Macromedaeus sp. A

Macromedaeus sp. A View in CoL ( Figs. 18A–H View Fig , 19A–C View Fig )

Material Examined: 2 ñ, NMNS 8772-59–60, 3.0–4.3 × 2.3–3.1, Shitiping, Taitung County, coll. Y.-W. Tzeng, 25 March 2011.

Description: Carapace ( Fig. 18A–C View Fig ) transversely ovate, width to length ratio about 1.30–1.39, dorsal area slightly convex transversely, longitudinally; dorsal surface well covered by microscopic granules, glabrous; regions weakly defined, divided by shallow grooves. Front moderately advanced, about 0.41–0.43 times as long as carapace width, slightly deflexed ventrally, margin granulate, outer angles well marked and separated by V-shaped notch from orbital rim; divided into 2 lobes by narrow V-shaped notch, continuing posteriorly as shallow median groove on dorsal carapace. Anterolateral margin convex, granulate, divided into 4 low lobes, separated from each other by wide V-shaped or U-shaped notches with intercalated denticles; first lobe low; second and third lobe subequal in size, equilaterally triangular, tip blunt, pointing anterolaterally; fourth lobe small, pointing laterally, posterior margin continuous with carapace posterolateral margin. Posterolateral margin slightly longer than anterolateral margin, straight.

Orbits ( Fig. 18A–C View Fig ) suboval, margins granulate; inner pre-frontal supraorbital and exorbital tooth weakly developed; supraorbital margin with 2 fissures; infraorbital margin continuous. Eyes well developed, eyestalks short, stout, corneas large. Antennular fossae transversely oval; antennules folding transversely. Basal article of antenna short, subrectangular; flagellum freely entering orbital hiatus, short, tip slightly exceeding exorbital angle.

Third maxillipeds ( Fig. 19A–B View Fig ) subrectangular, length to greatest width ratio about 2.16; palp tapering distally, articles subcylindrical; merus subquadrate, length to greatest width ratio about 0.79, anterolateral angle rounded, slightly projecting, anterior margin sinuous, granulate, external surface well covered with granules; ischium subrectangular, about 1.80 times longer than merus, sulcate submedially, mesial margin cristate, serrated, lined with submarginal setae, external surface well covered with granules; exopod stout, margins slightly convex, tapering slightly toward distal end, distal end straight, external surface well covered with granules.

Thoracic sternum ( Fig. 18D View Fig ) margins cristate; sternites 1, 2 fused, external surface granulate; sternites 2, 3 and 3, 4 separated by deep and shallow sutures, respectively; sternite 4 with prominent median longitudinal line extending through half of its exposed length, lateral margins slightly convex; median longitudinal line interrupted on sternite 4 within anterior region of sternopleonal cavity, continued at posterior limit of sternite 4; sutures 4/5, 5/6 joining toward median longitudinal axis of thoracic sternum; vulvae oval, without operculum, located mesial third of sternite 5.

Chelipeds ( Fig. 18A, E–H View Fig ) subequal, moderately robust, external surface almost fully granulate, except partial surfaces of fingers. Meri moderate long, distal end extending slightly beyond carapace anterolateral margin in dorsal view, margins granulate. Carpi dorsal margin granulate proximally, longitudinal granule row bifurcated at middle area with 2 raised tubercles on each side of granule rows subdistally, forming groove appearance of dorsal margin in distal half, groove appearance continuing perpendicularly toward lower margin subdistally. Palm dorsal margin granulate with longitudinal row of tubercles, external upper surface with longitudinal row of tubercles. Fingers slightly thick, tips pointed, beige in alcohol; dactylus with 2 granulate submarginal crests, forming longitudinal groove toward subdistal end, distal area moderately deflexed, leaving small gap between fingers, 4 teeth on cutting edge with larger teeth at proximal end; pollex external surface of lower submargin with longitudinal groove, 5 teeth on cutting edge with 3 larger ones at distal end.

Ambulatory legs ( Figs. 18A View Fig , 19C View Fig ) flattened, broad, moderate in length, P3, P4 longest, coxa-to-dactylus length about 0.95 carapace width, P5 shortest, coxa-to-dactylus length about 0.73 times carapace width; surfaces entirely smooth, covered with shot setae, anterior margin of meri, carpi, propodi, dactyli denticulate, submargin of meri lined with long setae; posterior margin of meri, propodi, dactyli denticulate, dactyli with single large spine posterior to chitinous claw, single-tipped. P5 merus subrectangular, median length about 2.34 times greatest width; carpus curved, distal end distinctly wider than proximal end, median length about 1.29 times greatest width; propodus subrectangular, median length about 1.28 times greatest width; dactylus about as long as propodus, stout proximally, tapering distally, terminating in sharp, short, chitinous claw with length about 1.71 times greatest width.

