“Ascorhynchus cooki, new species, Fig. 2
Material examined – Southwest Pacific, SW of Macquarie Island, 59°58’S, 155°31’ E, 2985-2992 m, coll. Eltanin, sta 1964, 10 Feb 1967, holotype male (USNM 233601), 2 paratype females (USNM 233602). – N of Chatham Rise, New Zealand, 41°45’S, 178°05’W, 2610-2668 m, coll. Eltanin, sta 1711, 25 May 1966, 3 paratype females (USNM 233603). – SE of Cook Strait, New Zealand, 42°11’S, 175°11’E, 2612 m, coll. Eltanin, sta 25-371, 20 Nov 1966, paratype chelate juvenile (USNM 233604).
Description. – Size gigantic for genus, leg span 178 mm. Integument smooth, glabrous. Trunk slender, graceful posterior of first 3 segments flaring into cowls having dorsomedian tubercles with rounded tips. Lateral processes twice as long as maximum diameters, without setae, with low dorsodistal tubercles rounded at tips. Neck long, oviger implantation directly ventral to ocular tubercle which is placed just posterior to median neck length. Ocular tubercle twice as long as diameter with anterior pairs of eyes at median length, posterior pair pf eyes more distal. Proboscis slender, tripartite, only as far as first trunk segment, mouth flat. Abdomen slender, extending only to distal rim of first coxae on fourth legs, glabrous, carried slightly ventral with distal half curved dorsally.
Chelifore scapes with 2 segments, armed with 1-2 small distal setae. Scape segments subequal, slightly clubbed distally, short, each no longer than neck width. Chela tiny, vestigial, movable finger represented by tiny ventral bumps, glabrous.
Palp third segment 3.5 times longer than fourth, terminal 5 segments very slender, numbered from shortest to longest; 6, 7, 10, 9, with 8 longest, all armed with ventral fringe of tiny setae.
Oviger segment 5 about 0.8 length of segment 4, both armed with tiny lateral setae. Sixth segment clubbed distally, armed with distal fringe of short and long setae, some longer than segment diameter. Strigilis 4 segments increasingly shorter in length progressing distally, armed with 3-4 rows of denticulate spines, 1 row larger than lateral rows, larger row with formula 9:8:8:9, spines slender, with many lateral denticulation. Terminal claw well curved, short, only 0.35 length of terminal segment.
Legs long, slender, glabrous, femur longest segment with tibia 1 longer than tibia 2. Cement glands numbering 21-24 tiny pores on femur, 19-23 pores on entire length of tibia 1. Tarsus slender straight cylinder, subequal in length to slender slightly curved propodus, both armed with few tiny ventral setae. Claws of first pair of legs extremely tiny, only about 0.3 as long as other 6 claws, which only about 0.18 propodal length, none curved. Sex pores only on posterior 4 second coxae.
Female slightly larger, oviger without long setae and with fewer denticulate spines. Sexual pores on all second coxae.
Measurements (in mm). – Holotype: trunk length (chelifore insertion to tip 4th lateral processes) 25.5; trunk width (across 2nd lateral processes) 12.5; proboscis length 16; abdomen length 6; third leg, coxa 1, 4.0; coxa 2, 10.5; coxa 3, 4.75; femur 20.5; tibia 1, 22.0; tibia 2, 12.5; tarsus 4.0; propodus 4.0; claw 0.75; claw on first legs 0.2.
Distribution. – Known from the type locality, the SW Pacific, SW of Macquarie Island, in 2985-2992 m, and from N of the Chatham Rise and off Cook Strait, New Zealand, in 2610-2668 m.
Etymology. – The new species is named for the great Pacific explorer, Captain James Cook.
Remarks. – This species is very close to Ascorhynchus armatus (Wilson), as will be seen in the following key of the five giant species known to this genus. Were it not for the very widely separated collecting localities for this new species (SW Pacific) and those of A. armatus (N. Atlantic), I would be more inclined to attribute the differences among the two species a possible variations within a single species. Male cement gland(s) have proved to be a stable character in most genera and form a good diagnostic element. The cement gland pores in A. armatus appear to be consistently greater in number (53-90) than those of A. cooki (40-47). With only a single male on which to count the pores, the number is within a narrow range and will probably form a wider range when more specimens of this deep-living giant become available. I believe the few differences, including trunk and lateral process tubercle dissimilarities, between the two species are sufficient to keep them as separate species until it can be established whether or not A. armatus inhabits the Pacific and if there are transitional specimens bridging the differences enumerated in the key.
The five giant species known to this genus all share the following characters; trunks with median dorsal tubercles, long abdominal, 2-segmented scapes, many cement gland pores on multiple leg segments, a tarsus almost as long or equal to the propodal length , and trunks at least 13 mm long or greater. Measurements will, of course, vary among specimens of any species.” (Child 1987, p. 104-106)
