Six new species of Anthuridae (Peracarida: Isopoda) from the southern Mexican Pacific

Abstract. Marine isopods, despite being a very diverse group, have been little studied in the Mexican South Pacific. After a revision of 171 specimens collected from Guerrero and Oaxaca, six new species, belonging to five genera, were discovered: Amakusanthura guerrerensis sp. nov., Cortezura caeca sp. nov., Mesanthura antenniformis sp. nov., M. estacahuitensis sp. nov., Skuphonura oaxaquensis sp. nov., and Tinggianthura mexicana sp. nov. In this work, the genera Amakusanthura Nunomura, 1977 and Tinggianthura Chew, Abdul-Rahim & Haji Ross, 2014, are recorded for the first time in the Tropical Eastern Pacific. Also, the distribution range of the genus Skuphonura Barnard, 1925 is increased from the west coast of South America to the southern Mexican Pacific, this being the first record of this genus in the Mexican Pacific. This study doubles the number of species recorded of Anthuridae from the Mexican Pacific, of six to 12 species.

The Anthuridae family have been poorly studied in the Mexican Pacific, and the few studies available are focused on the northern region of the Pacific of Mexico. Among them stand out the descriptions of two species from Gulf of California, Cortezura penascoensis and Mesanthura nubifera Wägele, 1984. Additionally, in the Western coast of Baja California, Menzies (1962) and Campos & Villarreal (2008) recorded to Haliophasma geminata Menzies & Barnard, 1959 and Mesanthura occidentalis Menzies & Barnard, 1959; in the Gulf of California, Brusca (1980) only recorded to Mesanthura sp. and Espinosa-Pérez & Hendrickx (2001) recorded to M. occidentalis, both in the Gulf of California and in the central Pacific of Mexico.
In this study, we describe six new species of Anthuridae from southern Mexican Pacific, belonging to five genera.

Material and methods
The revised specimens are from the Crustacea section of the Scientific Collection (OAX-CC-249-11) of the Laboratorio de Sistemática de Invertebrados Marinos (LABSIM), Universidad del Mar, Puerto Ángel, Oaxaca. The specimens are derived from 13 localities along the coast of Guerrero and Oaxaca (Fig. 1). All material was collected from intertidal and subtidal zone (1-12 m depth) by free diving and scuba on different substrates such as rock, coral, coralline rocks, sand, algae and shells. Collected specimens were fixed 4% formalin and preserved in 70% ethanol.
The specimens were examined with a stereo microscope and separated by morphotypes. The best preserved specimens of each species were measured from the rostrum to the end of telson and the habitus was drawn with a camera lucida. Left appendages were dissected and mounted on glycerol and sealed with Entellan © on permanent slides. Drawings of each structure dissected were made using a digital camera and a WACOM brand graphic drawing tablet using Adobe Photoshop CS6 program.
The identification was made using the specialized literature and identification keys of Poore (2001) and Chew et al. (2014). Diagnoses and descriptions of the species were standardized and the nomenclature of the structures was based on the terminology of Negoescu (1994) and Garm & Watling (2013). All material examined was labeled, catalogued and deposited in the Crustacea section, Scientific Collection of Laboratorio de Sistemática de Invertebrados Marinos (LABSIM), Universidad del Mar.

