Nibilia machala, Colavite, Jessica, Windsor, Amanda & Santana, William, 2019

Colavite, Jessica, Windsor, Amanda & Santana, William, 2019, Three new species and a new genus of majoid crabs from the eastern Pacific (Decapoda, Brachyura), ZooKeys 825, pp. 1-24 : 9-13

Nibilia machala sp. n. Figure 5A, C, E

Holotype.

Ecuador, off Machala, near Isla Santa Clara, Southeast Pacific Biological Oceanographic Project (SEPBOP), R/V Anton Bruun, Cruise 18B, stn 771, 03°15'S; 80°50'W, 10.ix.1966, Smithsonian Oceanographic Sorting Center coll., 77-80 m, juvenile female, cl 58.4 mm, cw 35.00 mm (USNM 1462701).

Comparative material.

Nibilia antilocapra . United States of America, North Carolina, R/V Oregon II, stn 10695, 35°22'N; 74°57'W, 26.vii.1969, HB Roberts det., 104 m, 1 ovigerous female (USNM 1256400). Louisiana, Gulf of Mexico, R/V Pelican, stn NSF–RHODOLITH– 28, 27°58.925'N; 91°39.831'W, 6.v.2018, 72 m, 1 juvenile (USNM 1479292). Florida, Tortugas, southeast from n° 2 red buoy, 17.vi.1932, MJ Rathbun det., 1 male (USNM 72957). Mexico, Gulf of Mexico, Suez and Campeche, R/V Oregon, stn 406, 22°14'N; 91°26'W, 16.viii.1951, FA Chace det., 1 female (USNM 92648). Gulf of Mexico, R/V Pelican, stn 10, 4.ii.1938, W Anderson; M Lindner coll., 1 female (USNM 1236185). Southwest Gulf of Mexico, R/V Pelican, stn NFS–11– 034, 9.vi.2005, DL Felder coll., 94-93 m, 1 female, DNA only (ULLZ 7365). Nicaragua, R/V Oregon, stn 6426, 12°56'N; 82°21'W, 05.ii.1967, DJ Griffin det., 190 m, 1 female juvenile (USNM 1256401). Venezuela, R/V Oregon, stn 5641, 11°38'N; 69°27'W, 01.x.1965, DJ Griffin det., 55 m, 1 male juvenile (USNM 1256402). Guyana, R/V Oregon II, stn 10513, 08°26'N; 58°11'W, 27.iv.1969, DJ Griffin & HB Roberts det., 183 m, 1 male (USNM 1256403). Brazil, Pernambuco, CEPEMAR, stn 54 L2, 150 m, 2 females (MOUFPE 15488). Bahia, Alfredo coll., 1 male (MZUSP 20258).

Type-locality.

Ecuador, off Machala, near Isla Santa Clara, 03°15'S; 80°50'W, 77-80 m.

Diagnosis.

Carapace pyriform, very spinulose, with one small spine on each side of the contiguous portion of the rostrum; one long, acute supraorbital spine; hepatic region with two long, distinct spines. Merus of P2 smooth.

Description.

Carapace pyriform, longer than wide, with seven long lateral spines, eight spines in medial line; covered with sparsely distributed tufts of hooked setae, mainly in rostral, branchial regions. Carapace spines: base of rostrum with five spines, two between the orbits; two protogastric; six mesogastric; six metagastric; one urogastric; two long lateral, two smaller mesial hepatic. Branchial region with small sparse tubercles and short spines: eight protobranchial, with few interspaced tubercles; mesobranchial with six long lateral, four small mesial spines, few tubercles; three marginal metabranchial with acute tubercles interspaced; seven cardiac; two intestinal spines. Branchiostegal region with row of acute, strong spines along anterior-inferior half of molt line. Gastric, branchial, cardiac, intestinal regions delimited laterally by shallow grooves.

Rostrum long, bifurcated for distal 1/3 of entire length, divergent. Supraorbital spine long, acute; orbital margin with one small spine. Postorbital margin cup-shaped completely protecting eyes when retracted, with small medial spine on anterior margin. Basal article of antenna narrow, second article long with one long anterolateral spine aligned with supraorbital spine, one smaller posterolateral spine protecting eyestalk from below, one smaller spine below orbital fissure. Antenna almost exceeding rostral length (flagellum broken in holotype). Antennal article longest; third, fourth antennal articles thick, cylindrical; visible dorsally. Antennular fossae longitudinally ovate, longer than wider; posteroventral margin with one small projection. Interantennular septum long, compressed laterally, forming ventrally-directed keel.

