach a maximum length of 200 mm.
Material examined. Specimens found in two locations;
Norte Bahía de Caldera (MPCCL 3072014A, 1 specimen) and in Playa Mansa, in subtidal areas in exposed
rocks and in rocks associated with the giant kelp Lessonia
nigrescens Bory de Saint-Vincent, 1826.
Distribution. According to Ferreira (1986) this species is found from Talara, Peru (04°34’S; 81°16’W) to
Punta Tumbes, Bahía de Concepción, Chile (36°49’S;
73°03’W), and is limited to the intertidal zone and shallow subtidal, 0–4 m depth, on rocks often exposed to
heavy surf.
Remarks. This is one of the largest polyplacophoran in
Chile, differing from the also large Enoplochiton niger in
having conspicuous spines in the girdle, not sparse scales
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Ferreira 1986
Aguilera 2005a and
this study.
Plate 1902; Ferreira
1978 and this work
Kaas and Van Belle
(1983)
Marincovich (1973).
Marincovich (1973) and
Osorio et al. (2005).
Bullock (1988)
Ferreira 1986
Bullock (1988) and this
study
Reid and Osorio (2000)
and this study
Reid and Osorio (2000).
as in E. niger. This species prefers the subtidal zone and
wave-exposed shores, and it is often covered with algae and epibionts (Scurria species, Mytilus species, etc)
which allow this species to blend in with its surroundings.
The spines are often covered with encrusting algae in older specimens. This is a commercially important species
(Osorio 2002).
Genus Enoplochiton Gray, 1827
Type species. Chiton niger Barnes, 1824, by monotypy.
Enoplochiton niger (Barnes, 1824)
Plate 2, Fig. 1; Table 2
Chiton niger Barnes, 1824: 71, pl. 3, fig. 3. Enoplochiton
niger: Pilsbry 1893: 14: 252, pl. 52, figs 22–29; Marincovich 1973: 43, fig 99. Acanthopleura nigra: Ferreira
1986: 266, figs 106–111 and 113–N.
Description. Animal very large in size, up to 190 mm in
examined specimens. Tegmentum dark chocolate-brown,
shiny, but easily eroded. Anterior valve with 4–6 concentric, zig-zagged furrows. Lateral areas elevated, well defined by strong round rib at diagonal line, with zig-zagged
furrows as on anterior valve. Central areas well defined,
smooth jugum bordered by narrow, depressed area with
irregular, short, oblique furrows; para-jugal area smooth;
pleural area with longitudinal, parallel furrows, not usually reaching anterior border of valve. Girdle thick, muscular; dorsal surface dark brown, conspicuously dotted with
light brown scales, scales irregular in size (larger in middle
Zoosyst. Evol. 91 (1) 2015, 45–58
1/3 of girdle), up to 1.5–2 mm long in specimens 50 mm
long (larger in larger specimens), vaguely striate, usually
eroded at upper edge, clearly separated from each other by
area as wide as scale; on outer 1/5 of girdle, scales much
smaller, shorter, dark brown, erect, spine-like; girdle surface completely covered otherwise with minute, dark
brown, lanceolate spicules, up to 100 μm long, 25 μm
thick. Girdle bridges, empty in middle third, but crowded
with small, dark brown spiculoid elements (akin to those
on girdle proper) in outer thirds (After Ferreira 1986).
Material examined. Specimens found exposed on large
boulders in the surf–zone, in Playa Rodillo, Playa El
Pulpito (MPCCL 3072014E, 1 specimen) and in Norte
Bahía de Caldera.
Distribution. This species is confined to the western
temperate coast of South America, from Talara, Peru
(04°34’S; 81°16’W) to Coquimbo Bay, Chile (29°57’S;
71°20’W). Its bathymetric range is limited to the intertidal zone (Ferreira 1986).
Remarks. With sizes up to 200 mm (Sanhueza et al.
2008), this is one of the largest polyplacophoran species in
the country. It lives almost exclusively in exposed rocks or
in the surf zone. Although this species is mostly herbivore,
it has been described also as a generalist polyphagous consumer, and a potential omnivorous, (Sanhueza et al. 2008).
