Tanaidaceans (Crustacea) from the Central Pacific Manganese Nodule Province. I. The genera Collettea, Robustochelia and Tumidochelia Author Larsen, Kim text ZooKeys 2011 87 19 41 http://dx.doi.org/10.3897/zookeys.87.784 journal article http://dx.doi.org/10.3897/zookeys.87.784 1313-2970-87-19 Genus Robustochelia Kudinova-Pasternak, 1983 Type species. Leptognathia robusta (Kudinova-Pasternak, 1970) Diagnosis. (Modified after Jozwiak and Blazewicz-Paszkowycz 2007 ) Female. Antennule with four visible articles and one minute terminal article (often not visible in the compound scope as with Collettea and many other tanaidomorphans). Antenna with six articles, articles 2 and 3 with robust dorsodistal setae. Mandibular molar pointed. Labium consists of one pair of lobes with minute distal setulation, usually with medial processes (e.i. 'lobes' sensu Jozwiak and Blazewicz-Paszkowycz 2007 ). Maxillipedal palp robust; endites not fused, with distal setae but without distal denticles, narrower than basis. Chelipeds attached by ventral sidepiece, carpus and propodus massive, dactylus and fixed finger shorter than rest of propodus, and heavily chitinized. Pereopods 1-3 with coxa, dactylus and unguis combined shorter than, or as long as, propodus, unguis longer than dactylus. Pereopods 4-6 without coxa, dactylus and unguis not fused to a claw. Pleopods present. Uropodal exopod uniarticulated, endopod consisting of one (with pseudoarticulation) or two articles. Male:Similar to female, but antennule articles 1-3 much wider than in female. Gender. Feminine. Species currently assigned to this genus. Robustochelia angusticephala Kudinova-Pasternak, 1986; Robustochelia longa Kudinova-Pasternak, 1983; Robustochelia pacifica sp. n.; Robustochelia robusta (Kudinova-Pasternak, 1970); Robustochelia virilis Jozwiak and Blazewicz-Paszkowycz , 2007. Remarks. The genus Robustochelia is a rare, and exclusively deep-sea, genus ( Larsen 2005 ; Jozwiak and Blazewicz-Paszkowycz 2007 ). It is primarily recognized by the heavy cheliped with a calcified keel on the cheliped fixed finger but despite the recent clarifications by Jozwiak and Blazewicz-Paszkowycz (2007) it i still poorly defined and poorly studied genus, due to the rarity of both species and specimens. The genus currently consists of five species including the one described herein. Apart from the heavy cheliped, the defining characters of Robustochelia are the combination of a 'general leptognatid' morphology: consisting of an antennule with four plus one minute articles, a pointed mandibular molar, and a uniarticulated exopod. However the calcified cheliped keel is found in species of other genera ( Leptognathioides , Siphonolabium , Monstrotanais , and Robustochelia [?] solida) and the combination of the other 'general leptoganthid' characters all present in several other deep-sea genera ( Caudalonga , Filitanais , Forcipatia , Leptognathia , Leptognathiella , Stenotanais ). No other synapomorphic characters are present and several of the species of Robustochelia are only incompletely described. Unfortunately it is not unusual for tanaid systematists to have to rely on a character combination as this for genus diagnosis, but the homoplastic nature of all the characters in Robustochelia indicates that it is probably not monophyletic. Further studies, particularly genetic studies, needs to verify the status of this genus (Larsen and Froufe in progress). The labial medial processes or 'lobes' sensu Jozwiak and Blazewicz-Paszkowycz (2007) are in this authors opinion note 'lobes' in the true sence as seen in Leptochelia or Tanais but thin membranous lateral extensions).