The phylum Echinodermata is represented approximately by 7 000 living species, and 13 000 fossil species, and comprises five living classes (Pawson, 2007). In the Mexican Pacific, the taxonomy and ecology of the echinoderm species have been studied for more than a hundred years, being the Gulf of California the most extensively studied area (Solís-Marín et al., 2013).

The Southern Mexican Pacific (SMP) comprises the States of Guerrero, Oaxaca and Chiapas. This is a region with a high marine biodiversity and endemism, besides it has a large number of habitats (i.e. coral reefs, mangroves, coastal lagoons) and represents the main dispersal route to Mexico for species from Central America (Arriaga-Cabrera et al., 1998; Reyes-Bonilla & López-Pérez, 1998). A large amount of information has been published regarding the echinoderm fauna of the SMP, resulting in a research history that can be divided into three periods.

The first expedition carried out at the coasts of the SMP was Albatross in 1891. The leading scientist of the expedition was Alexander Agassiz, who collected marine specimens from the Eastern Pacific. The expedition resulted in the reports of Ludwig (1894) (Holothuroidea), Agassiz (1898, 1904) (Echinoidea), Lütken and Mortensen (1899) (Ophiuroidea) and Ludwig (1905) (Asteroidea). Although Albatross was the only expedition into the SMP during the 19th century, numerous taxonomic contributions were produced for this area mostly for Asteroidea (Gray, 1871; Perrier, 1875, 1878; Sladen, 1899) and Echinoidea (Agassiz, 1863, 1872, 1873, 1881, 1898; Lockington, 1876; Rathbun, 1886).

During the 20th century (in 1904 and 1905) the Albatross made a final expedition to the SMP. This expedition resulted in the extensive work of H.L. Clark (1920) about the Eastern Tropical Pacific Asteroidea. Along with the Albatross, during 1931-1941, the Velero III surveyed the SMP. As a result of the Velero III expeditions, Deichmann (1941, 1958) (Holothuroidea), H.L. Clark (1948) (Echinoidea) and Ziesenhenne (1940) (Ophiuroidea) published extensive works on the echinoderms of the area. During 1937-1938, the New York Zoological Society organized an expedition to the Eastern Pacific (Zaca) under the direction of William Beebe, which generated the works of Deichmann (1938) (Holothuroidea) and H.L. Clark (1940) (Asteroidea, Ophiuroidea, Echinoidea). In addition, during this century, there was an increase in systematic studies of echinoderms from the SMP. In particular, researchers such as H.L. Clark (1907a, 1907b, 1914, 1915, 1917, 1920, 1922, 1925, 1940, 1948), Deichmann (1936, 1937, 1938, 1941, 1958) and Caso (1944, 1945, 1946, 1948a, 1948b, 1949, 1951, 1954, 1958, 1962, 1963, 1964, 1965, 1967a, 1967b, 1970, 1977, 1978a, 1978b, 1979, 1980a, 1980b, 1983, 1986) produced a vast number of publications.

Recently, the study of echinoderms in the Southern Mexican Pacific has not only focused on systematics, but also on ecology (Benítez-Villalobos, 2001; Lirman et al., 2001; Calderón-Aguilera & Reyes-Bonilla, 2006;

López-Pérez et al., 2008; Zamorano & LeyteMorales, 2005a, 2005b, 2009), bioerosion (Herrera-Escalante et al., 2005; Benítez-Villalobos et al. 2008b), reproduction (Benítez-Villalobos & Martínez-García, 2012; Benítez-Villalobos et al., 2012, 2013), and symbiosis (GranjaFernández et al., 2013b).

Notwithstanding that the knowledge of the echinoderms in the SMP has increased since the 19th century, the large amount of work in the area has generated a myriad of names that not only have often been misspelled, but have also created longstanding taxonomic problems. To overcome this trend, the main goal of this contribution is to present the first updated checklist of all valid and synonymous names of echinoderms from the SMP based on published literature and from specimens deposited in collections, which will be useful as a baseline for future taxonomic, ecological and marine resource management studies.