A brown-colored variety of the limpet species, Scurria
variabilis (Sowerby, 1839), lives on the valves of this species, having been found in all the specimens examined in
this study. An unidentified barnacle was also observed on
the valves of a few specimens. In some places (Rodillo
beach, Obispito bay; Table 1) juvenile specimens can be
found among crevices of large boulders. It was observed
that this species is predated by the common gull, Larus dominicanus (Lichtenstein, 1823), an omnivore species that
also predates on the intertidal large keyhole limpets of the
genus Fissurella (Bahamondes & Castilla, 1986).
51
Dall 1909: 247. Chiton cumingsii: Reeve, 1847, pl. 1, figs
2a, b; Plate 1902: 46, pl. 3, figs 179–184, pl. 4. Chiton
cumingi: Pilsbry 1893: 164, pl. 30, figs 29–31. Chiton
(Amaurochiton) cumingsii: Bullock 1988: 166, figs 59–
63, 69, 74 and 77.
Description. Animal of large size, reaching almost 60
mm in length in examined specimens. Anterior valve
straight; post-mucronal slope of posterior valve slightly concave. Shell color yellowish white with concentric
brown bands crossing lateral triangle longitudinally, then
proceeding antero–medially over ribs of central area. Girdle light olive green or pinkish-brown. Interior of shell
white with some dull green in posterior depression (After
Bullock 1988).
Material examined. Specimens found in all the rocky
shore stations (except Playa Rodillo and Norte Bahía de
Caldera). Collected under rocks and rock slabs, Sur de
Playa Brava (MZUC 39613, 1 specimen).
Distribution. Marincovich (1973) cites this species
from Paita (05°05’S; 81°06’W), Peru to Puerto Montt
(41°28’S; 72°56’W), Chile.
Remarks. This colorful species is the most common and
abundant chiton distributed in the zone; found in almost
all the locations. It is commonly found in accumulations
of several individuals on the underside of rocks at low
tide, crawling quickly to the dark if exposed to sunlight.
Among the examined specimens, some of them had a
pink/orange coloration when juveniles with some adult
specimens retaining a uniform pink coloration. This species has been cited as an introduced species in Las Palmas
Port, Canary Islands (28°06’N, 15°25’W), being one of
the few alien polyplacophoran found in European waters
(Arias and Anadón 2013).
Chiton (Chiton) granosus Frembly, 1827
Plate 1, Fig. 6; Table 2
Family Chitonidae Rafinesque, 1815
Subfamily Chitoninae Rafinesque, 1815
Genus Chiton Linnaeus, 1758
Type species. Chiton tuberculatus Linnaeus, 1758, by
subsequent designation.
Chiton (Chiton) cumingsii Frembly, 1827
Plate 1, Fig. 5; Table 2
Chiton cumingsii Frembly, 1827: 198, suppl. pl. 16, fig. 3;
Chiton granosus Frembly, 1827: 200, suppl. pl. 17, fig. 1;
Plate 1902: 56, pl. 4, fig. 190; Pilsbry 1893: 167, pl. 30.
figs 27, 28; Dall 1909: 247. Chiton (Chiton) granosus:
Marincovich 1973: 43, fig. 98. Chiton (Chondroplax)
granosus: Bullock 1988: 185, figs 96, 97, 103, 140, 141,
143, and 144; Osorio 2002: 56.
Description. Animal of large size, up to 45 mm in examined specimens. Intermediate valves often eroded and
rather flat. Anterior valve convex, post-mucronal slope
straight. Mucro moderately blunt; centrally located on
posterior valve. Jugal tract smooth, central areas with
somewhat beaded longitudinal ribs. Lateral triangle barely raised; low, broad, nodular rib extends along diagonal
line. Often a few other radiating rows of nodules appear
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52
Araya, J. F. & Araya, M. E.: The shallow-water chitons (Mollusca, Polyplacophora) of Caldera...
on lateral triangle. Terminal areas with 10–12 radiating
rows of widely spaced nodules. Color of tegmentum nearly totally dark brown to greenish brown, with occasional
streaks of cream white on jugal and central areas. Girdle
black. Interior of valves white with dull blue muscle scars
and reddish brown on posterior slope of callus (After
Bullock 1988). According to Osorio (2002) this species is
gonochoric, like almost all other chiton species that have
been studied. It can reach a maximum length of 80 mm.
