On a new genus and species of Hemicytheridae ( Ostracoda , Crustacea ) from the southern Brazilian coast

This study is based on 62 samples of bottom sediments and phytal collected in the upper rocky sublitoral (≤ 3 m water depth) of the central and northern coasts of Santa Catarina State (26°10’/27°50’S – 48°26’/48°40’W), southern Brazil. Living and dead ostracodes distributed among 16 families were recovered. In this paper is emphasized one new hemicytherid genus and species that are described and richly illustrated: Auricythere sublitoralis gen. nov., sp. nov. Some ecological and zoogeographical aspects of this new ostracode are briefly discussed.

The study of benthic marine ostracodes from Brazil began with Brady (1880), in his monumental work on benthic ostracodes from different oceans, identified some species of ostracodes recovered, including from deep-waters of northeastern region of Brazil, all of them collected during the H.M.S. Challenger Expedition.Hartmann (1955Hartmann ( , 1956) ) described some new species from samples collected by hand off Santos city and Bela Island, both places localized in the north coast of the state of São Paulo, southeastern Brazil.Later, Pinto et al. (1978), a landmark in the study of these microcrustaceans in this country examined hundreds of bottom sediment samples collected along 7,408 km of the continental shelf, identifying, preliminarily, about 50 genera of Ostracoda.Following them, ramos (1996), CoimBra et al. (1999), maCHado et al. (2005) and Bergue & CoimBra (2008) continued these studies where a more detailed bibliographic review is presented.
Most work on marine benthic ostracodes of Brazil has been devoted to the study of species recovered from the continental shelf, and more recently from the slope (Bergue & CoimBra, 2008).Ostracodes from coastal regions are still poorly understood, highlighting herein the studies of Hartmann (1955Hartmann ( , 1956))

MATERIAL AND METHODS
This study was based on samples of phytal and bottom sediments collected along rocky beaches of eight municipalities of the state of Santa Catarina, between the coordinates 26°10'/27°50'S and 48°26'/48°40'W (Fig. 1; Tab.I).Most of the southern and southeastern coast of Brazil, including the sampled region, presents micro-tidal regime (amplitude ≤ 2 m), and is inserted in the Southeast Coastal Region (Cabo Frio -Cabo de Santa Marta), formed mainly by sandy beaches with intermittent rocky spits (CoutinHo, 2000;tessler & goya, 2005).According to Pereira et al. (2009), the seawater average surface temperature ranges from 21° to 24°C in the months of April and May, during which the fieldwork was conducted (see HesP et al., 2009 for additional information on the study area).
The samples were collected handly, immediately after the low tidal mark, reaching up to 3 m of depth.Encrusting algae were scraped off and bagged, while arborescent algae had some branches involved in a plastic bag and then this piece of seaweed was cut off from the plant.The sediment was collected with the aid of a small shovel.All 62 samples (10 from bottom sediments and 52 phytal) were fixed in 8% formaldehyde in the field.In the laboratory, the algal material was washed through a 0.250 mm mesh and all specimens (living and dead) were picked under stereomicroscope.Living specimens were stored in vials containing alcohol 70%, and empty carapaces and isolated valves were glued in micropaleontological slides.
The material herein examined is held in the collections of the 'Museu de Paleontologia', Universidade Federal do Rio Grande do Sul (UFRGS), Section of Ostracoda.The figured specimens are identified by the prefix MP-O.All SEM photographs were taken at the 'Centro de Microscopia Eletrônica' at UFRGS.Morphological abbreviations: LV, left valve; RV, right valve; c, carapace; v, valve; ♀, female; ♂, male.Unfortunately, the paratype MP-O-2469 was lost after SEM procedures.
