First description of the male of Oonops nigromaculatus Mello-Leitão , 1944 ( Araneae : Oonopidae ) with the redescription of the female and new records

The male of Oonops nigromaculatus Mello-Leitão 1944 is described for the first time and the female is redescribed from recently collected specimens. New records from Argentina and Uruguay are provided.


INTRODUCTION
The Oonopidae is a family of small to very small haplogyne, ecribellate, six-eyed spiders whose greatest diversity occurs in tropical regions (Jocqué & Dippenaar-Schoeman, 2006).They comprise around 507 described species in 73 genera (Platnick, 2009), although there is evidence that these numbers represent only a small fraction of current oonopid diversity (Fannes & Jocqué, 2008).Simon (1890) established the family, and later classified the then known genera according to their degree of body sclerotization, dividing them into two informal subgroups, the «loricati», with abdominal scuti, and «molles», with soft abdomens (Simon, 1890(Simon, , 1893)).The monophyly of these groups is, however, doubtful, as the monophyly of the whole family (Fannes & Jocqué, 2008), but see Burger & Michalik (2010).
Among the «molles», 13 South American species are currently listed in Oonops Templeton (see Platnick, 2009); two of them were described from Argentina: O. tucumanus Simon 1907, from Tucumán (whose type should be located in Museum National d'Histoire Naturelle, Paris), and O. nigromaculatus Mello-Leitão 1944, from Buenos Aires, whose type is deposited in Museo de La Plata.This genus, unfortunately, has been usually treated as a wastebasket group for soft-bodied oonopids with spinose forelegs.Recent studies suggest that at least the New World species currently attributed to the genus are not congeneric with the type species, O. pulcher Templeton.For example, a large group of these entities, containing the circum-Caribbean species without strong macrosetae on the forelegs and with spinose female pedipalps, has been transferred to the genus Heteroonops Dalmas 1916 (Platnick & Dupérré (2009b).Apart from the 13 species described, judging by several collections under study, this group appears as very diverse, with a large number of species undescribed, that could belong to a still uncertain number of new genera.
In this contribution, we present the redescription of one of the two species previously described from Argentina: O. nigromaculatus.The examination of the syntypes of O. nigromaculatus and the comparison with newly collected material allowed us to identify the still unknown male of the species, which is described in this paper.The aim of this paper is to characterize the species describing the unknown male, redescribing the female from recently collected specimens, and provide distribution data.Although this species may not be closely related to Oonops pulcher, we postpone further taxonomic actions until an ongoing revision of the «molles» oonopids from South America is completed.

MATERIALS AND METHODS
Specimens were deposited in the following collections: Museo de La Plata (MLP, Luis E. Pereira), Museo Argentino de Ciencias Naturales «Bernardino Rivadavia», Buenos Aires (MACN, Cristina L. Scioscia) and American Museum of Natural History, New York (AMNH, Norman I. Platnick).Female genitalia were observed in clove oil.Drawings were made with a camera lucida mounted on an Olympus BH-2 compound microscope.Photographs of the preserved specimens were taken with a digital camera Leica DFC 290 mounted on a stereomicroscope Leica M165 C, and the focal planes were composed with Helicon Focus 4.62.2.The format of descriptions follows mostly Platnick & Dupérré (2009a).All measurements are expressed in millimeters.We report GPS coordinates of the localities when available; otherwise, we provide approximate coordinates (denoted with «ca.») calculated with Google Earth (http://earth.google.com)from label data.

SYSTEMATICS Family OONOPIDAE Simon 1890
Genus Oonops Templeton 1835 Diagnosis.O. nigromaculatus is the only species among all the currently listed in Oonops in which the males have a narrow, darkened, sclerotized stripe on the anterodorsal part of the abdomen (Fig. 10).Females are distinguished by the shape and conformation of the internal genitalia (Fig. 6-9, although this feature has not been reported for most of the species of the genus).
Remarks.The syntypes are in poor condition (Figs. 1, 2), but the genitalia are still observable and very similar to those of the newly collected females here considered conspecific (Figs. 4,(8)(9).The female from Córdoba has a remarkably widened distal part of the anterior receptacle, but this variation is presumed as intraspecific, given that this feature is also observed in the specimen here designated as lectotype.The dark semicircular spots at the sides of the spinnerets (very conspicuous in the lectotype, and that gave the specific name, Fig. 2) are not evident in all the specimens.In the original description, Mello-Leitão mentioned three spines on the anterior femora, but the syntypes and the newly collected specimens have only two prolateral ventral spines on the femur I, and only one on the femur II.
Natural history.Some specimens were collected in Parque Nacional El Palmar with pitfall traps in a grassland, and sifting leaf litter in a forest close to a small river.