Stylopallene cheilorhynchus Clark, 1963

Staples, David A., 2014, A reassessment of the pycnogonid genus Stylopallene (Arthropoda, Callipallenidae) with description of a new genus, Memoirs of Museum Victoria 72, pp. 121-129 : 122-124

Stylopallene cheilorhynchus Clark, 1963 .

Stylopallene cheilorhynchus . Clark, 1963: 36-38 — Stock, 1973a: 117 — Stock, 1973b: 92 — Staples, 1997: 1055 — Staples, 2005: 166- 168 — Arango and Brenneis, 2013: 430

Remarks. The leg span is about 20 mm. The segmentation between trunk segments 3 and 4 is present but indistinct. The first two pairs of lateral processes are often more widely separated than the others, processes 2-4 are touching throughout most of their length or narrowly separated. The length of the narrow distal part of the proboscis is about 40% of the basal part. The abdomen is short, broad, shield-shaped and directed slightly downward. A depression at the base of the abdomen gives the impression that it is segmented and possibly accounts for Clark’s illustration of a segmentation line ( Clark, 1963, fig. 19A). The oviger spines are variable and irregular in shape; the spine teeth are generally poorly developed. The terminal claw is strong, about one-third the length of segment 10 and with a slightly irregular inner margin but without teeth.

A piece of a fragmented exuvia shows that the trunk separates around the lateral ecdysial line and that the dorsal surface of the trunk is discarded inclusive of the lateral processes and abdomen. The transverse suture that divides the trunk from the lateral processes remains intact. The abdomen does not separate into dorsal and ventral components ( fig. 1F).

This species is most-often recorded in association with Amathia wilsoni Kirkpatrick, 1888 . Specimens are present in large numbers seasonally with fertile specimens commonly observed from November to April in water temperatures of 15-26 degrees centigrade and less frequently at other times of the year. Fifty-two protonymphon which probably represents more than one mating event have been recorded from a single oviger. Ovigerous and larvae-bearing males together with juveniles at various stages of development are recorded from the same bryozoan colony. Juvenile chela fingers are slender, distorted of the form described by Staples (2005 figs. 5B).

Body markings. Specimens are usually described as being ‘banded’. The abdomen, central region of trunk and proboscis are typically cream; lateral processes are dark. The cephalon is mostly dark dorsally, widening from the ocular tubercle to the base of the chelifores. The chelifore scapes are light and the chelae black. The distal half to one-third of the femur and tibiae are black, tarsus black, dorso-distal surface of propodus black and claw light. Distal oviger segments black. The light colour may vary slightly from cream to yellow or with a slightly green tinge.

Stylopallene cheilorhynchus is widely distributed and often recorded along the southern Australian coastline.

Distribution. Southern New South Wales to southern Western Australia and Tasmania at 1.0 to 90 m depth.