Etymology
This species is named after Guerrero, the Mexico State where the type material was collected. MAxillipEd (Fig. 2D). Palp with three articles. Article 1 rectangular with one simple seta; article 2 with one long medial seta and three distal setae, internal margin with setulated scales, bilobed and projected distal angle; article 3 small, oblique with five distal setae. Endite reaching half of the first article of palp.
MAndiBlE (Fig. 2F). Symmetrical; palp with three articles, first article 0.6 times as long as article 2 with a long distal seta; second article 2.5 times as long as article 3 with three distal setae; article 3 with five pectinate setae. Incisor with three teeth; lacinia mobilis with four denticles.
pErEopods 2-3 ( Fig. 3B-C). Similar in shape and size. Carpus triangular, truncated apically with a small tooth and two long robust setae; propodus elongated oval, 2.1-2.2 times as long as wide, internal margin with a row of simple setae and setulated scales, distoventrally one slightly serrated sensory spine; proximal internal margin of the dactylus with small teeth, distal margin with a robust spine and a group of simple and plumose setae.
pErEopods 4-7 ( Fig. 3D-G). Very similar in shape and size. Merus with a row of long simple setae and setules on inner margin; carpus subpentagonal, ventrodistal margin with a sensory spine and simple setae, dorsodistal margin with a plumose sensory seta; propodus sub-cylindrical, 1.8 times as long as wide in P4-6, and 2.5 times in P7; ventral margin with simple seta and setulated scales, ventrodistal margin with a denticulate sensory spine. P7 ventrodistally with two pectinate sensory spines; dactylus with setulated scales.

Distribution and habitat
From Ixtapa, Guerrero to Huatulco, Oaxaca. In algae, coral, coral rock, tubes of sabellariids and molluscan shells; intertidal to subtidal (6 m).

Remarks
Amakusanthura guerrerensis sp. nov. shares the following characteristics with 41 previously recorded species of the genus: (1) maxillipedal palp with three free articles, the internal angle of the second article  projected; (2) pleon longer than wide; (3) pleonites 1-3 with dorsal suture lines and 4-5 dorsally fused. The new species differs by presenting a unique combination of characteristics: antenna with scales in the internal margin of the second article; palm of the pereopod 1 with a medial projection as a step armed with eight short setae; exopod of pleopod 1 with one proximal and medial simple seta, and 48 distal plumose setae. Amakusanthura guerrerensis sp. nov. is similar to A. californiensis (Schultz, 1964), the only species recorded in the eastern Pacific, with the following characteristic: (1) more than eight setae in the distolateral part of the telson. The new species, however, differs from A. californiensis in the presence of a pigmented line in the pereonites 3-7 and pleonite 5, distal article of the mandibular palp with five pectinate setae, palm of the pereopod 1 with a medial projection as a step armed with eight short setae and pleonite 6 is strongly emarginated. In comparison, A. californiensis has no pigment, the distal article of the mandibular palp has four setae, palm straight, and the pleonite 6 is slightly emarginated.

