Description and phylogenetic position of a new species of Metarthrodes ( Opiliones : Gonyleptidae : Caelopyginae ) from Bahia , northeastern Brazil

We describe Metarthrodes oxum sp. nov. from Camacan, state of Bahia, Brazil, the second species of Caelopyginae described from the state, after Metarthrodes xango Pinto-da-Rocha, 2002. Metarthrodes oxum sp. nov. can be recognized by the presence of a pair of white spots on area I, white C-shaped stripes on lateral grooves of area III, posterior margin with transverse white stripe, grooves of mesotergal areas well-marked, posterior margin of dorsal scute slightly concave, and medial third of femur IV of male with three large and spiniform retrolateral tubercles. We tested the generic placement of the new species via cladistic analysis. Metarthrodes oxum sp. nov. clustered within Metarthrodes, forming a clade with M. pulcherrimus (Mello-Leitão, 1931), M. nigrigranulatus Roewer, 1913 and M. longipes (Soares, 1945), which was unresolved in the consensus cladogram of the 72 optimal trees found, and is supported by the following synapomorphies (all present in males only): trochanter IV with long internal apophysis; retrolateral submedian tubercle on femur IV, and a pair of white spots near the groove. We also provide an updated identification key for the species of Metarthrodes.

The Caelopyginae comprises 30 species grouped into nine genera, and includes medium-sized gonyleptids, usually yellow to greenish, with white spots on the dorsal scute.Species in this group are highly endemic, and are found in the Atlantic Forest of eastern Brazil, from the state of Bahia, in the North, to the state of Santa Catarina, in the South (PINTO-DA-ROCHA 2002, DASILVA & PINTO-DA-ROCHA 2012).
Caelopyginae forms a clade with Gonyleptinae, Sodreaninae, Progonyleptoidellinae and Hernandariinae (KURY 1992, 1994, 1995, PINTO-DA-ROCHA 2002, DASILVA & PINTO-DA-ROCHA 2010, PINTO-DA-ROCHA & BRAGAGNOLO 2010, CAETANO & MACHADO 2013).Those closely related Gonyleptinae-like subfamilies (referred to as K92 by CAETANO & MACHADO 2013: 8) are characterized by having a deep parabolic cleft on the distal margin of the ventral plate of the penis, which is pyriform and bears extremely developed basal lobes that are dorsally directed (instead of laterally) (KURY 1992, 1994, 1995, KURY & PINTO-DA-ROCHA 2007).The monophyly of clade K92 has been corroborated by various cladistic analyses, and additional morphological synapomorphies have been found for the group: characters in the pedipalpus, the armature of the anterior margin of the dorsal scute and the armature of femur IV of the male (PINTO- Before this contribution, Metarthrodes Roewer, 1913 included nine species, distributed in the Atlantic Forest from the state of Bahia to the state of São Paulo (with a questionable record of M. nigrigranulatus Roewer, 1913 from the state of Paraná) (PINTO-DA-ROCHA 2002).In this paper we describe an additional species in Metarthrodes.The new species is also the second known record of Caelopyginae from Bahia, Brazil.In order to confirm the phylogenetic position of the new species, we performed a parsimony analysis using morphological data from PINTO-DA-ROCHA ( 2002) and DASILVA & PINTO-DA-ROCHA (2012).