Materials and methods

We present a list of all known valid names and synonyms of echinoderm species (classes Asteroidea, Ophiuroidea, Echinoidea and Holothuroidea) from Guerrero (GRO), Oaxaca (OAX), Chiapas (CHIS) and the Gulf of Tehuantepec (GT), México. The Gulf of Tehuantepec comprises the States of Oaxaca and Chiapas; some of the records in the area do not mention a specific State, thus we refer to them as Gulf of Tehuantepec.

The checklist is based on an exhaustive published literature search (131 references) and records of specimens deposited in museums or properly curated reference collections (AMNH-American Museum of Natural History, New York; AMS-Australian Museum, Sydney; CAS-California Academy of Sciences, San Francisco; FMNH-The Field Museum, Chicago; ICML-UNAM-Colección Nacional de Equinodermos “Dra. Ma. Elena Caso”, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, México City; LACM-Los Angeles County Museum, Los Angeles; MACN-Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Buenos Aires; MCZ-Museum of Comparative Zoology, Cambridge; UMAR-Colección de equinodermos de la Universidad del Mar, Puerto Ángel, México; USNM-National Museum of Natural History, Washington; YPM-Yale Peabody Museum of Natural History, New Haven).

Systematic arrangements follow the criteria of A.M. Clark (1989, 1993, 1996), A.M. Clark and Mah (2001) and Mah (2014) for the Asteroidea; Smith et al. (1995), Stöhr et al. (2014) for the Ophiuroidea; Mortensen (1928, 1935, 1943a, 1943b, 1948, 1950, 1951), Kroh and Smith (2010) and Kroh and Mooi (2014) for the Echinoidea; Pawson and Fell (1965), Rowe (1969), Solís-Marín et al. (2009), Smirnov (2012) and WoRMS (2014) for the Holothuroidea. The taxonomic status of all species (valid names and synonyms) was tracked in the literature back to the original description, and was constructed with the help of systematics experts. The current checklist includes only those synonyms that have been used in the SMP, but some species can have a larger synonym list in other geographic areas.

Results and discussion

Historical review

Asteroidea

A total of 39 references addressed the Asteroidea in the SMP. During the 19th century, only six works were written; in the 20th century 24 references were published and during the current one, nine works have been published (Fig. 1A). The authors who contributed with the highest number of works were H.L. Clark (1907b, 1920, 1940), Caso (1944, 1945, 1948b, 1970, 1977, 1979) and A.M. Clark (1989, 1993, 1996).

The study of Asteroidea in the SMP began in 1867 when Verrill (1867a, 1867b) mentioned the presence of Phataria unifascialis in Acapulco, Guerrero. Four years later, Gray (1871) described Luidia latiradiata as Platasterias latiradiata for the Gulf of Tehuantepec, which was thought to be a living fossil species of Somasteroidea, an extinct group from the Orvidician (Fell, 1962b). The species was further transfered to Luidiidae and no longer considered as a survivor member of this archaic group (Blake, 1972). Based on specimens donated by the Museum of Comparative Zoology, Cambridge to the Museum of Natural History of Paris, Perrier (1875) recorded Nidorellia armata, Pharia pyramidatus, Heliaster kubiniji and Heliaster microbrachius from Acapulco, Guerrero.