Description
Holotype (♀, UMAR-PERA 534) Body (Figs 5A, 20B). Length 7.1 mm, about 11.8 times as long as wide with a whitish color, without pigment. Body proportion: C<1=2>3<4<5>6>7. Cephalon 1.3 times as long as wide, rostral process equal to lateral lobes, eyes absent; overlapping antennas, forming a flattened surface. Pleon equals to the length of the pereonite 7; pleonites 1-5 fused, pleonite 6 free. Telson 2.6 times as long as wide, tapering distally with two proximal statocysts, mid-distal margin with a group of short setae; apex broadly truncate, slightly sinuous with eight sub-marginal and eight marginal setae. AntEnnulE (Fig. 5B). Peduncle with three articles. First article 1.2 times as long as second, with four simple setae and plumose sensory setae; article 2 with four long simple setae and scales in ventral margin; article 3 narrow than others with a group of ventrodistal setae and a long apical seta; flagellum of three articles, distal article with three aesthetascs. AntEnnA (Fig. 5C). Peduncle with five articles. Article 2 with scales in ventral margin; articles 3 and 4 sub-equal; article 5 subrectangular, 1.2 times as long as article 4; flagellum with three articles, article 1 longer than the others; distal articles with numerous setae.
MAxillA (Fig. 5E). With seven stout distal teeth. MAndiBlE (Fig. 5F). Symmetrical; palp with two articles, article 1 with a simple distal seta; distal article 1.8 times as long as article 1, whit three mid-distal setae and one long apical. Incisor with three teeth; lacinia mobilis with approximately 13 denticles, sharp molar.
pErEopod 1 (Fig. 6A). Subchelate; carpus triangular, apically rounded with a group of distal simple setae; propodus ovate, palm curved, slightly medially convex with a row of 11 short setae; dactylus reaching almost half the palm, internal distal angle with a tooth; unguis slender, reaching the apical margin of the carpus. pErEopods 2-3 ( Fig. 6B-C). Similar in shape and size. Ischium, merus and carpus with numerous ventral simple setae; inner margin of merus denticulate; carpus triangular, partially below the propodus with 2 robust setae on the distal margin; propodus cylindrical, 2 times as long as wide, internal margin with setulated scales, distoventrally one serrated sensory spine and a group of simple setae.
pErEopods 4-7 ( Fig. 6D-G). Similar in shape and size. Inner margin of ischium and merus slightly denticulate and numerous simple setae; carpus pentagonal, ventrodistal margin with a single sensory spine and a group of long setae; propodus cylindrical, approximately half the width of the carpus, internal margin with a group of simple setae and setulated scales, ventrodistal margin with a serrate sensory spine and 1-2 pectinate spines; pereopod 7 dactylus with setulated scales on the inner and outer margins. Pereopods 2-7 basis with a long simple seta and plumose sensory setae; merus, carpus and propodus with scales.
MAndiBlE. Mandibular palp with two articles; distal article with seven long setae.
plEopod 2 (Fig. 7G). Similar to the female; exopod surrounded distally by 10 plumose setae; endopod surrounded by seven plumose setae; male appendix emerging from the middle part of the endopod, slightly longer than ramus, apex rounded and slightly bent towards the inside.

Distribution and habitat
From Puerto Ángel to Huatulco, Oaxaca. In coral, sand and sediment; subtidal (12 m).

Remarks
Cortezura caeca sp. nov. differs from the two previously recorded species of this genus, C. penascoensis, described from Puerto Peñasco, Sonora, and C. confixa (Kensley, 1978) described from Cubagua Island, Venezuela, by the following unique characteristics: distal article of the mandibular palp with four medial setae and one apical, lacinia mobilis with 13 denticles, telson with distolateral carina, distal region with eight subapical setae and eight apical. Cortezura caeca sp. nov. is similar to C. penascoensis as follows: (1) form of telson, (2) palm of pereopod 1, and (3) maxilla. However, in C. caeca sp. nov. the distal article of the mandibular palp has four medial setae and one apical, lacinia mobilis with 13 denticles, distally tapered telson and the apex is truncated, pereopods 2-7 with scales on the merus, carpus and propodus. And in C. penascoensis the distal article of the mandibular palp has six medial setae and one apical, lacinia mobilis presents 8 teeth, pleon with six conspicuous segments. The antennular flagellum of the male of Cortezura caeca sp. nov. has four articles and the palm of pereopod 1 has a strong tooth projected transversally, while C. penascoensis has one article on the flagellum, palm of pereopod 1 with tooth projected proximally.
AntEnnA (Fig. 8C). Peduncle with five articles. Second article 1.4 times as long as the subsequent peduncular articles; internal angle projected with two simple setae, distal margin with small sinuosities; article 3 partially covered by second article; last article 1.1 times as long as article 4 with simple and sensory plumose setae in the distal region; flagellum with five articles, sub-equal to the length of the last peduncle article, square article with numerous thin setae.
MAxillipEd (Fig. 8D). Palp with three articles. Article 1 rectangular, half the length of the second with a single ventrodistal seta; distal article small, oblique with six setae, proximal and distal plumose setae, a medial pectinate seta and a simple one.
MAndiBlE (Fig. 8E). Symmetrical; palp with three articles, article 2 cylindrical, 2.2 times as long as the first with a subdistal seta; distal article with 5-6 robust marginal setae; incisor with three teeth; lacinia mobilis with five denticles and small molars.
pErEopod 1 (Fig. 8G). Subchelate; carpus triangular, apical margin rounded with four simple setae; palm slightly convex with four marginal setae, distal margin crenulated; dactylus with a spine in the distoventral angle and a group of setae. pErEopods 2-3 ( Fig. 9A-B). Similar in shape and size. Carpus triangular with three apical setae; propodus elongated, cylindrical, 2.1-2.2 times longer than wide, ventral margin slightly curved with two long setae, distoventral angle with a denticulate sensory spine; dactylus curved with one spine and a group of distal setae.
pErEopods 4-7 ( Fig. 9C-F). Similar in shape and size. Carpus trapezoidal with a sensory spine at the ventrodistal margin and three simple setae, external margin with a plumose sensory seta; propodus cylindrical with a denticulate sensory spine at the distal inner angle; dactylus curved. Pereopod 7 propodus with setulated scales and two robust pectinate spines on internal angle. Propodus of all pereopods with plumose sensory setae.