Epistome narrower, more depressed than antennular fossae; posterior margin crenulate, antennal gland open in epistome with one tubercle at same level, another on mouthfield border. Endostome with two prominent, obliquely longitudinal endostomial ridges, completely closed.

Buccal field sub-rectangular, longer than wide, posterior edge narrower, with crenulated anterolateral angles with one strong acute spine on anterolateral margins. Pterygostomial region sub-triangular with four acute spines on lateral margin, 3-4 sub-equal tubercles; sub-hepatic region delimited from pterygostome by distinct slope.

Third maxillipeds completely covering buccal frame. Exopod long, nearly reaching distal margin of merus; dorsal face with one small process extending into posterolateral margin of merus; ventral margin with strong spine in distal third. Ischium distinctly longer than broad, dorsal face with longitudinal, smooth, deep “L” shaped groove; crista dentata with small, rounded, irregular sized teeth. Merus slightly longer than half of ischium, anteromesial border partially covering propodus; anterior margin deeply incised, anterolateral margins slightly expanded. Palp cylindrical, slightly overreaching ischiomeral suture. Carpus, propodus, dactylus smooth; propodus, with long distomesial setae, dactylus fringed with row of long setae.

Juvenile female thoracic sternites I–IV fused, broadly triangular, smooth, dense, covered by closely adhered pubescence. Anterior half of fused sternites I–IV sloping down in ventral view. Sterno-pleonal cavity completely closed by telson. Female sternites V–VII smooth; Margin of episternites IV–VII smooth.

Juvenile female pleonal somites I–VI, telson free, slightly raised medially forming low longitudinal ridge. One small spine in first somite; somites II–VI smooth. Telson triangular. Juvenile female holotype with a sealed pleon.

Juvenile female chelipeds subequal, long; ischium unarmed; merus armed with seven strong dorsal spines, row of six laterodistal tubercles, sparse tubercles present; carpus with sparse tubercles; propodus smooth; dactylus and fixed finger distinctly shorter than palm, slender, cutting edges with subequal teeth, tip incurving down. P2 slender, cylindrical, with a distinct spine in distal margin of merus, densely covered with small setae and sparse hooked setae. Only P2 preserved in the holotype.

Distribution.

Only known from the type-locality in Ecuador, near Isla Santa Clara, 03°15'S; 80°50'W.

Etymology.

The specific epithet machala is a noun in apposition referring to the coastal city of Machala, Ecuador.

Remarks.

Nibilia machala superficially resembles N. antilocapra (Stimpson, 1871) in the highly spinulose appearance of the carapace, the long and semi-contiguous rostral spines, the distinct “L” shaped sulcus imprinted on the dorsal margin of the ischium of the third maxilliped, P2 with a distinct spine on the dorso-distal margin of merus, and similar shape of the female pleon (Fig. 5). Nibilia machala , however, differs from N. antilocapra by (i) the presence of one small spine on each side of the contiguous portion of the rostrum (vs. the contiguous portion of the rostrum unarmed in N. antilocapra ) (Fig. 5A, B, black arrow); (ii) one long, acute supraorbital spine (vs. two acute spines, one long and one shorter in N. antilocapra ) (Fig. 5A, B); (iii) hepatic region with two long, distinct spines (vs. one long, distinct spine in the hepatic region of N. antilocapra ) (Fig. 5C, D, white arrow); (iv) P2 merus smooth (vs. P2 armed with two rows of six or seven spines in N. antilocapra ) (Fig. 5E, F). Pisa praelonga Stimpson, 1871, is apparently a juvenile stage collected at the same locality of N. antilocapra , thus, considered a junior subjective synonym of N. antilocapra ( Rathbun 1925; see also figures on Milne-Edwards and Bouvier 1923: pl 11, Figs 4-7). Nibilia erinacea A Milne-Edwards, 1878 is also considered a junior subjective synonym of N. antilocapra . The description and the figure presented by A Milne-Edwards (1878: 133, pl 25) fully agree with the description of Pisa antilocapra Stimpson, 1871. Both, Pisa praelonga and Nibilia erinacea where described from western Atlantic material.