Ophioderma hendleri sp. nov. (Echinodermata: Ophiuroidea: Ophiodermatidae) and its congeners from the Eastern Pacifi c

The widespread Ophioderma hendleri sp. nov., from the Eastern Tropical Pacifi c (Mexico to Colombia) is distinguished from its congeners by having radial shields covered by granules, naked adoral shields, up to 11 arm spines, and by its brown and beige coloration. Ophioderma hendleri sp. nov. belongs to the group of species with naked adoral shields (i.e., O. pentacanthum H.L. Clark, 1917, O. variegatum Lütken, 1856), and it has frequently been misidentifi ed as O. panamense Lütken, 1859 or O. variegatum. Therefore, the main aim of the present work was to describe Ophioderma hendleri sp. nov. and differentiate it from its congeners. The original description of O. panamense was incomplete; thus, we provide a redescription. Due to the confusion in previous designations of its type material, we designate a lectotype and paralectotype of O. variegatum. Finally, we expand the distribution range of O. pentacanthum to Cocos Island, Costa Rica. With this work, the total number of valid species of Ophioderma Müller & Troschel, 1840 in the world increases to 33 and in the Eastern Pacifi c to nine species. European Journal of Taxonomy 729: 11–41 (2020) 12


Introduction
The study of Ophioderma in the Eastern Pacifi c began in 1860, focusing mainly on taxonomic papers on conspicuous species such as O. panamense and O. teres (e.g., Nielsen 1932;Ziesenhenne 1955;Granja-Fernández et al. 2014), but in the case of less conspicuous species such as O. vansyoci or O. pentacanthum, few published works exist (H.L. Clark 1917;Ziesenhenne 1955;Hendler 1996;Hernández-Herrejón et al. 2010). The most important works about Ophioderma of the Eastern Pacifi c are Nielsen (1932), Ziesenhenne (1955), Pineda-Enríquez et al. (2013) and Granja-Fernández et al. (2014), who provided important descriptions, taxonomic keys and comments on the species, but none of them revised the type material. Stöhr et al. (2009) mentioned that although there are many important morphological characters to separate the species of Ophioderma, these characters are often rather variable, which causes some diffi culties for their identifi cation. It is important to take into account that specimens (e.g., of O. panamense, O. pentacanthum and O. variegatum) in various scientifi c collections may have been misidentifi ed (e.g., Caso 1951;Ziesenhenne 1955), because Ophioderma is highly cryptic (e.g., Stöhr et al. 2020b). Closer observations often reveal that these previously confused cryptic species differ by subtle differences, often in color pattern, or novel morphological characters, and differences in habitat preference or life history (Boissin et al. 2011). For these reasons, Ophioderma hendleri sp. nov. has been misidentifi ed previously and confused with its congeners. Therefore, the aims of this work are: 1) to describe the new species O. hendleri sp. nov., 2) to redescribe O. panamense, 3) to designate a lectotype and paralectotype for O. variegatum, and fi nally, 4) to provide detailed descriptions, morphological characters, and photographs for each species used as a comparison between O. hendleri sp. nov., O. panamense, O. variegatum and O. pentacanthum.

Material and methods
Ophioderma hendleri sp. nov. was collected between 2007 and 2016 on rocky and coral reefs, at different depths (intertidal to 37 m) at localities on the Pacifi c coast of Mexico and Costa Rica. The animals were hand collected by scuba diving. All the collected ophiuroids were anesthetized using menthol buffered with seawater, to prevent autotomy; afterwards, all specimens were fi xed and preserved in 70% ethanol.
Additionally, specimens of O. hendleri sp. nov., O. panamense, O. pentacanthum and O. variegatum, stored in different scientifi c collections, as well as type material, were examined and taxonomically reviewed.
These were housed at: All the examined material is listed in the Supplementary material.
All the type specimens of the species in this work were photographed using an Olympus SZX16 stereo microscope with an adapted Nikon D750 camera or a Velab VE-S5 stereo microscope with an adapted Canon SX700-HS camera. Ossicles of some specimens from the type series of O. hendleri sp. nov. and non-type specimens of O. panamense and O. variegatum were prepared by dissolving all soft tissue in undiluted bleach; dissociated ossicles were then mounted for scanning electron microscopy (SEM). All the microstructures were mounted on aluminum stubs, gold coated and examined in a Hitachi S-2460N SEM at the Laboratorio de Microscopía, Instituto de Biología, Universidad Nacional Autónoma de Mexico, Mexico. Individuals of O. pentacanthum were not disarticulated due to the low number of specimens.

Diagnosis
Radial shields covered by granulation. Adoral shields naked, as long as broad. Up to 11 arm spines, dorsalmost the shortest and blunt, ventralmost the largest and robust. In vivo coloration, disc dark brown and mottled with small white spots, ventral margin beige and brown; arms dark brown with transverse white bands.

