Chiroderma villosum Peters, 1860

Garbino, Guilherme S. T., Lim, Burton K. & Tavares, Valéria Da C., 2020, Systematics of big-eyed bats, genus Chiroderma Peters, 1860 (Chiroptera: Phyllostomidae), Zootaxa 4846 (1), pp. 1-93 : 48-51

Chiroderma villosum Peters, 1860

Synonyms: See under subspecies.

Type Material. The lectotype of Chiroderma villosum ( ZMB 408 ), designated by Thomas (1891), is a stuffed skin. The skull is inside the skin and the skin around the lips is everted, exposing all of the teeth except M2 and m2. The free portion of the noseleaf spear is broken. The wing patagia are crumbly and several fragments have fallen off. The tips of the ears are also crumbly. The skin appears to preserve the original color, the interocular stripes are barely visible, but the genal pair is not visible. Dorsal pelage is pale brown and three bands can be distinguished: a dark brown base, and buff middle. The dorsal stripe appears to be lacking.

The I1s are parallel to each other, not in contact, and have slightly diverging tips. The p2 is small and clearly separated from p4. The forearm measures 47.9 mm. According to Thomas (1891), the individual depicted in Peters’ (1906) plate, published posthumously, is probably the type. In the illustration, the skull is separate from the skin, suggesting that the skull could have been removed and later re-inserted in the skin ( Fig. 31 ). The other possibility is that the skull Peters illustrated belonged to the partial skeleton referred to, but not examined by Carter & Dolan (1978:59).

Distribution. See under subspecies.

Description and Comparisons. Dorsal pelage may be pale brown, dark brown, reddish brown, or grayish brown. Most of the 328 specimens we examined have a pale brown dorsum (61%, n=201). The second most common color of the dorsal pelage is dark brown (38%, n=125). Dorsal hairs are tri-banded, the base is always dark brown, and the middle band is pale buff. Facial stripes were not detected in 191 (58%) of the 328 analyzed specimens. In 36.2% of the sample (n=119), the stripes were detected, but not conspicuous. The interocular pair was the only pair of facial stripes detected in 82.3% of the specimens, while both pairs were present in 17.7%. Only 13 specimens (3.9% of the sample) had conspicuous facial stripes, with the interocular pair more conspicuous than the genal. The dorsal stripe was not detected in 152 of 333 specimens (45.6%) scored for this character. The stripe was faint in 154 specimens (46.2%), and, in some the only evidence of a stripe was a short white mid-dorsal line. Only 22 specimens (6.6%) had a conspicuous dorsal stripe. Five specimens (1.5%) had a median dorsal stripe, but they were not scored as to conspicuousness. The tragus and base of the ears are yellow, but the remainder is uniformly brownish. The tip of the noseleaf is notched in 49 (74.2%) of the 66 specimens scored for this character. The noseleaf is nearly uniformly pale brown, with the central rib of the spear having a more pinkish tone and the lateral margin of the horseshoe slightly paler.

The skull of C. villosum is similar in size to C. d. vizottoi and C. scopaeum , and measurements have some overlap with small C. d. doriae , C. salvini , and large C. trinitatum ( Tables 7 and 8). The braincase is relatively deep and globose. A sagittal crest is present in 356 (85.5%) of the 416 C. villosum crania scored for this character, and varied from high and conspicuous to low and inconspicuous. The orbits are relatively large. The nasal notch is long, extending back into the interorbital region close to post-orbital processes.

A posterior palatine process was present in 280 (83%) of the 336 skulls scored for this character, and varied from a long and conspicuous to a small nub. When cranium and mandible are in occlusion, a wide lateral gap, bordered by C, P3 and P4, and p2 and p4, is evident ( Fig. 9 ). The occluded teeth also form a W-shaped frontal gap rimmed by lower canines, lower incisors, and upper inner incisors ( Fig. 14 ).

The I1s were parallel to each other (76.2%, n=314), medially convergent (22.3%, n=92) or divergent (1.4%, n=6) in the 512 crania scored for this character ( Fig. 32 ). M2 usually has a cingulum around the protocone, which projects lingually. Lower canines are narrow and tall, with the tips level with the top of the coronoid process when the mandible is viewed laterally. The crown of p2 is approximately ¼ the height of p4. The p2 is in contact with the canine, but not with p4. Compared to the other species of Chiroderma , the protoconid of p4 is narrow.

The subspecies C. v. jesupi and C. v. villosum differ in size, with the former averaging smaller in forearm length and in every cranial dimension we analyzed ( Table 9). As previously mentioned, our decision to recognize two subspecies was mainly due to the presence of haplotypes exclusive to the trans-Andean portion of the distribution of C. villosum .

