Typton granulosus, Ayón-Parente, Manuel, Hendrickx, Michel E. & Galvan-Villa, Cristian Moises, 2015

Ayón-Parente, Manuel, Hendrickx, Michel E. & Galvan-Villa, Cristian Moises, 2015, A new species of the genus Typton Costa (Crustacea: Decapoda: Palaemonidae: Pontoniinae) from the eastern tropical Pacific, Zootaxa 3926 (3), pp. 430-438 : 431-437

publication ID	https://doi.org/ 10.11646/zootaxa.3926.3.7
publication LSID	lsid:zoobank.org:pub:0747BBEA-C1DC-489A-88F0-27AD9A356C4E
DOI	https://doi.org/10.5281/zenodo.6093944
persistent identifier	https://treatment.plazi.org/id/FB61BB57-FF9E-FFE3-FF38-7C796A5EEDCE
treatment provided by	Plazi
scientific name	Typton granulosus
status	sp. nov.

Treatment

Typton granulosus View in CoL sp. nov.

Figs. 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5

Material examined. Holotype: female (pocl/cl 1.8/ 2.2 mm), Isla Colorada, Bahía Chamela, Jalisco, Mexico, 19°32´24´´N 105°5´32´´W, 7 m, Scuba, 12 Nov 2013, LEMA CR-463. Paratypes: 1 female (pocl/cl 1.8/ 2.2 mm), same data, LEMA CR-464. 1 ovigerous female (pocl/cl 2.1/ 2.5 mm), Barra de Navidad, 19°11´24´´N 104°41´38´´W, low intertidal, 11 Sep 1982, EMU-8828. 2 ovigerous females (pocl/cl 2.2–2.8/ 2.6–3.3 mm), off Río Suchiate, Gulf of Tehuantepec, 14°21´48´´N 92°34´24´´W, 64 m, 13 May 1992, EMU-8842.

Description. Carapace ( Fig. 1 View FIGURE 1 A–F) slightly compressed, glabrous, smooth, longer than wide. Rostrum short, simple, triangular, about 0.45 length of ocular peduncle, slightly curving upward; paraorbital processes well developed, usually slightly exceeding the rostrum and reaching anterior margin of the cornea in lateral view, exceeding by half of its length level of anterior pterygostomial margin, weakly divergent in dorsal view, pointing slightly upward in lateral view. Orbit feebly demarcated, without distinct inferior orbital angle or antennal spine; pterygostomial margin slightly produced anteriorly, rounded to somewhat angular.

Eyes ( Fig. 1 View FIGURE 1 A–F) well developed, cornea rounded, weakly dilated, obliquely set on stalk; inner margin of stalks straight; anterior margin of cornea reaching distal third of first segment of the antennular peduncle.

Abdomen ( Fig. 1 View FIGURE 1 A, D) elongated, smooth, glabrous, about 2.5 times CL; first to fourth somites with broadly rounded pleura, fifth bluntly angular; sixth segment 0.25 of CL, posterolateral angle spiniform, posterodorsal margin ( Fig. 1 View FIGURE 1 G) without median tooth; fifth and sixth segments subequal in length; first to sixth sternites unarmed.

Telson ( Fig. 1 View FIGURE 1 G) moderately slender, tapering, about 2.5 times length of sixth somite, 2.5 times longer than wide; lateral margins convex, converging to a broad, rounded posterior margin; dorsal surface with two pairs of well-developed spines, each about 0.14 times telson length, approximately at 0.1 and 0.5 of telson length; 3 pairs of posterior spines, lateral pair minute, intermediate pair long, slender, plumose, about 0.15 of telson length, median pair as long as intermediate, slightly stouter, one simple seta between median and intermediate spines.

Antennular peduncle ( Fig. 2 View FIGURE 2 A) slender, proximal article subcylindrical, 3.3 times as long as distal width; statocyst well-developed, with statolith; stylocerite acute, short, about 0.1 times length of article; intermediate article shorter than distal article, their combined length equal to about 0.4 of proximal article length; lateral (= superior) flagellum short, stout, with 8–9 groups of aesthetascs, short ramus distally, longer ramus with 5–6 segments; mesial (= lower) flagellum long, with 9–10 segments.

