Two new Brazilian species of Chelodesmidae of the genera Iguazus and Tessarithys ( Diplopoda : Polydesmida )

Two new species of Chelodesmidae from the Brazilian northeast are described, Iguazus robustus sp. nov., from the state of Paraíba, and Tessarithys exacuminatus sp. nov., from the states of Pernambuco and Sergipe. Iguazus robustus sp. nov. differs from other species of the genus by having a constriction in the zone of the gonopodal acropodite tip and an extra branch at the tip of the acropodite. Tessarithys exacuminatus sp. nov. differs from the other species of the genus by the large and ascending subterminal dorsal branch of the prefemoral process of the gonopod. Brief reviews of the taxonomy, geographic distribution and a key for males of the respective genera are provided.


INTRODUCTION
Among the Diplopoda, with almost 5,000 described species in 31 families, the Polydesmida Leach, 1814 is the most speciose order (Brewer et al. 2012).Within the order, Chelodesmidae constitutes the second largest family, with about 800 described species.Members of this family occur in western Africa (Prepodesminae Cook, 1896) and South America (Chelodesminae Cook, 1895), according to Hoffman (1980).The systematics of Chelodesminae was reviewed by Hoffman (1980), who placed some genera and species in tribes.The remaining species were not reviewed by Hoffman (1980) or described after his classification.As a result, of the 171 genera and ca 800 species in Chelodesmidae, 89 genera and 455 species are currently not assigned to a tribe.
During the examination of the Diplopoda collection of the Instituto Butantan, Brazil, two new species of Chelodesminae from the Brazilian Northeast were found.The first belongs to Iguazus Chamberlin, 1952 and the other to Tessarithys Hoffman, 1990.Neither genera has been assigned to a tribe within the Chelodesmidae.
Many members of various groups within the Chelodesmidae share character states in their external morphology, and are mostly differentiated by variations in the structures of the male gonopod.These differences in the gonopod indicate that it has undergone rapid divergent evolution in the genitalia, as evidenced in numerous other arthropod groups (Eberhard 2010).Thus, discrimination among species in many chelodesmid groups depends on the analysis of the male gonopod.
In this work we describe the new species Iguazus robustus sp.nov.from Araruna, state of Paraíba and Tessarithys exacuminatus sp.nov.from São Caetano, state of Pernambuco and provide a map of their records.

MATERIAL AND METHODS
Morphological observations and illustrations were made using a Leica MZ12 stereomicroscope with a camera lucida.Photographs were taken with a Leica DFC 500 digital camera mounted on a Leica MZ16A stereomicroscope.Extended focal range images were composed with Leica Application Suite version 2.5.0.All measurements are in millimeters.The terminology of the gonopodal structures follows Pena- Barbosa et al. (2013) and Hoffman (1990), while the terminology used to describe somatic traits follows Attems (1898), Brölemann (1900)   Diagnosis.Males of Iguazus differ from other chelodesmid genera by the following combination of characters: gonopodal acropodite slender, unbranched and sinuously curved, prefemoral process massive in form of a narrow blade or branch, with one or two secondary processes arising proximally from the midlength region (Figs 1-3).
Distribution.Known from the states of Paraíba, Alagoas and São Paulo, Brazil and in Misiones, Argentina.
Description.Female: Unknown.Male (Holotype, IBSP 4397): Head reddish with a yellow labrum, Tömösvary organ suboval in shape.Antennae reddish brown, terminal antennomere with invaginations between the four apical sense cones.Body reddish brown and paranota tip yellow, gradually losing the brown color towards the posterior body rings, reddish brown color in the mid-body ring restricted to the anterior and posterior edge and yellow filling the remaining portion .Body rings: tegument smooth; alignment of paranota ventrally curved; paranota with posterior edges acutely produced from body ring 5; ozopore centrally situated on body ring 5; and posteriorly situated on the other body rings; ozopore arrangement at the edge of paranota: 5, 7, 9, 10, 12, 13, 15-19 (following the standard polydesmid pore formula).Penultimate body ring with reduced paranota (Fig. 12, arrows).Stigma oval and elongated.Coxae of leg pair 2 nd with rectangular shaped genital papilla (Fig. 7, arrows).Sternite of body ring 5 with a pair of elongated projections (Fig. 8).Sternite of body ring 8 presenting two pairs of pointed projections in the zone anterior to the coxae (Fig. 9, arrows).Gonopod aperture on seventh body ring: elliptical, posterior edge without folds.Legs whitish yellow, with rounded ventro-apical process on the prefemur and with an apical-ventral Distribution.Known only from the type locality (Fig. 28).

Key to males of
Diagnosis.Males of Tessarithys differ from other chelodesmid genera by the combination of the following characters: sternite of body ring 5 with four projections (Fig. 14).Legs with apical-ventral projection on the tibia (Fig. 17).Gonopodal prefemoral process exceeding the acropodite apex and forming a distinct sheath on the ectal side, also displaying a subterminal dorsal branch on the middle portion.Acropodite are divided into two slender and acuminate branches .
Gonopods : gonopod coxae equivalent to about half the length of the telopodite and prominent in ectal view (Fig. 6).Coxae with two bristles in the distal dorsal side.Spiniform projection absent.Cannula (Fig. 4): hook-shaped.Prefemoral region short, ventrally developed, 1/3 the size of telopodite.Presence of a conspicuous groove near the first portion of the acropodite, in the ectal view (Fig. 6,arrow).Prefemoral process (PfP) long, parallel to the acropodite (A); displays a long and acuminated subterminal dorsal branch on the middle portion (Figs 4-6, X).The final portion of the prefemoral process passes on the back of the acropodite, forming a distinct protection on the lateral side, with two blades forking in the terminal portion (Fig. 4).Acropodite (A) long and slender, with solenomere and one additional branch (Fig. 4).Spermatic groove mostly visible in mesal view except at the base of the acropodite where it diverts to the ectal side.
Variation.The body of the paratype (IBSP 4434) shows reddish brown coloration, with the edges of the paranota whitish yellow, tegument smooth and with a median band present, weakly developed .
Distribution.State of São Paulo, Brazil and Misiones, Argentina.