Etymology
This species is named after Dr. Gordon Hendler, an eminent ophiuroid taxonomist, curator of echinoderms at the Natural History Museum of Los Angeles County.

Holotype description
DD = 14.8 mm; 5 arms, AL = 69.1 mm. Disc fl at, nearly circular. Dorsal disc densely covered by rounded, small granules, slightly separated from each other; granule density 113 mm -2 . Granules at periphery of disc and on base of arms slightly larger than on central part of disc. Radial shields covered by granules (Fig. 1A). Interradii covered with granulation, similar to periphery and base of arms (Fig. 1B). Four genital slits in each interradius (Fig. 1B); proximal genital slits oval, in contact with distal part of oral shield and with 1 st LAP; distal genital slits rounded, elongated, placed between 5 th and 6 th arm segment and close to margin of disc, surrounded by granulation and numerous, elongated and imbricated scales next to side of lateral arm plates (Fig. 1B).
Oral shields slightly broader than long, rounded triangular, with convex obtuse proximal angle, straight to convex distal edge, obtuse lateral angles. Madreporite with central, circular, shallow depression, located in distal part of oral shield. Adoral shields naked, as long as broad, triangular and completely separated from each other. Jaws bear 8-9 oral papillae on each side: LyOs small, 2 × as long as broad, angled upwards; AdShSp largest, rounded; 2°AdShSp elongated and narrow; LOPas 4-5 conical and pointed, slightly separated; IPa reduced, elongated and pointed; TPa pair at apex of jaw, elongated, robust and pointed, slightly separated. vT similar in shape and slightly larger than TPa. Four teeth: ventralmost broader than long, quadrangular but with rounded borders; dorsalmost pointed, slender and smallest. One OPRSp, large and pointed at each side, visible within buccal cavity. Granules covering oral plates and below adoral shields larger than those on dorsal disc and interradii ( Fig. 1C-D).     Dorsal base of arms covered by granules and with approximately 11 oval scales, located laterally at fi rst 3 dorsal arm plates (Fig. 1E). Dorsal arm plates 3 × broader than long, rectangular, overlapping; proximal edge straight, distal edge slightly concave with rounded lateral edges (Fig. 1F). Distalmost dorsal arm plates smaller, longer than broad, triangular. First ventral arm plate small, broader than long, with rounded edges; in contact with adoral shields. Second ventral arm plate quadrangular, as broad as long (Fig. 1C). Next ventral arm plates slightly longer than broad, quadrangular; proximal margin truncate and distal edge convex (Fig. 1G). Distalmost ventral arm plates wider distally, with a tapering proximal angle. Paired rounded depressions between most proximal ventral arm plates (Fig. 1B). LAPs conspicuous, semicircular, broader than long (Fig. 1H). LAP with up to 11 arm spines. First and 2 nd LAP with 3 arm spines; 3 rd with 4 arm spines; 4 th with 5; 5 th with 6; 6 th with 7; 7 th with 8; 8 th with 9; 9 th -30 th arm plates with 10-11 arm spines; 35 th with 9 spines; 40 th -50 th with 8; 60 th with 7; 70 th with 6; 75 th with 5; 80 th with 4; >80 th with 3 arm spines. Arm spines with blunt tip; length approximately ⅓ of LAP. Dorsalmost arm spine shortest, blunt; ventralmost arm spine longest and more robust, as long as 1 arm segment, almost in contact with tentacle scale of succeeding joint (Fig. 1H). Two tentacle scales; adradial tentacle scale ovoid, approximately ½ × length of ventral arm plate; abradial tentacle scale slightly shorter, subtriangular (Fig. 1G).
General coloration dark brown (dry specimen) (Fig. 1I). Dorsal side: disc dark brown and mottled with small white spots; middle of margin on each interradius of disc bearing white spot (Fig. 1A); arms dark brown with small black spots only observed microscopically and with every 5-6 arm plates with transverse white bands, located between distal part of ventral plate and proximal part of next arm plate ( Fig. 1F, I). Ventral side: interradii, center and proximal part beige, margin dark brown with some beige marks (Fig. 1B). Jaw beige but oral shields can display brown color (Fig. 1C). Ventral arm plates beige, but that on tip of arms dark brown with some beige transversal lines (Fig. 1G). LAPs dark brown with some beige marks; arm spines dark brown and generally beige color on base and tip (Fig. 1H).

Disarticulated ossicles
Specimen analyzed: 1 spec., paratype ICML-UNAM 18323 (DD = 15 mm, AL = 80.8 mm). Radial shield (external view) irregularly triangular, with convex proximal margin, incised abradial edge with projection, convex to straight distal edge and irregular adradial edge, series of 8 pores on median to proximal margin (which are covered/overlapped by disc scales and granules in intact animal) ( Fig 2N). Dental plate consists of several pieces, 1 st piece bears 2 TPas on small round socket and 1 wide tooth socket, while rest of pieces with single tooth socket per piece (4 in total), none of sockets penetrate plate (Fig. 2O). Oral plates as long as high, abradial face with muscle fossa highly triangular, almost covering whole surface ( Fig. 2P), adradial face in middle part with foot basin (Fig. 2Q).