Pleon ( Fig. 18D View Fig ) moderate long relative to thoracic sternum, tip of telson reaching level median to sternal condyles of P1 coxae; somites 1, 2 trapezoidal, much wider than long; all somites free, base of somite 3 widest, distal somites progressively narrower, combined lateral margin straight; somite 6 subrectangular, much wider than long, lateral margins slightly convex; telson subtriangular, angles rounded, basal width about as long as median length.

Distribution: Known only from the coast of East Taiwan.

Remarks: The morphology of Macromedaeus sp. A resembles that of M. adelus Mendoza, 2021 , M. distinguendus (De Haan, 1835) , and M. voeltzkowi ( Lenz, 1905) , particularly in having four teeth on the anterolateral margins of the carapace ( Fig. 18A, B View Fig ; Serène 1984: 178, pl. XXV F; Mendoza 2021: 470, 474, figs. 5A, 7A; Yuan et al. 2022: 8, 10, 16, figs. 3A, B, 4A, B, 8A, B). However, Macromedaeus sp. A can be distinguished from M. adelus by the following features: 1) smaller carapace width/length ratio (1.30–1.39 versus mean 1.59; Mendoza 2021: 469); 2) carapace regions are weakly defined and separated by shallow grooves (versus well-defined, separated by deep, acute furrows) ( Fig. 18A, B View Fig ; Mendoza 2021: 471–472, fig. 5A); 3) the dorsal carapace region 6L is divided by an oblique furrow (versus undivided) ( Fig. 18A, B View Fig ; Mendoza 2021: 471–472, fig. 5A); 4) anterior margin of lobes is not separated from preorbital tooth by a deep notch (versus separated by a deep notch, appearing as a small fossa from an anterior view) ( Fig. 18C View Fig ; Mendoza 2021: 471–472, figs. 5A, 6A); 5) outer surface of the third maxilliped is densely covered with large granules (versus micro granules) ( Fig. 19A, B View Fig ; Mendoza 2021: 472, fig. 6B); 6) pigmentation of the pollex does not extend onto palm (versus extending onto palm) ( Fig. 18E–H View Fig ; Mendoza 2021: 470, fig. 5G, H); 7) greater length/width ratio of P5 merus (3.43 versus 2.11) (cf. Mendoza 2021: 470, fig. 5F); and 8) presence of a row of denticle teeth on the lower margin of P5 dactylus and a large tooth behind the claw (versus few scattered submarginal denticle teeth and a large tooth behind the claw) ( Fig. 19C View Fig ; Mendoza 2021: 472, fig. 6G). Macromedaeus sp. A differs from M. distinguendus by: 1) front submedian lobules divided by a notch (versus undivided) ( Fig. 18A, B View Fig ; Yuan et al. 2022: 11, 16, figs. 5B, 8B); 2) dorsal carapace region 6L divided by an oblique furrow (versus entire) ( Fig. 18C View Fig ; Serène 1984: 177; Yuan et al. 2022: 16, fig. 8A, B); 3) pollex pigmentation not extending onto the palm (versus extending) ( Fig. 18E–H View Fig ; Yuan et al. 2022: 16, fig. 8E, F); 4) row of denticle teeth present on the upper margin of P5 merus (versus absent) ( Fig. 19C View Fig ; Yuan et al. 2022: 12, fig. 6B); 5) greater length/width ratio of P5 dactylus (3.43 versus 2.50) ( Fig. 19C; c.f View Fig . Yuan et al. 2022: 12, fig. 6B); and 6) row of denticle teeth on the lower margin of P5 dactylus and a large tooth behind the claw (versus absent) ( Fig. 18E–H View Fig ; Yuan et al. 2022: 12, fig. 6B). Compared to M. voeltzkowi , Macromedaeus sp. A has: 1) carapace regions weakly defined and separated by shallow grooves (versus well-defined, divided by deep, acute furrows) ( Fig. 18A, B View Fig ; Barnard 1950: 226, fig. 41d; Serène 1984: 177, pl. XXV F); 2) dorsal carapace region 6L divided by an oblique furrow (versus transverse furrow) ( Fig. 18C View Fig ; Barnard 1950: 226, fig. 41d; Serène 1984: 177, pl. XXV F); 3) dorsal surface covered by microscopic granules (versus irregularly granular) ( Fig. 18A, B View Fig ; Barnard 1950: 226, fig. 41d; Serène 1984: 177, pl. XXV F); and 4) pollex pigmentation not extending onto the palm (versus extending) ( Fig. 18E–H View Fig ; Lenz 1905: 353, pl. XLVII 6a). The present morphological characters observations are based on juvenile female specimens. Potential sexbased variations or ontogenetic changes in this species remain unclear.