Rapipontonia, Marin, 2007

Marin, Ivan, 2007, A new genus and species of pontoniine shrimp (Crustacea, Decapoda, Palaemonidae, Pontoniinae) associated with plumularid hydroids (Hydroidea, Plumularidae) in Vietnam, Zoosystema 29 (4), pp. 775-786 : 776-777

Genus Rapipontonia n. gen.

TYPE SPECIES. — Rapipontonia paragalene n. sp., by present designation.

SPECIES INCLUDED. — Rapipontonia paragalene n. sp.; Periclimenes galene Holthuis, 1952 ; Periclimenes platalea Holthuis, 1951 .

ETYMOLOGY. — The name of the new genus is derived from the grasping mechanism of the dactylus-propodus articulation of ambulatory pereiopods: rapina, Latin for seizure, capture, claw; Pontonia – the type genus of the Pontoniinae . Gender feminine.

DIAGNOSIS. — Medium-sized pontoniine shrimps. Carapace smooth, with antennal, hepatic and epigastric spines; hepatic spine smaller than antennal, situated posterior and slightly above level of antennal spine; epigastric spine well marked, smaller than proximal dorsal rostral tooth, clearly separated from rostral teeth, either separated from carapace by well marked suture or fused to carapace. Rostrum long and slender, with well developed dorsal carina bearing six teeth, ventrally unarmed; four proximal dorsal rostral teeth large, acute, two distal dorsal teeth small. Inferior orbital angle produced. Abdomen smooth, third tergite non-carinate or posteriorly produced; pleura posteroventrally rounded; telson slender, tapering distally, with two pairs of small dorsal spines and three pairs of posterior marginal spines. Ophthalmic somite without ocellar beak. Antennule and antenna normal, without special features, scaphocerite well developed. Eyes with globular cornea. Epistome unarmed. Mandible without palp. Maxillula with bilobed palp, well developed upper and lower laciniae. Maxilla with slender palp, well developed scaphognathite, basal endite well developed; coxal endite lacking. First maxilliped with simple palp, basal endite broad, coxal endite smaller, exopod well developed, caridean lobe well developed, epipod bilobed. Second maxilliped with non-modified endopod, exopod as in first maxilliped, with caridean lobe, epipod small, simple, without podobranch. Third maxilliped with slender segments, ischiomerus and basis fused, with distinct suture, exopod well developed, coxa with rounded lateral plate, single small arthrobranch and several long, plumose setae. Fourth thoracic sternite without finger-like median process, fifth to eighth unarmed. First pereiopods slender, fingers simple, with spoon-like tips. Second pereiopods slender, unequal in length and shape; fingers simple, with well developed cutting edges, without molar process and fossa. Ambulatory pereiopods slender, propodus with three to five pairs of long straight distolateral spines and distinctive plumose setae; dactyls simple, long, slender, curved. Pleopods normal; endopod of male second pleopod with appendix interna bearing terminal cincinnuli; appendix masculina with two terminal serrated setae. Uropods slender, without specific features.

SYSTEMATIC POSITION

Rapipontonia n. gen. is morphologically similar to Manipontonia Bruce, Okuno & Li, 2005 .The two genera share a long, slender rostrum with well developed

dorsal carina and unarmed ventral margin; presence of antennal, hepatic and epigastric teeth; absence of podobranch on the second maxilliped; and presence of single arthrobranch on the third maxilliped. The presence of long plumose setae on the coxa of third maxilliped, an unusual feature for pontoniine shrimps ( Bruce et al. 2005), is an additional synapomorphy of these two genera. However, Rapipontonia n. gen. can be clearly distinguished from Manipontonia by the presence of a single basal endite on the maxilla (vs. both basal and coxal endites present in Manipontonia ); the presence of a well developed caridean lobe on the first maxilliped (reduced in Manipontonia ); a well marked suture between the ishiomerus and basis of the third maxilliped (ischiomerus and basis being completely fused in Manipontonia ); the third pereiopod with three to five pairs of long distoventral spines; the epigastric tooth separated from the carapace by a distinct suture, as in R. galene and R. paragalene , or at most partly fused, as in R. platalea (vs. completely fused in Manipontonia ); and the unarmed dorsal rostral teeth (distoventrally serrated in Manipontonia ).

Rapipontonia differs from Periclimenes sensu stricto with the type species P. amethysteus (Risso, 1827) (see Marin 2006 for short diagnosis), by the presence of plumose setae on the coxa of the third maxilliped (absent in Periclimenes ); the presence of a suture between basal segments of the third maxilliped (completely fused in Periclimenes ); spatulated fingers of the second pereiopod (simple in Periclimenes ); the simple dactylus of the third pereiopod (biunguiculate in Periclimenes ); and the third pereiopod with three to five pairs of long distoventral spines (one pair of small distoventral spines in Periclimenes ). Thus the long distoventral spines with additional plumose setae and long curved simple dactylus forming grasping mechanism of the dactylus-propodus articulation on the third to fifth pereiopods is an autapomorphy of Rapipontonia n. gen., clearly separating it from all other pontoniine genera.