Paraxiopsis, de Man, 1905

Felder, Darryl L., 2021, Description of Paraxiopsis kensleyi n. sp., a new axiid lobster from the Gulf of Mexico (Crustacea: Decapoda: Axiidea), Zootaxa 4965 (1), pp. 129-141 : 139

Key to western Atlantic species of Paraxiopsis

1. Carapace dorsally with submedian gastric carina (immediately to either side of median carina) multidentate, subdivided into row or weakly curved longitudinal arc of short teeth or spines (typically 4–8)..................................... 2

-- Carapace dorsally with submedian gastric carina sometimes marked anteriorly by a tooth, tubercle, abrupt elevation, or medially directed curvature, mostly defined as continuous or nearly continuous crest, sometimes slightly broken or weakly tuberculate ................................................................................................... 6

2. Pleonal pleura 2–4 ventral margins rounded in lateral view, at most with obtuse corner positioned ventrally to posteroventrally...................................................................................... 3

-- Pleonal pleura 2–4 ventral margins subtriangular to subquadrately truncate in lateral view, tapered to acute corner positioned ventrally or posteroventrally............................................................................. 4

3. Carapace distinctly pitted; major first cheliped merus upper margin armed with multiple spines or spinules................................................................................................ Paraxiopsis foveolatus

-- Carapace mostly smooth; major first cheliped merus upper margin armed with single spine (sometimes in addition low denticles distally)............................................................................ Paraxiopsis defensus

4. Pleonal pleura 2–4 ventral margins truncate, appearing subquadrate laterally, margins of pleura 3 and 4 weakly sloped to posteroventral corner; pleuron 2 broad, height subequal to maximum length in lateral view..... Paraxiopsis kensleyi n. sp.

-- Pleonal pleura 2–4 ventral margins appearing subtriangular laterally, strongly tapered to acute ventral corner; pleuron 2 narrow, height exceeding maximum length in lateral view........................................................... 5

5. First pereopod chela densely setose and tuberculate; pleonal pleura 2–5 lacking strong marginal spine, often with small subacute denticle on anterior margin .......................................................... Paraxiopsis granulimana

-- First pereopod chela mostly smooth, not heavily setose or conspicuously tuberculate; pleonal pleura 2–4 with strong sharp elongate (sometimes weakly hooked, rarely compound) spine on anterior margin............... Paraxiopsis spinipleura

6. Carapace dorsally with submedian carina without anterior tubercle, abrupt elevation, or sharp tooth, anterior end slightly curved medially............................................................................. Paraxiopsis vicina

-- Carapace dorsally with submedian carina marked anteriorly by tubercle, abrupt elevation, or sharp tooth................ 7

7. Carapace dorsally with submedian carina terminating anteriorly in a sharp tooth, surface overall appearing smooth, with few sparse setae; uropodal exopod dorsal surface lacking spines along either of weak longitudinal ridges proximal to transverse suture........................................................................... Paraxiopsis gracilimana

-- Carapace dorsally with submedian carina terminating anteriorly in a blunt tubercle or abrupt elevation; uropodal exopod dorsal surface with multiple small spines along lateral of two weak longitudinal ridges proximal to transverse suture........... 8

8. Carapace and pleura of pleon mostly with dense cover of short bristles........................... Paraxiopsis hispida -- Carapace and pleura of pleon relatively smooth, without dense cover of short bristles............. Paraxiopsis pindatyba

In addition to distinctions in structural morpology, predominantly orange to reddish orange coloration in Paraxiopsis kensleyi n. sp., with minimal patterning ( Fig. 3A–C ), was characteristic of freshly collected specimens of all sizes, and readily distinguishes the species from the closely related species P. spinipleura ( Fig. 3D, E ). This comparison of mature specimens was enabled only by the fortunate noctural collection of live P. spinipleura in Dominica, where several individuals were netted below a surface light while our vessel was at anchor in 11 m depth (see Acknowledgements). Immature specimens of the latter species, which represent most collections of it other than the holotype, show only early traces of the mature color pattern in life, being primarily a semi-transparent off-white ( Fig. 3F, G ), while the mature adults were uniquely patterned with violet purple to yellow orange. For other western Atlantic species, confirmed color patterns of P. hispida , P. pindatyba , P. vicina , and P. defensus remain unknown, with that suggested by Poupin (2018:82, fig. 68D) to perhaps represent P. defensus remaining of uncertain identity. However, coloration in P. foveolata , P. gracilimana , and P. granulimana has been documented in specimens from the Gulf of Mexico ( Fig. 4A–F ). In all cases, predominant pigmentation in fresh specimens of these species is shades of reddish orange, though in available examples, this pigment is somewhat more complexly patterned than seen in P. kensleyi n. sp.

Figures

FIGURE 3. Paraxiopsis kensley n. sp., male paratype, pocl 8.7 mm (USNM 1548303 = ULLZ 14979), northwestern Gulf of Mexico: A, habitus, dorsal; B, habitus, right side. P. kensleyi n. sp., male holotype (lacking minor cheliped), pocl 15.5 mm (USNM 1638661 = ULLZ 18301), northwestern Gulf of Mexico: C, habitus, left side. Paraxiopsis spinipleura, female, pocl 13.0 mm (USNM 1409793), Dominica: D, habitus, dorsal; E, habitus left side. P. spinipleura, juvenile male, pocl 5.4 mm (USNM 1547855 = ULLZ 14659), Belize: F, habitus, dorsal; G, habitus, left side.

FIGURE 4. Paraxiopsis foveata, ovigerous female, pocl 10.3 mm (USNM 1542866 = ULLZ 8402), northwestern Gulf of Mexico: A, habitus, dorsal; ovigerous female, pocl 13.0 mm (USNM 1541111 = ULLZ 5740), northwestern Gulf of Mexico: B, habitus, left side. Paraxiopsis gracilimana, male, pocl 6.7 mm USNM 1547846 = ULLZ 14645), Belize; C, habitus, dorsal; D, habitus, right side, cheliped detached; juvenile female, pocl 5.7 mm (USNM 1545577 = ULLZ 11134), Belize: E, habitus, dorsal. Paraxiopsis granulimana, male, pocl 10.9 mm (USNM 1540500 = ULLZ 4696), northwestern Gulf of Mexico: F, habitus, right side.