Molossus aztecus Saussure, 1860

Loureiro, Livia Oliveira, Gregorin, Renato & Perini, Fernando Araujo, 2018, Diversity, morphological phylogeny, and distribution of bats of the genus Molossus E. Geoffroy, 1805 (Chiroptera, Molossidae) in Brazil, Zoosystema 40 (18), pp. 425-452 : 434-435

Molossus aztecus Saussure, 1860

Molossus aztecus Saussure, 1860: 285 .

Molossus molossus – Willig et al. 1986: 671.

EMENDED DIAGNOSIS. — Medium-sized Molossus with dense and long dark dorsal fur. Dorsal hair reaching 6.0 mm and varying from dark cocoa brown to blackish. Monochromatic dorsal hairs or with a small pale basal band covering no more than 1/4 of the total length. Forearm length averages 39.5 mm in males (35.9- 41.5) and 39.0 mm in females (35.0-41.9). Greatest length of skull averages 17.6 mm (16.3-18.3) in males and 16.7 mm (16.1- 18.6) in females ( Table 1 ). Basioccipital pits moderate in depth ( Fig. 6A ). Occipital complex rectangular in posterior view due to the development and inclination of the lambdoidal crests ( Fig. 6B ). Inflated rostrum and rounded braincase ( Fig. 6C ). Infraorbital foramen opening laterally in frontal view ( Fig. 6D ). Nasal process of the premaxilla well developed in males, protruding over the nasal cavity ( Fig. 6C ). Skull with mastoid processes oriented ventrally in posterior view. Triangular rostrum in frontal view with narrow dorsal portion ( Fig. 6D ). Upper incisors spatulated with convergent tips ( Fig. 6D ).

VARIATION. — The dorsal pelage varies from dark grayish to blackish. In females, the occipital complex may be less distinctly squared due to smaller lambdoidal crests. Sagittal crests in females are also lower and less robust than males, and the nasal process of the premaxilla is less developed. The upper incisors vary among individuals with some specimens being less spatulated and more elongated than average (AMNH 10245).

DISTRIBUTION. — M. aztecus is widely distributed from Mexico and Central America ( Dolan 1989) to South America, in Venezuela ( Handley 1976; Ochoa et al. 1993; Lim & Engstrom 2001) and southeastern Brazil ( Gregorin et al. 2011). This study extends the distribution of M. aztecus to nine Brazilian states confirming the occurrence of the species in Mammanguapé (Paraíba), Huimatá (Amazonas), Rio de Janeiro (Rio de Janeiro), São José do Piauí (Piauí), Corumbá (Mato Grosso do Sul), Crato (Ceará), Lavras and Sete Lagoas (Minas Gerais), Exu (Pernambuco), Salvador (Bahia), and Ilha dos Búzios (São Paulo) ( Fig. 7 ).

REMARKS

The body size of M. aztecus is very similar to M. molossus and therefore, these two taxa are frequently confused. However, both species are distinguished by several qualitative characters, such as a pale band at the base of the dorsal hair, which is discrete or imperceptible in M. aztecus , and long and obvious in M. molossus . The dorsal fur of M. aztecus is grayish to blackish, while M. molossus usually has a cocoa to cinnamon brown colouration. M. aztecus has a shorter and inflated braincase and domed skull ( Fig. 6C ), while in M. molossus the skull is more elongated. The sagittal and lambdoidal crests in M. aztecus are more developed ( Fig. 6B ) than in M. molossus . In M. aztecus , the rostrum is triangular ( Fig. 6D ), whereas in M. molossu s it is rectangular. The infraorbital foramen in M. aztecus opens laterally ( Fig. 6D ) while in M. molossus it opens frontally. The occipital in M. aztecus has a clear quadrangular format ( Fig. 6B ), while in M. molossus this structure is triangular or rounded. The upper incisors in M. aztecus are flat and spatulated ( Fig. 6D ), per incisors with parallel tips. Although some authors do not consider M. aztecus as a valid species ( Jennings et al. 2000; Eger 2008), our data indicate that it is consistently distinguishable from M. molossus and M. coibensis based on morphological characters, corroborating Dolan (1989) and Gregorin et al. (2011).

Figures

FIG. 6. — Molossus aztecus Saussure, 1860 skull: A, ventral view; B, posterior view; C, lateral view; D, frontal view. Scale bar: 1 mm.

FIG. 7. — Geographic range of Molossus aztecus Saussure, 1860 in Brazil (Gregorin et al. 2011). -, represents new records for the country,the numbers represent the localities described in Appendix 1.