Pseudorhachotropis longipalpus, Ortiz & Winfield & Chazaro-Olvera, 2024

Ortiz, M., Winfield, I. & Chazaro-Olvera, S., 2024, A new genus and species of Eusiridae (Crustacea, Amphipoda, Amphilochidea) from bathyal sediments off the southwestern Gulf of Mexico, Zootaxa 5468 (3), pp. 569-580 : 571-579

publication ID	https://doi.org/ 10.11646/zootaxa.5468.3.9
publication LSID	lsid:zoobank.org:pub:5BD0F46F-CE0B-44D1-BEA9-F900E90A935A
DOI	https://doi.org/10.5281/zenodo.12190437
persistent identifier	https://treatment.plazi.org/id/3357879B-B232-FFAB-FF50-7093194CFB1F
treatment provided by	Plazi
scientific name	Pseudorhachotropis longipalpus
status	sp. nov.

Treatment

Pseudorhachotropis longipalpus sp. nov.

( Figs 2–5 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Diagnosis. The same as the genus.

Type material. Holotype male, 6.2 mm; CNCR37074 , dissected. Type locality. Bay of Campeche , SW Gulf of Mexico, 20°27’58.48’’N and 94°24’48.35’’W. The material was collected from soft–bottom characterized by mud (silty–clay) sediments of terrigenous origin at 2321 m in depth, on July 08, 1965 GoogleMaps .

Etymology. This species in named after Latin longipalpus because of the long size of mandibular palp article 1.

Description. Holotype male, 6.2 mm. Body ( Fig. 2 View FIGURE 2 ): head without eyes; rostrum short, pointed, slightly directed downward; pereonal segments smooth dorsally; pleonal segments 1–3 posterodorsal teethed; urosomal segments 1–2 large with posterodorsal processes; epimeron 3 small with three–minute teeth at posteroventral corner ( Fig. 5E View FIGURE 5 ). Antenna 1 ( Fig. 3A View FIGURE 3 ) slightly longer than antenna 2, peduncle article 1, 1.4 x articles 2–3 combined, peduncle article 3 embedded; accessory flagellum 5–articulate, flagellum 12–articulate, article 1 of flagellum as length as articles 2–3 combined. Antenna 2 ( Fig. 3A View FIGURE 3 ) peduncular article 4 subequal in length to 5, flagellum 9–articulate.

Mouthparts ( Fig. 3 View FIGURE 3 ). Maxilla 1 ( Fig. 3B View FIGURE 3 ) outer plate with nine robust distal setae; inner plate with one long robust distal seta; palp article 1 naked, article 2 with four distal robust setae, two simple outer marginal setae, another inner margin, and two facial setae. Maxilla 2 ( Fig. 3C View FIGURE 3 ) outer plate wider than inner, with 15 distal simple setae; inner plate with three distal setae, other seven inner margin. Maxilliped ( Fig. 3D View FIGURE 3 ) inner plate half–length outer, with three molariform distal setae, and six anterolateral simple setae; outer plate with five long, other four short inner margin setae; palp article 1 with a lateral simple seta, another distal simple seta; article 2 as long as article 3, both settled in right angle; article 2 with seven inner margin robust setae, one distal and another outer margin robust setae; article 3 with six inner margin robust setae; article 4 half–length of article 3, set of tiny setae distal inner margin. Lower lip ( Fig. 3F View FIGURE 3 ) extended laterally, inner plate missing, mandibular lobe poorly developed, naked. Upper lip ( Fig. 3E View FIGURE 3 ) wider than long, lower margin somewhat bilobate. Left mandible ( Fig. 3G View FIGURE 3 ) with seven incisors; lacinia mobilis quadrate, with five teeth; molar a small protuberance with two large and another small robust setae, and four small rakers; palp article 1 as long as article 2, one distal robust seta article 2; article 3 half–length of article 2, with one distal robust seta. Right mandible ( Fig. 3H View FIGURE 3 ) with four incisors; lacinia mobilis subcircular, distal margin finely serrated; two subdistal robust setae palp article 2; rest of mandible like left one.

