Molossus rufus E. Geoffroy St.-Hilaire, 1805

García, Franger J., Ochoa-G, José, Poma-Urey, José L., Miller, Bruce W., Falcão, Fábio C. & del Valle Alvarez, Martín Roberto, 2024, Expanding the knowledge of the bat fauna of the Brazilian Caatinga: new geographical records of molossid bats (Chiroptera, Molossidae) for the Chapada Diamantina region, with taxonomic notes, ZooKeys 1210, pp. 333-371 : 333-371

Molossus rufus E. Geoffroy St.-Hilaire, 1805

Summary of captures.

Nine females ( CMARF 2172–2181) and 16 males ( CMARF 2182–2197).

External measurements and weights.

Females: TLB: 130.09 (120.00–140.00), TL: 47.13 (38.45–50.00), LHL: 9.16 (6.28–11.00), EL: 14.96 (13.00–16.73), W: 28.60 (25.00–35.00). Males: TLB: 137.75 (130.00–145.00), TL: 48.48 (39.43–58.00), LHL: 8.74 (6.59–9.96), EL: 15.68 (14.69–18.02), W: 30.75 (25.00–38.00).

Morphological description.

Dorsal and ventral pelage with dark coloration, with predominantly dusky hue unicolored hairs (Fig. 11 ). Dorsal hairs longer than 4 mm. Skull with an inflated rostrum and an elongated braincase (Fig. 11 ). Mastoid process extending laterally in posterior view. The occipital region has a square shape. Lambdoidal crests are highly developed and inclined. Sagittal crests are present and well-developed, with a more pronounced development in males. Infraorbital foramen opens laterally in frontal view. Basioccipital pits moderately depth. Rostrum with triangular shape in frontal view. Upper incisors are short and spatulated, with convergent tips. Presence of a pair of bilobed lower incisors. Some skull measurements are shown in Table 2 .

Identification.

The relatively larger forearm length and skulls, along with the unicolored dorsal and ventral pelage, serve as characteristics to distinguish individuals of M. rufus from its smaller congeners ( Loureiro et al. 2018 b). The short and spatulated upper incisors, with convergent tips, differentiate this species from Molossus pretiosus Miller, 1902 ( Loureiro et al. 2018 b). The length of hairs longer than 4 mm, average forearm lengths of 51.98 mm in males and 50.36 mm in females, along with the greater skull lengths for both sexes of M. rufus , distinguish this species from M. fluminensis ( Loureiro et al. 2020) . Furthermore, a pair of lower incisors and other externally visible characters distinguish M. rufus from members of the genus Promops P. Gervais, 1856 ( Eger 2008), which can be confused due to their morphological similarities.

Molossus sp. 1

Summary of captures. One female ( CMARF 2198) and seven males ( CMARF 2199–2205).

External measurements and weights. Female: TLB: 103.00, TL: 40.00, LHL: 9.00, EL: 12.00, W: 10.00. Males: TLB: 104.00 (98.00–111.00), TL: 39.85 (35.00–46.00), LHL: 6.55 (5.66–7.52), EL: 12.07 (10.00–15.40), W: 13.00 (12.00–14.00).

Morphological description. Dorsal fur is unicolored (dark brown), with hairs at the shoulders measuring 2 mm in length. Ventral coloration subtly contrasts with the dorsum, showing pale brown bases. Rostrum broad and convex, with a developed keel. Upper incisors elongated (similar to M. molossus ) and anteriorly projected. The infraorbital foramen is exposed anteriorly in the female, while in some males, this structure is anteriorly exposed, and in others, it is laterally positioned. Nasal process present. Occipital complex with a triangular shape. Mastoid processes developed (large) and ventrally oriented. Presence of a pair of bilobed lower incisors. Some skull measurements are shown in Table 2 .

Identification. The morphology of these specimens exhibits unique characteristics in the facial morphology (rostrum broad and convex, with a developed keel), distinguishing them from M. aztecus , M. currentium , and M. molossus . Furthermore, the mastoid processes are developed (large) and oriented ventrally, differentiating them from Molossus sp. 2 , while the uniform coloration of the dorsal pelage (unicolored) and the broad, convex rostrum with a developed keel, distinguish them from Molossus sp. 3 .

Molossus sp. 2

Summary of captures. Three males ( CMARF 2206–2208).

External measurements and weights. TLB: 102.66 (100.00–106.00), TL: 35.00 (32.00–37.00), LHL: 6.14 (5.23–7.00), EL: 12.28 (11.91–12.95), W: 13.00 (12.00–14.00).

Morphological description. Rostrum broad and convex, with a developed keel. Dorsal fur is weakly bicolored (hairs with pale brown bases and a broad band of dark chocolate brown in the rest). Hairs at the shoulders 2 mm in length. Ventral and dorsal coloration with slight contrast shows pale brown bases and chocolate brown tips.

Infraorbital foramen laterally positioned in two specimens and anteriorly positioned in one. Upper incisors elongated (similar to M. molossus ) and projected anteriorly. Nasal process undeveloped. Basioccipital pits are absent in one, while in two specimens they are present but scarcely visible. Occipital complex with triangular shape. The mastoid process is scarcely developed (short) and ventrally oriented. Presence of a pair of bilobed lower incisors. Some skull measurements are shown in Table 2 .

Identification. Like Molossus sp. 1 (see above), the morphology of these specimens exhibits unique characteristics in facial morphology (broad and convex rostrum with a developed keel), distinguishing them from M. aztecus , M. currentium , and M. molossus . However, the scarcely developed (short) and ventrally oriented mastoid processes set them apart from Molossus sp. 1 . Additionally, the uniform, weakly bicolored dorsal pelage, combined with the broad and convex rostrum with a developed keel, differentiates them from Molossus sp. 3 .

Molossus sp. 3

Summary of captures. One female ( CMARF 2209).

External measurements and weight. TLB: 101.00, TL: 41.00, LHL: 6.00, EL: 11.00, W: 10.50.

Morphological description. Rostrum narrow, with a slightly undeveloped keel. Dorsal fur is bicolored, with a white basal band and dark chocolate brown color in the rest. Ventral fur contrasts with the dorsum, with hairs showing broad gray bases and pale brown tips. Hairs at the shoulders is 3 mm in length. Upper incisors show only the bases (completely worn). Frontal foramen laterally positioned. The nasal process developed. Occipital complex with triangular shape. Mastoid process elongated and ventrally oriented. Basioccipital pits are present but shallow. Presence of a pair of bilobed lower incisors. Some skull measurements are shown in Table 2 .

Identification. This specimen shows unique characteristics in its facial morphology (narrow rostrum, with poorly developed keel) and in the coloration of the ventral pelage, which contrasts with the dorsum. This morphological and chromatic pattern distinguishes it from other small species of Molossus (e. g., M. aztecus , M. currentium , M. molossus , Molossus sp. 1 , and Molossus sp. 2 ).

Figures

Figure 11. A, B Molossus molossus (CMARF 2159) and C, D Molossus rufus (CMARF 2182) A, C dorsal and ventral views of the skull in two species of Molossus collected in the Caatinga, northeastern Brazil B, D individuals of M. molossus and M. rufus photographed in the field (not to scale). Scale bar 5 mm.