Antenna ( Fig. 2 View FIGURE 2 B) basicerite stout, unarmed, conspicuous antennal gland tubercle medially; carpocerite slender, subcylindrical, reaching distal margin of intermediate antennular peduncular segment, about 8 times as long as wide, 2.3 times merocerite length, flagellum slender, short, about 4 times carpocerite length; scaphocerite reduced, about 0.4 carpocerite length, 3 times as long as proximal width, tapering distally, terminally rounded, without distolateral spine or setae.

Mandibles ( Fig. 2 View FIGURE 2 C, D) with slender corpus, without palp; molar processes slender, tapering, obliquely truncate distally, left with several spines, right distally acute, with two stout processes; incisor process slender, tapering, obliquely truncate distally, with 6 (left) and 7 (right) small acute teeth.

Maxillula ( Fig. 2 View FIGURE 2 E) palp bilobed, upper lobe reduced, lower lobe larger, with long slender, simple terminal seta; upper lacinia well developed, 1.3 times longer than broad, distal margin with double row of about 10 stout, denticulate spines, and 8 plumodenticulate setae; lower lacinia slender, tapering distally, distal setae spiniform, ventral setae plumose.

Maxilla ( Fig. 2 View FIGURE 2 F) with short slender, non-setose palp; basal endite well developed, bilobed, upper lobe larger and broader than lower, lobes each with about 13 slender, feebly setulose setae; coxal endite obsolete; scaphognathite well developed, slender, 4 times longer than width at mid length, with marginal plumose setae, anterior lobe 2.5 times longer than wide, medially concave.

First maxilliped ( Fig. 2 View FIGURE 2 G) with short tapering palp, one subterminal simple seta; basal endite large, densely spinulated medially, spines minutely denticulate; coxal endite reduced, non setose; exopod with well-developed setose caridean lobe, flagellum slender, with single long simple terminal setae; epipod bilobed.

Second maxilliped ( Fig. 2 View FIGURE 2 H) dactylar article broad, 3 times longer than maximal width, densely spinose medially, spines robust, minutely denticulate; propodal article distomedially rounded, not produced, marginal spines similar to dactyl; carpus, merus, and ischio-basis without special features; exopod flagellum slender, four long plumose terminal setae; epipod ( Fig. 2 View FIGURE 2 I) subrectangular.

Third maxilliped ( Fig. 2 View FIGURE 2 J) antepenultimate article broad, penultimate article twice as long as ultimate, 0.6 times as long as the antepenultimate article; exopod reaching slightly beyond anterior margin of antepenultimate article, two short simple, subdistal setae, four slender plumose, distal setae.

First pereiopods ( Fig. 3 View FIGURE 3 A, B) exceeding second minor pereiopod by length of the palm. Palm of chela slender, swollen in appearance, subcylindrical, slightly compressed, about 2.5 times as long as wide. Fingers robust, short and stout, about 0.45 of palm length, strongly spatulate, cutting edges entire, that of dactyl thicker, tip with three small stout teeth, fixed finger tip with three teeth, cutting edge thin, outer and mesial surfaces of fingers bearing some tufts of serrulate setae. Carpus about 4.7 times longer than wide, about 1.8 times as long as palm, tapering proximally. Merus slender, about 6.4 times longer than broad, 1.3 times as long as carpus. Ischium short, stout, broader than merus, about 3 times as long as broad, 0.6 times length of merus. Basis shorter and more slender than ischium.

Second pereiopods unequal. Major pereiopod ( Fig. 3 View FIGURE 3 C, D) exceeding minor cheliped by length of dactyl. Palm of chela stout, slightly compressed, about twice as long as wide; mesial surface with small, triangular, spiniform granules, which extend on lower and upper margins. Fingers robust, short, stout, spatulate, about 0.67 width of palm. Dactyl with cutting edge entire, tip terminating in a corneous claw. Fixed finger with proximal molar tooth ending in corneous claw, outer and mesial surfaces of fingers with numerous tufts of setae. Carpus stout, short, 1.2 times longer than broad, strongly extended distally, ventro-mesial angle with 1 to 2 denticles. Merus short, stout, 1.5 times longer than broad, slightly shorter than carpus, dorsal and ventral margins convex, ventral margin bearing small acute tubercles. Ischium about twice longer than broad, slightly longer than merus. Minor second pereiopod ( Fig. 3 View FIGURE 3 E–G) with palm about 1.8 times longer than maximal depth, oval in section, converging distally, with small, triangular, spiniform granules on mesial surface and dorsal and ventral margins, dactyl spatulate, compressed, about 0.4 of palm length, 1.75 times longer than maximal depth, dorsal margin curved with some tufts of long setae, cutting edge almost straight, entire, with subdistal concavity, ending in strong tooth; fixed finger about twice longer than proximal width, cutting edge deeply grooved, medial flange sharp, entire, lateral flange broadly triangularly expanded; carpus 0.4 of carpal length palm, smooth, about 1.5 times as long as maximal height, much wider distally; merus 1.5 times as long as broad, about 0.9 of carpal length and 0.4 of palm length, with small conical teeth on ventral surface; ischium about 1.5 times length of merus, unarmed.

