Molossus barnesi Thomas, 1905

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 : 154-159

Molossus barnesi Thomas

Figures 61–63

VOUCHER MATERIAL: 2 females (AMNH *269105; MNHN *1995.951); see table 63 for measurements.

IDENTIFICATION: Thomas (1905a) originally described Molossus barnesi 17 from a single female specimen collected at Cayenne, French Guiana. Thomas noted that M. barnesi could be distinguished from other small Molossus species based on length of the dorsal fur (shorter in barnesi ), color of the fur (lighter in barnesi ), height and ribbing of the muzzle (both less pronounced in barnesi ), length of the forearm and hind leg (both shorter in barnesi ), and degree of inflation of the braincase (greater in barnesi ). Thomas (1905a) particularly noted that barnesi could be easily distinguished from specimens of M. obscurus (= M. molossus ) collected in the same area based on length of the forearm (33.7 mm in barnesi , 39.0–40.0 in obscurus ).

No specimens other than the holotype have been referred directly to Molossus barnesi . However, Cabrera (1958) suggested that M. cherriei Allen (1916) from the Mato Grosso might be a junior synonym based on the published description. Cabrera likewise noted that a small specimen identified by Vieira (1942) as M. obscurus from Manaus might also represent M. barnesi .

Although Cabrera (1958) and Husson (1962) recognized Molossus barnesi as a distinct species, several recent authors have not.

Freeman (1981) listed barnesi (which she spelled ‘‘ burnsei ’’) as a synonym of M. molossus, Brosset and Charles­Dominique (1990) considered barnesi a synonym of M. m. crassicaudatus , and Koopman (1994) list­ ed barnesi as a valid subspecies of M. molossus . However, none of these authors presented any justification for treating M. barnsei and M. molossus as conspecific.

In contrast to these taxonomic assessments, we conclude that Molossus barnesi and M. molossus are distinct species. Among other characters, these species can be distinguished by their upper incisors, which taper to a set of pincers in molossus , whereas in barnesi they form a flattened bladelike or spatulate array (figs. 61, 63). Measurement comparisons (table 63) demonstrate that our Paracou specimens of barnesi and molossus can be distinguished unambiguously by forearm length, tibia length, tail length, condyloincisive length, mastoid breadth, and length of the maxillary toothrow. Molossus barnesi is the smaller of the two species in all dimensions except tail length and mastoid breadth. There is at least some overlap in the other measurements we recorded, but comparisons of mean values suggest that molossus has a longer hindfoot, longer skull, narrower braincase, and narrower postorbital region than does barnesi (table 63). In addition, length of the dorsal fur is different (3– 4 mm in molossus , ≤ 2 mm in barnesi ), as is color and banding of the fur. In our Paracou material of molossus , the dorsal fur is dark brown with a white base that comprises roughly two­thirds the length of the hairs in the shoulder region and one­half the length of the hairs over the lower back; the ventral fur is slightly lighter brown, also with an extensive white base. In contrast, the dorsal fur in our specimens of barnesi is reddish brown with a white base that comprises approximately one­half the length of the hairs in the shoulder region and somewhat less over the lower back; the ventral fur is a slightly paler reddish brown with little or no white base except in the throat region. We found no obvious differences between these species in ear or facial morphology.

In her revision of the Central American species of Molossus, Dolan (1989) treated barnesi as a junior synomym of M. coibensis Allen (1904) based on measurement data and the unusual spatulate form of the upper incisors. Our comparisons of Thomas’ (1905a) measurements of the female holotype of barnesi (table 64) with measurements of female coibensis from Central America (in Dolan, 1989) confirm that barnesi falls within the range of variation reported for coibensis in all standard measurements. However, Dolan (1989: 59) also noted that

J. E. Hill of the British Museum graciously compared Panamanian coibenesis collected during this investigation with the holotype of M. barnesi and noted no differences in the construction of the upper incisors (personal communication). However, based on variation in the extent of the white basal band in the dorsal fur, features of the basisphenoid pits, breadth of the mesopterygoid canal, and absence of geographically intermediate populations, Hill argued for continued recognition of M. barnesi .

