MAMMALIAN SPECIES Balantiopteryx plicata. No. 301, pp. 1-4,4 figs. By Joaquin Arroyo-Cabrales and J. Knox Jones, Jr. Published 15 January 1988 by The American Society of Mammalogists Balantiopteryx Peters, 1867 Least Sac-winged Bats Balantiopteryx Peters, 1867:476. Type species Balantiopteryx plicata Peters, by monotypy. CONTEXT AND CONTENT. Order Chiroptera, Suborder Microchiroptera, Family Emballonuridae, Subfamily Emballonuri- nae. Three species are recognized in the genus, which is known to occur from northwestern Mexico south to Costa Rica, and in north- western South America. Key to species follows: Margin of alar membrane white; forearm 38 to 46 mm; length of maxillary toothrow 5 mm; inner margin of ear conch straight Balantiopteryx plicata No white on margin of alar membrane; forearm 35 to 41 mm; length of maxillary toothrow < 5 mm; inner margin of ear conch conca ve 2 2 Rostrum inflated both anteriorly and posteriorly; known only from northwestern South America ..... Balantiopteryx infusca Rostrum inflated only anteriorly; occurring in southern Mex- ico, Belize, and Guatemala Balantiopteryx io DIAGNOSIS. Balantiopteryx is one of four New World emballonurid genera possessing a sac in the antebrachial membrane; it differs from the others in that the sac is located in the middle of the membrane, its opening directed proximally. Rostrum greatly inflated terminally on each side, causing a distinct concavity in the cranium (anterior to the braincase) best seen in lateral view; pre- maxillae slender and rudimentary; basisphenoidal pits divided or not by median septum; PI small and peglike, and in space between the canine and P2 that is relatively greater than in related genera; p l small, barely fillinggap between canine and p2 (Miller, 1907; Phillips and Jones, 1969; Sanborn, 1937). Balantiopteryx plicata Peters, 1867 Peters' Sac-winged Bat Balantiopteryx plicata Peters, 1867:476. Type locality Puntare- nas, Costa Rica. Balantiopteryx ochoterenai Martinez and Villa, 1938:339. Type locality Cuautla, Morelos. CONTEXT AND CONTENT. Context as given above for the genus Balantiopteryx. Two subspecies currently are recognized: B. P: plicata Peters, 1867:476, see above (ochoterenai a synonym). B. p. pallida Burt, 1948:1. Type locality San Bernardo, Rio Mayo, Sonora. DIAGNOSIS. Size small for an emballonurid (Fig. 1), but largest species in genus Balantiopteryx; forearm 38 mm, greatest length of skull usually 13.0 mm, length of maxillary toothrow 5.0 mm. Color usually pale gray to rich brown, not dark brown; white border on wing membrane from calcar to fourth digit; inner margin of ear straight, not concave; interfemoral membrane thinly furred dorsally to about point of exsertion of tail; inter pterygoid fossa narrow, V-shaped. GENERAL CHARACTERS. External nares directed slight- ly outward, no dorsal furrow between them; ear slightly rounded distally, outer margin straight or slightly convex (slightly concave opposite base of tragus), terminating at level with angle of mouth; tragus rounded distally, outer margin slightly convex with a "tooth" projecting near the base, inner margin straight. Wing slender, at- tached at ankle; border of interfemoral membrane somewhat concave between tibia and calcar; tip of tail projecting about 6 mm from midpoint of uropatagium; legs relatively long, feet delicate; thumb long (about 5 mm) and slender; second phalanx of third finger terminal and cartilaginous. Pelage varies from dull gray to brownish dorsally, slightly paler below (hairs lightly tipped with buff on flanks and venter). There is no dorsal stripe. Wing membranes brownish except for whitish bor- der; pelage extending on to membrane dorsally as far as line from middle of humerus to distal third of tibia; uropatagium almost naked ventrally. Males have a conspicuous glandular sac (Fig. 2) in the middle of the anterbrachial membrane that opens proximally; in adults the interior is white and moist (Bradbury and Vehrencamp, 1976), but Lopez-Forment (1981) reported that the gland varies in color, size, and texture with age and season. The sac is rudimentary in females. Average external measurements (in mm, extremes in parentheses) of a series of 13 B. p. plicata (11 males, two females) from Oaxaca in the collection of Texas Tech University are: total length, 66.6 (63 to 70); length of tail, 16.2 (12 to 21); length of hind foot, 8.3 (6 to 9); length of ear, 14.7 (12 to 16); length of forearm, 41.2 (39.2 to 42.6). Extremes in cranial measurements (Jones et al., 1972) of 22 B. p. plicata from southern Sinaloa (10 males, 12 females), followed by those of 17 of the smaller B. p. pallida from northern Sinaloa (seven males, 10 females) are: greatest length of skull, 13.8 to 14.8, 13.0 to 13.8; zygomatic breadth, 8.8 to 9.4, 8.3 to 8.9; postorbital constriction, 3.1 to 3.5, 2.9 to 3.5; breadth of braincase, 6.7 to 7.3, 6.5 to 7.0; mastoid breadth, 8.0 to 8.6, 7.5 to 8.0; length of maxillary toothrow, 5.3 to 5.6, 5.0 to 5.4. Mean weight for 32 males from Costa Rica was 6.1 g; 24 nonpregnant females from there were significantly larger (P < 0.001), averaging 7.1 g (Bradbury and Vehrencarnp, 1976). Skull light and compact (Fig. 3); rostrum short and broad (broader than braincase), inflated terminally, concave anterior to braincase; faint sagittal crest and slender postorbital processes pres- ent. The dental formula, as in other American emballonurids, is i 1/3, c 1/1, P 2/2, m 3/3, total 32. Upper incisors small, unicuspid, convergent distally; diastema between incisors and canines. Lower incisors trilobed and seated compactly between canines. Both upper and lower canines delicate, those above slightly the larger; both have a distinct cingulum, with an anterointernal cusp on the upper teeth and a posterointernal cusp on lower pair. Upper premolars small, the first separated by evident gap from canine; p2 twice the height of p l, almost as high as canine, which p l abuts. Molars with W -shaped crowns. Except where specifically cited, the above descriptive ma- terial is mostly from Dobson (1878) and Martinez and Villa (1938). FIG. 1. Live specimen of Balantiopteryx plicata from Jalisco (photograph courtesy of Robert J. Baker). Downloaded from https://academic.oup.com/mspecies/article/doi/10.2307/3504133/2600309 by guest on 10 November 2022