Distribution and habitat
Central coast of Oaxaca, from Agua Blanca to Estacahuite Beach. In coral, tubes of sabellariids, rocks and algae; intertidal to subtidal (7 m).

Remarks
Mesanthura antenniformis sp. nov. differs from previously recorded species of Mesanthura in the following unique characteristics: second article of antenna strongly projected and winding on the distal margin; palm of pereopod 1 straight. Between the three eastern Pacific species (Table 1), M. antenniformis sp. nov. is more similar to M. occidentalis, described from Point Conception, California, by the following characteristics: (1) last article of mandibular palp with five setae, (2) dorsal surface of the telson with some setae; however, differs because in that M. antenniformis sp. nov. has a dense pigmentation pattern, the palm of pereopod 1 is straight with the distal margin crenulate, propodus of pereopod 2 with setulated scales, apical part of the telson slightly emarginated and with six pair of setae, while, M. occidentalis has a slightly pigmented body in a circular pattern, palm of pereopod 1 medially projected, propodus of pereopod 2 with cuticular scales and the telson has eight pairs of setae.
AntEnnA (Fig. 11C). Peduncle with five articles; articles 2-5 with grooved external margin, article 2 sub-square; article 3 shorter than the others; article 4 square; last article 1.3 times as long as article 4 with a group of apical setae; flagellum 0.6 times as long as last peduncle article with four articles decreasing distally and with numerous fine setae.
MAxillipEd (Fig. 11D). Palp with three articles. Article 1 rectangular, 1.3 times as wide as long with a long seta in the internal distal angle; article 2 with two setae in the inner angle; article 3 oblique, with five setae, one proximal and two distal plumose.
MAxillA (Fig. 11E). Slender, bent distally with five teeth. MAndiBlE (Fig. 11F). Symmetrical; palp with three articles, article 1 rectangular, almost half the length of second; article 2 with an apical seta; article 3 with eight serrated robust setae. Incisor with three teeth; lacinia mobilis with four denticles and molars rounded.  pErEopod 1 (Fig. 12A). Subchelate; carpus triangular, rounded distally, with three long setae; propodus oval, 2 times as long as wide, palm projected medially with crenulated margin, proximal region with a row of four setae, distal region with a group of smooth setae; dactylus reaching the projection of the palm with two long setae in internal distal angle.
pErEopods 2-3 ( Fig. 12B-C). Similar in shape and size. Carpus triangular, with three apical setae; propodus sub-cylindrical, 2.2 times as long as wide in P2 and 2.7 times as long as wide in P3, internal margin with scales, ventrodistal angle with a denticulate sensory spine; distal margin of dactylus with a spine and a group of smooth and plumose setae.
pErEopods 4-7 ( Fig. 12D-G). Similar in shape and size. Carpus sub-pentagonal with a sensory spine on the ventrodistal margin, external margin with a plumose sensory seta; propodus cylindrical, slightly curved, internal margin with setulated scales; ventrodistal angle with a denticulate sensory spine and two pectinate spines in P7; dactylus with a denticle in the internal proximal margin.
uropodAl protopod (Fig. 13F). Rectangular, 1.6 times as long as wide with a row of plumose setae on the inner margin.

