Molossus sinaloae J. A. Allen, 1906

Simmons, Nancy B. & Voss, Robert S., 1998, The mammals of Paracou, French Guiana, a Neotropical lowland rainforest fauna. Part 1, Bats, Bulletin of the American Museum of Natural History 237, pp. 1-219 : 165-168

Molossus sinaloae J. A. Allen

Figures 64 , 65 , 67

VOUCHER MATERIAL: 6 females (AMNH *267542, *267543, *269107, *269109; MNHN *1995.974, *1995.975) and 6 males (AMNH *267547, *267549, *269110, *269112; MNHN *1995.972, *1995.973); see table 65 for measurements.

IDENTIFICATION: Molossus sinaloae was named by Allen (1906) based on a specimen collected in the Mexican state of Sinaloa, and Goodwin (1959) described M. trinitatus from a specimen collected at Port of Spain, Trinidad. Although Goodwin noted that his specimen resembled sinaloae in having long bicolored fur, he emphasized differences in size ( trinitatus is larger) and cranial breadth (the skull is narrower in trinitatus ). However, the holotype of sinaloae (AMNH 24524) is a female while the holotype of trinitatus (AMNH 179987) is a male, making such comparisons hard to interpret given the sexual dimorphism characteristic of Molossus . Five years later, Goodwin and Greenhall (1964) reported more material of trinitatus (including adult male and female topotypes), and reiterated that trinitatus and sinaloae appeared clearly distinguishable. However, collections of additional material from southern Central America and northern South America have subsequently blurred the distinctions Goodwin observed. Most recent authors have considered trinitatus and sinaloae to be no more than subspecifically distinct (e.g., Handley, 1966; Ojasti and Linares, 1971; Hall, 1981; Dolan, 1989; Koopman, 1993, 1994).

Contra those authors listed above, Freeman (1981) concluded that Molossus trinitatus was clearly distinct from M. sinaloae on the basis of a morphometric analysis. In addition to her own observations, Freeman (1981) cited the work of Brown (1967), who noted that the baculum of trinitatus is somewhat longer than that of sinaloae , and that the base of the baculum in trinitatus is more pointed than in any other species of Molossus . However, both of these studies were

based on very small samples of each species drawn from extremes of the geographic range. Dolan (1989) included many more specimens of sinaloae in her morphometic analyses, and concluded (op. cit.: 56) that ‘‘the position of the holotype of M. trinitatus clearly within the M. sinaloae cluster... argues against specific recognition.’’

To identify our material from Paracou, we compared our specimens (table 65) with the holotypes of sinaloae and trinitatus (table 66), two topotypes of trinitatus (table 66), specimens of sinaloae from Mexico (AMNH 204985, 204986), Honduras (AMNH 265132, 1265133), and Nicaragua (AMNH 41190, 41193, 41195), and measurements of sinaloae and trinitatus published by Alvarez and Aviña (1964), Jones et al. (1971), Ojasti and Linares (1971), Marinkelle and Cadena (1972), Husson (1978), and Dolan (1989). We were unable to find any characters that unambiguously separate sinaloae and trinitatus . Although specimens referred to trinitatus are usually larger than those referred to sinaloae , measurements of our Paracou material overlap in all dimensions with measurements of specimens from Nicaragua reported by Jones et al. (1971). In the absence of a thorough revision, we therefore follow the current consensus and treat trinitatus and sinaloae as conspecific. Given apparent size differences, recognition of two subspecies (M. s. sinaloae and M. s. trinitatus ) might be justified; if so, our material from Paracou represents the latter.

FIELD OBSERVATIONS: We captured 12 Molossus sinaloae at Paracou, all of which were taken in nets suspended 17–23 m over a narrow dirt road.

Figures

Fig. 64. Dorsal (A) and ventral (B) views of the skull of Molossus rufus (AMNH 269101; female) from Paracou. Dorsal (C) and ventral (D) views of the skull of M. sinaloae (AMNH 269107; female) from Paracou. Scale bars = 10 mm.

Fig. 65. Lateral views of the skull and lower jaw of (A) Molossus rufus (AMNH 269101; female) and (B) M. sinaloae (AMNH 269107; female). Scale bars = 10 mm.

Fig. 67. Comparative palatal cross sections of (A) Molossus rufus (AMNH 269101; female), (B) M. sinaloae (AMNH 269107; female), and (C) Promops centralis (AMNH 269114; female).