The 20th century was the period with the highest addition of Asteroidea to the SMP fauna (20 species). Ludwig (1905) described Eremicaster pacificus, Pseudarchaster pulcher, Mediaster transfuga, Hymenaster violaceus, Zoroaster hirsutus and Freyella insignis from Acapulco and other areas of the Tropical Eastern Pacific. Ludwig (1905) also reported Porcellanaster waltharii from Acapulco, now considered as a synonym of Eremicaster crassus (A.M. Clark, 1989). It is important to note that P. waltharii has been incorrectly spelled as P. waltherii (A.M. Clark, 1989), in contrast with the original spelling (Ludwig, 1905). Döderlein (1936) added Pentaceraster cumingi from Acapulco to the list, which had also been named as Oreaster occidentalis in some studies (Clark H.L., 1940; Salcedo-Martínez et al., 1988). Caso (1977) described Asterina agustincasoi based on specimens collected in Ixtapa Island (Guerrero) but O´Loughlin (2002) synonymized this species with Meridiastra modesta. Luke (1982) published a catalog of the benthic invertebrate collections of the SCRIPPS institution of oceanography and recorded for the first time Ceramaster leptoceramus for the SMP, which was collected in the Gulf of Tehuantepec. Salcedo-Martínez et al. (1988) published an inventory of benthic macroinvertebrates in rocky bottoms of Zihuatanejo (Guerrero). This work represented the first inventory of marine fauna from Guerrero and added the species Mithrodia bradleyi. Years later, Solís-Marín et al. (1993) recorded Luidia bellonae, Luidia columbia, Linckia columbiae, Astropecten ornatissimus and Heliaster helianthus for Guerrero and Oaxaca. The 20th century era concluded with the work of Gamboa-Contreras and TapiaGarcía (1998) from the Gulf of Tehuantepec, the authors included the record of Luidia foliolata, Astropecten armatus, Astropecten regalis and Astropecten verrilli. It is important to emphasize that A. regalis has been reported in the Greater Antilles, the Caribbean, the Gulf of México as well as in areas of the Eastern Pacific such as Costa Rica, Panamá and México (Solís-Marín et al., 2005; Honey-Escandón et al., 2008; Pawson et al., 2009; Alvarado et al., 2010; Miloslavich et al., 2010). Astropecten verrilli was called Astropecten californicus (e.g. Verrill, 1914; Honey-Escandón et al., 2008); but according to Döderlein (1917) the valid species is the former.

So far, the current century is the era with the lowest number of new records of Asteroidea for the SMP. A.M. Clark and Mah (2001) reported Heliaster polybrachius, while Benítez-Villalobos et al. (2008a) and HoneyEscandón et al. (2008) added Luidia superba, Luidia tessellata and Asteropsis carinifera The species Gymnasteria spinosa has been reported in the SMP as Asteropsis spinosa (BenítezVillalobos et al., 2008a; Honey-Escandón et al. 2008), but according to Perrier (1875) the valid species is A. carinifera. According to BenítezVillalobos et al. (2008a) and Bastida-Zavala et al. (2013), Leiaster teres inhabits Oaxaca (USNM E6635). This specimen was collected by Ricketts between 1940-1943 in Puerto Escondido during an expedition conducted in the Gulf of California; therefore the record is not valid for Oaxaca.

All species of Asteroidea that have been collected from the SMP are deposited in all the consulted museums, except the YPM. The collections with a major number of deposited species were ICML-UNAM (13), LACM (9) and the USNM (9) (Table 1).

Ophiuroidea

The Ophiuroidea is represented by the lowest number of publications (27) in the SMP. In the 19th century there were published only four works, in the 20th century, 15 and in the 21st century, eight (Fig. 1B). The authors who have largely contributed to the study of Ophiuroidea in the area were Lyman (1860), Verrill (1867a, 1867b), Lütken and Mortensen (1899), Clark (1915, 1940), Boone (1926, 1938), Tortonese (1933a), Ziesenhenne (1937, 1940), Caso (1951, 1979, 1986), Downey (1969), Rowe and Pawson (1977), Luke (1982), Salcedo-Martínez et al. (1988), Gamboa-Contreras and Tapia-García (1998), Benítez-Villalobos (2001), Zamorano and Leyte-Morales (2005a), Honey-Escandón et al. (2008), Granja-Fernández and López-Pérez (2011, 2012), Benítez-Villalobos et al. (2012) and Granja-Fernández et al. (2013b, 2014).

The brittle star Ophiocoma alexandri was the first ophiuroid reported in the SMP (Lyman, 1860). Ophioderma teres, Ophioderma panamensis and Ophiocoma aethiops were recorded in the SMP by Verrill (1867a, 1867b), since then the species have been frequently reported by a large number of authors (Table 1). One of the most seminal works on Eastern Pacific Ophiuroidea is that of Lütken and Mortensen (1899) who described almost 50 species for this area. They described six new species (Ophiacantha moniliformis, Amphiophiura superba, Ophiernus adspersus annectens, Amphiura serpentina, Dougaloplus gastracanthus, Ophiomusium variabile, all of them collected in deep waters (902 to 4 082 m depth) from Guerrero, and they also documented for the first time in the area the cosmopolitan Ophiactis savignyi. The species Dougaloplus gastracanthus was originally described as Amphiura gastracanthus, nevertheless Clark (1970) transferred the species to the genus Dougaloplus.

