Myotis cf. simus, Thomas, 1901

Novaes, Roberto Leonan M., Claudio, Vinicius C., Diaz, M. Monica, Wilson, Don E., Weksler, Marcelo & Moratelli, Ricardo, 2022, Argentinean Myotis (Chiroptera, Vespertilionidae), including the description of a new species from the Yungas, Vertebrate Zoology 72, pp. 1187-1216 : 1187

Myotis cf. simus

Comments.

The M. simus complex was taxonomically revised resulting in the recognition of the recently described species Myotis midastactus Moratelli & Wilson, 2014, based on individuals originally identified as M. simus from Bolivia ( Moratelli et al. 2011b; Moratelli and Wilson 2014). Subsequently, populations of M. simus from Paraguay were reidentified as M. midastactus based on morphological traits ( Moratelli et al. 2015). Moratelli et al. (2019a) considered that M. simus has two disjunct populations, one in dense humid forests along the Amazon Basin and the other in Brazilian Pantanal and Humid Chaco from Argentina and Paraguay. However, specimens from Argentina can be distinguished from M. simus from the Amazon Basin by paler pelage, and larger skull with lower sagittal crest. Considering the geographic discontinuity ( Moratelli et al. 2011c) and morphological differences, it is likely that samples from Argentina represent a distinct taxon from M. simus from the Amazon Basin. On the other hand, one specimen from Argentina is more similar to M. midastactus in fur color (MACN 18033) but differs slightly in cranial traits. Other specimens from Argentina differ conspicuously from M. simus and M. midastactus in fur color. Thus, samples from Argentina may (i) represent a population of M. midastactus (with subtle geographic variation in relation to fur color); (ii) represent Myotis guaycuru Proença, 1943, a species described for the Brazilian Cerrado-Pantanal transition and currently considered a junior synonym of M. simus ; (iii) represent a third and unnamed species, with occurrence restricted to the Argentinean Humid Chaco. If the third hypothesis is confirmed, M. guaycuru could be the valid name for the populations currently considered as M. midastactus from Bolivia and Paraguay. However, due to morphological similarity and the absence of phenotypic discontinuity, the resolution of this issue depends on the analysis of new specimens from all ecoregions based on morphological and molecular approaches.

In Argentina, this taxon is medium to large-sized (FA 38.0-41.3 mm, body mass 8.0-9.5 g; Table 6 ; Fig. 11 ), with wooly and very short fur (LDF 2.7-3.4 mm, LVF 2.5-2.9 mm). Ears are comparatively short (length 10-14 mm). Dorsal fur ranges from Clay Color to Wood Brown, without contrast between bases and tips. The ventral fur weakly bicolored, with Drab bases (1/2 hair length) and tips (1/2 hair length) ranging from Colonial Buff to Pale Olive-Buff. Membranes and ears are Clove Brown or lighter. Legs and dorsal surface of uropatagium are naked. A fringe of hairs along the trailing edge of the uropatagium is absent. The plagiopatagium attached to feet at the ankles level or on the base of the toes by a narrow band of membrane. Skull medium to large in size (GLS 14.0-15.0 mm, BCB 6.8-7.5 mm), and the rostrum comparatively short and broad. The P3 smaller than P2 and usually displaced to lingual side in the toothrow. Sagittal crest and lambdoidal crests present and ranging from low to medium. Parietals slope anteriorly; occipital region flattened and subtly projects beyond the occipital condyle limits; postorbital and interorbital constrictions comparatively wide.

Argentinean populations of M. cf. simus are present in Humid Chaco and Mesopotamian Savanna from Formosa and Corrientes Provinces, and in the Delta e Islas del Paraná in Santa Fe Province, occupying an altitudinal range from 46 to 200 m ( Pavé and Gavazza 2022).

Figures

Figure 11. Adult male of Myotis cf. simus (MACN 18033) from Corrientes, Argentina.