We compared our material of Molossus barnesi with the holotype of M. coibensis (AMNH 18731) and with 10 additional specimens of coibensis from Panama (AMNH 18732, 18733, 18738, 31432, 31435, 31436, 63800, 173919, 183864, 183867) and found consistent differences in the same pelage and cranial features mentioned by Hill. The white base of the dorsal fur over the shoulders comprises less than one­fourth of the length of the hair in coibensis , but approximately one­half in barnesi . The mesopterygoid canal is wider in barnesi than in coibensis , and the bony ridge separating the right and left basisphenoid pits is also wider in barnesi than in coibensis . On the basis of these features, we agree with Hill and conclude that coibensis and barnesi represent distinct species.

To further check the identity of our material, we examined the holotypes of Molossus bondae (AMNH 23661), M. cherriei (AMNH 36669), M. daulensis (AMNH 36257), M. debilis (USNM 110935), M. pygmaeus (USNM 102104), and M. verrilli (AMNH 25764), and reviewed literature accounts for these taxa as well as for M. aztecus , M. crassicaudatus , M. fuliginosus , M. fortis , M. lambi , M. longicaudatus , M. minor , M. major , M. molossus , M. obscurus , and M. tropidorhynchus ( Saussure, 1860; Miller, 1900, 1913; Allen, 1904, 1916; Thomas, 1905a; Husson, 1962, 1978; Gardner, 1966; Carter and Dolan, 1978; Genoways et al., 1981; Dolan, 1989; Brosset and Charles­ Dominique, 1990). The taxonomic history of M. molossus is complex, and we did not attempt to address the many problems of synonymy that remain unresolved (see summaries in Husson [1962] and Dolan [1989]). Instead, we followed Dolan (1989) in recognizing the following as synonyms of Molossus molossus : crassicaudatus , daulensis , debilis , fortis , fuliginosus , longicuadatus, milleri , minor , major , obscurus , pygmaeus , tropidorhynchus , and verrilli .

Morphological features distinguishing Molossus barnesi from all named forms of M. molossus include the differences in fur length, extent of banding of the dorsal fur, and incisor morphology mentioned earlier; differences in external and craniodental measurements likewise separate these species where they occur sympatrically (see summary above). Molossus bondae resembles M. coibensis and M. barnesi in length and color of the fur, general shape of the skull, and incisor morphology; however, bondae differs from both barnesi and coibensis by its larger size and unicolored dorsal fur ( Dolan, 1989). The affinities of M. cherriei are difficult to assess since the skull of the holotype is missing, but we agree with Dolan’s observation that forearm length, pelage length and coloration, and presence of a minute white band at the base of the hairs suggest that cherriei is a junior synonym of coibensis . Molossus aztecus from northern Central America apparently represents a distinct species distinguished from barnesi by larger size in most dimensions and by having shorter white bases on the dorsal hairs (for a summary of characters of aztecus see Dolan, 1989). The status of M. lambi is more difficult to assess. Originally named by Gardner (1966) as a subspecies of aztecus , lambi was recognized as a junior synonym of coibensis by Dolan (1989) based on pelage similiarity and measurement data. We tentatively agree with Dolan’s assessment although we have not seen the holotype of lambi .

FIELD OBSERVATIONS: Both of our specimens of Molossus barnesi were captured in ground­level mistnets over roadside puddles.

Figures

Fig. 61. Dorsal (A) and ventral (B) views of the skull of Molossus barnesi (AMNH 269105; female) from Paracou. Dorsal (C) and ventral (D) views of the skull of M. molossus (AMNH 269102; female) from Paracou. Note species differences in size, relative breadths of the postorbital region and braincase, and incisor morphology. Scale bars = 10 mm.

Fig. 62. Lateral views of the skull and lower jaw of (A) Molossus barnesi (AMNH 269105; female) and (B) M. molossus (AMNH 269102; female). Scale bars = 10 mm.

Fig. 63. Anterior view of the skull and upper dentition of (A) Molossus barnesi (AMNH 269105; female) and (B) M. molossus (AMNH 269102; female). Note the species difference in shape of the upper incisors, which are spatulate in barnesi but taper to pincerlike points in molossus. Scale bars = 5 mm.