Distribution and habitat
Known only in the type locality, Estacahuite Beach, Oaxaca. In coral rock; subtidal (4 m).

Remarks
Mesanthura estacahuitensis sp. nov. differs from previously recorded species of Mesanthura by the following unique characteristics: pigmentation pattern, last article of mandibular palp with eight setae, palm of pereopod 1 crenulated and projected medially. Mesanthura estacahuitensis sp. nov. is more similar to M. nubifera, described from Turner Island, Sonora than to the other species (Table 1) as follows: (1) projection to palm of pereopod 1, (2) mandible, (3) shape and dorsal ornamentation of the telson. However, in M. estacahuitensis sp. nov. the distal article of the antennular flagellum has four aesthetascs, flagellum of antenna with four articles, last article of maxillipedal palp with three plumose setae, internal margin of the carpus and propodus of the pereopods 2-7 with setulated scales and 1-2 simple setae, apical region of the telson with three pairs of simple setae and one pair of plumose setae, while M. nubifera has antennule with five aesthetascs, antennal flagellum with one article, last article of maxillipedal palp with one plumose seta and two pectinate setae, carpus and propodus of the pereopods 2-7 with cuticular scales and up to seven simple setae, and telson with nine pairs of apical setae.   Paratypes MEXICO • 1 ♂ (body length 7.3 mm); same collection data as for holotype; UMAR-PERA 549 • 12 ♀♀, 1 ♂; same collection data as for holotype; UMAR-PERA 550.

Description
Holotype (♀, UMAR-PERA 548) Body (Figs 14A-B, 20E). Length 7.9 mm, 8.4 times as long as wide with pigment in the cephalon and margins of each somite; body proportion: C<1>2≥3<4>5>6>7. Cephalon 1.2 times as long as wide, rostrum as long as the lateral angles of cephalon, base of the mouthparts with two sharp spines. Pereonite 7 rectangular, 1.3 times as wide as long; pleonites 1-5 fused, broadened distally, slightly longer than pereonite 7; telson linguiform, narrow distal region, mid-distal region with a group of seven setae, apex slightly excavated with three pairs of setae; a pair of the statocysts. AntEnnulE (Fig. 14D). Peduncle with three articles. Articles 1 and 2 with plumose sensory setae; article 2 rectangular, slightly more than half the length of the first with six long distolateral setae; article 3 sub-equal in length to second with one long seta in the external distal angle and two in the internal one; flagellum with three articles, last tiny article with three aesthetascs and two smooth setae.
AntEnnA (Fig. 14E). Peduncle with five articles. Article 2 with ventrodistal angle projected to article 3; flagellum with four articles with numerous thin setae. MAxillipEd (Fig. 14F). Palp with three articles; article 1 with concave external margin; article 2 larger to the others with sinuous internal margin; distal article subcircular with a row of distal setae.
MAxillA (Fig. 14G). With eight distal teeth. MAndiBlE (Fig. 14H). Symmetrical; palp with three articles, article 1 sub-equal in length to the second with a long pectinate seta; article 2 with three pectinate setae and setulated scales in dorsal margin; article 3 small, 0.4 times as long as second, with four distal setae; incisor with four teeth; lacinia mobilis with 11 denticles and molars with two rounded tubercles.
pErEopod 1 (Fig. 15A). Subchelate; basis with dorsodistal angle lobate; carpus subtriangular, distal angle projected transversally; palm concave with a strong proximal tooth; proximal margin with six setae, distal margin with eight setae; internal margin of dactylus slightly concave with a cuticular ridge; unguis slightly more than half the length of dactylus with a slight curvature distally.    Fig. 15B-C). Similar in shape and size. Merus internal margin with cuticular ridges and numerous setae; carpus triangular, distal margin with a denticulate seta; palm with numerous setae and setulated scales, ventral angle with a denticulate sensory spine and a group of smooth setae. pErEopods 4-6 ( Fig. 15D-F). Similar in shape and size. Merus margin with cuticular ridges; carpus subtriangular, truncated distally with a simple sensory spine and simple setae; propodus cylindrical, 2-2.1 times as long as wide in P4 and P5, 2.3 in P6, internal margin with setulated scales and simple setae, ventrodistal angle with a denticulate sensory spine and simple setae.
pErEopod 7 (Fig. 15G). Slenderer than the preceding ones, propodus 3.3 times as long as wide, ventrodistal margin with setulated scales and one denticulate sensory spine and two pectinate spines; lateral margins of dactylus with setulated scales.
Male (dimorphic characters; based on the paratype ♂, UMAR-PERA 549) Body. Mid-region of the cephalon (Fig. 14C) with a poorly developed spine. AntEnnulE (Fig. 16E). Peduncle with three articles; article 1 and 2 with plumose sensory setae; article 2 with six long setae in the external distal angle; flagellum with nine articles, distal article with three aesthetascs.
plEopod 2 (Fig. 16G). Endopod and exopod sub-equal in length; exopod surrounded distally by 11 plumose setae; endopod surrounded distally by seven plumose setae; male appendix thin, longer than the branches, emerging from the middle proximal part of the endopod, ending in a pointed apex.