Material examined. Specimens found in Playa El Pulpo, Norte de Bahía de Caldera, Playa Mansa and Sur
de Bahía de Caldera, in crevices in large rocks, often
in surf zone in large colonies. Playa el Pulpo (MPCCL
3072014D, 1 specimen).
Distribution. Marincovich (1973) gives the northernmost distribution for this species at Paita (05°05’34”S;
81°06’07”W), Peru. Osorio et al. (2005) records the
southernmost record of this species at Boca del Guafo
(43°39’S; 74°00’W), Region of Aysén, southern Chile.
Remarks. This species is somewhat uncommon in shallower waters; it is found mostly in crevices and in rocky
outcrops, mostly in clustered distributions. Juvenile specimens are somewhat similar to the juvenile specimens
of Chiton cumingsii differing in the paler coloration (of
various shades of green), the granulation on the valves
and in the overall wider body. It has been reported that
this species feeds on barnacle cyprids (Moreno and Jaramillo 1983, Aguilera 2005) and is preyed on by the common gull Larus dominicanus (Lichtenstein, 1823). It was
observed also that some specimens had barnacles on the
valves. This species is a physiological omnivore, having
the digestive flexibility and enzymatic capacity to digest
and assimilate animal preys (Camus et al. 2009) and it
is also a commercially important species (Osorio 2002).
Chiton (Chiton) magnificus Deshayes, 1827
ly concave posterior margin at both sides of faintly protruding apex, lateral areas slightly elevated, sculptured
with up to 5 radial ribs between a wider diagonal ridge
and a very wide posterior rib; tail valve semicircular with
an anterior mucro; post-mucronal area with same sculpture as head valve and lateral areas (After Schwabe et al.
2006). According to Osorio (2002), this species can reach
a maximum length of 174 mm.
Material examined. Specimens found in Aguas Verdes,
Sur de Playa Ramada and in Playa Chorrillos, in subtidal
areas attached to large boulders.
Distribution. Bullock (1988) gives a distribution for this
species from Isla San Lorenzo, Peru south to Bahía Tictoc
(43°36’40”S; 72°57’15”W), Chiloé Province, southern
Chile. This species can be found in rock pools and boulder fields with strong water exchange, from the intertidal
down to a maximum of 30.5 m depth at the Comau Fjord
(42°23’S; 72°27’W), Region of Aysén (Schwabe et al.
2006). Smith and Ferreira (1977) considered the records
of this species from Galapagos Islands as erroneous.
Remarks. A shiny, large and conspicuous chiton, this species has been overlooked in recent molluscan literature,
being cited by Valdovinos (1999) as Chiton latus and by
Osorio (2002) as Chiton magnificus boweni. It seems to
be an uncommon species, restricted to specific localities
along the coast of Chile. Juvenile specimens may be misidentified as Chiton cumingsii, differing from this species
in having a wider and flatter body, with smoother sculpture and with bright blue spots on the valves, which are
cream white to greenish yellow in color. Apparently, in
northern Chile this species is found only in subtidal areas.
This is a commercially important species (Osorio 2002).
Genus Radsia Gray, 1847
Type species. Chiton barnesii Gray, 1893 by monotypy.
Table 2
Chiton (Chiton) magnificus Deshayes, 1827: 454. Chiton
magnificus: Pilsbry 1893: 160, pl. 30, figs 23, 24; Chiton
(Amaurochiton) magnificus magnificus: Bullock 1988:
163, figs 52–54, 57, 58, 64, 65, 68, 72, 73 and 76. Chiton magnificus: Schwabe et al. 2006: 9, figs 7, 8 and 15.
