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Deep-sea ophiuroids from western Mexico have been documented since 1899, but mostly by non-Mexican expeditions. TALUD is a Mexican project designed to study the deep-sea fauna from Mexico. As part of it, the present contribution provides for the first time detailed information about the taxonomy and distribution, as well as images, of deep-sea ophiuroids from western Mexico, representing a useful taxonomic identification tool for Ophiuroidea from the eastern Pacific. A total of 38 species of ophiuroid (35 identified at species level, one at genus level, and two as confer) were collected from 83 stations located at 123‒2,309 m depth. At a regional scale, several new species records are presented: six for western Baja California, five for western Baja California Sur, two for the Gulf of California, four for Jalisco, 14 for Colima, and five for Guerrero. Geographic (six) and bathymetric (seven) distribution ranges of species are extended. An updated list of deep-sea ophiuroids (61 species) from western Mexico is provided together with an identification key to species collected during this survey. In addition, nine records of deep-sea ophiuroids for the Mexican Pacific are unproven, doubtful or invalid. We corroborated the presence of Ophiacantha eurypoma and Ophiacantha pacifica in the study area and added Amphiura gymnogastra as the first record for Mexico. We propose to transfer Ophiacantha phragma to Ophiolimna on account of it having both granules and spines on the dorsal disc and striated arm plates. TALUD cruises collected 57 % of the total deep-sea species known to occur off Mexico, making it the most important survey of deep-sea Ophiuroidea carried out in western Mexico to date.

Previous studies documented colonies of the cheilostome bryozoan Biflustra irregulata rafting across the Pacific Ocean on debris from the 2011 Great East Japan megathrust earthquake and resulting tsunami. They arrived in the eastern Pacific on floating non-biodegradable tsunami debris from 2014 to 2016. Based on a newly discovered occurrence of this species off the west coast of Mexico, we report that this species has successfully expanded its range from the Indo-Pacific to the northeast Pacific following this dispersal event. Colonies were found encrusting barnacles on spiny lobsters from the southeastern Gulf of California.

Ten species belonging to the families Paraphronimidae and Vibiliidae were collected during a deep-water survey off western Mexico: two species of Paraphronima and eight species of Vibilia. This represents about 40% of all known species of these two genera world-wide. A total of 419 males and 607 females were obtained in 39 samples from localities in the Gulf of California (33) and off southwestern Mexico (6). Vibilia armata was by far the most frequently (32 localities) and most abundantly (687 specimens, 67% of the total) collected species, followed by V. longicarpus (231 specimens in nine localities) and P. crassipes (35 specimens in 9 localities). Co-ocurrence of species of Vibilioidea in our samples was very low, with maxima of seven and five species collected in the same sample, once each. Considering previous records, a total of 16 species of Vibilioidea (almost 70% of all known species) have now been reported from western Mexico: two species of Paraphronima and 14 species of Vibilia, including V. australis occasionally reported in the area as its junior synonym, V. wolterecki.

In order to complete the information related to the little studied deep-sea planktonic fauna of western Mexico, samples from a wide depth range (surface to 1550 m depth) were obtained using different gear. Six species and 108 individuals of hyperiid amphipods of the family Amphithyridae were collected at 26 localities, including a new species of Amphithyropsis Zeidler, 2016, which is herein described based on an adult male and a gravid female. Other species include Amphithyrus bispinosus Claus, 1879, the most abundant and frequently collected species (70 specimens at 17 localities), A. muratus Volkov, 1982 (11 specimens at 8 localities), A. sculpturatus Claus, 1879 (14 specimens at 7 localities), Paralycaea gracilis Claus, 1879 (10 specimens from 6 localities), and P. hoylei Stebbing, 1888 (one specimen from one locality). Worldwide and regional distributions are provided for each species.

A redescription of Paguristes aztatlanensis Glassell, 1937 is presented together with the description of Paguristes turkayi n. sp. from the Mexican Pacific. Paguristes turkayi n. sp. is close to P. digueti and P. sanguinimanus, but can be separated from these two species by the following: P. turkayi features a slender rostrum; the ocular peduncles are proportionally larger relative to the shield in P. turkayi n. sp. than in P. digueti, but proportionally shorter than in P. sanguinimanus; the anterodorsal plates of the carapace are unarmed in Paguristes turkayi n. sp. and P. sanguinimanus (versus armed with small teeth in P. digueti); in P. turkayi n. sp., the palm and carpus of the chelipeds bear fewer but larger spines and tufts of very long setae, while in P. digueti and P. sanguinimanus the chelipeds are armed with many small spines and very short setae.