Distribution and habitat
Known only from the type locality, Estacahuite Beach, Oaxaca. In coral rock; subtidal (4 m).

Remarks
Skuphonura oaxaquensis sp. nov., and three other species of genus: S. kensleyi Brusca & Müller, 1991, S. itapuca Kensley, 1980and S. lindae Menzies & Kruczynski, 1983 (Table 2), share the following two characters: anterior margin of the cephalon as wide as the posterior margin and the anterolateral lobes are sub-equal to the rostral process, while in S. ecuadorensis Kensley, 1980 andS. laticeps Barnard, 1925, the anterior margin of the cephalon is wider than the posterior and the lobes are longer than the rostral process.
Skuphonura itapuca, described from Nichteroy, Rio de Janeiro, Brazil, is the closest species to S. oaxaquensis sp. nov. by the following characteristics: (1) absence of a mid-ventral spine in the pereonite 1, (2) mid-ventral region of cephalon with two processes, (3) second article of mandibular palp with three long setae. However, in S. oaxaquensis sp. nov. the body is partially pigmented, cephalon slightly wider medially, flagellum of antennule with three articles, distal article with three aesthetascs, flagellum of antenna with four articles, and carpus of pereopod 1 is externally projected and palm with one proximal tooth; while, S. itapuca lacks pigment, anterior margin of the cephalon is slightly wider than the posterior, flagellum of antennule with two article and two distal aesthetascs, flagellum of antenna with one article, carpus of pereopod 1 projected apically and palm with one proximal and one distal spine. Skuphonura oaxaquensis sp. nov. and S. kensleyi, described from Santa Marta, Punta de Betín, Colombian Caribbean, are similar by the following characteristics: (1) pigmentation pattern, (2) cephalon slightly wider medially, (3) antennular flagellum, (4) carpus of pereopod 1. However, in S. kensleyi the pereonites and pleon have reticulated pigmentation, antennular flagellum with one aesthetasc, antennal flagellum with one article, the second article of the mandibular palp with two distal setae and three proximal setae, lacinia mobilis with six denticles, and palm of the pereopod 1 has a medial tooth; while, in S. oaxaquensis sp. nov. the reticulated pigmentation is partial in pereonite 4 and pleon.
Skuphonura oaxaquensis sp. nov. differs from the preceding species by the following unique characteristics: (1) body pigmentation, (2) last article of mandibular palp with four setae, (3) lacinia mobilis with 11 denticles, (4) inner margin of the second article of maxillipedal palp sinus, and (5) Table 3 Etymology This species is named after Mexico, the country where the second species of the genus is described. Paratypes MEXICO • 1 ♂ (body length 3.9 mm); same collection data as for holotype; UMAR-PERA 562 • 3 ♀♀, 2 ♂♂; same collection data as for holotype; UMAR-PERA 563.