MATERIAL AND METHODS
The original photographs were taken with a Sony Cybershot DSC-V1 attached to an Olympus dissecting microscope.In order to obtain images with a greater depth of field, we used focus stacking, a digital image processing technique which combines multiple images taken at different focus distances using  2012).We also made schematic illustrations directly from the photographs, or using a camera lucida.We followed the morphological nomenclature of PINTO-DA-ROCHA (2002) and adaptations of DASILVA & PINTO-DA-ROCHA (2012).
The collections mentioned in this paper and their respective acronyms are: Museu de Zoologia, Universidade Federal da Bahia, Salvador, Brazil (MZ-UFBA); Museu Nacional, Universidade Federal do Rio de Janeiro, Brazil (MNRJ).All measurements are given in millimeters (mm).The tarsal formula is given as follows: I, II, III, IV, with numbers for legs I-II followed by the distitarsal count within parentheses.
In order to test the generic placement of our new species, we added Metarthrodes oxum sp.nov. to the matrix of PINTO-DA-ROCHA (2002), with Thereza murutinga DaSilva & Pinto-da-Rocha, 2012, Pristocnemis caipira DaSilva & Pinto-da-Rocha, 2012, and the modifications proposed by DASILVA & PINTO-DA-ROCHA (2012) (see Parsimony analysis section).We performed an heuristic search with multiple random addition sequences (1,000 replicates) saving up to 1,000 trees per replication, swapping trees with TBR using the program TNT (GOLOBOFF, FARRIS & NIXON 2008).Characters were treated as unordered and equally weighted.We evaluated branch-support by absolute Bremer support (BREMER 1994), relative Bremer support (RBS, relative fit difference; GOLOBOFF & FARRIS 2001), and bootstrap (FELSENSTEIN 1985), also implemented by TNT.The Bremer support was calculated by searching for suboptimal trees, increasing the number of suboptimal trees in steps.The bootstrap analysis was performed with 3,000 replicates with tree bisection-reconnection branch swapping.We studied the distribution and optimization of the characters on the optimal trees obtained using WINCLADA (Nixon 2002).
Diagnosis.Resembles M. nigrigranulatus by possessing a blunt armature pair in area III and a pair of white spots on the prosoma, behind the ocularium; differs from it by having the posterior margin with transverse white stripe, grooves of mesotergal areas well-marked, posterior margin of dorsal scute only slightly concave and male femur IV with three large and spiniform retrolateral tubercles on medial third.
Differs from other species by the brownish body (yellow or green in other species), and a pair of C-shaped white stripes on lateral grooves of area III.
Description.Male holotype.Measurements.Prosoma length 2.3; prosoma maximal width 3.5, opisthosoma length 4.1, opisthosoma maximal width 6.1.Measurements of appendages as in Table I.   and 5-7).Anterior margin of dorsal scutum with two spiniform parallel median tubercles on frontal hump.Ocularium with pair of small tubercles.Carapace with disperse tubercles lateral and posterior to the ocularium.Mesotergum with tubercles irregularly distributed.Area I divided in left right halves by a median longitudinal groove.Areas I-III each with median pair of round tubercles, larger in area III.Posterior margin slightly concave.Posterior margin and free tergites each with a row of small tubercles.Dorsal anal operculum unarmed, with sparse granules.Venter (Figs 2 and  6).Coxae I-II with transversal rows of setiferous tubercles, the median row with larger tubercles.Coxae III-IV with small setiferous tubercles irregularly distributed.Posterior margin of stigmatic area and free sternites with a row of granules.Ventral anal operculum unarmed.Chelicerae (Figs 1-3 and 5-7).Segment I with small setiferous prolateral tubercle on bulla; II-III with three and five teeth, respectively.Pedipalpi (Figs 1,2,8,and 9).Long and thin.Coxa smooth.Trochanter with small setiferous ventral tubercle.Femur and patella smooth.Tibia mesal Iii; ectal iI(Ii).Tarsi mesal ectal II.Legs (Figs 1 -3, 5, 6, and 10-14).Coxae I-II with one dorso-anterior tubercle; III smooth; IV tuberculate with prolateral apical apophysis directed backwards, 1.5 longer than retrolateral.Trochanters I-III with scattered ventral tubercles; IV with basal prolateral blunt tubercle and sub-apical retrolateral spiniform apophysis, twice as long as prolateral.Femora I-III straight and with small tubercles; IV sub-straight in dorsal view and slightly curved in lateral view; with one dorsal row of tubercles, larger and conical on medial third; one ventral row of tubercles, increasing in size and taking a more retrolateral position towards apex, the 3-4 distal tubercles larger and spiniform; one prolateral row of tubercles on proximal half, and one prolateral row of blunt tubercles beginning at middle, 3 distalmost tubercles larger and spiniform; one retrolateral row of tubercles, three largest and spiniform on medial third and one apical spiniform.Patellae I-III with small ventral tubercles; patella IV tuberculate, with long spiniform ventral tubercles.Tibiae I-III smooth; tibia IV densely tuberculate on ventral region.Tarsal counts: 8(3), 16-17 (4), 16-17, 16-17.Color (in ethanol) (Figs 1-4).Dorsal scute brownish-yellow, covered by dark-brown tubercles, with dark-brown reticulation in carapace and mesotergal areas, darker in area III.Legs with brownish-yellow background, with strong darkbrown reticulation.Chelicerae and pedipalpi yellow, chelicerae with dark-brown reticulation and pedipalpi with dark-brown reticulation on femora, patellae, tibiae and tarsi.Prosoma with pair of white spots behind ocularium.Mesotergal area I with paramedian pair of white spots.Area III with pair of C-shaped white stripes on lateral grooves of area III (resembling parentheses).Posterior margin with transversal white stripe; dorsal anal operculum with anterior white arch stripe, ventral anal operculum with pair of white spots.Penis .Distal part of truncus with dorsal part enlarged and subapical ventral deep cleft, giving a sinuous aspect in lateral view to the penis.
Ventral process of glans with cleft, without prominences.Stylus short and thick, without microsetae apically.Ventral plate thick, densely covered by ventral microsetae and with short, U-shaped cleft on apical margin.Three pairs of distal setae, located apically, and five pairs on basal lobe (basal long).
Female.Unknown.Distribution.The species is known only from the type locality, an area of evergreen alluvial forests (IBGE 2012).The state of conservation of the vegetation in Serra Bonita varies, with some areas apparently untouched, but also including others in different stages of ecological succession, and areas where cocoa is cultivated (Amorim et al 2009).
Etymology.Oxum is an Orisha (minor god) from the Yoruba religion, whose pantheon (set of gods) was incorporated by Afro-Brazilian religions such as the Candomblé and Umbanda, religions widely practiced in Bahia.Oxum is represented as a charming female deity, who reigns over lakes and rivers.We chose Oxum in reference to the other species of Caelopyginae from Bahia, Metarthrodes xango, because Oxum is also one of the spouses of Xango.

