Onycocaridella Bruce, 1981

Marin, Ivan, 2008, A revision of the generic position of Typton australis Bruce, 1973 (Decapoda: Palaemonidae: Pontoniinae), with a new diagnosis for the pontoniine shrimp genus Onycocaridella Bruce, 1981, Zootaxa 1897, pp. 64-66 : 64-65

Onycocaridella Bruce, 1981

Onycocaridella Bruce, 1981: 241 .

Diagnosis. — Small sized pontoniine shrimps, associated with sponges. Carapace stout, subcylindrical, smooth; hepatic and antennal teeth absent; inferior orbital angle rounded; rostrum short and slender, strongly reduced, pointed distally, sometimes with small dorsal subapical tooth. Telson with 2 pairs of dorsal and 3 pairs of posterior spines. Antenna with reduced blade of scaphocerite, subequal to the length of the basal segment of antennular peduncle, with small distolateral tooth or without it. Mandible without palp, with feebly developed incisor process; endite of maxillae simple or bilobed; all maxillipeds with exopods. First pereiopod with fingers stout, equal to palm, subspatulated, with pointed tips and entire cutting edge. Second pereiopods robust, unequal; palm cylindrical, about twice longer than wide; fingers are stout, less than half of palmar length, simple, with entire cutting edges; fixed finger without lateral flange. Ambulatory pereiopods normal and stout; dactylus biunguiculate, with small smooth cylindrical accessory tooth significantly smaller than unguis, with smooth or serrated ventral surface. Uropods are normal; exopod with lateral margin smooth and disto-lateral angle with fixed tooth and movable spine.

Species included. — Onycocaridella prima Bruce, 1981 [type species], O. antokha Marin, 2007 , O. australis ( Bruce, 1973) comb. nov.

Remarks. — The taxonomic position of two species, former Onycocaridella stenolepis ( Holthuis, 1952) and O. monodoa ( Fujino & Miyake, 1969) , should be changed. These species have morphological features of the genera Onycocaris Nobili, 1904 or Typtonychus Bruce, 1996 . Such features of both species as produced inferior angles of the carapace, well-developed scaphocerite with well-developed distolateral teeth, and spatulated fingers of the first pereiopods are similar to the species of the genus Onycocaris . Conversely, the position of the second pereiopod mentioned by Bruce (1981: 242) and small accessory tooth of the third pereiopods are more similar to Typtonychus than to Onycocaris . Species of both genera possess a well-developed rostrum bearing dorsal teeth. Thus, the taxonomic position of both species can be clearly verified only after re-examination of the type material. Nevertheless, it is clear that these species are not referable to Onycocaridella and are transferred back to Onycocaris as Onycocaris stenolepis Holthuis, 1952 and O. monodoa Fujino & Miyake, 1969 , respectively.

Onycocaridella Bruce, 1981 now includes three species and clearly differs from the most closely related genus Typton Costa, 1844 by: 1) the absence of antennal or paraorbital teeth (large paraorbital teeth are present in the type species of the genus Typton spongicola ; 2) scaphocerite of antenna never less than half the length of the basal segment of antennular peduncle (versus scaphocerite almost completely reduced in the genus Typton ) and 3) subspatulated fingers of the first pereiopod pointed distally (versus spatulated shovel-like fingers rounded distally).

From the genus Onycocaris , Onycocaridella also differs by 1) smooth normal non-produced inferior orbital margin of carapace (versus it is produced in all species of the genus Onycocaris ); 2) reduced scaphocerite (versus scaphocerite is well developed, with well developed distolateral tooth); 3) subspatulate fingers of the first pereiopod equal to palmar length (versus spatulated shovel-like fingers significantly smaller than palm); 4) cylindrical palm and entire cutting edge of the fingers of the second pereiopods (versus second pereiopods with compressed palm and fingers bearing large teeth along the cutting edge); 5) smooth cylindrical accessory tooth significantly smaller than unguis on the dactylus of the third pereiopod (versus large compressed triangular accessory tooth almost equal to the length of the unguis on dactylus of third pereiopod).

The related genus Typtonychus Bruce, 1996 can be clearly distinguished by the well-developed rostrum bearing large dorsal teeth, presence of an antennal tooth, the specific structure of the third maxillipeds and fingers of the second pereiopod.