Myotis pampa, Novaes & Wilson & Moratelli, 2021

Novaes, Roberto Leonan M., Wilson, Don E. & Moratelli, Ricardo, 2021, A new species of Myotis (Chiroptera, Vespertilionidae) from Uruguay, Vertebrate Zoology 71, pp. 711-722 : 711

Myotis pampa sp. nov.

Holotype.

The holotype (AMNH 205471) comprises the skin and skull of an adult female (Figs 4 - 5 ), collected by M. D. Tuttle in January, 1963. The specimen is deposited in the mammal collection at the American Museum of Natural History (New York, USA).

Type locality.

Ca. 6 km NW from Belén, Artigas, Uruguay (30°37'S; 57°50'W; 32 m elevation).

Paratypes.

Five individuals from ca. 6 km NW from Belén, Artigas, Uruguay (30°37'S; 57°50'W, 32 m of elevation; AMNH 205461 ♀, AMNH 205464 ♀, AMNH 205467 ♀, AMNH 205472 ♀, AMNH 205476 ♀); and nine individuals from 40 km NW to Tacuarembo city, Tacuarambó, Uruguay (31°38'S; 56°19'W, 240 m of elevation; AMNH 205541 ♀, AMNH 205545 ♀, AMNH 205546 ♂, AMNH 205552 ♂, AMNH 205553 ♀, AMNH 205562 ♀, AMNH 205563 ♂, AMNH 205564 ♀, AMNH 205565 ♂).

Distribution and habitat.

Known from only two localities in the provinces of Artigas and Tacuarembó, Uruguay (Fig. 6 ). The records come from the Uruguayan Pampas, between 30 and 240 m in altitude. The region is characterized by grassland plains with shrubby vegetation patches typical of subtropical landscapes. However, the margins of rivers can present denser riparian forests, with arborescent ferns, orchids, lianas and several trees with more than 10 m in height ( Sganga 1994; Panario et al. 2011). According to information available on museum labels, most individuals were captured with mist-nets near watercourses.

Etymology.

We name Myotis pampa after the Pampas ecoregion, the main habitat occurrence for the species. Pampa is a Quechua word for “plain”, and in Latin languages it is used in the masculine gender, which agrees with the generic name Myotis , also masculine ( ICZN 1958; Pritchard 1994).

Diagnosis.

The tricolored ventral fur, with a Drab basal band, Smoke Gray middle band, and yellowish (generally Naples Yellow) tip is unique among South American Myotis . In addition, the following set of traits distinguishes Myotis pampa from all its South American congeners: small to medium sized species (FA 33.8-36.3 mm; sagittal crest absent or very low; elongated skull (GLS 13.4-14.4 mm); braincase not inflated and low in profile; braincase roof formed by the parietal bone strongly straight and not inclined forward; frontal bone steeply sloped towards the rostrum; posterior region of the braincase rounded and projected beyond the limit of the occipital condyles; mastoid processes narrower and practically not visible in dorsal view; dorsal fur notably long (7-9 mm), woolly and bicolored, with tips Dresden Brown or paler Ochraceous-Tawny, and bases brownish-gray (giving a fuliginous aspect); ventral fur moderately long (6-7 mm); legs and dorsal surface of the uropatagium covered by scattered fur that extends up to the knees; plagiopatagium inserted into the foot by a broad band of membrane.

Morphological description and comparisons.

Myotis pampa is a small to medium species of Myotis (FA 33.8-36.3 mm; other measurements in Table 2 ) and the fur texture (wooly) and cranial morphology (broad skull with sagittal and lambdoidal crests presents) resembles species allocated to the Myotis ruber -group (q.v., Moratelli et al. 2013, 2019a). Ears are Mummy Brown and comparatively medium sized (EL 11-14 mm), reaching the portion of the rostrum between the eyes and nostrils when extended forward. Tragus is long and slender, with a wide base and a narrower spear-shaped terminal half, almost straight anterior edge, and rounded tip. Membranes are Mummy Brown; the dorsal surface of tibia, and uropatagium has scattered hairs extending to the level of the knees. The uropatagium lacks the fringe of hairs along the trailing edge. The plagiopatagium is attached to the foot at the level of the toes by a broad band of membrane.

Dorsal and ventral fur are wooly and long (LDF 7-9 mm, LVF 6-7 mm). The dorsal pelage is bicolored with brownish-gray bases (3/4 of the total fur length) and reddish tips (1/4 of the total fur length), ranging from Dresden Brown to paler Ochraceous-Tawny. The dorsal fur has a coloration that looks like the bat is partially covered by soot and with the tip of the hairs burned. The ventral fur is tricolored, with Drab bases (1/4 of the total fur length) progressively turning Smoke Gray in the middle band (2/4 length) and light-yellow tips (1/4 [ranging from Naples Yellow to Cream-Buff]). The tricolored ventral fur is unique among all South American Myotis species (Fig. 2 ). However, this pattern may be less evident in some lighter specimens, where the coloration of the middle band may be confused with the tip band of the hairs.

Dental formula is I 2/3, C 1/1, PM 3/3, M 3/3 = 38, typical of all New World species of Myotis . Skull delicate and medium-sized in length (GLS 13.1-14.1 mm), resembling Myotis of the Myotis ruber -group species. The 2nd upper premolar (P3) is in the toothrow, not displaced to the lingual side and smaller than first upper premolar (P2). The 1st lower molar (m1) is myotodont, with the postcristid connecting hypoconid and entoconid. Braincase delicate and elongated; sagittal crest and lambdoidal crests are absent or very low; the occipital region is rounded and projects beyond the posterior limits of the occipital condyles; mastoid processes weakly developed. Frontal bone slightly sloping; rostrum comparatively short and narrow.