During the 20th century, a larger number of papers were published about Ophiuroidea in the SMP. Clark (1915) reported for the first time Ophiernus seminudus, Ophiothrix (Ophiothrix) spiculata and Ophionereis annulata for this area. Twenty five years later, Clark (1940) added seven reports of brittle stars (Amphiura arcystata, Amphichondrius granulatus, Amphiodia (Amphispina) urtica, Ophioderma variegata, Diopederma daniana, Ophiolepis fulva and Ophiolepis variegata) to the area. Ziesenhenne (1940) described an important number of new species of Ophiuroidea (19) from the Eastern Pacific. He described the species Ophiomisidium leurum, Amphichondrius laevis, Amphiodia sculptilis and Ophiophragmus papillatus for the SMP (Guerrero and Oaxaca) in depths up to 91 m. Caso (1951) recorded Ophiothrix (Ophiothrix) rudis and Ophiolepis pacifica in Zihuatanejo, Guererro. Luke (1982) added Ophiura (Ophiuroglypha) irrorata irrorata, Amphiura seminuda, Stegophiura ponderosa, Ophiactis simplex and Ophiomusium glabrum, but except by O. simplex all species were collected from deep waters (up to 3 610 m depth). Finally, Caso (1986) recorded the presence of Ophiophragmus marginatus, and Salcedo-Martínez et al. (1988) cited Amphipholis squamata to the SMP.

During the current century, the unique work with new additions of Ophiuroidea to the SMP was published by Honey-Escandón et al. (2008) who reported 10 species (Asteronyx longifissus, Ophiomyxa panamensis, Ophiotoma paucispina, Ophiernus adspersus adspersus, Amphioplus coniortodes, Amphiodia platyspina, Amphiodia tabogae, Ophiocnida hispida, Ophiothela mirabilis and Ophionereis perplexa). It is important to note that both O. adspersus adspersus and A. coniortodes are species distributed in the Caribbean and the Gulf of México (Lyman, 1883; H.L.Clark, 1918; Pawson et al., 2009; Miloslavich et al., 2010), therefore the record of the species in the SMP should be treated with caution. Finally, Ophiacantha paucispina originally described by Lütken and Mortensen (1899) was transferred to the genus Ophiotoma (Clark, 1915; Martynov, 2010). The ophiuroid Amphioplus (Unioplus) daleus was reported in the Gulf of Tehuantepec at 590 km south of Puerto Ángel, Oaxaca (Turner & Hallan, 2011; Granja-Fernández & López-Pérez, 2012), however, since the original locality of recollection was off Mexican waters (Station 3414; 10 °14´ N - 96° 28´ W) (Lütken & Mortensen, 1899), we excluded the record from the current checklist.

Almost all the consulted museums had records of Ophiuroidea from the SMP, except CAS, MACN, AMNH and YPM. The museums with the highest number of species from the study area were LACM (24) and ICMLUNAM (23) (Table 1). Museum review render two new reports of Ophiuroidea, Microphiopholis platydisca from Acapulco, Guerrero at 20.1 m depth (LACM 38-136) and Chacahua Bay, Oaxaca from 73.1 to 91.44 m depth (MCZ 5666), and Ophiostigma tenue from Petatlán Bay, Guerrero at 45.7 m depth (LACM 34.138), and Chacahua Bay, Oaxaca from 73.1 to 91.44 m depth (MCZ 5668). The brittle star M. platydisca was originally described by Nielsen (1932) as Amphipholis platydisca, posteriorly the species was transferred to the genus Microphiopholis (Turner, 1985).

Echinoidea

The Echinoidea is the class with the highest number of published works (64) from the SMP, most of them of Agassiz (1863, 1872, 1873, 1881, 1898, 1904), Caso (1946, 1948a, 1949, 1978a, 1978b, 1979, 1980a, 1980b, 1983) and Clark (1914, 1917, 1925, 1940, 1948). During the 19th century a total of 11 works were produced, while in the 20th and 21st century 36, and 17 were published, respectively (Fig. 1C).