Diagnosis.Carapace small, somewhat ear-shaped mainly in LV lateral view.LV conspicuously larger than RV; overlap pronounced in dorsal region and immediately above the caudal process.Surface ornamented by costae and reticulae.Ribs predominantly low, thick and somewhat truncated.Ocular tubercle well developed, crossed by a strong rib.Ventro-lateral rib not superimposed on the corresponding margin.Posterior region with vertical rib bifurcated at the top and the bottom.Accommodation groove well developed.Hinge holamphidont; LV posterior socket with a conspicuous aurila-tooth and an auxiliary anti-slip tooth at its posterior end (sensu Jellinek, 1995).Central muscle scars with three frontal and four adductors (1+2+1+1).The frontal ones sometimes not well defined; upper and middle scars frequently somewhat anastomosed.Large duplicature with anterior vestibule.Radial porecanals numerous, simple and straight.Sexual dimorphism not prominent; females a bit higher and longer.
Etimology.From Latin origin, auris = outline similar a human ear.
Remarks.According to Benson (1961), the hemicytherid ostracodes invariably have one or two of the four adductor scars subdivided.However, Hazel (1967) claims that Hemicytherinae is the only subfamily of Hemicytheridae with one or more subdivided adductor scars.
Regarding to the frontal muscle scars, Hemicytherinae can be subdivided into two groups with two or three scars (Benson, 1961;morkHoven, 1963;Hazel, 1967).Jellinek (1995, tab.2) presents a comparative table of the genera grouped into the Tribe Aurilini, highlighting that this would be the only tribe to include genera of  Hemicytherinae with two frontal scars.Hazel (1967) proposes that Hemicytherinae should be subdivided into three major groups: Orionina-group, Aurila-group and Muelerina-group.However, Hartmann & Puri (1974) erects, among others, the tribes Orioninini, Aurilini and Urocythereidini, and includes, in each of them, the same genera proposed by Hazel (1967), respectively, with minor changes.In turn, yaJima (1982) follows the proposal of Hazel (1967) and inserts a fourth group (monogeneric) in Hemicytherinae, Finmarchinella Swain, 1963.Diagnostic features compared among the different tribes of Hemicytherinae, confronted to those of the new genus, indicate that Auricythere gen.nov. is best allocated in Aurilini.For more details of the diagnostic characters of this tribe see Jellinek (1995).
Auricythere gen.nov.occurs in the study area along with species of two other aurilinid genera: Auradilus costatus (Hu, 1979) and Aurila ornellase Coimbra & Bergue, 2003. Auradilus Jellinek, 1995 differs from Auricythere gen.nov.by well-defined diagnostic features, such as the pattern of the adductor muscle scars [1(2)+2-2-1] and the characteristic postero-dorsal shoulder.In turn, the highly diverse and cosmopolitan genus Aurila Pokorný, 1955 is more ear-shaped in LV lateral view and possesses a quite distinct ornamentation constituted by punctae and/ or reticulae, often concentric about mid-point; never with heavy ribs.For more details of morphological features of all Aurilini genera see Jellinek (1995, tab.2), and only for a review of the diagnosis of Aurila see Harrison et al. (2000).
