Lacertopontonia, Marin, Ivan, 2011

Marin, Ivan, 2011, Lacertopontonia chadi gen. et sp. nov., a new oyster-associated Pontonia - like pontoniine shrimp (Crustacea, Decapoda, Palaemonidae) from the Great Barrier Reef of Australia, Zootaxa 2968, pp. 57-68 : 58-59

Lacertopontonia gen. nov.

Type species. Lacertopontonia chadi gen. et sp. nov., by present designation and monotypy.

Etymology. The genus is named after Lizard Island, GBR, Australia, the type locality; “ lacertus” (Latin, masculine) meaning “a lizard” and its general similarity with the Eastern Pacific pontoniine shrimp genus Pontonia Latreille, 1829 (the type genus of the subfamily Pontoniinae ). Gender feminine.

Diagnosis. Medium-sized pontoniine shrimp with swollen, slightly depressed subcylindrical body; body and appendages smooth, generally glabrous, distal part of propodi and dactyli of ambulatory pereiopods covered with tufts of simple setae. Carapace swollen, without antennal or hepatic teeth, with inferior orbital angle acutely terminating; rostrum well developed, but short and broad, curved downward, dorsally and ventrally unarmed, reaching midlength of basal antennular segment in females and distal part of basal antennular segment in males, with well developed lateral carina, ventral carina forming broad distinct keel between antennular segments. Abdominal somites unarmed, smooth, with non-carinate tergites; three last pleomeres small, with feebly developed rounded pleurae. Telson stout, tapering distally, with three pairs of small, stout dorsal spines, with posterior margin of the telson blunt armed with two pair of spines and a row of long submarginal setae. Eyes large, swollen, stout, smooth; eyestalk swollen, cylindrical; cornea large, rounded, well pigmented. Antennula and antenna without specific features, slightly reduced; basal antennular segment with well marked ventromedial and distolateral teeth; scaphocerite of antenna well developed, with large acute distolateral tooth separated from blade by distinct notch. Mandible well developed, without palp, lateral margin of incisor process smooth. Maxillula with bilobed palp. Maxilla normal, with pointed simple palp and single distally rounded endite furnished with styliform elongated setae along distal and lateral margins; scaphognathite broad, furnished with short plumose setae. Maxilliped I normal, with earshaped epipod bearing distinct lateral notch, with slender exopod with expanded caridean lobe; basal and coxal endites completely fused; epipod well marked, distally rounded. Maxilliped II with normal rounded epipod and slender exopod overreaching propodal segment; propodus with distolateral margin broadly rounded, with dorsal margin convex furnished with slender setae, dactylar segment slender, about 3 times as long as broad. Maxilliped III normal, with well developed epipod and exopod; ischiomeral segment broad furnished with simple setae along its lateral margins. Appendages robust, unarmed, smooth. Pereiopod I normal, with slender segments and simple non-spatulate fingers. Pereiopods II small and robust, equal in size and shape, with unarmed smooth segments, fingers of chela equal, broad and compressed, about 0.6 of palm length. Ambulatory pereiopods (p-p III – IV) similar, robust, smooth, with simple dactyli, with distal part of propodi and dactyli densely covered with simple setae. Uropod stout, with exopod about 0.6 of endopod length; exopod with bluntly-rounded distolateral angle, without movable distolateral spine. Endopod of pleopod II in males with short appendix masculine, about 1.5 times shorter than appendix interna, without specific features, covered with numerous simple setose setae.

Remarks. The new genus can be clearly distinguished from all known pontoniine genera by the combination of the following morphological characters: smooth glabrous body, the absence of antennal and hepatic teeth, broad toothless rostrum turned downward, telson with three pairs of dorsal submarginal spines and two pairs of posterior spines, simple non-spatulate fingers of pereiopod I, short and robust equal pereiopods II with equal fingers, simple dactyli of ambulatory pereiopods, short uropodal exopod (about 1.5 times shorter than uropodal endopod), and the absence of movable spine at the distolateral angle of uropodal exopod. The most distinctive feature of the new genus is the presence of three pairs of dorsal submarginal spines on the telson which is a unique feature within the subfamily Pontoniinae . Among other Pontonia -like genera (see Fransen, 2002) and species similar characters have been found only in ascidian-associated Odontonia sibogae (Bruce, 1972) having up to five pairs of dorsal spines on the telson. The latter species is easily distinguished from the new genus by the biunguiculate dactyli of ambulatory pereiopods. Conchodytes nipponensis (De Haan, 1844) , and Conchodytes -related Chernocaris placunae Johnson, 1967 possess the lateral pair of terminal telson spines also rather distant from the distal margin (see Johnson, 1967; Fransen, 1994) but both species clearly differ by biunguiculate dactylus of ambulatory pereiopods.

The second distinguishing feature of the new genus within the Pontonia -like bivalve-associated pontoniine genera is simple dactylus of ambulatory pereiopod III. Such a feature is characteristic only for a few bivalve-associated Pontonia -like shrimps such as Pseudopontonia minuta ( Baker, 1972) , species of the genus Platypontonia Bruce, 1968 , Pontonia pilosa Fransen, 2002 , Pontonia simplex Holthuis, 1951 , Odontonia seychellensis Fransen, 2002 and Odontonia simplicipes (Bruce, 1996) .

Pontonia pilosa and P. s i m p l e x can be clearly separated by the presence of well marked antennal tooth on carapace, longer slender compressed rostrum overreaching basal antennular segment, the presence of two pairs of dorsal spines on telson as well as the geographical distribution – exclusively in the Atlantic basin ( Fransen, 2002). Pseudopontonia minuta can be clearly separated by deeper rostrum, the presence of two pairs of dorsal and numerous distal spines on telson, and different mouthparts (see Bruce, 1972).

Platypontonia is similar to the new genus in the form of dactyli of ambulatory pereiopods and short uropodal exopod but can be clearly separated by the presence of well marked antennal tooth on carapace, shorter rostrum turned forward, the presence of additional medial lobe at distolateral angle of basal antennular segment (vs. pointed broad triangular angle in Lacertopontonia ), the absence of a notch between distolateral tooth and blade of scaphocerite (the feature also characteristic for the genus Pontonia ), the presence of two pairs of small dorsal spines on telson, more slender chela of pereiopods II having longer fingers equal to the length of palm and the presence of a minute movable spine at the distolateral angle of uropodal exopod ( Bruce, 1968; Hipeau-Jacquotte, 1971).

Odontonia seychellensis and O. simplicipes clearly differ from Lacertopontonia by the presence of two pairs of dorsal spines on the telson and ecologically, inhabiting tunicates ( Ascidiidae , Ascidiacea) (see Fransen, 2002).

In general the new genus is particularly morphologically similar to Bruceonia ardeae ( Bruce, 1981) representing a monotypic genus Bruceonia Fransen, 2002 known only from the Great Barrier Reef of Australia ( Bruce, 1981; Fransen, 2002). Nevertheless, the new genus can be clearly distinguished from the latter by smooth body (vs. densely setose body in Bruceonia ), the presence of three pairs of relatively large robust submarginal dorsal spines on telson (vs. two small submarginal spines in Bruceonia ), different shape of maxillula and maxilla and simple dactyli of ambulatory pereiopods ( Bruceonia has biunguiculate dactyli with small but distinct accessory tooth) (see Bruce, 1981; Fransen, 2002). Some features such as shape of maxillula and other mouthparts as well as the presence of a distinct notch between distolateral tooth and blade of scaphocerite show probable relationships between the new genus and species of the genus Pontonia occurring in the Eastern Pacific region and Atlantic ocean.