Gnathopods similar than those in genus Rhachotropis . Gnathopod 1 ( Fig. 4A View FIGURE 4 ) coxa quadrangular, slightly directed forward; basis with three setae anterior margin, and 10 setae posterior margin; ischium and merus with one seta on posterior margin; carpus posterior lobe 0.4 x long dactylus, with three distal long setae; propodus subovoidal, with three distal setae; palmar margin convex, with minute plumose setae; dactylus fixing palm. Gnathopod 2 ( Fig. 4B View FIGURE 4 ) coxa subrectangular; basis, ischium, and merus naked; carpus posterior lobe longer than dactylus, anterior and posterior margins with 6–9 setae, two plumose setae, and another one simple short seta, all distally; propodus more subovoidal than in gnathopods 1; palmar margin slightly convex with minute simple setae, palmar angle with one long robust seta, another simple seta distally; dactylus not fixing palm; gill 0.7 x long basis.

Pereopod 3 ( Fig. 5A View FIGURE 5 ) coxa subrectangular; basis to propodus slender; basis with four setae anterior margin, subequal in length to merus and carpus combined; propodus as long as merus; dactylus very short, gill half– length basis. Pereopod 4 ( Fig. 5B View FIGURE 5 ) coxa rectangular; basis to propodus slender; basis 0.9 x long merus and carpus combined, propodus with three subdistal setae posterior margin, other two distally; propodus subequal in length to merus: dactylus 0.6 x long propodus; dactylus as long as carpus; gill half–length basis. Pereopod 5 ( Fig. 5C View FIGURE 5 ) coxa subtriangular, posteroventral corner irregular; basis 0.9 x long merus and carpus combined; basis with three setae anterior and posterior margins; carpus with three setae anterior margin, other six setae posterior margin; propodus 0.6 x long merus; dactylus missing, gill 0.3 x long basis. Pereopod 6 ( Fig. 5D View FIGURE 5 ) coxa triangular, notched posteroventral corner; basis subequal in length to ischium and merus combined; carpus as long as propodus, with four setae anterior and posterior margins; propodus with three setae anterior and posterior margins; propodus 1.2 x long carpus; dactylus missing, gill 0.3 x long basis. Pereopod 7 ( Fig. 5E View FIGURE 5 ) coxa ovoidal, notched ventrally; basis as long as merus, with four setae anterior margin; merus with two setae anterior margin, four setae posterior margin, and other five distally; rest of pereopod missing.

Uropod 1 ( Fig. 6A View FIGURE 6 ) peduncle 1.2 x longer than outer ramus, one subdistal robust seta inner margin; inter–ramal robust seta, 0.2 x long outer ramus; outer ramus 1. 3 x longer than inner ramus, with three inner margin setae, another one distal robust seta; inner ramus with three inner margin setae, other two short distal setae. Uropod 2 ( Fig. 6B View FIGURE 6 ) peduncle as long as rami, with two setae outer margin, distal peduncle outer notch; rami subequal in length; outer ramus naked; inner ramus with four inner margin setae, other three outer margin setae. Uropod 3 ( Fig. 6C View FIGURE 6 ) peduncle 1.2 x longer than rami, distal margin notched; rami subequal in length; inner ramus flat, with three setae on each margin; inner ramus narrow, naked. Telson ( Fig. 6D View FIGURE 6 ) as long as wide, “V” inverted shape; incised 0.3 x posterior margin, each lobe with 1–2 robust setae.

Remarks. The new genus Pseudorhachotropis is easily distinguished for the known genera of eusirid amphipods by antenna 1 with accessory flagellum 5–articulate; mandibular molar smooth conical protuberance with large robust setae; dorsal ornaments pattern, such as pereonal segments smooth, pleonal segments 1–3 with posterodorsal teeth, urosomal segments 1–2 large posterodorsal processes; coxa 1 quadrangular, unproduced anteriorly; uropod 1 interramal robust seta present; epimeron 3 with three teeth at posteroventral corner; telson as long as wide, “V” inverted shape incised 0.3 x in length to posterior margin, each lobe with 1–2 robust setae. In addition, a distinctive morphological character is the palp article 1 long, subequal in length to article 2. Specific differences among eusirids genera are summarized in Table 1 View TABLE 1 .