Description.Carapace small, thick-shelled, somewhat ear-shaped mainly in LV lateral view.Maximum height at anterior cardinal angle.In dorsal view, compressed and with subparallel sides.Maximum width in the posterior region, poorly defined.LV conspicuously larger than RV, the margin of which overlaps it in dorsal region and immediately above the caudal process.In lateral view, anterior margin rounded, gently concave immediately in front of the anterior cardinal angle in RV.Posterior margin with discrete caudal process, more developed in RV.Dorsal margin slightly convex, sloping posteriorly, obscured by the ornamentation in LV.Ventral margin sinuous, with evident oral concavity more developed in RV.Surface ornamented by numerous ribs intercalated by depressed and reticulate areas.Ribs predominantly low, thick and somewhat truncated.Posterior region with a vertical rib subparallel to the correspondent margin, bifurcated at the top and the bottom: at the top, a short branch runs forwards and upwards while the second one reaches the posterior cardinal angle; at the base, a longer and sinuous branch runs forwards and downwards while the shorter and more rectilinear branch runs downward, turning forward before reaching the ventral margin.Eye tubercle conspicuous, crossed by a strong rib, more robust in its anterior branch that ends at about half height.Ventro-lateral rib delicate, not overlapping the corresponding margin.Six to seven well-developed reticulae adjacent to the anterior margin.Normal pore-canals sieve-type, scattered on the costae and muri.Internal view.Accommodation groove well developed in LV.Hinge holamphidont.LV posterior socket with a conspicuous aurila-tooth and an auxiliary small anti-slip tooth at its posterior end (sensu Jellinek, 1995).Large duplicature with a conspicuous selvage nearest to the external margin anteriorly.Anterior vestibule narrow and elongated.Radial pore-canals numerous, simple and straight, more abundant anteriorly.Central muscle scars with three frontal and four adductors (1+2+1+1), as follows: dorsal rounded, dorsomedian subdivided, dorsoventral sinuous and elongated, and ventral subelliptical.The frontal ones sometimes not well defined; upper and middle scars frequently somewhat anastomosed.Sexual dimorphism not prominent.Males with a little more developed caudal process and a less arched dorsal margin.
Remarks In respect to the ornamentation, Mutilus bears a typical butterfly-shape in the central area of the valves, present in all its species.Besides, this aurilinid fossil genus possesses a well-defined frame-rib, not developed in A. sublitoralis sp.nov.On the other hand, Auradilus features outline, ornamentation and central muscle scarsvery different of the new ostracode herein described, as already discussed above.The meaning of this upwelling in the distribution and abundance of this species is a matter of an ongoing project.
Auricythere sublitoralis sp.nov.was recorded along rocky beaches of four municipalities (Tab.I).This species occurs in three major algal groups, as follows: (i) green algae, which occurs mostly in clusters of different species, as already verified by PuPo et al.Previous analysis of 500 samples collected both by Phillips and van Veen grabs during a series of cruises throughout the Brazilian continental shelf between Rio de Janeiro (lat.21°S/long.40°W)and Rio Grande do Sul states (lat.35°S/long.54°W), and did not record the presence of this new taxon.The study of these samples is part of a long-term project whose goal is to describe the Ostracoda living on the southern Brazilian continental shelf (see ramos et al., 2004, 2009, 2012 for further details).
Therefore, this new taxon is an ostracode typical of euhaline and temperate very shallow waters, occurring mainly on phytal substrates.As it is the first record of this new genus and species, the complete geographical distribution of Auricythere sublitoralis sp.nov. is still unkown.
author acknowledge Dr. Cláudia Pinto Machado (UCS) for early discussions on Ostracoda morphology and taxonomy.A. L. M. M. and J. C. C. thank the "Conselho Nacional de Desenvolvimento Científico e Tecnológico" (CNPq) for a scholarship and for the financial support (proc.304453/2013-7), respectively.This paper was significantly improved with the suggestions of anonymous referees and of the associated editor.

Fig. 1 .
Fig. 1.Location map of the study area, state of Santa Catarina, Brazil.
(2011); (ii) brown algae of the genus Sargassum, also forming groups of different species, which also agrees with the observations of PuPo et al. (2011); and (iii) red algae, represented by fewer species.The ecological significance of the distribution of this new taxon is an ongoing project.
The main purpose of this study is the description of one new hemicytherid genus and species, Auricythere sublitoralis gen.nov., sp.nov., recovered living and dead from the upper rocky sublitoral (≤ 3 m water depth) of the central and northern coasts of the state of Santa Catarina (26°10'/27°50'S -48°26'/48°40'W).The other species of ostracodes recorded in the study area, distributed in 16 families, are part of an ongoing project.
Tab. I. Occurrence of Auricythere sublitoralis gen.nov., sp.nov. in the study area.