The two smallest Chiroderma ( C. gorgasi and C. trinitatum ) differ from C. villosum by size, presence of conspicuous facial and dorsal stripes, bicolored noseleaf, shorter nasal notch, convergent I1s, and taller p2. The insular C. improvisum is easily distinguished from C. villosum by its larger size, relatively lower braincase, longer rostrum, more robust dentition, and p 2 in contact with p4.

Among similar-sized species, C. villosum can be differentiated by the weaker facial and dorsal stripes (conspicuous in C. doriae , C. salvini , and C. scopaeum ), paler dorsal pelage (usually darker in C. d. doriae and C. salvini ), notched tip of noseleaf (simple tip in C. doriae , C. salvini , and C. scopaeum ), deeper braincase (shallow in C. d. doriae ), longer nasal notch (shorter in C. doriae , C. salvini , and C. scopaeum ), larger orbits (smaller in C. doriae , C. salvini , and C. scopaeum ), I1s parallel or divergent (convergent in C. doriae , C. salvini , and C. scopaeum ), smaller p2 (large in C. doriae ), narrower and taller canines (wider and shorter in C. doriae and C. scopaeum ), and presence of a frontal gap when cranium and mandible are in occlusion (gap absent in C. doriae , C. salvini , and C. scopaeum ).

Geographic Variation and Phylogeography. Phylogenetic analyses of sequences of COI representing 133 C. villosum recovered a clade composed of sequences exclusively from México, Central America, and trans-Andean South America ( Figs. 33 , 35 ). The samples from cis-Andean South America, however, form a polytomy, which does not suggest geographic structuring because specimens from distant regions, such as Bolivia and Trinidad, group together.

There is geographic variation in size among the subpopulations of C. villosum . Specimens from the Atlantic rainforest of eastern Brazil (n=48) are larger than the other geographic groups ( Table 13, Fig. 34 ). Specimens from Trinidad and Tobago also had larger dimensions; however, the sample size was smaller (n=7). Populations from the Amazon north of the Amazonas River and from México and Central America and trans-Andean South America had the smaller dimensions. We suggest there is clinal variation in size, with larger specimens in the extreme east and southeast part of the distribution and smaller individuals in the northwestern part of the range. There is overlap between measurements from adjacent geographic groups, but the populations from the western portion of the distribution, which would correspond to subspecies C. v. jesupi , are significantly smaller than the others ( Fig. 34 ).

Subspecies. We recognize two subspecies in Chiroderma villosum .

Figures

FIGURE 9. Lateral view of skull and mandible in occlusion for A) Chiroderma salvini (ROM 99703), B) Chiroderma scopaeum (TTU 110649), C) Chiroderma d. doriae (TTU 99569), D) Chiroderma villosum (USNM 560607), and E) Chiroderma improvisum (ROM 126002).

FIGURE 14. Frontal view of skull and mandible in occlusion for A) Chiroderma salvini (ROM 99703), B) Chiroderma scopaeum (TTU 110649), C) Chiroderma d. doriae (TTU 99569), D) Chiroderma villosum (USNM 560607), E) Chiroderma improvisum (ROM 126002).

FIGURE 31. Plate of the lectotype of Chiroderma villosum by Wilhelm Peters, published posthumously.

FIGURE 32. Individual variation in the disposition of the inner upper incisors in Chiroderma villosum. A) parallel (USNM 520558, Panamá); B) convergent (USNM 520557, Panamá); C) divergent tips (USNM 540676, Trinidad); and D) base and tips divergent (USNM 499481, Colombia).

FIGURE 33. Haplotype network of Chiroderma villosum and C. improvisum, built using the “Median Joining” algorithm (epsilon = 0; 2,000 iterations).

FIGURE 34. Predefined groups of C. villosum used in the geographic variation analysis (above). Boxplot of the first principal component (PC1), extracted from the variance-covariance matrix of a principal component analysis of 13 cranio-dental measurements (below). A = México/Central America/trans-Andean South America; B = northern Venezuela; C = Trinidad and Tobago; D =northern Amazonia and the Guianas; E = Southern Amazonia; F = Chaco and Cerrado; G = Atlantic coast.

FIGURE 35. Phylogenetic relationships between Chiroderma improvisum and C. villosum, based on 141 sequences of the cytochrome c oxidase subunit 1 gene. Localities in parentheses are detailed in the gazetteer (Appendix 1). This subtree is a detailed version of the clades named “improvisum” and “villosum” in figure 4.