Twelve species of the family Oxycephalidae were collected during a deep-water survey off western Mexico: four species of Rhabdosoma, three species of Streetsia, two species of Oxycephalus, and one species each of Cranocephalus, Glossocephalus, and Leptocotis. In total, 321 specimens were collected, 114 males and 207 females, in 33 sampling localities in the Gulf of California (28) and off southwestern Mexico (5). Two species dominated in the samples and co-occurred in 17 of the 33 samples containing hyperiids: Oxycephalus clausi (24 localities, 152 specimens) and Rhabdosoma whitei (20 localities, 121 specimens). Considering this study and previous records, a total of 16 of the 18 described species of Oxycephalidae (89%) have been reported from western Mexico. Distribution of this new material off western Mexico is provided together with update data on species occurrence in the eastern Pacific.

Thirteen species belonging to five genera of pelagic amphipods of the family Lestrigonidae were collected during a deep-water survey off western Mexico: four species of Hyperietta, two species of Hyperioides, five species of Lestrigonus, and one species each of Phronimopsis and Themistella. This represents 93% of all known species of Lestrigonidae world-wide. A total of 1092 specimens were obtained in 40 sampling localities in the Gulf of California (35) and off southwestern Mexico (5). Although sampling methodology was rather heterogeneous, two species, Hyperioides sibaginis and Lestrigonus bengalensis, were particularly abundant (336 and 562 specimens) and frequent (present in 24 and 31 localities) in the samples, representing 82% of the total catch. The southernmost distribution limit of Hyperietta stebbingi is extended to off SW Mexico. Of the 13 species that were collected during this survey, 10 and 8 species co-occurred at two sampling localities in the SE Gulf of California.

Four species of squat lobsters were collected off the northwestern coast of the Baja California Peninsula, Mexico, during an exploratory survey of fishing resources. Janethogalathea californiensis, described from California was previously known from off the west coast of the Baja California Peninsula (two localities) and from the Gulf of California (three localities). Of the three species of Munida collected during the survey, M. tenella is recorded off the west coast of the Baja California Peninsula for the first time. These are the fourth record of M. hispida and the second record of M. quadrispina in western Mexico.

Thirteen species belonging to five genera of pelagic amphipods of the family Lestrigonidae were collected during a deep-water survey off western Mexico: four species of Hyperietta, two species of Hyperioides, five species of Lestrigonus, and one species each of Phronimopsis and Themistella. This represents 93% of all known species of Lestrigonidae world-wide. A total of 1092 specimens were obtained in 40 sampling localities in the Gulf of California (35) and off southwestern Mexico (5). Although sampling methodology was rather heterogeneous, two species, Hyperioides sibaginis and Lestrigonus bengalensis, were particularly abundant (336 and 562 specimens) and frequent (present in 24 and 31 localities) in the samples, representing 82% of the total catch. The southernmost distribution limit of Hyperietta stebbingi is extended to off SW Mexico. Of the 13 species that were collected during this survey, 10 and 8 species co-occurred at two sampling localities in the SE Gulf of California.

The rare pelagic mysid Amblyopsoides ohlinii (W.M. Tattersall, 1951) is reported for the first time off western Mexico and represents the first record in the Pacific Ocean south of Japan and the Kurile-Kamchatka Trench. So far, this species only has been recorded from seven localities in the North Atlantic and in the North Pacific. A complete description of the only specimen available (a male), including illustrations of all appendages and SEM images of the mandibles, is provided.

A single ovigerous female specimen of a new species of Epimeria Costa in Hope, 1851 was collected from deep sea, off southwestern Mexico, in the eastern Pacific. Epimeria karamani sp. nov., is most similar to females of E. cora J.L. Barnard, 1971, E. pacifica Gurjanova, 1995 and Epimeria morronei Winfield, Ortiz & Hendrickx, 2013. However, it differs from these species by: eyes long and slightly kidney-shaped; pleonite 3 strongly carinate, with dorsal tooth produced and acute; urosomite 1 with a wide mid-dorsal notch and a strong, upright blunt tooth; coxa 3 anterior margin slightly truncate and with two processes marginally; coxa 4 ventral margin linear, with facial granules and simple setae; gnathopods palm with distal bifid setae; telson straight medially, distal margin crenulate and with minute setae. The new species described herein increases the number of Epimeria species from the Pacific Ocean to 14, and from the eastern Pacific to three.

