Histiotus Gervais 1856

Histiotus Gervais, 1856

Plecotus: I. Geoffroy St. -Hilaire, 1824: 446; part; not Plecotus É. Geoffroy St. -Hilaire, 1818.

Vespertilio: J. B. Fischer, 1829: 118 ; part; not Vespertilio Linnaeus, 1758 .

Nicticeius Poeppig, 1830 : column 218; incorrect subsequent spelling of, but not Nycticeius Rafinesque, 1819 .

Nycticeius: Poeppig, 1835: 451 ; part; not Nycticeius Rafinesque.

Nycticeus: Lesson, 1836: 120 ; part; incorrect subsequent spelling of, but not Nycticeius Rafinesque.

Nycticejus: Lesson, 1842: 22 ; part; incorrect subsequent spelling of, but not Nycticeius Rafinesque.

Histiotus P. Gervais, 1856: 77 , pl.13, fig. 6a and 6b (but not fig. 6 [= Plecotus auritus ]); type species Plecotus velatus I. Geoffroy St. -Hilaire, 1824, by monotypy.

Vesperus: W. Peters, 1864: 383 ; part; not Vesperus Latreille, 1829 (Hymenoptera) .

Vesperugo: Dobson, 1878: 188 ; part; not Vesperugo Keyserling and Blasius, 1839 .

Eptesicus: Olrog, 1951: 508 ; part; not Eptesicus Rafinesque, 1820 .

Histictus Ruschi and Bauer, 1957: 40; incorrect subsequent spelling of Histiotus P. Gervais.

Type species: Plecotus velatus I. Geoffroy St. -Hilaire, 1824.

Other species: H. macrotus (Poeppig, 1835); H. montanus (Philippi & Landbeck, 1861); H. magellanicus (Philippi, 1866); H. colombiae Thomas, 1916; H. laephotis Thomas, 1916; H. alienus Thomas, 1916; H. humboldti Handley, 1996; H. diaphanopterus Feijó et al., 2015; H. cadenai RodrÍguez-Posada et al., 2021; and H. mochica Velazco et al., 2021.

Distribution: Histiotus is endemic to South America, where it has been recorded from almost every country, except from the Guianas and Trinidad and Tobago. Despite its wide distribution on the continent, most records from the genus are from cooler areas along the Andes, and also from southern, eastern and central Brazil, with only scattered records from the Amazon Basin.

Diagnosis: Histiotus can be distinguished by the following characters: ears long (> 21 mm) and connected by a band of skin with variable development; skull delicate, narrow, and long; sagittal and lambdoidal crests weakly developed; postorbital process of the jugal well developed; eyes enlarged, larger than lower canines and nostrils; auditory bullae large, the space between auditory bullae is smaller than the width of each bullae; length of dorsal fur usually long (averaging 11.4 mm); length of forearm ranging from 44.0– 52.6 mm (averaging 47.8 mm); tragus long, pointed and notched; GLS 17.4–19.8 mm (averaging 18.4 mm); and MTL 5.6–7.1 mm (averaging 6.3 mm).

Description: Histiotus includes medium-sized to large species. Dorsal fur long (LDF 8.0– 14.5 mm), usually more than 10 mm; hairs ranging from almost unicolored to strongly bicolored; dark bases length from 1/2 to almost the entire length of hairs; the contrast between bands ranges from faint to very strong; distal portion of hairs ranging from dark brown to golden orangish or yellowish. Ventral fur long (LVF 6.0– 12.6 mm), usually more than 8 mm; hairs bicolored with dark brown bases extending from 1/2 to about 3/4 of hairs length, distal portion of hairs ranging from dark brown to nearly white. Wing membranes naked, usually dark brown. Plagiopatagium attached to the base of the toe. Dorsal surface of the uropatagium somewhat paler than wing membranes, almost naked, with scarce hairs that do not extend beyond the knees.Ventral surface of the uropatagium usually brown, with scarce hairs close to the base of the tail. Ears greatly enlarged, connected by a band of skin of variable development, varying from oval to triangular; tragus wider at the base, straight to slightly curved, very long, notched and pointed. Muzzle broad and slightly inflated.

Skull delicate; rostrum short and flattened, usually straight in lateral profile; braincase slightly wider than the rostrum. Posterior region of the braincase rounded, regular.Nasal opening V- to U-shaped. Frontal expanded laterally towards the orbit. Sagittal and lambdoidal crests weakly developed, not connected, occipital helmet absent. Triangular, flattened bony plate where the sagittal and lambdoidal crests connect ranging from absent to well developed.Zygomatic arches thin and greatly widened medially. Basisphenoid pits absent.Palate extends well beyond molars, ending in a concave posterior edge, with a weakly- to mid-developed medial spine.

Dental formula is I 2/3, C 1/1, P 1/2, M 3/3 (×2) = 32. I 1 separated, spatulate and strongly bilobed; wide and short, with inner and outer cusps well-developed. I 1 usually about three to four times the size of I 2. I 1 usually not aligned to I 2 on a transversal axis of the skull. I 2 and C 1 usually separated by a small gap, C 1 with two slightly concave faces on the lingual region, and one slightly concave face on the labial region. P1 well-developed, reaching 1/2 of C 1 in height; P 1 in contact with C 1 and molars. M 1 and M 2 about the same size, almost square shaped, with W-shaped cusps. M 3 reduced, triangular, with only 3 cusps. I 1 to I 3 reduced, trilobed, and occupying all the space between canines. P 2 about three times P 1 in height. Molars have well developed cusps and decrease in size from M 1 to M 3.

See Neoeptesicus gen. nov. account, and Table 3 for comparisons.