A new species of Atlantoscia Ferrara & Taiti , 1981 ( Oniscidea : Philosciidae ) from Rio Grande do Sul , Brazil

To date the genus Atlantoscia Ferrara and Taiti, 1981 includes two species, A. floridana (van Name, 1940) and A. rubromarginata Araujo and Leistikow, 1999. The species Atlantoscia petronioi sp.n. is described on the basis of material collected in a coastal dune forest area of the southern Rio Grande do Sul state, Brazil. This new species is characterized by antenna with accentuate setose sulcus from the peduncle to the distal article of the flagellum, outer endite of maxillula with slender seta among the outer group teeth and accessory tooth, one trifid tooth in the inner group, and male pleopod 1 endopod with distal part pointed and subapically not swollen.


Introduction
The genus Atlantoscia Ferrara and Taiti, 1981 presently includes two species, A. floridana (van Name, 1940), with a distribution in coastal regions of Florida, Brazil, Argentina, and Ascension and Saint Helena islands; and A. rubromarginata Araujo and Leistikow, 1999, with records in Sergipe, Brazil (Araujo and Leistikow, 1999;Schmalfuss, 2003).The phylogenetic relationships of Atlantoscia are still obscure.Leistikow (2001) proposed a phylogeny of South American Philosciidae in which Atlantoscia shares a polytomy with Benthana Budde-Lund, 1908 and Rhyscotidae, based on the character "maxilliped endite without setation, distal margin transverse".
The present contribution describes a
Atlantoscia petronioi n. sp.1G).Antenna when extended posteriorly reaching anterior margin of fifth pereonite, with accentuate setose sulcus along peduncle and flagellum (Hoese, 1981, see remarks); flagellum proximal and distal articles similar in length, middle article slightly shorter, free sensilla as long as cuticular sheath, inserted at one-quarter of length of apical organ (Figs.1H, 5C).Mandibles with at least five branches on pars molaris, pars intermedia with dense tuft of coniform setae, right mandible with two penicils on incisor process, and left mandible with three penicils (Figs.2A, B).Medial endite of maxillula with two short penicils, inserted transversely, and distal portion rounded, outer endite with 4+6 teeth, outer group with slender seta and accessory tooth, inner set with five cleft teeth, one of them trifid (Fig. 2C).Lateral lobe of maxilla robust, twice as wide as median  lobe, distal margin sinuous, and covered with trichiform setae; median lobe rounded, and covered with trichiform setae (Fig. 2D).Maxilliped with rectangular base, cuticle scaled proximally, sparse piliform scale-setae, and distal margin slightly prominent; endite rectangular, longitudinal ridge bearing dense setae in rostral view, distal margin curved, bearing two hooks, medial seta surpassing distal margin (Fig. 2E).
Pleopods with narrow respiratory areas (Figs.4A, C, E-G).Uropod with endopod and exopod inserted at different levels, with sparse long setae along inner and outer margins, exopod twice length of endopod, with five sensory setae on apex, and endopod with three sensory setae on apex (Fig. 4H).
Etymology: The species name honors the late Professor Petrônio Alves Coelho for his contributions to the knowledge of Crustacea.
Remarks: Atlantoscia petronioi sp.n. is characterized by the low number of ommatidia (14-16 vs. 20 in A. floridana and 23 in A. rubromarginata), number of aesthetascs on the antennule (12 + 2 vs. 8 + 2 in A. floridana and 3 + 1 in A. rubromarginata), presence of the accentuated setose sulcus on the antenna, accessory tooth and the slender seta on the outer endite of the maxillula, and the shape of the distal part of the male pleopod 1 endopod subapically not swollen.Hoese (1981) described the setose sulcus of the antenna as part of a water conducting system of the terrestrial isopods, which can be well developed, from the antennal base to the tip, vestigial or absent.In relation to Atlantoscia representatives, we analyzed material of A. floridana and A. rubromarginata from the same collection used by Araujo and Leistikow (1999) and examined the type material of A. floridana described by Ferrara and Taiti (1981).We also examined, a large material of