Four specimens of the sea cucumber Ypsilocucumis californiae Massin & Hendrickx, 2011 were obtained during sampling operations off western Mexico. These specimens permit identification of this species as a member of the deep-water holothuroid community off the west coast of the Baja California Peninsula. Previous records correspond to four locations (including the type locality) in the Gulf of California, where eight specimens were collected. SEM ossicles images are provided for the first time and new ecological data associated with the presence of this species are available: temperature, 5.34‒8.38 °C; dissolved oxygen, 0.15‒0.28 ml O2/l and salinity, 34.42‒34.51 ups. The specimens were present in a wide variety of sediments with an organic carbon content of 3.18‒5.20 mg C/g (5.47‒8.95 % organic matter). Density values indicated low abundance of this species in the area (2.63‒3.94 orgs/ha). Records presented here were in a depth range from 540 to 776 m, which corresponds to the lower limit of the Oxygen Minimum Zone of the eastern Pacific. Additional records are provided for the West Atlantic Ypsilocucumis asperrima (Théel, 1886) and a key to the species of Ypsilocucumis is provided.

During a survey of the deep-water fauna off western Mexico a large series of specimens of Gnathophausiidae was collected in a benthic sledge operating between 296 and 2136 m. Five species known to occur in the area were collected: Gnathophausia scapularis Ortmann, 1906, G. zoea Willemoes-Suhm, 1873, Neognathophausia gigas (Willemoes-Suhm, 1873), N. ingens (Dohrn, 1870), and Fagegnathophausia gracilis (Willemoes-Suhm, 1875). Additional distribution data are provided for these species in the area. A sixth species, G. childressi Casanova, 1996, previously known only from the type locality, off California, was also collected in three localities. Several external morphological characters in F. gracilis are analyzed according to individual size. The general and regional (off western Mexico) distributions of these six species is analyzed.

A rare species of pandalid shrimp, Heterocarpus nesisi Burukovsky, 1986, is rediscovered in deep water off western Mexico. Previous to this capture, this species was known only from the holotype, a mature male captured at 800 m depth, originally described in the genus Heterocarpus and later transferred to Plesionika. A second, unconfirmed record, was provided in 1989: a female captured at 898 m near the southern tip of the Baja California Peninsula. Heterocarpus nesisi is redescribed and appendages are illustrated. The general morphology of this species makes it difficult to fit within Heterocarpus or Plesionika, and a new genus, Heteronika gen. nov., is proposed to accommodate it. Heteronika nesisi is associated with the lower boundary of the Oxygen Minimum Zone occurring off western Baja California.

Brachyuran crabs from the Mexican Pacific and surrounding areas are well known and have been treated in several monographs (e.g., Garth 1958; Hendrickx 1997, 1999). Checklists of species occurring off western Mexico and the eastern tropical Pacific are also available (e.g., Hendrickx 1993, 1995, 2005). In many cases, particularly in species inhabiting the continental shelf or deeper waters, however, there is a significant lack of records due to sampling difficulty and cost.

Specimens of the sea cucumber Synallactes virgulasolida were obtained during sampling operations off western Mexico. Based on a total of 190 specimens and on additional records available in the Scripps Institution of Oceanography collections, new geographical (southern California to Chile) and bathymetric (712‒1300 m) distributions are provided. SEM photographs of ossicles are provided for the first time for this species. New ecological data associated with the presence of this species are also provided: 4.17‒5.81 °C, 0.15‒0.48 ml O2/l, and in 34.40‒34.48 ups. The species occurs in a wide variety of sediments with an organic carbon content of 17.93‒52.02 mg/g (1.79–5.20 % of organic matter) and is occasionally very dense (up to 170.32 orgs/ha). All Mexican records correspond to a bathymetric fringe located below the Oxygen Minimum Zone, thus indicating that S. virgulasolida is able to tolerate hypoxic conditions.

Specimens of Petalophthalmus armiger Willemoes-Suhm, 1875, were collected off western Mexico during a deep-water survey. Six males and 32 females were obtained from 18 sampling localities in western Mexico. The species is redescribed in detail, including illustrations of body and appendages, and SEM photographs of the mandibles. The new material indicates that P. armiger is widely distributed in the area and more common than previously thought in the eastern Pacific. Samples indicate that P. armiger inhabits water far offshore, where total depth exceeds 1000 m. Due to the lack of discrete samplings in the water column, however, the precise depth interval where P. armiger occurs cannot be defined.