Paratype variations
Large specimens showed some differences in morphology compared to small ones (Figs 1, 3-4). Large individuals have granules and scales on the base of the arms (Fig. 1E), but in the smallest specimens (DD = ~ 2-4 mm) the scales are covered by granules (Fig. 4B). The scales begin to appear as the animal grows; therefore, in specimens with DD = 4-6 mm there are up to 3 elongated scales to either side of the base of the arms (Fig. 3B), and with a DD = 7 mm there are up to six scales; the number of scales in larger specimens reaches 11 (Fig. 1E). Additionally, large individuals have numerous scales located on the distalmost part of the interradii ( Fig. 1B) but in the smallest specimens (DD = 3-6 mm) these scales are not evident, and instead, only granules are present (Figs 3F-G, 4F-G). In specimens larger than DD = 7 mm, a row of elongated scales in the distal genital slits is evident. Finally, in the smallest specimens the adoral shields are completely covered by granules, which disappear as the animal grows, and individuals with DD = 5 mm tend to have totally or partially covered adoral shields.
Some specimens can have beige specks on the LAPs, the arm spines and the tentacle scales. Moreover, some specimens from the Gulf of California (Mexico) have a large white spot in the center of the dorsal disc. It is important to note that in vivo coloration ( Fig. 5A-D), generally conserved in all preserved specimens (Figs 1, 3-4), can be used as a distinctive character in the fi eld.

Diagnosis
Radial shields naked, oval, small, and widely separated. Adoral shields covered by granules. Up to 12 arm spines, short and with a blunt tip. In vivo coloration: disc green, brown or grey mottled with red, orange or yellow; arms with transverse bands, lighter and darker.

Other material
See: Supplementary material.

Holotype redescription
DD = 21.9 mm; 5 arms, AL = 91.9 mm. Disc fl at and pentagonal. Dorsal disc densely covered by rounded and small granules, granule density 61 mm -2 ; rubbed off in some areas. Radial shields naked, small, oval, and separated (Fig. 5E). Ventral interradii covered with granules similar to those on dorsal side of disc (Fig. 5F). Four genital slits on each interradius; proximal genital slits rounded and shorter than distal slits, in contact with distal part of oral shield and with 1 st LAP; distal genital slits elongated and surrounded by granules and numerous and imbricated scales next to lateral arm plates (Fig. 5F).
Oral shields slightly broader than long, rounded triangular, with convex obtuse proximal angle, straight distal edge, obtuse lateral angles. Madreporite with a small, circular, and shallow depression located in distal part and larger than other oral shields. Adoral shields covered by granules, which are larger than those on rest of body. Jaws bear 7-8 papillae at each side: LyOs small, 1.5 × as long as broad, angled upwards; AdShSp largest, rounded; 2°AdShSp a little larger and similar in shape to LOPa; LOPa 3-4 conical and pointed, separated; IPa similar and separated from LOPa; TPa 1-2 at jaw tips, robust and pointed, larger and more robust than LOPa, widely separated. vT similar in shape but slightly larger than TPa. OPRSp 1, large and pointed at each side, visible within buccal cavity. Granules covering oral plates, larger than those on dorsal disc and interradii (Fig. 5G).
Dorsal base of arms covered by granules and with approximately 15 scales laterally at dorsal arm plates. Dorsal arm plates 3 × broader than long, overlapping and with an irregular to straight proximal and distal margin, with rounded lateral edges; a few dorsal arm plates can be fragmented in 2 pieces (Fig. 5H). First ventral arm plate small, broader than long; with a small indentation distally (Fig. 5G). Subsequent ventral arm plates quadrangular, slightly broader than long; distal edge slightly concave (Fig. 5I). Paired and rounded pores between 1 st and 2 nd , and 2 nd and 3 rd ventral arm plates (Fig. 5F-G). LAP with up to 8-9 arm spines. Arm spines with blunt tip and robust; length approximately ½ of size of LAP. Dorsalmost arm spine shortest and narrowest; ventralmost arm spine longest and slightly more robust, in contact with tentacle scale of succeeding joint (Fig. 5I). Two tentacle scales; adradial tentacle scale ovoid, elongated, approximately half length of ventral arm plate; abradial tentacle scale slightly shorter, subtriangular (Fig. 5I).