Parsimony analysis
The character states for the new species in the matrix of PINTO-DA-ROCHA (2002)    Notes on the codification: We coded M. oxum sp.nov.as having state 0 for character 35, "Truncus of penis without subapical projection (PINTO-DA-ROCHA 2002: 375).However, the ventral deep cleft in the truncus (Fig. 18) gives it a sinuous aspect, similar to the species that have a subapical projection: M. laetabundus, M. xango and Pristocnemis perlatus (Giltay, 1928).However we propose a new character to account for this similarity in the male genitalia: Character 59.Male genitalia, distal part, ventral subapical cleft: (0) absent; (1) present.Metarthrodes laetabundus, M. oxum sp.nov., M. xango and Pristocnemis perlatus were coded as "present"; the remaining terminal taxa were coded as "absent".
We also emended state 1 of character 51 (spots on area III of male; PINTO-DA-ROCHA 2002: 377) to "with pair of rounded or C-shaped white spots near groove IV".The spots in M. oxum sp.nov.are C-shaped (resembling parentheses), but their position on the groove suggests that they are homologous with the rounded spots.
The addition of M. oxum sp.nov.caused the relationships among some species of Metarthrodes to differ from the previous analysis (PINTO-DA-ROCHA 2002).However, the overall topology obtained by us is not only congruent with DASILVA & PINTO-DA-ROCHA ( 2012), but it also adds more resolution to it.We have also recovered a basal M. bimaculatus and the clade M. laetabundus + M. xango.However, in our topology, M. hamatus appears as the sister-group of M. nigrigranulatus + M. longipes + M. pulcherrimus, and M. leucopygus as sister-group of M. albotaeniatus, both clades with very low support (Fig. 19).We recovered the group M. nigrigranulatus + M. longipes + M. pulcherrimus, as in those previous analyses, but with the addition of M. oxum sp.nov.We could not elucidate the relationship among those species.As DASILVA & PINTO-DA-ROCHA (2012) had already stressed, we reinforce the need for new studies on phylogeny of Caelopyginae, using new character systems.

Table I .
Appendage measurements of the male holotype of Metarthrodes oxum sp.nov.