The type and additional material of Paguristes weddellii (H. Milne Edwards, 1848) were examined. The species is redescribed and illustrated in details. Comparison of P. weddellii with the monotypic genus Tetralobistes Ayón-Parente & Hendrickx, 2010b, shows many similarities, principally in the armature of the distal margin of the male first pleopod and the shape of the telson, which in both cases feature a tetralobular posterior margin, a character considered unique among the Diogenidae. Consequently, Pagurus weddellii is transfered to the genus Tetralobistes. Paguristes hirtus Dana, 1851, a subjective junior synonym of Pagurus weddellii is removed from the synonymy based on lack of direct evidences.

A large series of specimens of Plesionika sanctaecatalinae was obtained during sampling operations off the west coast of the Baja California Peninsula in 2012 and 2014 (TALUD cruises). This material was examined and compared to the original description, the holotype and two paratypes. Although the fresh material fit well with the type material examined, some discrepancies were noted in the illustrations of the original description, particularly regarding scaphocerite and the telson, and new illustrations are provided. The series of sample available from the TALUD cruises allow to increase considerably the number of localities known for this species in the California Current area. A series of unpublished records corresponding to material examined in the original description but not listed in details, allows for further increase of the number of reported localities where P. sanctaecatalinae has been collected. Its vertical distribution in the water column, however, remains unclear due to the fact that no discrete samples are available for this species.

A new species of Glyphocrangon has been collected during deep-water sampling off western Mexico, in the east Pacific. The series of specimens, including both males and females, was found between 780 and 1879 m depth. Glyphocrangon sp. nov. is close to G. sicaria Faxon, 1893 and G. vicaria Faxon, 1896, both occurring in the east Pacific. It differs from both species, however, by the absence of tubercles between the lateral carinae, the presence of a large tooth at the anterior end of the second anterior lateral carina, the size of the eye (proportionally smaller in G. vicaria), and the presence of two large rostral lateral teeth (one obsolete in G. sicaria). The new species is, however, strikingly similar to G. fimbriata Komai & Takeuchi, 1994, from the Mid-Pacific Mountains. It differs from the later species by the shape of the male endopod of first pleopod, the relative size and spination of the appendices interna and masculina, the presence of a large lateral tooth on pleura of abdominal somites 3–5, and the absence of curved setae on distal part of the dactyl of pereiopods 3–5.

An exhaustive revision of material identified as Dardanus sinistripes (Stimpson, 1859) in collections in Mexico and the USA, and of new material of Dardanus collected in several localities in the Eastern Pacific revealed the existence of five undescribed species closely related to D. sinistripes. Detailed study of this material allows us to redescribe D. sinistripes based on a neotype selected from a locality in Panama, and to describe D. nudus n. sp., D. stimpsoni n. sp., D. janethaigae n. sp., D. pilosus n. sp. and D. magdalenensis n. sp. The six species of the genus Dardanus in the Eastern Pacific are fully illustrated and compared.

The deep-water crangonid Parapontophilus occidentalis (Faxon, 1893) is endemic to the eastern Pacific and has been reported from Mexico to Chile, in depths of 837-4082 m. Material collected off the west coast of the Baja California Peninsula (BCP) during the TALUD XV, XVI and XVI-B cruises consists of a series of 136 specimens (M:F = 1:3.6) with 30 % of ovigerous females. The material examined was captured in depths of 1296-2093 m. Size ranged from 8.4 to 16.1 mm CL, with females being significantly larger than males. Number of eggs carried by ovigerous females ranged from 7 to 998, without a significant relationship between female size and number of eggs. Using only data of females carrying at least 100 eggs, egg mass weight varied from 0.036 to 0.181 g. Size of oval-shaped eggs also varied considerably (0.515 to 0.922 mm). Larger densities of P. occidentalis were observed between 1700 and 2100 m, where larger individuals were collected, and sex proportions differed across all depth strata. At the northern BCP, P. occidentalis was collected at dissolved oxygen concentrations from 0.76 to 1.83 ml l(-1), at temperature from 2.1 to 3.4°C, and salinity from 34.54 to 34.63 kg g(-1). Density of P. occidentalis was positively correlated with dissolved oxygen, salinity, and silt contribution to sediments, and negatively correlated with temperature and primary productivity five months before sampling.