During the 19th century, 10 species of echinoids were found for the first time in the SMP, all of them by Alexander Agassiz. Agassiz (1863), described the species Diadema mexicanum, Echinometra vanbrunti, Toxopneustes roseus, Rhyncholampas pacificus and Clypeaster rotundus, from Acapulco and recorded for the first time Meoma ventricosa grandis in the area. Agassiz (1872) also added Mellita longifissa for Acapulco. Finally, Agassiz (1898) described Aporocidaris milleri, Cystechinus loveni and Cystocrepis setigera, all of them from Acapulco at a depth of 3 436 m.

The 20th century had the highest addition of records of Echinoidea in the SMP. Agassiz (1904) did his last contribution adding to the list Brisaster townsendi from Acapulco, a species previously described from the Gulf of Panamá and 500 miles south Guaymas, Sonora. Clark (1914) described Clypeaster ochrus based in a specimen collected at Acapulco by the Hassler expedition in 1872. Grant and Hertlein (1938) in their important work on the West American Cenozoic Echinoidea reported for the first time the species Astropyga pulvinata, Clypeaster europacificus, Encope micropora and Encope perspectiva from Guerrero. Clark (1940) also recorded for the first time the species Eucidaris thouarsii in Zihuatanejo, Guerrero, and in 1948 the same author recorded Mesocentrotus franciscanus, Strongylocentrotus purpuratus, Encope micropora fragilis and Encope wetmorei from Guerrero. It is paramount to emphasize that Clark (1948: 279) commented about M. franciscanus: “There is in the present collection a very good adult specimen from Petatlán Bay, but it seems quite improbable and needs confirmation”, and about Strongylocentrotus purpuratus (Clark, 1948: 281): “The Velero has secured specimens at 46 stations, of which the southernmost at Petatlán Bay, México. As the only other stations south of the United States at which purpuratus was secured are at or near Cedros Island, the Petatlán Bay record needs confirmation. The specimens labeled Petatlán are undoubtedly purpuratus but, as in the case of franciscanus, the locality is hard to credit”. Years later, Caso (1978b) reported M. franciscanus and S. purpuratus from White Friars and Petatlán (Guerrero). In the Mexican Pacific, both species are recorded in the northernmost area of the country (Baja California and Baja California Sur) and in the Gulf of California (Solís-Marín et al., 2005; Honey-Escandón et al., 2008), moreover there is no record of the species elsewhere in the Eastern Pacific (Alvarado et al. 2010); therefore this record should be treated with caution. Although the name Strongylocentrotus franciscanus has been recently used for authors as Honey-Escandón et al. (2008), this species was replaced to the genus Mesocentrotus (Tatarenko & Poltaraus, 1993). Otherwise, Caso (1978a, 1980a, 1980b, 1983) recorded for the first time in the area the species Hesperocidaris asteriscus, Centrostephanus coronatus, Mellita notabilis, and Brissus latecarinatus. Harold and Telford (1990) reported Mellita grantii and Mellita kanakoffi from Acapulco. Mellita kanakoffi is an echinoid with both recent and fossil records (Upper Pleistocene), but in the studied area only living specimens have been added (Harold & Telford, 1990). Finally, GamboaContreras and Tapia-García (1998) reported the species Clypeaster elongatus from the Gulf of Tehuantepec. The other known report of this species is in the Eastern Pacific by Clark (1948) from the Galápagos Islands.

During the current century, Benítez-Villalobos et al. (2008a) and Honey-Escandón et al. (2008) reported Tripneustes depressus, Lovenia cordiformis and Agassizia scrobiculata. Further, Zamorano and Leyte-Morales (2009) conducted a study of echinoderms associated to coral reefs from Zihuatanejo and Acapulco and recorded for the first time the species Echinometra mathaei oblonga in the SMP. In the Eastern Pacific (México, Panamá and Galápagos Islands), Echinometra mathaei oblonga was named as Echinometra oblonga (Lessios, 2005; Solís-Marín et al., 2005; Honey-Escandón et al., 2008; Alvarado et al., 2010) but since 1943 Mortensen indicated that the correct name for this species was the former.