Disarticulated ossicles
Specimen analyzed: 1 spec., ICML-UNAM 3.18.60 (DD = 11.1 mm, AL = 44.4 mm). Radial shield (external view) irregularly rounded, with an indented proximal margin, an incised abradial edge with a projection, an indented distal edge, and convex adradial margin, it is bordered by 7 pores on median to proximal margin (which are covered/overlapped by disc scales and granules in intact animal) (Fig. 6A). Only exposed surface is domed center portion of radial shield. Outer surface of stereom is an open mesh of pores and knobs (Fig. 6A). Dorsal arm plate somewhat rectangular, 3 × as wide as long; proximal margin convex to straight, and distal margin straight, 7 spurs on proximal portion of external surface (Fig. 6B). Ventral arm plate as long as wide, quadrangular with proximal side truncated and with a pointed-shape spur, lateral sides concave forming border of a small tentacle pore, and distally indented (Fig. 6C). LAP D-shaped, 3 × as high as wide, with 8 spine articulations sunken in notches of distal edge (Fig. 6D-E). Ventral portion of LAP projecting ventro-proximalwards and ventro-distal tip projecting ventralwards (Fig. 6D). Proximal edge of LAP with 2 prominent and elongated spurs, which are protruding and modify central-proximal edge (Fig. 6D); between spurs and across remaining proximal margin a discernible band of different stereom structure is present (Fig. 6D). Outer surface fi nely meshed with relatively large rounded stereom knobs (Fig. 6G). Inner surface of LAP with a continuous ridge on proximal edge, and on ventro-distal margin with 2 spurs matching those on external surface (Fig. 6F), and 4 pores in center. Spine articulations ventralwards increasing in size (Fig. 6E). Lobes with a weak sigmoidal fold, tilted, and curved (Fig. 6H). Ventral lobe smaller than dorsal lobe (Fig. 6H). Proximal vertebrae (Fig. 6I) almost oval, as wide as long, with large aboral muscle fl ange and smaller oral muscle fl ange. Distal face of vertebrae with large muscle fl anges, with typical zygospondylous articulation (Fig. 6J). Tentacle scale longer than wide, with a scale-like surface (Fig. 6K). Spines with a scale-like surface, a blunt tip, and laterally fl attened (Fig. 6L). Dental plate consists of several pieces, 1 st piece bears 2 TPa and a single wide tooth, while rest of pieces with a single tooth socket per piece (4 in total), none of sockets penetrate plate (Fig. 6M).

Remarks
Lütken (1859) did not designate any specifi c type material in his description of O. panamense, but according to the International Code of Zoological Nomenclature (ICZN 1999), Article 73.1.2, the only specimen reported in the original description (NHMD-107679) must be treated as holotype by monotypy.

The description provided by Lütken (1859) is mostly based on the comparison of this species with other
Ophioderma from the Atlantic; therefore, a redescription of the holotype is provided in the present work.

Diagnosis
Radial shields covered by very small granules. Naked adoral shields, longer than broad. First ventral arm plate large and rhombic. Up to 6 arm spines, very large and slender; the dorsalmost is the shortest and the ventralmost is much larger than the rest, overlapping the tentacle scales of the contiguous segment. Adradial tentacle scale almost double in size of abradial one. In vivo coloration: disc orange with dark blotches, arms with transverse brown bands. Description (paratype MCZ OPH-4519) DD = 21.1 mm; 5 arms, LA = 147.7 mm. Disc fl at and rounded. Dorsal disc densely covered by rounded and fi ne granules, which are very close together, granule density 182 mm -2 ; granules extend to base of arms. Some granules rubbed off in some areas of disc. Radial shields completely covered by granules (Fig. 7A). Interradii covered with granulation, similar to on dorsal disc (Fig. 7B). Four genital slits on each interradius; proximal and distal genital slits elongated; distal genital slits surrounded by granules and few scales that are next to side of lateral arm plates (Fig. 7B).
Oral shields broader than long, rounded triangular, with convex obtuse proximal angle, straight distal edge, obtuse lateral angles. Madreporite with a small, circular, and shallow depression located in distal part of oral shield. Adoral shields naked, triangular, longer than broad, and separated. Jaws bear 8-9 papillae on each side: LyOs small, 1.5 × as long as broad, angled upwards; AdShSp largest, rounded; 2°AdShSp smaller but similar in shape to AdShSp; LOPa 3-4 conical, pointed, and separated, 1 st LOPa smaller but similar in shape to 2°AdShSp; IPa sometimes smallest, elongated, pointed and separated; TPa 2 at jaw tips, larger than LOPa, elongated, robust, and pointed, slightly or completely separated. vT 1; 4 teeth, all robust. OPRSp 1 large and pointed at each side, visible within buccal cavity. Granules covering oral plates, slightly longer than those on dorsal disc and interradii (Fig. 7C).
Dorsal base of arms with granules and with approximately 11 scales laterally at arm. Dorsal arm plates 3 × broader than long, overlapping and trapezoidal, with distal edge straight or slightly incised and rounded lateral edges (Fig. 7D). First ventral arm plate large, broader than long, rhomboid (Fig. 7C). Subsequent ventral arm plates quadrangular, slightly broader than long (Fig. 7E). Paired and large pores between ventral arm plates 1-2, 2-3, 3-4, 4-5, 5-6 ( Fig. 7B, G). LAP with up to 5-6 arm spines; distalmost segments with 3-4 arm spines. Arm spines with a blunt tip, slender and very large; approximately one arm segment length. Dorsalmost arm spine shortest and slender; ventralmost arm spine longest and more robust than rest, in contact with and covering tentacle scale of succeeding joint (Fig. 7E). Two tentacle scales; adradial tentacle scale ovoid and very elongated; abradial tentacle scale subtriangular and half size of adradial one (Fig. 7E, G).
Color light brown (dry specimen) (Fig. 7F). Dorsal side: disc light brown and mottled dark brown in center (Fig. 7A); arms light brown with transverse dark brown bands every 2 or 3 segments (Fig. 7D, F). Ventral side interradii: beige in center and in proximal part, and light brown on margin, with some beige marks (Fig. 7B). Jaw in general beige, but oral shields and granules brown in color (Fig. 7C). Ventral arm plates beige (Fig. 7E).

