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Stylocheiron insulare Hansen, 1910

Etymology: Stylocheiron - a column/hand; insulare - insular

Eye: The lower lobe is wide, almost spherical. The upper lobe is short and narrow, bearing 4-5 enlarged crystalline cones in a distal transverse row (Stylocheiron table). The length of the eye is 0.7-0.8 mm. The lower lobe is about 4 times wider than the upper lobe measured at the base of the crystalline cones (S. insulare eye & rostrum).

Peduncle of 1st Antenna: As in the generic diagnosis in Higher Taxa (S. insulare lappet lacking).

Rostrum: It is slender and acute in females. The frontal plate is short and acutely triangular in males (S. insulare dorsal head).

Carapace: The gastric region is domed with a small dorsal keel-like elevation (S. insulare).

Thoracic legs: The 3rd leg has a "false chela" (Stylocheiron-elongated legs) characteristic of the "S. longicorne group", formed of spiniform bristles from the propodal and dactyl segments.

Abdomen: The 6th segment appears short, <1.4 times as long as high. The anterior three-fourths of the ventral margin of the 6th segment is straight and parallel with the dorsal margin; the posterior one-fourth of the ventral margin angles sharply upward then posteriorly, forming a ventral-subterminal indentation (S. insulare ), even more pronounced than in S. suhmi .

Length: Adults are 6.5-8.2 mm.

Petasma: The terminal process is a broad blade, 3.5-4 times as long as broad, narrowing and then abruptly truncated distally. The proximal process is shaped like the terminal but is somewhat broadened distally, terminating more roundly than squarely. The lateral process is a bit shorter than the terminal and the proximal processes and is half as broad (S. insulare petasma).

Thelycum: Described by Costanzo and Guglielmo, 1991.

Comments: The eye is the stubbiest in the "S. longicorne group", with the upper lobe short and the lower lobe relatively broad. The acuteness of the ventral angle on the lower margin of the 6th abdominal segment is characteristic, although similar to S. suhmi.

S. insulare occurs only near the Indo-Australian Archipelago, extending northward to the southern Philippines and eastwards in the equatorial Pacific to about 165°E. It also occurs in the Indian Ocean near the Andaman Islands and off southern Sumatra and Java (S. insulare distribution). It has not been found in the South China Sea.

S. insulare is believed to live above 200 m.


Stylocheiron insulare