A more detailed bibliography and synonymy can be
found in Bullock (1988: 163).
Description. Animal of large size, reaching 115 mm in
examined specimens. Body dark bluish-grey, broad-oval,
slightly carinated, rather flat. Valves flattened to moderately carinated. Anterior valve sligthtly convex, semicircular, with wide V-shaped to straight posterior margin
unnotched in middle, with numerous radially arranged,
shallow ribs; intermediate valves rectangular with slight-
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Radsia barnesii (Gray, 1828)
Plate 1, Fig. 2; Table 2
Chiton barnesii Gray, 1828: 5; Reeve 1847: pl. 1, sp. 1.
Chiton (Radsia) barnesii: Pilsbry 1893: 190, pl. 29, figs
10–12; Dall 1909: 247. Chiton barnesii: Plate 1899: 59,
pl. 4, fig. 191; Leloup 1956: 46. Radsia barnesii: Bullock
1988: 282, figs 2,4,6,7, 11–13, 15, 31, 32. A more complete synonymy in Bullock (1988: 282)
Description. Animal of medium size, reaching a length
of 28 mm in the examined specimens. Anterior valve
straight; post-mucronal slope of posterior valve straight to
slightly concave. Valves quite flat. Jugal region smooth;
Zoosyst. Evol. 91 (1) 2015, 45–58
53
Plate 2. Chiton species photographed in situ; 1. Enoplochiton niger, Isla Playa Ramada, 123 mm; 2. Radsia barnesii, Sur Playa
Ramada, 22 mm; 3. Tonicia atrata, Sur de Playa Brava, 30 mm; 4. Tonicia chilensis, Playa Mansa, 32 mm. Scale bars are: 1 cm for
2 and 4, 2 cm for 3 and 4 cm for 1.
central area with numerous uneven longitudinal ribs.
Lateral triangle barely raised, with 5–7 irregular nodules.
Shell color cream white with reddish brown splotches on
central areas, irregular longitudinal dark reddish brown
bands on lateral triangles, and occasional dark reddish
brown on jugum. Girdle light greenish brown with faint
trace of alternating lighter bands in some specimens.
Interior of valves white (After Bullock 1988).
Material examined. Specimens found in three locations;
Peninsula Calderilla, Sur de Playa Ramada and in Playa
El Pulpo Beach (Table 1). Collected under rocks and rock
slabs, Peninsula Calderilla (MZUC 39614, 1 specimen).
Distribution. Bullock (1988) cites this species from Coquimbo (29°58’S; 71°21’W), to the Chonos Archipelago (45°0’0”S; 74°0’0”W), Chile. The present record (at
27°S) is now the northernmost record for this species.
darker alternating bands in the girdle. It can be misidentified as Chiton granosus; differing from this species in
the smaller size, the much smaller girdle scales, a much
weak valve sculpture and in the alternating bands of the
perinotum, absent in Chiton granosus.
Family Chitonidae
Subfamily Toniciinae Pilsbry, 1893
Genus Tonicia Gray, 1827
Type species. Chiton chilensis Frembly, 1827, non De
Blainville 1825 (= Chiton chilensis Frembly, 1827), by
subsequent designation (Gray 1847: 168).
Tonicia atrata (G.B. Sowerby II, 1840)
Remarks. This species was uncommon in the zone under
study; only a few specimens were found in the undersides
of rocks at low tide. This species is clearly identified from
the other species found in this work by having a wide,
flat shell, with narrower valves and a pattern of clear and
Plate 2, Fig. 3; Table 2
Chiton atratus G.B. Sowerby II, 1840: 294. Tonicia atrata Aldea & Valdovinos, 2005: 368, Table 1, fig.
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5I; Schwabe et al. 2006: 12, figs 9, 18; Gordillo and
Schwabe 2009: 267, fig. 2D. A more detailed synonymy can be found in Kaas and Van Belle (1998: 25).