Remarks
In the original description of O. pentacanthum, H.L. Clark (1917) designated an uncatalogued specimen as "heliotype" (= holotype), including four additional specimens, but a proper designation of the type material (including catalog numbers) was lacking at that moment. Downey (1969) considered the specimen USNM E726 (DD = 27 mm) as paratype, not recognizing it as the holotype in spite of a museum label marking it as type material by H.L. Clark (pers. comm. Pawson, 2020), also not considering the illustration already included in the original description. However, according to the International Code of Zoological Nomenclature (ICZN 1999), Articles 73.1.2 and 73.1.4, the described and illustrated specimen which corresponds to USNM E726 should be treated as the holotype. During the revision of the paratypes only two specimens were found: MCZ OPH-4519 and USNM E9798. The labels of the paratype USNM E9798 indicate the presence of two specimens, but the lot includes only one. Therefore, two specimens are "lost", one that is part of USNM E9798, and a second one whose catalog number is unknown, but in case they are found, they must be treated as paratypes.
All the morphological characters of the holotype, paratypes, and voucher specimens correspond with the original description by H.L. Clark (1917); nevertheless, we observed other relevant characters. H.L. Clark (1917) coined the named O. pentacanthum based on the number of arm spines (fi ve), but we observed that most of the examined specimens (MCZ OPH-4519, MZUCR-ECH 1413, MZUCR-ECH 1414) had up to six arm spines. It is important to mention that the low number of arm spines is one of the most important diagnostic characters for this species since O. pentacanthum is the only Ophioderma in the Eastern Pacifi c having up to six arm spines, while the rest of its congeners have more than eight. Another important characteristic that has not previously been mentioned is the elongation of the genital slits ( Fig. 7G-H, J), which is not found in other Ophioderma from the Eastern Pacifi c; perhaps, the large elongation of these genital slits is due to the large size of the specimens, but this must be confi rmed when more data from specimens of different sizes is obtained. One of the most remarkable features of O. pentacanthum is the paired and large pores between the most proximal ventral arm plates. The paratype MCZ OPH-4519 (Fig. 7G) presents them on at least the fi rst six arm segments, but they cover ¾ of the arm in the Costa Rican specimens (Fig. 7H-K). Furthermore, the observed pores in such specimens are extremely large (occupying most of the proximal portion of the ventral arm plates) and elongated in the fi rst segments (Fig. 7H, J), decreasing in size and becoming more rounded towards the medial (Fig. 7I, K) and distalmost part of the arm. The reason why H.L. Clark (1917) did not observe these pores could be related to the smaller size of the type material (MCZ OPH-4519, DD = 21.1 mm) in comparison to the specimens from Costa Rica (MZUCR-ECH 1413, DD = 23 mm; MZUCR-ECH 1414, DD = 26.8 mm). Taking into account all the nominal species, it seems that smaller specimens of Ophioderma tend to have reduced and fewer pores (or even absent) in the ventral part of the arm, whilst larger specimens can have larger and more numerous pores being a characteristic inherent of growth; this agrees with observations made by Nielsen (1932). Nevertheless, more specimens are necessary to review and compare to corroborate this assumption and to determine whether the pores have any functional importance in the organisms (pers. com. Stöhr & Granja-Fernández, 2017). Lastly, it is important to remark that the fi eld notes of the specimens from Costa Rica mentioned that the in vivo color of O. pentacanthum was orange with brown botches on the disc and arms with transversal brown bands; this is the fi rst record of the in vivo coloration for this species.
H.L. Clark (1917) described this species from the Galapagos Islands but it was subsequently recorded in the Gulf of California, Mexico, and Guatemala (Ziesenhenne 1955;Solís-Marín et al. 2013). In the review of the genus Ophioderma by Ziesenhenne (1955), he mentioned that the occurrence of O. pentacanthum in the Gulf of California (one specimen deposited in the Allan Hancock Collection) was "rare". Nevertheless, many authors have considered this record as valid (Maluf 1991;Buitrón-Sánchez & Solís-Marín 1993;Maluf & Brusca 2005;Granja-Fernández et al. 2015a). We reviewed all the LACM Ophioderma material, where all the material of the Allan Hancock Foundation is deposited, and we could not fi nd any material corresponding to Ziesenhenne´s record. Moreover, in all the other visited collections we did not fi nd any specimens labeled and/or identifi ed as O. pentacanthum, except for the type material from the Galapagos Islands. Despite the rarity of O. pentacanthum in scientifi c collections, the reviewed specimens agree with the distribution in the Southeastern Pacifi c (Galapagos Islands and Cocos Island) at depths below 100 m (H.L. Clark 1917). Consequently, it is plausible that Ziesenhenne´s specimen does not correspond to O. pentacanthum but to a similar species (e.g., O. hendleri sp. nov.). Also, the Solís-Marín et al. (2013) record of O. pentacanthum from Guatemala is erroneous. Therefore, we suggest that the records from Mexico and Guatemala should be considered invalid. Lütken, 1856 Figs 8-9; Table 1 Ophioderma variegata Lütken, 1856: 21.

