Family DYNOMENIDAE Ortmann, 1892

Dynomene pilumnoides [from Alcock 1900: pl. 1 fig. 2]

Museums

Regional Maps

• Dynomenidae Ortmann, A.E. 1892. Die Decapoden-Krebse des Strassburger Museums, mit besonderer Berücksichtigung der von Herrn Dr. Döderlein bei Japan und bei den Liu-Kiu-Inseln gesammelten und zur Zeit im Strassburger Museum auf bewahrten Formen. V. Theil. Hippidea, Dromiidea und Oxystomata. Zoologische Jahrbücher. Abteilung für Systematik, Ökologie und Geographie der Tiere 6: 532-588 pl. 26 [541].

Introduction

Dynomenids are a small group of 'primitive' crabs living in tropical and warmer parts of the Atlantic, Indian and Pacific Oceans (McLay 1999). They are immediately recognisable by their broad, triangular, frontal margins. Most are shallow water reef-dwelling forms, although one species has been recorded to 540 metres depth. McLay (1999) revised the family and provided keys to genera and species, as well as extensive discussion on morphology, evolutionary relationships, and biology.

Diagnosis

Carapace typically wider than long, sometimes longer than wide, moderately convex; surface smooth spinous or areolate, usually densely covered in setae; lateral borders distinct, armed with teeth. Front broadly triangular, continuous, unarmed; frontal groove well marked, split posteriorly; cervical, postcervical, and branchial grooves present. Lateral linea present. Orbital, antennular and antennal fossae defined. Antennule can be concealed inside orbit at base of eyestalk. Third maxillipeds operculiform; completely covering buccal cavern; separated at bases by plate at same level as sternum; basis and ischium of endopod fused, but joint marked by shallow groove. Sternal sutures 7/8 of female end well apart on low tubercles behind bases of second walking legs. Chelipeds equal, stout; fingers hollowed and dented at tip. Last pair of legs reduced, dactyl rudimentary, with obsolete subchelate mechanism. Gills usually 19 (including six podobranchs) plus seven epipods; gill structure phyllobranchiate, but plates variable in shape with different numbers of epibranchial lobes. Abdomen 7-segmented (including telson), without pleurae; both sexes with five pairs of pleopods, first pair vestigial in female, last three pairs rudimentary in male. Telson much wider than long; retaining mechanism for abdomen usually present, but not effective. Uropods present as well-developed dorsal plates. Spermathecal apertures small and rounded, at level of genital openings. Coxa of P5 strongly modified by the penis. Male first gonopod with apical plate. (After McLay 1999).

General References

McLay, C.L. 1999. Crustacea Decapoda: Revision of the family Dynomenidae. pp. 427-569 in Crosnier, A. Résultats des Campagnes MUSORSTOM, Volume 20. Mémoires du Muséum national d'Histoire naturelle, Paris [1936-1950] 180: 1-588

History of changes