Family RHYNCHOTHORACIDAE Thompson, 1909
Introduction
Rhynchothoracidae are a very rare lineage of pycnogonids, usually found in interstitial habitats. Eighteen species occur amongst sediment and rubble in tropical, temperate and polar environments. Usually a single or very few specimens are known for a species. Tiny, rugose and compact, Rhynchothorax species are among the most intriguing of pycngonids. Their phylogenetic affinities are still to be thoroughly tested (see Nakamura et al. 2007).
Diagnosis
Size tiny, compact; integument usually pebbled, with dorsal tubercles; proboscis short, lips vertical; chelifores lacking in adults; palps 4- or 5-segmented, usually with dorsodistal tubercle; ovigers tiny, without strigilis, with recurved claw on terminal segment, 10-segmented in males, sometimes with 9 segments in females. Cement glands rarely visible, mostly unknown. Eight legs.
General References
Arnaud, F. & Krapp, F. 1990. The genus Rhynchothorax (Pycnogonida) in the Mediterranean Sea. Beaufortia 41(1): 1-7
Nakamura, K., Kano, Y., Suzuki, N., Namatame, T. & Kosaku, A. 2007. 18S rRNA phylogeny of sea spiders with emphasis on the position of Rhynchothoracidae. Marine Biology, Berlin 153: 213-223