Diagnosis
Radial shields covered by granules. Base of the arms and distal genital slits with granulation. First ventral arm plate large, broader than long. Oral shields oval, larger than broad, proximal margin rounded with an obtuse angle, distal edge convex, lateral margins straight. Naked adoral shields, longer than broad. Up to 9 arm spines, very large and slender; dorsalmost and ventralmost a little bit shorter than the rest. In vivo coloration: dorsal disc olive-green with dark pink or red; arms with transverse olive-green and dark pink-red bands.

Designation of lectotype and paralectotype
In the original description of Ophioderma variegatum, Lütken (1856) only mentioned the existence of one uncatalogued specimen (DD = 14 mm) as part of the type material. However, three specimens are present in this lot (pers. com. Schiøtte, 2019) all of similar size (DD = ~12.5 mm). The similarities of the morphological characters and sizes make it impossible to determine which of them corresponds to the specimen described by Lütken (1856). There are some discrepancies between the measurements from Lütken (1856) and our measurements which could be due to the preservation of the specimens through time. Because of this, and according to Recommendation 73F of the International Code of Zoological Nomenclature (ICZN 1999), we propose the designation of the specimen NHMD-107680 as the lectotype and NHMD-619214 contains the paralectotypes (two specimens) for O. variegatum.

Other material
See: Supplementary material. Description (Lectotype) DD = 12.4 mm; 5 arms, AL = 62 mm. Disc fl at and rounded. Dorsal disc densely covered by rounded and very small granules, granule density 222 mm -2 ; granules extend to base of arms. Some granules rubbed off in some areas of disc. Radial shields covered by granules (rubbed off in some parts due to preservation) (Fig. 8A). Interradii covered with granules, similar to those on dorsal disc (Fig. 8B). Four genital slits on each interradius; proximal genital slits elongated and shorter than distal slits, in contact with distal part of oral shield and with fi rst LAP; distal genital slits elongated and surrounded by granulation (Fig. 8B).
Oral shields longer than broad, oval, proximal margin convex obtuse angled, distal edge convex, lateral margins straight. Madreporite with a small, circular and shallow depression located in center of oral shield. Adoral shields naked, triangular, longer than broad, separated. Jaws bear 8-9 papillae on each side: LyOs very small, as long as broad, angled upwards; AdShSp largest, rounded; 2°AdShSp smaller but similar in shape to AdShSp; LOPa 4-5 conical, pointed and separated, 1 st LOPa similar in shape to and smaller than 2°AdShSp; IPa sometimes large, elongated, pointed and separated; TPa 2 at jaw tips, larger than LOPa, elongated, robust and pointed, separated. Granules covering oral plates slightly longer than those on dorsal disc and interradii (Fig. 8C).
Dorsal base of arms with granules. Dorsal arm plates, 2 × broader than long, trapezoidal, overlapping (Fig. 8D). First ventral arm plate large, broader than long, oval (Fig. 8C). Subsequent ventral arm plates quadrangular, slightly broader than long; distal edge slightly concave (Fig. 8E). Paired, rounded, and very small holes between 1 st and 2 nd , and 2 nd and 3 rd ventral arm plates ( Fig. 8B-C). LAP with up to 7-8 arm spines. Arm spines with a blunt tip, slender, and very large. All arm spines of almost same size except dorsalmost and ventralmost, which are just a little shortest than rest (Fig. 8E); length approximately ⅔ of size of LAP. Tentacle scales 2; adradial tentacle scale ovoid, elongated; abradial tentacle scale slightly shorter, subtriangular (Fig. 8E).
Specimen (ethanol preservation) discolored but with a disc with different shades of brown and arms with transverse dark brown bands (Fig. 8F).