Description. Animal of medium to large size, reaching 51
mm in examined specimens. Shell elongate-oval, moderately elevated, subcarinated dorsum. Color reddish brown
to blackish purple. Head valve semicircular, with straight
posterior valve margin unnotched in middle; intermediate
valves broadly rectangular, with distinct protruding apex
and concave posterior valve margins. Lateral area hardly
elevated, but clearly indicated by faint depression in front of
diagonal ridge. Jugal area weakly developed, but showing
partly a more or less distinct keel, especially in the more
posterior intermediate valves. Tail valve with centrally situated, forward-directed, and slightly elevated mucro, straight
antemucronal area and rather steep, straight postmucronal
slope. Jugal area of tail valve extending towards anterior.
Tegmentum without sculpture, except for growth marks
and faint radial striations on terminal valves and lateral areas. Perinotum wide and fleshy (After Schwabe et al. 2006).
Material examined. Specimens collected in a single location; Playa Mansa, in submerged rocky platform (Table
1), MPCCL 011928A, 1 specimen.
Distribution. According to Reid and Osorio (2000), this
species distributes in Chile between 40°S and 54°S, at
Tierra del Fuego and around the Falkland Islands. The
species ranges in depth from the low eulittoral to a depth
of 36 m (Schwabe et al. 2006). The record presented here
(at 27°S) is now the northernmost record for this species.
Remarks. Two specimens of this species were found in a
single location; among a community of Tonicia chilensis,
from which it distinguishes in attaining larger sizes and in
having a darker body and almost smooth valves with minute
granulation at the sides. It is interesting to note also that the
valves of the examined specimens were widely separated,
almost as in Tonicia disjuncta (Frembly, 1827). The presence of this species extends considerably the northernmost
record of this species in about 1040 km (from 40°S to 27°S).
Tonicia chilensis (Frembly, 1827)
Plate 2, Fig. 4; Table 2
Chiton chilensis Frembly, 1827: 203, pl. 17, fig. 6; Reeve
1847: pl. 4, f. 19. Tonicia elegans Subspecies chilensis:
Pilsbry 1893: 196, pl. 41, figs 22–24, pl. 42, figs 31–35.
Tonicia chilensis: Gordillo and Schwabe 2009: 269, fig.
2E, F. A more complete synonymy can be found at Kaas
and Van Belle (1998: 45).
Description. Animal of medium to large size, reaching
43 mm in examined specimens. Shell elongate-oval, not
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much elevated, the dorsal ridge rounded, side-slopes
straightened. Color umber-brown at the sides, becoming
chestnut in the middle, delicately and peculiarly speckled
and blotched and streaked with buff or buff-white. Lateral areas hardly raised, but separated from the central
areas by an obtuse diagonal ridge bearing a series of low
tubercles, sometimes subobsolete; sculptured with subradiating rows of small granules, and showing a band of
irregularly placed black eyes on the forward part. Central
area of second valve having in the middle, a keel or a
group of lirae; central areas of the other valves having
a narrow smooth dorsal band with several longitudinal
furrows on each side of it; and at the sides there are longitudinal diverging delicate rows of granules. End valves
radially sub-granulate, and crowded with eye-spots subradially arranged (After Pilsbry 1893).
Material examined. Specimens found on rocks at low
tide in Aguas Verdes, Sur de Playa Ramada, Playa Mansa
(MPCCL 3072014F, 1 specimen), Sur Bahía de Caldera
and in Calderilla.
Distribution. According to Reid and Osorio (2000) this
species distributes in Chile and Peru between latitudes
12° and 54°S. It has a bathymetric range from 0–28 m
(Schwabe et al. 2006).
Remarks. This species has large and colorful mantles and plates of variable shades, which are similar to
the encrusting calcareous algae commonly found in the
rocky coasts. Due to the high diversity of forms, several
synonyms have been described (see Kaas and Van Belle
1998), and this species needs a complete revision according to Schwabe et al. (2006). This species was found only
in the lower intertidal to the subtidal areas, especially in
protected locations.