Third pereiopod ( Fig.4 View FIGURE 4 A–C) stout, reaching distal margin of carpus of major cheliped. Dactyl biunguiculate, compressed, about 0.3 propodus length and twice longer than its basal width, ventral margin of corpus slightly concave, crenulate, with acute, triangular, ventrally pointing secondary unguis; terminal unguis distinctly demarcated, about half as long as corpus, strongly curved, not crenulated proximally; propodus about 3.3 times as long as wide, ventral margin with 2–5 irregularly spaced spines, distal pair of stouter spines fringing base of dactylus; carpus about 0.9 length of propodus, nearly 3 times as long as distal width, unarmed; merus about twice as long as broad and 1.3 times length of carpus, unarmed; ischium about 0.9 times length of merus, unarmed.

Fourth pereiopod ( Fig. 4 View FIGURE 4 D) similar to third; dactyl biunguiculate, twice as long as basal width; ventral margin corpus conspicuously crenulated, with triangular, ventrally pointing secondary unguis; terminal unguis equal or slightly shorter than half-length of corpus; propodus about 3.5 as long as wide; ventral margin with 1 to 3 spines and distal pair of stouter spines; carpus slightly shorter than propodus, about 2.5 times as long as distal width; merus about 2.5 times as long as wide; ischium about as long as merus, 2.5 times longer than distal width.

Fifth pereiopod ( Fig. 4 View FIGURE 4 E, F) more slender than third and fourth, with dactyl biunguiculate, compressed, about 0.3 of propodus length, 2.5 times as long as basal width, unguis well demarcated, about 0.67 of corpus length, 2.5 times longer than basal width, curved, crenulated proximally, corpus 1.3 times longer than basal width, with dorsal and ventral margins slightly convex, ventral margin crenulated, with strong, subacute, ventrally pointed secondary unguis; propodus about 6 times as long as broad; ventral margin with one subdistal and one distal spine, distal 0.3 with brush of grooming setae; carpus 0.7 times length to propodus, about 2.5 times as long as distal width, unarmed; merus about 3.6 times as long as wide and 1.4 length of carpus, unarmed; ischium about 0.7 length of merus, unarmed.

First female pleopod ( Fig. 5 View FIGURE 5 A) endopod reaching half-length of exopod, margins with long plumose setae. Second female pleopod ( Fig. 5 View FIGURE 5 B) 0.9 length of exopod; appendix interna ( Fig. 5 View FIGURE 5 C) inserted at mid-length of mesial margin, with long, lateral plumose seta and 8 subdistal cincinnuli.

Uropods protopod ( Fig. 1 View FIGURE 1 G) unarmed; exopod ( Fig. 1 View FIGURE 1 G) oval, slightly longer than telson, outer margin nonsetose, distolateral margin ( Fig. 5 View FIGURE 5 D–I) serrate in distal third, with 5–9 acute or subacute teeth, distolateral angle with acute tooth, reaching approximately half-length of stout, terminal spine; diaeresis inconspicuous; endopod ( Fig. 1 View FIGURE 1 G) slightly longer than exopod, proximal parts of lateral and mesial margins non-setose.

Numerous ova, suboval, with mean diameter 0.4 mm.