The echinoids from the SMP are deposited in all the museums, except the FMNH. Most of the species are deposited in the ICML-UNAM (17 spp.) and MCZ (16 spp.). During museum revision, two new records were added to the fauna of the SMP, Arbacia stellata from Acapulco (MCZ 471), and Encope laevis from Bahía de Petatlán, Guerrero at depths of 9.1 to 18.3 m (CAS-IZ 87348.00). Along the Eastern Pacific (México, El Salvador, Nicaragua, Costa Rica, Panamá, Colombia, Perú), A. stellata has currently named as Arbacia incisa (Hooker et al., 2005; Neira & Cantera, 2005; SolísMarín et al., 2005; Honey-Escandón et al., 2008; Alvarado et al. 2010), but according to Mortensen (1935) the valid name is A. stellata. Meanwhile, E. laevis is an echinoid distributed in Nicaragua, Costa Rica and Colombia (Neira & Cantera, 2005; Alvarado et al., 2010), therefore this is the first record of this species in the Mexican Pacific.

Holothuroidea

To date, the current number of references for the class Holothuroidea in the SMP is 35. During the 19th century there were only four works, during the 20th century 22 papers were published and only nine works during the current century (Fig. 1D). Caso (1954, 1958, 1962, 1963, 1964, 1965, 1967a, 1967b, 1986) and Deichmann (1936, 1937, 1938, 1941, 1958) were the authors with most of the published works on Holothuroidea in the study area.

The 19th century addressed the lowest number of Holothuroidea reports in the SMP. Verrill (1867b) was the first to record Holothuroidea in the area; he reported Afrocucumis ovulum, Holothuria (Halodeima) kefersteini and Holothuria (Selenkothuria) lubrica from Acapulco. Twenty-seven years later, Ludwig (1894) added Pseudostichopus mollis, Pannychia moseleyi, Oneirophanta mutabilis mutabilis, Benthodytes incerta, Benthodytes sanguinolenta and Molpadia musculus from Guerrero.

The highest addition of records occurred during the 20th century. Deichmann (1937) reported Isostichopus fuscus from Acapulco. One year later, Deichmann (1938) made an important contribution on the holothurians from Lower California, Central America and the Galápagos islands. In this work, Deichmann reported for the first time in the study area Lissothuria ornata, Neothyone gibber, Euthyonidiella zacae, Pentamera chierchiae, Pentamera zacae, Pseudocnus californicus, Holothuria (Semperothuria) languens, Holothuria (Thymiosycia) arenicola and Holothuria (Thymiosycia) impatiens. Euthyonidiella zacae and P. zacae were originally described from Tangola-Tangola Bay, Oaxaca, México. In 1941, Deichmann reported Neothyone gibbosa, Pachythyone pseudolugubris, Trachythyone peruana, Thyone strangeri and Leptopentacta panamica from the studied area, but the type localities are located in the Gulf of California and Colombia (Deichmann, 1941). On the other hand, T. strangeri is the unique species with its type locality in the SMP (Isla Grande, Guerrero at 12.8 m depth). It is important to highlight that Deichmann (1941) made a mistake when recorded the latitude of the type locality as “170° 46´ N”, instead of “17° 46´ N”. Caso (1958) reported Holothuria (Halodeima) inornata from Zihuatanejo and Deichmann (1958) reported three more species of the genus Holothuria (Holothuria (Mertensiothuria) hilla, Holothuria (Selenkothuria) portovallartensis and Holothuria (Semperothuria) imitans) from Guerrero and Oaxaca. Caso (1965) carried out the most important work on Holothuroidea from Zihuatanejo reporting a total of six new records (Holothuria (Cystipus) inhabilis, Holothuria (Cystipus) rigida, Holothuria (Halodeima) atra, Holothuria (Mertensiothuria) leucospilota, Holothuria (Platyperona) difficilis and Labidodemas maccullochi) for the SMP. Luke (1982) reported for the first time in the area Abyssocucumis abyssorum and Ypsilothuria bitentaculata, which are distributed in deep waters (more than 3000 m depth) (SolísMarín et al., 2009; Massin & Hendrickx, 2011). Salcedo-Martínez et al. (1988) recorded Thyone parafusus in Zihuatanejo, Guerrero, which correspond to the only record of the species for the entire Eastern Pacific, being SalcedoMartínez et al. (1988) and Honey-Escandón et al. (2008) the only authors addresing this species. Herrero-Pérezrul and Reyes-Bonilla (1997) added Euapta godeffroyi from Zihuatanejo. Finally, Solís-Marín and LaguardaFigueras (1999) described Cucumaria flamma after material collected from Zihuatanejo.