Discussion
Schwabe and Sellanes (2010) reported 41 species of chitons from Chilean waters. Our results from the Region of
Atacama, with eleven species found, accounts for 27 % of
those reported species. All of the species occurring in the
area have distributions in the southeastern Pacific Ocean,
from Peru to southern Chile, with Calloplax vivipara,
Radsia barnesii and Tonicia atrata as the only species
endemic to the Chilean coast. The polyplacophoran diversity of the Region of Atacama is thus comparable
to that described for southern areas of Chile, including
central Chile (Aldea and Valdovinos 2005), the Comau
fjord (Schwabe et al. 2006) and the Estero Elefantes and
Laguna San Rafael areas (Osorio and Reid 2004), from
where a similar diversity of this molluscan class has been
recorded (with eleven, nine and nine species, respectively). With the exception of Callistochiton pulchellus, all of
the species found in the Region of Atacama also occur in
central and southern Chile.
Zoosyst. Evol. 91 (1) 2015, 45–58
All of the studied species can be classified in two main
groups according to their habitat; species with a higher
relative frequency on exposed areas include the very large
species Acanthopleura echinata and Enoplochiton niger.
The other group includes species associated with protected intertidal areas: Callistochiton pulchellus, Calloplax
vivipara, Chiton cumingsii, Chiton granosus (mostly
found in rock fissures and crevices) and Radsia barnesii.
Chiton magnificus was found in the Region of Atacama
only in subtidal areas, always near large boulders in holdfast communities of the giant kelp Lessonia nigrescens.
Chiton magnificus, however, is much more common in
central and southern Chile, being found mostly in intertidal areas (Osorio 2002). The small-bodied species, Callistochiton pulchellus and Calloplax vivipara, were always restricted to submerged rocks in the bottom of tidal
pools. This last habitat may explain the feeding behaviour
of these small species, living over encrusting sponges and
calcareous algae. Regarding feeding preferences; most of
the large species of chitons from the Region of Atacama
should have generalist diets, however it is possible that
the smaller species have more specific diets, for example
feeding in sponges, algal species, diatoms or barnacles.
The new distribution records of Callistochiton pulchellus, Radsia barnesii and Tonicia atrata and the
new record of Calloplax vivipara may reflect the lack
of sampling in the Atacama region or in northern Chile
in general, where the scientific studies on invertebrates
are still lacking. In particular, Callistochiton pulchellus
and Calloplax vivipara may be more widespread in the
country; however their particular habitat (and small adult
size) may prevent their sampling by traditional methods.
Some of these species may have also been overlooked or
misidentified as juvenile specimens of other chiton spe-
55
cies (for example Radsia barnesii as Chiton granosus).
The considerable new range extension of Tonicia atrata
found in this study may reflect the current complicated,
unresolved status of the genus Tonicia in Chile; the revision of some particular species or species-groups is thus
imperative, considering the great diversity in the valve
and mantle morphology, which has derived in a large
synonymy for some species, for instance for Tonicia
chilensis (Schwabe et al. 2006).
The absence of other species, for example those cited
by Valdovinos (1999) in the last complete revision of the
Chilean mollusks (which have been traditionally considered as having distribution records in northern Chile), including Acanthochitona hirudiniformis (Sowerby, 1832),
Acanthopleura granulata (Gmelin, 1791), Chaetopleura
benaventei Plate, 1902, Chaetopleura hennahi (Gray,
1828), Ischnochiton imitator (Smith, 1881), Ischnochiton
(Ischnochiton) punctulatissimus (Sowerby in Broderip &
Sowerby, 1832) or Ischnochiton pusio (Sowerby, 1832)
may be explained because the sampling activities in the
Region of Atacama were restricted to, at most, sublittoral areas (2 m depth). Deep water areas must definitely
harbor more unrecorded or undescribed species, as is the
case with other invertebrate groups like sponges (Reiswig
and Araya 2014) or stony corals (Araya et al. in prep.). It
is, then, very probable that the number of chitons known
from the Region of Atacama, or northern Chile in general, will increase with larger collecting efforts, including
additional sampling methods such as dredges and samples from greater depths, even subtidal waters (incorporating also the bycatch of the commercial deep water fisheries). Like other zones of Chile, the deep water areas off
Caldera (or off northern Chile in general) have not been
investigated in detail and could yield interesting results.