Additional material of species of Gennadas was collected off western Mexico during the TALUD survey aboard the R/V "El Puma". Gennadas sordidus was by far the most common species collected and only a few specimens of the other three species, G. incertus, G. propinquus and G. scutatus, were obtained. New and previous records indicate that Gennadas sordidus is widely distributed along the west coast of Mexico, although there is only one record for it south of the Gulf of California. In this study it was collected in as many as 35 localities, both in the Gulf of California and off the west coast of Southern Baja California. Numbers of specimens also confirmed that it is the dominant species of Gennadas in the area. Gennadas incertus was found in six samples, all from off the west coast of northern Baja California. The other two species occurred each in two samples only, with sampling localities widely spread along the Baja California Peninsula. Compared with the rest of the eastern Pacific, the diversity of Gennadas in Mexican waters is intermediate (6 species) vs. 9 in Chile and 4 in the NW Pacific.

A new species of commensal shrimp of the genus Typton from holothurians is described and illustrated. The specimens were collected from a single specimen of Holothuria (Halodeima) inornata Semper, 1868 at a depth of 7 m. This is the first record of an association between a shrimp of the genus Typton and echinoderms. With this record, five species of Typton are now known from the eastern Pacific region and four of them are found in the Mexican Pacific. In Typton granulosus sp. nov., the distal part of the outer margin of the uropodal exopod is serrated, a feature shared with T. fapespae Almeida et al., 2014, T. holthuisi De Grave, 2010, T. prionurus Holthuis, 1951, T. serratus Holthuis, 1951, and T. spongicola Costa, 1844. However, the new species can be separated from the other five species of the genus by several morphological characters.

The taxonomic status of Paguristes praedator Glassell, 1937, and Paguristes oxyophthalmus Holthuis, 1959, is reevaluated, and the two species redescribed and illustrated in detail. Both species are transferred to the genus Areopaguristes RahayuMcLaughlin, 2010, a genus previously defined to accommodate species of Paguristes sensu lato with 12 pairs of gills instead of 13. Two important characters in both species were found to differ or have not been mentioned in the current definition of Areopaguristes, i.e., the first maxilliped lacking epipod, and dactyls of second and third pereopods unarmed on the ventral margins. The presence of other diagnostically significant characters (e.g., lack of first pleopods in females) previously noted in other species of Areopaguristes, requires the generic emendation of this genus presented herein. With the transfer of A. praedator nov. comb. and A. oxyophthalmus nov. comb. to Areopaguristes, this genus now contains 27 species, of which nine occur in the Americas (four in the eastern tropical Pacific, and five in the western Atlantic).

Four species of Spirontocaris are known from a few records along the coast of the Baja California Peninsula, Mexico: S. prionoata (Todos Santos Bay), S. sica (between San Benito and Cedros Islands), S. snyderi (Cedros Island), and S. truncata (off San Carlos Point). During exploratory surveys off the west coast of the Baja California Peninsula, Mexico, two specimens of Spirontocaris holmesi Holthuis, 1947, and 143 of S. sica Rathbun, 1902 (10 males, 128 females, 2 ovigerous females, and 3 damaged specimens) were collected in benthic trawl and sledge. Both species are illustrated and described. The material of S. holmesi was collected in a single locality, at 220 m depth (known depth range is 150–300 m) and is the first record for western Mexico, while the material of S. sica was collected in five localities, from 710–1102 m depth (known range, 88–849 m), increasing significantly the number of specimens known for this species. Environmental data indicate that S. sica lives below the Oxygen Minimum Zone, in poorly oxygenated water (0.22 to 0.40 ml O 2 /l), in a temperature range of 4.38 to 5.81 °C. Sediments associated with this species are dominated by silt (>72% in 4 out of 5 localities), with organic carbon content of 18 to 52 mgC org /g.

The first larval stage of Enallopaguropsis guatemoci is described in detail and illustrated. The larva is compared with larvae known for other genera of Paguridae except Pagurus. A synthesis of all characters provided herein indicates that first larvae of E. guatemoci can be separated from all known pagurid larvae (except Pagurus) by the combination of the following characters: carapace with long dorsal carina, posterolateral spines absent; abdominal somites 3–5 with pair of moderately long spines; telson narrowly triangular, not forked; spine at antennal protopod as long as endopod.