Description
Holotype (♀, UMAR-PERA 561) Body (Figs 17A, 20F). Length 3.7 mm, 9.9 times as long as wide with a pigment line on the cephalon and pereonites 2-6; body proportion: C<1>2<3<4=5>6>7. Cephalon as long as wide, 0.4 times as long as pereonite 1, rostrum as long as lateral angles; eyes small, rounded. Pereonite 1 long compared to the others, pereonite 7 the shortest. Pleon sub-square, 1.4 times as long as pereonite 7; pleonites 1-5 fused with ventrolateral suture lines, distal margin of pleonite 6 emarginated. Telson linguiform, 2.3 times as long as wide with a pair of proximal statocysts; dorsal surface squamous with a row of distal and medial setae, apex with a small excavation with three pairs of setae, two short and one long. AntEnnulE (Fig. 17B). Peduncle with three articles. Article 1 and 2 with plumose sensory setae; article 2 with four long setae; article 3 with four long setae on the external margin and one on the internal distal angle; flagellum with three articles, second article 3.6 times as long as third, article 3 with three aesthetascs.
AntEnnA (Fig. 17C). Peduncle with five articles. Article 2 larger compared to the others, 1.2 times as long as wide and 2.2 times as long as the third one, article 3 sub-equal to article 4, article 4 square with simple and sensory setae in the internal distal angle, last article 1.3 times as long as article 4, distal margin with a group of smooth and sensory plumose setae; flagellum with three articles, article 1 visible, distal articles smaller, difficult to distinguish with numerous setae.
MAxillipEd (Fig. 17D). Palp with two articles, first article with one proximal seta, one medial and two distal; article 2 oblique with five setae. Endite absent.
MAxillA (Fig. 17E). With six distal teeth. MAndiBlE (Fig. 17F). Symmetrical; palp with three articles, article 1 with one seta; article 2 with four long setae; article 3 reduced, 0.25 times the length of the article 1 with a robust denticulate seta; incisor with three teeth; lacinia mobilis with four denticles and molar blunt.
pErEopod 1 (Fig. 18A). Subchelate; carpus triangular, apically rounded with a cuticular ridge and seven simple setae; propodus oval, 2 times as long as wide, palm convex with a cuticular ridge and a row of eight setae; dactylus with a long seta in the ventrodistal angle; unguis longer than dactylus. pErEopods 2-3 ( Fig. 18B-C). Similar in shape and size. Carpus triangular with an apical denticle and two robust setae; propodus 1.9 times as long as wide, internal margin with 4-5 simple setae and one ventrodistally denticulate sensory spine, dorsal margin with a simple seta. pErEopods 4-6 ( Fig. 18D-F). Similar in shape and size. Merus inner margin denticulate; carpus trapezoid, ventrodistal margin with a simple sensory spine and a plumose sensory seta in the dorsal margin; propodus cylindrical, internal margin with setulated scales and two simple setae, ventrodistal angle with one denticulate sensory spine.
pErEopod 7 (Fig. 18G). Similar to pereopods 4-6, slender. Propodus 2.6 times as long as wide, ventral margin with one simple seta and setulated scales, ventrodistal angle with one denticulate sensory spine and two pectinate spines; dactylus with setulated scales on ventral and dorsal margins. Basis of all pereopods with simple and plumose sensory setae.
plEopod 1 (Fig. 19A). Protopod with three retinaculae and two setae on the inner margin; exopod operculiform, 2.1 times as long as wide and 2.6 times as wide as endopod, internal proximal margin   with a simple seta, distal margin surrounded by 29 plumose setae; endopod surrounded distally by four plumose setae.
Male (dimorphic characters; based on the paratype ♂, UMAR-PERA 562) AntEnnulE (Fig. 19E). Peduncle with three articles; article 1 almost twice as long as second, outer margin with plumose sensory setae; article 2 sub-square, outer margin with three long setae and sensory setae in distal margin; article 3 with three long setae in the dorsodistal angle and two on the ventral one; flagellum with four article, article 1 tiny; article 2 with a group of long aesthetascs; distal article with three aesthetascs and simple setae.
pErEopod 1 (Fig. 19F). Similar to the female; carpus triangular, rounded distally with a cuticular ridge and simple setae; palm slightly convex with a cuticular ridge and seven short marginal setae, mesial region with a row of smooth and pectinate setae.