Considering species from the Myotis ruber -group ( Myotis armiensis , Myotis elegans , Myotis keaysi , Myotis midastactus , moratellii, Myotis pilosatibialis , Myotis riparius , Myotis ruber , Myotis simus ), and species from the Myotis albescens -group in the South American southern cone ( Myotis albescens , Myotis chiloensis , Myotis dinellii , Myotis izecksohni , Myotis lavali , Myotis levis , Myotis nigricans ), M. pampa can be distinguished from all by the set of diagnostic traits reported above.

These specimens of M. pampa were originally identified as M. riparius and this identification was maintained by LaVal (1973) and López-González et al. (2001). In fact, M. pampa resembles M. riparius , but it can be distinguished by its smaller skull (GLS < 14.4 in Myotis pampa and generally > 14.5 mm in Myotis riparius ), braincase lower in lateral view, sagittal crest lower (Fig. 1 ), longer and bicolored dorsal fur with grayish base, tricolored ventral fur (Fig. 2 ), and presence of scattered hairs along the leg and dorsal surface of the uropatagium. Myotis riparius have a higher braincase in lateral view, sagittal crest well-developed, shorter and unicolored dorsal fur, bicolored ventral fur and absence of scattered hairs along the leg and dorsal surface of the uropatagium.

Myotis pampa can also be confused with M. ruber , but it can be easly distinguished by its smaller size (both external and cranial; FA > 37.5 mm and GLS > 14.0 mm in M. ruber ), skull more delicate, braincase lower in lateral view, mastoid processes less developed, dorsal fur longer and clearly bicolored with grayish base (unicolored in Myotis ruber ), tricolored ventral fur (bicolored in Myotis ruber ), and presence of scattered hairs along the leg and dorsal surface of the uropatagium (absent in Myotis ruber ).

Myotis pampa differs from M. armiensis , M. keaysi , and M. pilosatibialis by its external smaller size (FA > 36 mm in M. armiensis and M. keaysi ), more delicate skull, braincase lower in lateral view, sagittal crest lower, mastoid processes less developed, dorsal fur longer and clearly bicolored with grayish base, tricolored ventral fur, and pelage on the dorsal surface of the uropatagium composed of scattered hairs not extending beyond the knees. It differs from M. elegans by larger size in general (both external and cranial; FA < 34.5 mm, GLS < 13.0 mm, and BCB < 6.3 mm in Myotis elegans ), skull more robust in general, parietal bone not inclined forward, rostrum longer, dorsal fur clearly bicolored with grayish base, ventral fur tricolored. Myotis pampa can be easily distinguished from M. simus and M. midastactus by its smaller size (generally FA > 36 mm and GLS > 13.5 mm in M. simus and M. midastactus ), more delicate and narrower skull (BCB < 6.8 in Myotis pampa and > 6.8 in Myotis simus and Myotis midastactus ), dorsal fur longer and clearly bicolored, ventral fur tricolored, dorsal surface of the uropatagium covered by scattered hairs that extend up to the knees; plagiopatagium inserted into the foot by a broad band of membrane.

In comparison to species from the Myotis albescens -group, M. pampa can be distinguished from M. albescens , M. dinellii and M. levis by the absence of a fringe of hairs on the posterior margin of the uropatagium, reddish dorsal fur bicolored with grayish base, and braincase less inflated. In addition, M. pampa differs from M. dinellii and M. levis by its generally smaller size and comparatively shorter ears. It differs from M. izecksohni and M. nigricans by the braincase less inflated and reddish dorsal fur clearly bicolored with grayish base. Myotis pampa can be distinguished from M. chiloensis from its smaller size in general, skull lower in lateral view, braincase less inflated, dorsal fur shorter and bicolored, with grayish bases and reddish tips. It differs from M. lavali by its second upper premolar (P3) smaller than first upper premolar (P2), and by its reddish fur with grayish bases (being blackish bases in M. lavali ). In addition, M. pampa can be distinguished of all species from the Myotis albescens -group by its wooly fur (silky in Myotis albescens -group species), ventral fur tricolored, and fur composed of scattered hairs on dorsal surface of the uropatagium.

Figures

Figure 1. Lateral, dorsal and ventral views of skulls of Myotis sp. nov. from Uruguay (AMNH 205471 [holotype]), Myotis riparius from Panama (USNM 310255 [holotype]), and Myotis ruber from Paraguay (USNM 115097 [neotype]). The images of the mandibles of M. riparius and M. ruber are inverted.

Figure 2. Dorsal and ventral views of the skins of of Myotis sp. nov. from Uruguay (AMNH 205471 [holotype]), Myotis riparius from Panama (USNM 310255 [holotype]), and Myotis ruber from Paraguay (USNM 115097 [neotype]).

Figure 4. Dorsal (upper left), ventral (upper right), and lateral (lower) views of the skull and mandible of Myotis pampa holotype (AMNH 205471) from the Uruguayan Pampas.

Figure 5. Skin in dorsal (left) and ventral (right) views of the holotype of Myotis pampa (AMNH 205471) from the Uruguayan Pampas.

Figure 6. Map with localities of occurrence for Myotis pampa, including the type locality (red star).