Oxymycterus misionalis Sanborn

D’Elía, Guillermo, Mora, Ismael, Myers, Phil & Owen, Robert D., 2008, New and noteworthy records of Rodentia (Erethizontidae, Sciuridae, and Cricetidae) from Paraguay, Zootaxa 1784, pp. 39-57 : 46-47

Oxymycterus misionalis Sanborn

Fig. 5 . Table 1

Type Locality: Río Paranay, Misiones, Argentina; restricted to the confluence of the Paranay Guazú and Paraná Rivers, General San Martín, Misiones by Pardiñas et al. (2007).

Distribution: Known from the Argentinean province of Misiones and from Alto Paraná in Paraguay.

New records: ALTO PARANA: 6) Puerto Bertoni, 25º.38’ S 54º.40’ W, 91 m (BMNH 21.4.21.4). CA- NINDEYU: 7) Colonia Britez Cue, 24º 15’ 05.2’’ S 55º 18’ 24.1’’ W, 222 m (TK 130587); 8) Colonia Britez Cue, 24º 14’ 21’’ S 55º 16’ 04’’ W, 266 m (TK 121751, TK 121752, TK 141169). Figure 1 . The record from Alto Paraná was taken from the unpublished dissertation of Joäo A. Oliveira (1998).

Taxonomy: In spite of recent advances (e.g. Oliveira 1998; Hoffmann et al., 2002), the alpha taxonomy of Oxymycterus remains confused in several aspects, and as explained below, difficult issues continue to arise. Our records may play a key role to solve a complex Oxymycterus nomenclatorial and taxonomic issue, as they approximate the probable collection locality of the type of O. rufus (Fischer) and by extension, the population which should be ascribed to this taxon. By their morphology, our specimens belong to the species presently bearing the name O. misionalis , not to O. rufus as it is currently understood (for a detailed revision of Oxymycterus see Oliveira 1998). However, they may in fact represent the latter taxon. Fischer (1814) named Oxymycterus rufus on the basis of Azara’s (1801) description of the “rat roux” ( Contreras & Teta 2003). Azara based his description on a mouse sent to him by his friend Pedro Blas Noceda, a priest that practiced at the towns of Santiago, Santa María de Fe, and San Ignacio, in southern Paraguay. This convinced Galliari et al. (1996) to restrict the type locality of O. rufus to San Ignacio in the Department of Misiones, Paraguay. By the same line of reasoning, more than 150 years earlier, Rengger (1830) restricted the type locality of O. rufus to an area (Ñu Guazu) near Asunción, the Paraguayan capital. The view that the type locality of O. rufus lies in Paraguay was followed, sometimes with simplifications, by later authors (e.g., Gyldenstolpe 1932 indicated only “ Paraguay ” as the type locality; Cabrera 1961). The actual place where Noceda collected the specimens, however, remains unknown. This uncertainty, in conjunction with two other issues, has led most authorities of sigmodontine taxonomy during the last two decades to consider the terra typica of O. rufus to lie in Argentina rather than Paraguay (e.g., Hershkovitz 1994, Oliveira 1998; Musser and Carleton 2005; but see Contreras & Teta 2003). The first of these issues is that a second specimen of Oxymycterus (“hocicudo”) described by Azara (1802) was incorrectly assumed to be the same individual that served as the diagnosis basis of the rat roux (see details in Contreras & Teta 2003). In his 1802 book, Azara provided latitudinal information (32 ½ degrees) for the collection site of the hocicudo. Musser and Carleton (1993) and Hershkovitz (1994) assumed that the hocicudo and the rat roux were the same specimen and as a result, erroneously suggested that the bibliographical type of O. rufus was collected at that latitude, which falls outside of Paraguayan borders. Moreover, it was assumed that Paraguay was inhabited only by a blackish form of Oxymycterus described as O. delator Thomas (a report by de Roguin, 1986: 1819-1829, of a reddish specimen collected in 1982 near Ciudad del Este in eastern Paraguay, and identified as O. rutilans --a synonym of O. rufus-- was overlooked.) As a result, currently most authorities list the type locality of O. rufus as lying outside Paraguay. Our records, together with the observation of de Roguin (1986), of a relatively reddish form from Paraguay suggest, in accordance with Contreras and Teta (2003), among others, that Azara may indeed have used a Paraguayan mouse to describe the rat roux. In turn, this implies that the type locality of O. rufus may be restricted to a location within Paraguay. We note that our records are about 275 and 340 km from San Ignacio, the area to which Galliari et al. (1996) restricted the type locality of O. rufus , but more than likely in Azara’s time forest habitats were continuous between the two areas.

We are aware of the important nomenclatorial changes that the scenario we pose would cause in Oxymycterus taxonomy. But we also note that that taxonomy would revert, at least in part (i.e., the placement of the O. rufus type locality within Paraguay), to a scenario that was abandoned only recently (i.e., Musser & Carleton 1993; Hershkovitz 1994). Here, we do not innovate in this respect and refer these Paraguayan specimens to O. misionalis , preferring to reserve further treatment of this problem for an upcoming contribution focused on Oxymycterus systematics by D’Elía and collaborators.

On a related issue, Musser and Carleton (2005) considered O. misionalis and O. judex as junior synonyms of O. quaestor Thomas. It is worth noting that a cyt b haplotype recovered from the Paraguayan specimen TK 12151 ( EU449517 ) is only 0.5 % divergent from O. misionalis (one specimen) from Argentina and from O. judex (two specimens) from Brazil, and is 2.8 – 2.9 % divergent with haplotypes referred to O. quaestor (three specimens) from Brazil. We recognize that the relationship among misionalis , judex , and quaestor is yet another unresolved taxonomic issue within the genus Oxymycterus , and therefore, pending further study, we prefer to follow the most recent reviews (Oliveira, 1998 and Hoffmann et al. 2002), in recognizing O. misionalis as a valid species.

Comments: These records constitute the first citation of the O. misionalis for Paraguay (but see above, especially concerning the specimen reported by de Roguin 1986). This report confirms that two species of Oxymycterus inhabit Paraguay; these are currently referred to as O. delator and O. misionalis . Specimens of the latter were collected in low secondary forest and abandoned crop fields. A female and a male collected in February (2007) had vagina open and scrotal testes, respectively. An adult female collected in June (2006) had the vagina closed. Others (all adults) captured and released in June included one female with vagina closed, three males with testes scrotal, and one with testes abdominal. Other sigmodontines collected in the same trap lines with O. misionalis include Akodon montensis , Calomys callosus (Rengger) , and Necromys lasiurus .

Figures

FIGURE 1. Map of Paraguay indicating the localities where the specimens reported here were collected. Locality numbers refer to those of the text.

FIGURE 5. Dorsal, ventral and lateral views of the cranium and mandible of Oxymycterus misionalis from Paraguay (TK 121752). Scale bar = 5 mm.