Chiroderma gorgasi Handley, 1960

Lim, Burton K., Loureiro, Livia O. & Garbino, Guilherme S. T., 2020, Cryptic diversity and range extension in the big-eyed bat genus Chiroderma (Chiroptera, Phyllostomidae), ZooKeys 918, pp. 41-63 : 41

Chiroderma gorgasi Handley, 1960

Chiroderma gorgasi Handley, 1960:464

Chiroderma trinitatum gorgasi Barriga-Bonilla, 1965:246

Material examined.

Holotype. - USNM 309903 (Field number COH 5436), adult male with skin, skull and partial skeleton. Collected on March 6, 1959, by C. O. Handley, Jr, and B. R. Feinstein in Tacarcuna Village (8°05'N, 77°17'W), 3200 feet [975 meters], Río Pucro, Darién, Panama.

Geographic distribution.

Chiroderma gorgasi is distributed west of the Andes in northwestern Ecuador ( Albuja 1989), western Colombia ( Gardner 2008), Panama ( Handley 1960), Costa Rica ( LaVal and Rodríguez-Herrera 2002), and Honduras ( Turcios-Casco et al. 2020) (Fig. 6 ).

Description.

Chiroderma gorgasi is a small species of Chiroderma (FA 37.0-40.5; GLS 20.2-22.5) that is similar in size to C. trinitatum (sensu stricto) (Table 2 ). Overall, the dorsal pelage is tricolor varying from light to dark brown (Fig. 7 ). The dorsal hairs have a dark brown band at the base, a buff coloration in the middle, and brown tips. A white medial stripe extends from the interscapular region to the base of the rump. Proximal two-thirds of forearm hairy. Basal third of uropatagium hairy. Conspicuous white facial stripes extend from the noseleaf to the inner base of the ears, and from the posterior part of the upper lip to the base of the ears. The uropatagium is medium brown. The skull has an elongated braincase with an undeveloped sagittal and lambdoidal crest. The nasal aperture is short, not extending beyond the second premolar. The occipital is rounded in posterior view. The upper incisors are thin and elongated with parallel or convergent tips, which may or may not touch apically. The second lower premolar lacks a third cusp (Fig. 5 ). The postorbital processes are undeveloped and rounded (Fig. 8 ).

Comparisons.

Chiroderma gorgasi is morphologically very similar to C. trinitatum . Both species have a small cranial and body size for the genus (Table 2 , Fig. 4 ), an undeveloped sagittal and lambdoidal crest, a rounded occipital complex, a short nasal aperture, and undeveloped supraorbital region. However, C. trinitatum has a third posterior cusp on the second lower premolar, which is absent in C. gorgasi (Fig. 5 ). This cusp in C. trinitatum may vary from very pointed and developed to rounded and less marked, but is always present. In addition, C. gorgasi tends to have a broader braincase (Table 4 ) and a flatter supraorbital region, which tends to be deeper in C. trinitatum .

Chiroderma gorgasi is easily distinguished from other species of the genus by its smaller cranial and body size (Table 2 ). C. villosum shares with C. gorgasi an elongated braincase, rounded occipital region in dorsal view, and absence of a third cusp on the second lower premolar. However, C. gorgasi has an undeveloped postorbital processes, a short nasal aperture, and conspicuous white stripes on the face and back, whereas C. villosum has a very developed and pointed postorbital processes, a long nasal aperture, which extends beyond the first molar, a conspicuous posterior palatine spine, and usually incipient white stripes on the face and back. Chiroderma salvini resembles C. gorgasi in the undeveloped sagittal and lambdoidal crest and by the rounded postorbital processes, but a set of other cranial characters distinguish both species, such as a triangular occipital complex and a long nasal aperture. In the dentition, C. gorgasi can be readily distinguished from C. salvini and C. villosum by having a tall first lower premolar, with a crown height approximately 2/3 the height of the crown of the second lower premolar, and placed approximately in the middle of the distance between the canine and the second lower premolar. In C. salvini and C. villosum , this tooth is much smaller, usually with a low crown, shorter than the mesiodistal length of the tooth, and is nearer to the canine than to the second lower premolar.

Chiroderma doriae and C. improvisum are the largest species of the genus, and unlike C. gorgasi have a triangular occipital complex in dorsal view, a pointed and developed supraorbital region, a relatively more developed sagittal and lambdoidal crest, and a long nasal aperture. In addition, C. doriae also tends to have a relatively broader braincase than C. gorgasi and the presence of an undeveloped third cusp in the second lower premolar. We were not able to examine specimens of the more recently described C. vizottoi , but it is larger than C. gorgasi and most similar to C. doriae in qualitative craniodental traits.

Figures

Figure 4. Principal Component Analysis (PCA) carried out using the correlation matrix of ten measurements for six taxa of the big-eyed bat Chiroderma. C. trinitatum gorgasi (■) C. trinitatum trinitatum (□), C. salvini (x), C. villosum (+), C. doriae (●), and C. improvisum (◊).

Figure 5. Lateral view of the second lower premolar on the right mandible of A Chiroderma gorgasi and B C. trinitatum. The arrow points to the accessory cusp that is absent in C. gorgasi and present in C. trinitatum. But note the variation in cusp formation in C. trinitatum.

Figure 6. Geographic distribution of Chiroderma gorgasi (▲) and C. trinitatum (●) localities analyzed in our study (See Appendix 3) (gray circle) Represents marginal localities reported for C. trinitatum and (gray triangle) C. gorgasi reported by previous papers (Handley 1967; Pine et al. 1970; Ojasti and Linares 1971; Gardner 1976; Albuja 1989; Timm and LaVal 1998; Lim and Engstrom 2001; Genoways et al. 1981; Webster and Fugler 1984; Anderson 1997; Ochoa et al. 1988; Simmons and Voss 1998; Gardner 2008).

Figure 7. Dorsal view of the skin of the holotype of Chiroderma gorgasi (USNM 309903).

Figure 8. Dorsal, ventral, and lateral views of the skull of the holotype of Chiroderma gorgasi (USNM 309903).