In contrast to the other classes of echinoderms, the Holothuroidea have the highest number of records (12) during the 21st century. Despite the type localities for the species Molpadiodemas neovillosus are Caroline and Galápagos Islands, O’Loughlin and Ahearn (2005) reviewed material from Punta Maldonado, Guerrero (3 436 m). In the same year, Zamorano and Leyte-Morales (2005a) added Holothuria (Selenkothuria) theeli and Holothuria (Stauropora) fuscocinerea to the SMP. The work of Honey-Escandón et al. (2008) may be the most important work since it added 6 holothuroid records (Psolidium dorsipes, Pachythyone lugubris, Neopentamera anexigua, Holothuria (Theelothuria) paraprinceps, Labidodemas americanum and Chiridota aponocrita) for the study area. Massin and Hendrickx (2011) recorded the deep-water species Psolidium gracile (740-790 m depth) and Laetmogone scotoeides (1 180 - 1 420 m depth) from Guerrero.

The Holothuroidea of the SMP are deposited in the collections of CAS, ICML-UNAM, LACM, MCZ, UMAR and USNM. The collection with the highest number of deposited species is the ICML-UNAM, with 32 species. The revision of the material in the ICML-UNAM added two new records for the Southern Mexican Pacific: Thyone bidentata from Playa del Hotel Caleta, Guerrero (ICML-UNAM 5.66.1), and Chiridota rigida from Playa Contramar, Guerrero (ICML-UNAM 5.74.11), Playa Las Gatas, Guerrero (ICML-UNAM 5.74.12), Estacahuite, Oaxaca (ICML-UNAM 5.74.14), Playa Panteón, Oaxaca (ICML-UNAM 5.74.15) and La Mina, Oaxaca (ICML-UNAM 5.74.16).

Diversity and distribution

The checklist of echinoderms from the Southern Mexican Pacific includes 162 species, 96 genera, 54 families, 20 orders and four classes (Table 1). The Holothuroidea were the most numerous with 52 species followed by the Ophiuroidea (46 species), Echinoidea (34) and Asteroidea (30) (Table 2). No records in the literature or in museum collections refer to the Crinoidea from the SMP. The orders with the highest number of species were Ophiurida (Ophiuroidea, 45 species), Aspidochirotida (Holothuroidea, 22), Dendrochirotida (Holothuroidea, 22), Paxillosida (Asteroidea, 13) and Clypeasteroida (Echinoidea, 13); while the orders Velatida and Brisingida (Asteroidea), Euryalida (Ophiuroidea), Arbacioida and Cassiduloida (Echinoidea), and Molpadida (Holothuroidea) were represented by a single species. The best represent families were Holothuriidae (Holothuroidea, 19 species) and Amphiuridae (Ophiuroidea, 18 species). Both families are considered the most diverse and dominant in shallow tropical waters (O´Loughlin et al., 2007; Stöhr et al., 2012).

For the entire Mexican Pacific, SolísMarín et al. (2013) reported 216 species, the Ophiuroidea being the most numerous with 63 species followed by the Asteroidea (59), Holothuroidea (53), Echinoidea (37) and Crinoidea (4) (Table 3). Similar trend is observed for the Gulf of California (232 species, Solís-Marín et al., 2013) and the Pacific side of Central America (282 species, Alvarado et al., 2010) where the Ophiuroidea and Holothuroidea are the most diverse (Table 3). It is important to note the following between studies: 1) the databases structures are different; while the present study and Alvarado et al. (2010) contain reports from published resources and museums, Solís-Marín et al. (2013) includes only museum records; 2) the studied areas are highly contrasting regarding coastal extension; while the present study includes approximately 1 200 km along the coast of the States of Guerrero, Oaxaca and Chiapas, the entire Mexican Pacific has 7 800 km, the Gulf of California, 3 000 km and Central America, 3 800 km. The results suggest that in just 40 % of the coastal line, the SMP comprises 70 % of the total echinoderm fauna compared with, for example, the Gulf of California. This suggests that the echinoderm biodiversity from the SMP is not small considering that the Gulf of California is extensively and far better studied.

