Myotis chiloensis (Waterhouse, 1840)

Novaes, Roberto Leonan M., Pedro, Annia Rodríguez-San, Saldarriaga-Córdoba, Mónica M., Aguilera-Acuña, Omayra, Wilson, Don E. & Moratelli, Ricardo, 2022, Systematic review of Myotis (Chiroptera, Vespertilionidae) from Chile based on molecular, morphological, and bioacoustic data, Zootaxa 5188 (5), pp. 430-452 : 442-443

Myotis chiloensis (Waterhouse, 1840)

Type. Neotype FMNH 24029 , adult female collected by J. Vera in 1923; skull partially damaged, mandible, and skin (see LaVal 1973).

Type locality. Cucao, Chiloé Island, Los Lagos, Chile.

Distribution. Occurs in Southern Chile, eastward into western Argentina and southward to Tierra del Fuego, occupying the Hyper-oceanic Temperate and Patagonian bioclimatic zones, in Deciduous Forest, Evergreen Forest, Valdivian Rainforest, and Magellanic Moorland ( Ossa & Rodríguez-San Pedro 2015; Novaes 2019). Records are from sea level to ca. 1,400 m a.s.l.

Diagnosis. Medium to large size (FA 36.3–40.0 mm; GLS 13.8–15.3 mm); dorsal fur long (6.5–8.5 mm), woolly, unicolored or subtly bicolored, with medium-brown bases (near Mummy Brown) and tips generally Brussels Brown or Cinnamon Brown; ventral fur bicolored, with Mummy Brown bases and Dresden Brown tips; dorsal surface of the uropatagium naked; fringe of hairs on the distal border of the uropatagium absent; plagiopatagium connected to the feet by a broad band of membrane. Sagittal crest usually absent; broader skull; braincase high in profile and elongated in dorsal view; braincase roof formed by the parietal bone is straight; forehead subtly sloping in lateral view; broad and short rostrum; posterior region of the braincase rounded and quite projected beyond the limit of the occipital condyles; mastoid processes narrow.

Description and comparisons. Dental formula is I 2/3, C 1/1, PM 3/3, M 3/3 (2x) = 38, and the teeth are robust and well developed. The second upper premolar (P3) is approximately the same size as the first upper premolar (P2), aligned in the toothrow, and visible labially. Skull medium to large with braincase elongated in dorsal view; parietals slope subtly forward to frontal bone; braincase roof is straight; mastoid processes narrow and poorly developed; rostrum long and broad; the sagittal crest is usually absent and lambdoidal crests are present and low; and the occipital region is rounded and projected beyond the posterior surfaces of the occipital condyles.

Ears comparatively short in size, not reaching the nostrils when extended forward. Membranes and ears are Mummy Brown. Plagiopatagium is connected to the feet at the level of the toes by a broad band of membrane; a fringe of scattered hairs on the distal border of the uropatagium is absent. Dorsal surface of the uropatagium virtually naked. Woolly and medium to long fur; dorsal hairs generally Brussels Brown or Cinnamon Brown, with the basal half subtly darker. Ventral fur bicolored, with Mummy Brown bases (1/2 of total hair length) and Dresden Brown tips (1/2 of total hair length).

Considering either the assemblage of Myotis that occurs along mountainous habitats or in the lowland portion of the western side of the Andes ( M. albescens , M. atacamensis , M. arescens , M. bakeri , M. keaysi , and M. oxyotus ), M. chiloensis can be distinguished from all by the set of diagnostic traits. It is morphologically closer to M. arescens , from which it can be distinguished by its darker ventral fur (near Dresden Brown in chiloensis and near Pale Olive Buff on the tips in arescens ), comparatively shorter ears (in arescens the ears reach the nostrils when extended forward), fringe of hairs on the distal border of the uropatagium absent (present in arescens ), and broader rostrum (BAC ≥ 3.6 in chiloensis, BAC ≤ 3.6 in arescens ). Furthermore, M. chiloensis is larger than M. arescens in general, with only the smallest individuals reaching sizes similar to those in the largest arescens individuals ( Table 3 ).

Myotis chiloensis can be distinguished from M. atacamensis and M. bakeri by its general smaller size (e.g., FA> 36 in chiloensis, FA <35 in atacamensis and bakeri ); woolly fur with dorsal hair cinnamon-brown weakly contrasting between bases and tips, and venter brownish; in M. atacamensis and M. bakeri the fur is silky, dorsal hairs with strong contrast between bases (blackish) and tips (yellowish), and venter whitish.

From M. albescens , it can be distinguished by the darker ventral fur color being entirely brownish with little contrast between base and tip in M. chiloensis ; while M. albescens have the throat yellowish, grading to whitish towards the abdomen and sides of the body, with hairs strongly bicolored (blackish base and whitish tips). In addition, M. albescens has a more globular braincase (see Moratelli & Oliveira 2011); whereas in M. chiloensis the braincase is elongated.

Myotis chiloensis can be distinguished from M. oxyotus by its shorter and woolly fur, with dorsal hairs cinnamonbrown with bases slightly darker, and ventral fur weakly bicolored, Dresden Brown in color; whereas in M. oxyotus the fur is silky and very long (LDF> 8 mm), bicolored, with blackish bases and generally Mummy Brown or Brownish Olive tips, and ventral fur strongly bicolored with blackish bases and tips ranging from Pale Pinkish-Buff to Deep Olive-Buff. In M. chiloensis the parietals slope subtly to the frontal bones and the braincase is elongated in dorsal view; whereas in M. oxyotus the parietals slope steeply to the frontal bones and the braincase is inflated in dorsal view. Myotis chiloensis can be distinguished from M. keaysi by its fur color, with dorsal hairs cinnamonbrown unicolored or with bases slightly darker, and ventral fur weakly bicolored, Dresden Brown in color; whereas in M. keaysi the dorsal fur is reddish-brown (from Cinnamon Brown to Ochraceous Tawny) with the base being remarkably darker, and ventral fur with Clove Brown bases and tips ranging from Ivory Yellow to Light Drab. In relation to skull morphology, it differs from M. keaysi by sagittal crest absent, mastoid process narrower and poorly developed, and parietals sloping subtly to frontal bones; in M. keaysi a sagittal crest is always present, mastoid process larger and well-developed, and parietals slope steeply to frontal bones.