Identification key
This key is primarily macroscopic (intended for identification of adult specimens) including external characters as shell
features and general girdle features.
1
1a
2
2a
3
3a
4
4a
5
5a
6
6a
Whitish or cream colored chiton, of small size (up to 14 mm) .................................................................................... 2
Animal of green, brown, pink or black coloration........................................................................................................ 3
Animal bright whitish in color, with 10–16 radial ribs on head valve, with rounded depressions on the lateral areas of the
valves .................................................................................................................. Callistochiton pulchellus (Gray, 1828)
Animal whitish-cream in color, with about nine radial ribs on head valve, with longitudinal riblets in the lateral areas ...
Calloplax vivipara (Plate, 1902)
Girdle naked or covered with small scales or by blunt spines ..................................................................................... 4
Girdle covered by hairs, which can be also found between the valves, fleshy girdle .......................................................
Chaetopleura peruviana (Lamarck, 1819)
Girdle covered by visible round scales, in neat rows ................................................................................................... 5
Girdle fleshy, naked or with spare spines ................................................................................................................... 8
Valves visible granulose, often eroded and rather flat, with two white fringes on the central areas of the valves, terminal
areas with 10–12 radiating rows of widely spaced nodules, girdle black ......................... Chiton granosus Frembly, 1827
Valves striated in the middle, central valves narrow .................................................................................................. 6
Valves carinate, of green, light brown or pink-yellowish color, girdle with alternating bands of color..............................
Chiton cumingsii Frembly, 1827
Valves rather flat, olive green to black ....................................................................................................................... 7
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Araya, J. F. & Araya, M. E.: The shallow-water chitons (Mollusca, Polyplacophora) of Caldera...
7
Girdle with alternating pale and dark bands, central valves with uneven longitudinal ribs, color olive green, size small
(up to 35 mm) and rather flat .........................................................................................Radsia barnesii (Lesson, 1828)
7a Girdle black, valves flattened with central areas with fine longitudinal lirae, color dark green to nearly black, with tiny
blue points, size up to 174 mm ................................................................................ Chiton magnificus Deshayes, 1827
8
Girdle naked, ample, decorated with green and pink spots, plaques with variegated colouration ............................... 10
8a Girdle muscular, covered by blunt spines or lanceolate spicules................................................................................. 9
9
Girdle covered by blunt spines, anterior valve with some ten radial rows of rounded granules, valves usually encrusted
with algae ..........................................................................................................Acanthopleura echinata (Barnes, 1824)
9a Girdle covered with irregularly–sized scales, anterior valve with 4-6 concentric, zig-zagged furrows, valves often eroded
.................................................................................................................................Enoplochiton niger (Barnes, 1824)
10 Valves sculptured with minute granulation, central areas with a narrow smooth dorsal band or a group of lirae, with an
obtuse diagonal ridge bearing a series of low tubercles ............................................... Tonicia chilensis (Frembly, 1827)
10a Valves almost smooth; only sculptured by growth marks and faint radial striations on terminal valves and lateral areas
.......................................................................................................................... Tonicia atrata (G. B. Sowerby II, 1840)
Acknowledgements
We are thankful to Raúl Zuñiga and to Edison Villalobos
(Caldera, Chile), for their help in field collections. We
also give our thanks to Douglas Eernisse (Department of
Biological Science, California State University Fullerton,
Fullerton, California, U. S. A.) and to an anonymous reviewer for their helpful corrections, suggestions and comments, which greatly improved our manuscript. We are
also indebted to the academic editor, Matthias Glaubrecht
(Museum für Naturkunde, Leibniz Institute for Evolution
and Biodiversity Science, Berlin, Germany) for his essential collaboration with this work.
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