According to our results, Guerrero was the State with the highest number of recorded species (135 spp.), followed by Oaxaca (94 spp.), Chiapas (15 spp.) and the Gulf of Tehuantepec (14 spp.). Specifically, the Holothuroidea were the most diverse in Guerrero (48 spp.) and Oaxaca (33 spp.), while the Echinoidea (7 spp.) and the Asteroidea (8 spp.) were the most diverse in Chiapas and the Gulf of Tehuantepec, respectively (Fig. 2).

Holothuroidea have not been recorded in the Gulf of Tehuantepec, but there are records of Trachythyone peruana and Holothuria (Halodeima) kefersteini from Chiapas (Fig. 2). Of the 30 species of Asteroidea, 14 spp. were only reported in one State, most of them from Guerrero; while, Astropecten armatus and Heliaster microbrachius were widespread in the entire region. Twenty-seven species of Ophiuroidea were reported in one State, mostly for Guerrero, while Diopederma daniana was the only species distributed in the entire SMP.

Fifteen species of Echinoidea were reported in one State (mostly in Guerrero), but Astropyga pulvinata, Echinometra vanbrunti, Clypeaster europacificus and Encope micropora were widespread in the entire region. Finally, the Holothuroidea were distributed mostly in one State (22 spp.).

Respect to the most complete and recent works of echinoderms from the Mexican Pacific (Honey-Escandón et al. 2008) and Oaxaca (Bastida-Zavala et al., 2013), this work increases the number of known species in 35% for Guerrero, 62 % for Oaxaca, and 7 % for Chiapas. Compared with previous works, we found a substantial increase in regional diversity after the compilation of information from 131 references and the review of several specimens deposited in 11 museums and reference collections.

The historic revision of SMP echinoderms has allowed us to identify valid names, synonyms, misspelled names and erroneous distributions. The checklist provided in this study is an important baseline for future studies in western México, but also for the entire Eastern Tropical Pacific, given that most of the included species are widespread in the area and inhabit multiple substrates and habitats within the region.

Altough the SMP is considered a poorly studied region within the Mexican Pacific (Bastida-Zavala et al., 2013), echinoderm studies have lasted over a century (1860-2013) and have resulted from intensive collaborative effort of national and overseas researches in all disciplines but mainly in systematics. This contribution reveals that the SMP harbors a large number of echinoderm species (chiefly Ophiuroidea and Holothuroidea) being comparable to larger regions such as the Mexican Pacific and the Gulf of California (Table 3). Recent studies addressing the biodiversity of echinoderms in the area indicate, for example, that the States of Oaxaca and Chiapas could harbor two to three times the observed biodiversity (GranjaFernández & López-Pérez, 2012; López-Pérez et al., 2012a).

Although the historical revision provides valuable information for systematics and ultimately for species management, it also provides an insight of the completeness and gaps regarding the knowledge of the echinoderm fauna in the SMP. In this regard, we encourage a full field survey for the entire region at different depths and across different habitats, especially in soft and rocky bottoms from Chiapas since ongoing in this area suggests its potential to render new records and species yet to be discovered. Currently, the States of Oaxaca and Chiapas have experienced an increase in anthropogenic pressure, mostly in the zones of Zihuatanejo and Acapulco (Guerrero), and Puerto Escondido and Bahías de Huatulco (Oaxaca) (CONANP, 2003; López-Pérez et al., 2012b), therefore these areas are required to be monitored.

Acknowledgments

The authors are very grateful to S. Stöhr (Swedish Museum of Natural History), A. Kroh (Natural History Museum Vienna) and C. Mah (USNM) for assistance in systematics matters. Special thanks to A. Baldinger and P. Benson (MCZ), G. Hendler (LACM), P. Greenhall (USNM), C. LeBeau (AMNH), E. Rodríguez (AMNH), S. Keable (AMS), R. Mooi (CAS), A. Tablado (MACN) and A. Martínez-Melo (ICML-UNAM) for sharing museum records. We thank M. Hendrickx, R. Bastida-Zavala, A. Durán-González, P. Medina-Rosas, A. Hernández-Morales and C. Aparicio-Cid for providing valuable literature. This project was founded by CONABIO (HJ029, JF047). This work is part of the PhD thesis of RGF at UAM. While this work was done, RGF was supported by a scholarship from CONACYT (336853). We thank the reviewers for commenting and improving the manuscript.

References

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