Disarticulated ossicles
Specimen analyzed: 1 spec., ICML-UNAM 3.20.4 (DD = 13.6 mm, AL = 66.5 mm). Radial shield (external view) irregularly rounded, with an incised proximal margin, a slightly indented abradial edge with a tiny projection, a convex distal edge, and convex adradial margin, bordered by 9 pores along median to proximal margin (which are covered/overlapped by disc scales and granules in intact animal) (Fig. 9A). Dorsal arm plate arched and somewhat trapezoid-shaped, 2 × as wide as long; proximal edge convex with 5 spurs on proximal portion of external surface, distally straight and incised (Fig. 9B). Ventral arm plate 2 × as wide as long, rectangular-shaped with proximal side truncated and with a pointed-shape spur, lateral sides concave forming border of tentacle pore, distal margin convex (Fig. 9C). LAP D-shaped, 2 × as high as wide, with 9 spine articulations sunken in notches of distal edge (Fig. 9D-E). Ventral portion of LAP projecting ventro-proximalwards (Fig. 9D). Proximal edge of LAP with 2 prominent and elongated spurs, which are protruding and modify central-proximal edge (Fig. 9D), between spurs and across remaining proximal margin a discernible band of different stereom structure is present (Fig. 9D). Outer surface fi nely meshed with rounded stereom knobs (Fig. 9G). Inner surface of LAP with a continuous prominent ridge on proximal edge (see arched view) and on ventrodistal margin 2 spurs matching those on external surface, with 1 perforation on vertical furrow (Fig. 9F). Spine articulations ventralwards increasing in size (Fig. 9E). Lobes with a weak sigmoidal fold, tilted, and curved (Fig. 9H). Ventral lobe less conspicuous than dorsal lobe (Fig. 9H). Proximal vertebrae with a wing-like muscle fl ange (Fig. 9J). Distal face of vertebrae almost round, as wide as long, with large and irregular (sinuous) aboral muscle fl ange, with typical zygospondylous articulation (Fig. 9I). Spines with a scale-like surface, a blunt tip and laterally fl attened (Fig. 9K). Dental plate consists of several pieces, 1 st piece has 2 TPa and 1 wide tooth, while rest of pieces with 1 tooth socket per piece (5 in total), none of sockets penetrate plate (Fig. 9L). Oral plate as long as high, adradial plate with a less indented middle section, and 4 oral papillae sockets (Fig. 9M).

Remarks
In the original description of O. variegatum, Lütken (1856) provided just a brief description, but later he extended it (Lütken, 1859). However, the description provided in the present work is the most complete to date. All the characters mentioned by Lütken (1856Lütken ( , 1859 correspond with the lectotype and paralectotype designated in this work. Although the type specimens are discolored, many authors (Lütken 1859;Verrill 1867;Lütken & Mortensen 1899;H.L. Clark 1913H.L. Clark , 1940Koehler 1914;Boone 1933) and our present work coincide that the coloration of this species consists of an olive-green disc with irregular blotches of bright rose-red and the arms banded with lighter and darker grayish green, brown or white every two to fi ve dorsal segments.
Although O. variegatum and O. panamense are completely different in overall morphology (Table 1), during our revisions we observed that it is very common to fi nd specimens of O. variegatum identifi ed as O. panamense, and vice versa. This tendency is very common in some published works (see references below); for example, we detected that in the description (i.e., naked radial shields and covered adoral shields) as well as the images of the species by Caso (1951Caso ( , 1962Caso ( , 1979Caso ( , 1986, the specimens identifi ed as O. variegatum were misidentifi ed and corresponded to O. panamense. All the specimens studied by Caso are deposited at ICML-UNAM, and this identity was corroborated (see: Supplementary material). It is very feasible that the material mentioned in Caso et al. (1996) also corresponds to O. panamense, but neither a description nor images of the studied specimens are provided in this work and therefore we cannot confi rm it.
The jaw of the type material of O. variegatum was closed, but like the other species of Ophioderma, voucher specimens with open jaws have one large and pointed OPRSp on each side, visible within the buccal cavity. It is important to recall that OPRSp were previously mentioned as spiniform structures or as a conspicuous pointed papilla (e.g., H.L. Clark 1917). Hendler (2018) coined the term suggesting that OPRSp in Ophioderma (along with OPa and teeth) are used to grip food between the closed jaws and to retain items in the buccal cavity, facilitating a feeding habit of predation and scavenging.
According to our study, O. variegatum is less abundant and less conspicuous in rock and coral reef zones of the Eastern Pacifi c compared to O. panamense. Ophioderma variegatum tends to inhabit deeper areas (up to 110 m) and it is commonly collected by dredging, whereas O. panamense is easily collected by hand in shallow waters (up to 20 m depth). Maluf & Brusca (2005) reported O. variegatum for Gorgona Island (Colombia) but without any supporting data; therefore, we suspect that this record is invalid. Nevertheless, due to the wide geographic distribution of the species, it is very plausible to fi nd it in Colombia (or even further south), but specimens are needed to confi rm this record.