Variation. The most obvious variable character are the paraorbital processes, which can reach the basis of the cornea ( Fig. 1 View FIGURE 1 A–E) or half of the ocular peduncle length ( Fig. 1 View FIGURE 1 F). The pterygostomial region varies from broadly rounded ( Fig. 1 View FIGURE 1 C–E) to more angularly protruding ( Fig. 1 View FIGURE 1 F). The number of spines on the ventral margin of the propodi in the third and fourth pereiopods vary from 2 to 5 and from one to 3, respectively. There is also a significant variation in the number of teeth on the distolateral margin of the uropodal exopod, ranging from 5–9 (not including terminal tooth adjacent to strong spine), and in the number of mobile spines adjacent to terminal tooth, ranging from 1 to 3 ( Fig. 5 View FIGURE 5 D–I).

Type locality. Isla Colorada, Bahía Chamela, Jalisco, Mexico.

Etymology. The name of the species is derived of the latin granum (grain), which makes reference to the minute granules present on the mesial surface of the major second pereiopod.

Distribution. Known from Bahia Chamela and Barra de Navidad, Jalisco, and off Río Suchiate, Gulf of Tehuantepec, Chiapas, Mexico.

Ecology. The specimens of Typton granulosus sp. nov. from Bahía Chamela were collected on Holothuria (Halodeima) inornata Semper, 1868 (Echinodermata: Holothuridae ), a tropical species commonly found in the Mexican Pacific and distributed from the Gulf of California to Ecuador ( Solís-Marín et al. 2009). The sea cucumber was found in a mixed sand-rubble bottom area near Isla Colorada. Typton granulosus sp. nov. probably lives in association with this holothurid. Other species of Typton (e.g., T. tortugae and T. wasini Bruce, 1977 ) are known to be commensal of sponges ( Bruce 1978, 1987).

Remarks. Typton granulosus sp. nov. is close to Typton serratus from the eastern Pacific, T. holthuisi from the central Atlantic, T. spongicola from the eastern Atlantic, and T. fapespae and T. prionurus , both from the west Atlantic. These five species have the distal part of the outer margin of the uropodal exopod serrated. Typton granulosus sp. nov. can be easily separated from T. holthuisi , T. fapespae , and T. spongicola by the absence of a strong median tooth on the posterodorsal margin of the sixth abdominal somite ( De Grave 2010, Fig. 1 View FIGURE 1 D; Almeida et al. 2014, Fig. 1 View FIGURE 1 F; Bruce 2009, Fig. 3 View FIGURE 3 J), the rostrum is shorter than the paraorbital processes, and the number of teeth on the distolateral margin of uropods is higher [5–9 vs. 3–4 in T. holthuisi ( De Grave 2010, Fig. 1 View FIGURE 1 K, L), 2–6 in T. fapespae ( Almeida et al. 2014, Fig. 3 View FIGURE 3 I–L), and 3 in T. spongicola ( Bruce 2009, Fig. 2 View FIGURE 2 D, E)].

Given the morphological similarity of Typton granulosus sp. nov. and T. prionurus , they can be considered sister species occurring on both sides of the American continent. Typton granulosus sp. nov. can be distinguished from T. prionurus by a proportionally shorter rostrum in relationship to the ocular peduncles length, and by the fact that the antennal peduncle reaches the distal margin of the penultimate antennular segment in lieu of the antennal peduncle reaching the end of the antennular peduncle ( Holthuis 1951, Fig. 52a, b); the palm of the major cheliped is proportionally longer than wide (twice vs. 1.67 times) and the carpus is shorter in relation to the chela (0.25 vs. 0.4) in T. granulosus ; the mesial surface of the palm of the major and minor chelae of T. granulosus bears minute, triangular, spiniform granules which are absent in the Atlantic species. Typton granulosus sp. nov. also differs from T. serratus by the size of the rostrum, proportionally longer than the paraorbital processes in the latter ( Holthuis 1951, Fig. 53b); also, the palm of the major cheliped is slightly convex on dorsal and ventral margins in Typton granulosus sp. nov., while in T. serratus those margins are straight ( Holthuis, 1951, Fig. 53i); the serration of the uropodal exopod is confined to the distal third in T. granulosus while the serrated region is much larger in T. serratus ; finally, the pair of dorsal spines on the telson is widely separated in T. granulosus vs. closely set together, in the anterior quarter of the telson, in T. serratus ( Holthuis 1951, Fig. 53c).

Typton granulosus sp. nov. can be easily distinguished from all other eastern tropical Pacific species of Typton by the presence of a serration on the laterodistal margin of the uropodal exopod.