A new species of Bresilia Calman, 1896, representing the first record of this genus for the East Pacific, is described from deep water off the Pacific coast of Mexico. The new species is close to B. atlantica Calman, 1896, the type species of the genus with which it shares the general shape of the carapace and rostrum, the latter with a reduced number of small dorsal teeth, and the shape and relative size of the first pereiopod. It also shares with B. atlantica a similar antennular peduncle and a distally very wide scaphocerite. The first maxilliped has a long crescent-shaped exopod, without a flagellum and a strongly reduced caridean lobe, two characters found in B. atlantica and in only one other known species of Bresilia, i.e., B. corsicana ForestCals, 1977. The new species can be distinguished from the other seven species of Bresilia by the armature of the rostrum (few, very small spines) and a much wider scaphocerite, with an anterior margin twice as wide as the proximal margin.

Calyptraeotheres camposi sp. nov. is described from the Gulf of California, Mexico. The new species is close to C. granti (Glassell, 1933) and C. pepeluisi CamposHernández-Ávila, 2010 from the Mexican Pacific and to C. hernandezi Hernández-ÁvilaCampos 2006 from the Western Atlantic. These four species feature a third maxilliped with a 2-segmented endopod palp and the exopod with unsegmented flagellum. Calyptraeotheres camposi sp. nov. differs from C. granti and C. hernandezi by having the eyes visible in dorsal view, the carapace with arcuate anterolateral margins, the dorsal, longitudinal depressions connected with the transversal depression, and the propodus of pereiopod 2 equal or slightly longer than the carpus. From C. pepeluisi it is distinguished by the absence of a transversal depression on the carapace and the longitudinal depressions not connecting, the carpus and propodus of the third maxilliped being sub-trapezoidal and sub-conical, respectively, in lieu of subrectangular, and the inner surface of the fixed finger nude instead of bearing short setae near the cutting edge and ventral margin.

Eight species of the genus Neogonodactylus have been reported from the eastern Pacific. Up to now, only three of these species have been collected in Mexican waters: Neogonodactylus stanschi (Schmitt, 1940), N. lalibertadensis (Schmitt, 1940), and N. zacae (Manning, 1972). Recent sampling of stomatopods in several localities of the Pacific coast of Mexico, from Mazatlan, in the southwestern Gulf of California, to Oaxaca, allowed us to collect fresh material of these three species and five specimens that agree with the general description of N. lalibertadensis, but with differences in the telson ornamentation and the length of the ophthalmic somite. A close examination of this material and examination of photographs of the holotype led us to establish that it shows slight variation from the typical form. A revised key to the species of Neogonodactylus occurring in the eastern Pacific is provided.

A new species of Leptalpheus is described from Estero Pérula, Jalisco, on the Pacific coast of Mexico. Leptalpheus corderoae sp. nov. is most similar to Leptalpheus azuero Anker, 2011 from Panama and Leptalpheus axianassae DworschakCoelho, 1999 from Brazil, differing from both of them by a combination of morphological characters, especially the presence of tubercles on the ventral surface of the major chela palm and pollex. The most common host of L. corderoae sp. nov. at the type locality is the callianassid ghost shrimp Lepidophthalmus bocourti (A. Milne Edwards, 1870). Additional specimens of Leptalpheus mexicanus RíosCarvacho, 1983, from Estero de Urías, Sinaloa, are reported and compared to the type material from Río Mulegé, as well as to Leptalpheus bicristatus Anker, 2011 from Panama. Finally, Leptalpheus hendrickxi Anker, 2011 is reported from Mexico for the first time, representing a significant northward range extension of the species. In Estero Pérula, L. hendrickxi lives in burrows of Lepidophthalmus bocourti, sometimes together with L. corderoae sp. nov.

A new species of the stenopodid shrimp Odontozona is described from deep-water off the west coast of Mexico. It is distinguished from the three other species of the genus known in the area, from O. rubra Wicksten, 1982, and O. foresti Hendrickx, 2002, by the absence of a series of spines on the posterior half of the carapace, behind the post-cervical groove, and from O. spongicola (AlcockAnderson, 1899) by the presence of spines on the ventral margin of somites 1-5 (smooth in O. spongicola) and by the much slender third pair of pereiopods in the new species. A new record is provided for O. foresti, and the first male specimen, the third specimen on record, is compared with the female holotype.