Discussion
Previously, a total of seven valid Ophioderma species (O. panamense, O. pentacanthum, O. peruanum, O. sodipallaresi, O. teres, O. vansyoci, and O. variegatum) and one species with unclear taxonomic status (O. teres var. unicolor) were reported for the Eastern Pacifi c (Lütken 1856(Lütken , 1859Lyman 1860;H.L. Clark 1917H.L. Clark , 1940Caso 1986;Hendler 1996;Pineda-Enríquez et al. 2013) but with the contribution of the new species O. hendleri sp. nov., the number increases to nine. These Ophioderma can be separated in two groups: species with adoral shields covered by granules (O. panamense, O. peruanum, O. sodipallaresi, O. teres, O. teres var. unicolor, O. vansyoci) and species with naked adoral shields (O. hendleri sp. nov., O. pentacanthum, O. variegatum). Although the group of Ophioderma with naked adoral shields consists of just three species, they have frequently been confused among each other and with the conspicuous O. panamense (with covered adoral shields). In this regard, 1) O. hendleri sp. nov. has been misidentifi ed as O. variegatum or O. panamense, 2) O. panamense as O. teres or O. variegatum, and 3) O. variegatum as O. panamense. Despite the above, the revision of the type material and voucher specimens reveals that all these species are different in morphology (Table 1).
One of the most common Ophioderma in the Eastern Pacifi c, along with O. hendleri sp. nov., is O. panamense and the misidentifi cation between both species could be due to sympatry (Mexico, Costa Rica and Panama) and because they share similar bathymetrical ranges (intertidal to approximately 40 m) and habitats (rocky and coral reefs) (Granja-Fernández et al. 2014). Ophioderma hendleri sp. nov. cannot be morphologically confused with O. panamense because the latter species has naked radial shields as well as adoral shields covered by granules (Table 1). On the other hand, the confusion between O. hendleri sp. nov. and O. variegatum is more reasonable since both species have radial shields covered by granules and naked adoral shields; nevertheless, they have signifi cant different morphological characters like the number, shape, and length of the arm-spines, the shape of oral and adoral shields, and the coloration (Table 1; Granja-Fernández et al. 2014).
It is important to note that O. hendleri sp. nov. is more closely related to O. pentacanthum than the rest of the species, and they can be differentiated by 1) up to 11 arm spines in O. hendleri sp. nov. and up to six in O. pentacanthum, the ventralmost being much larger than the rest; 2) adradial tentacle scale slightly larger than abradial in O. hendleri sp. nov., but in O. pentacanthum the adradial tentacle scale is much larger; 3) short and rounded genital slits in O. hendleri sp. nov. and large and slender in O. pentacanthum; and fi nally, 4) O. hendleri sp. nov. is distributed in shallow waters and O. pentacanthum in deeper waters (Table 1).
The mix-up of O. panamense with other Ophioderma was very common in all the scientifi c collections. The main differences between O. panamense and O. teres can be consulted in Granja-Fernández et al. (2014). Ophioderma panamense can be distinguished from O. variegatum by: 1) naked radial shields versus radial shields covered by granules, respectively; 2) base of the arms and distal genital slits covered by granules and scales in O. panamense but only covered by granules in O. variegatum; 3) arm-spines shorter and robust versus very large and thin in O. variegatum; 4) oral shields broader than long and rounded versus longer than broad and oval in O. variegatum; 5) covered adoral shields versus naked in O. variegatum; and, 6) O. panamense occurs in shallower depths than O. variegatum (Table 1).
We attribute the persistent confusion of the species of Ophioderma from the Eastern Pacifi c to their cryptic diversity, but mostly to a lack of the study and comparison of the type materials. Moreover, the material of some species (e.g., O. pentacanthum) is scarce which impedes the improvement of their knowledge. During this work, the collection of more specimens and the study of the type material allowed us to expand the known geographical distribution range of O. pentacanthum (from Galapagos Islands, Ecuador to Cocos Island, Costa Rica) as well as to fi nd the new species O. hendleri sp. nov. and with this discovery, the total number of valid species of Ophioderma in the world increases to 33.
Along with Ophiactis, Ophiocoma, Ophiocomella, Ophionereis, and Ophiothrix, Ophioderma is one of the most conspicuous genera of ophiuroids, with the greatest number of species in shallow rocky and coral reefs of the Eastern Pacifi c. Despite the above, this work reveals that there is much work to do with the taxonomy of Ophioderma because its morphology is often confused, and with the use of molecular markers it will highly increase our knowledge, as it has previously been noted that Ophioderma has clear examples of cryptic speciation (Stöhr et al. 2020b). Also, it is important to investigate the reproductive seasonality of the species from the Eastern Pacifi c, as well as their dispersal mechanisms to understand their geographic ranges. In this work we focus on the Ophioderma with naked adoral shields (besides O. panamense) but it is of importance to provide a further work of the species with covered adoral shields to complete the analysis of Ophioderma of the Eastern Pacifi c.