Distribution and habitat
From Ixtapa, Guerrero to Huatulco, Oaxaca. In coral, coral rock, algae, tubes of sabellariids and sand; intertidal to subtidal (6 m).

Remarks
Tinggianthura alba Chew, Abdul-Rahim & Haji Ross, 2014, described from Pulau Tinggi, Johor, Malaysia, is the only other species of this genus and differs from T. mexicana sp. nov. by having the following unique characteristics: body slightly pigmented; article three of mandibular palp with one pectinate seta; pleopod 1 with inner margin of protopod with two distal setae and exopod with inner proximal seta; and telson and uropodal exopod with scales on dorsal surface. Tinggianthura mexicana sp. nov. is similar to T. alba by the following characteristics: (1) the article 3 of the mandibular palp is almost a third of 1, (2) maxillipedal palp with two free segments, (3) palm of the pereopod 1 without a marginal projection, and (4) pleon as long as wide. The new species differs from T. alba by (1) distal setae of telson, (2) antennal flagellum, (3) lacinia mobilis, (4) molar process, and (5) palm of pereopod 1. While in T. alba the telson has three setae on the lateral margins and eight on the dorsal surface, the antennal flagellum has two articles, lacinia mobilis with five denticles, molar process is strongly projected, and the palm of pereopod 1 has many setae. In comparison, in the new species the telson has five lateral and 10 dorsal setae, antennal flagellum with three articles, lacinia mobilis with four teeth, molar process is truncated, and palm of the pereopod 1 with eight robust setae (Table 3).

Discussion
Although the Anthuridae are the largest and most widespread anthuridean family (Poore 2001), the taxonomic knowledge of the group is very limited in some regions of the world (e.g., eastern Pacific). Also, many genera are very widespread, and probably old, such as Cortezura, Skuphonura and Tinggianthura, which are represented by few species having been recorded only once and with restricted distribution, so it could be thought that these species probably present a high endemism as mentioned Kensley & Schotte (2000).
Among the 26 genera of Anthuridae known in the world, five have been recorded in the tropical eastern Pacific, Cortezura, Cyathura Norman & Stebbing, 1886, Haliophasma Haswell, 1881, Mesanthura and Skuphonura (Espinosa-Pérez & Hendrickx 2001. With the present study, the number of genera increases to seven, recording for the first time Amakusanthura and Tinggianthura and the number of species increases from nine to 15. Also, Tinggianthura mexicana sp. nov. is the second species described in the genus. Likewise, Skuphonura oaxaquensis sp. nov. is the second species of the genus described from the tropical eastern Pacific, extending the distribution range of the genus from the coast of Ecuador to Oaxaca, Mexico. This study is the first work about anthurideans in the north eastern Pacific of Mexico, the discovery of these six new species is indicative of the marine biodiversity that still needs to be discovered from this region and, in general, from the Mexican Pacific (García-Madrigal et al. 2012;Bastida-Zavala et al. 2013;Jarquín-Gonzalez & García-Madrigal 2013). Therefore, an exhaustive sampling at other localities, other habitats, or even sampling in deeper waters from the Mexican Pacific would reveal more undescribed species of these anthuridean isopods.