Histiotus alienus Thomas, 1916

Claudio, Vinicius C., Almeida, Brunna, Novaes, Roberto L. M., Navarro, Marcos A., Tiepolo, Liliani M. & Moratelli, Ricardo, 2023, Rediscovery of Histiotus alienus Thomas, 1916 a century after its description (Chiroptera, Vespertilionidae): distribution extension and redescription, ZooKeys 1174, pp. 273-287 : 273

Histiotus alienus Thomas, 1916

Materials examined.

Holotype. Brazil • 1 ♀; Santa Catarina state, Joinville; sea level; W. Ehrhardt leg.; BM 9.11.19.1 . Other specimens. Brazil • 1 ♂; Paraná state, Palmas ; 26°30'10"S, 51°40'04"W; 1208 m a.s.l.; 21 Nov. 2018; Vinícius C. Cláudio and Marcos A. Navarro leg.; 21 Nov. 2018; in mist-net; MN 91624 .

Distribution.

Histiotus alienus is known only from two localities in southern Brazil, one each in Santa Catarina (Joinville) and Paraná (Palmas) states.

Diagnosis.

Histiotus alienus is distinguished from all other congeners by the following combination of characters: bicolored and dark dorsal fur; ventral fur bicolored and only slightly lighter than dorsal fur; ears intermediate in size when compared to congeners (EL ~ 27.5 mm) and slightly triangular; medial lobe of ear small (WMLE ~ 4.5 mm); transverse band of skin between pinnae low, 1-2 mm high at the edges and weakly fading toward the central portion, where it is practically absent.

Description.

Histiotus alienus is a medium-sized species within the genus (FL 43.3-44.5 mm; Table 2 ). Dorsal fur long (LDF ~ 11.5 mm) and bicolored, with Bone Brown bases that extend to about half the length of hairs and Light Brownish Olive tips; contrast between bands not well delimited. Ventral fur long (LVF ~ 9.5 mm) and bicolored, slightly lighter than dorsal fur, with Brownish Olive bases that extend to about half the length of hairs, and Light Yellowish Olive tips; contrast between bands visible, but not well delimited. Wing membranes naked, dark brown. Plagiopatagium attached to the base of the toe. Dorsal surface of the uropatagium slightly paler than wing membranes, almost naked. Ventral surface of the uropatagium dark brown, with scarce hairs close to the base of the tail. Ears greatly enlarged, slightly triangular, connected by a low band of skin; tragus wider at the base, slightly curved outward, long (~ 13 mm), notched, and pointed. Muzzle broad and slightly inflated.

Skull delicate; rostrum short and flattened dorsoventrally, straight in lateral profile; braincase slightly wider than the rostrum. Posterior region of the braincase rounded, regular. Nasal opening U-shaped in dorsal view. Frontals expanded laterally towards the orbit. Sagittal and lambdoidal crests weakly developed, not connected, occipital helmet absent. Triangular, flattened bony plate weakly developed where the sagittal and lambdoidal crests connect. Zygomatic arches thin and greatly widened medially. Basisphenoid pits absent. Palate extends well beyond molars, ending in a concave posterior edge, with a weakly developed medial spine (Fig. 4 ).

Dental formula I 2/3, C 1/1, P 1/2, M 3/3 ( × 2) = 32. I1 separated, spatulate, and strongly bilobed; wide and short, with well-developed inner and outer cusps. I1 about three times the size of I2. I1not aligned to I2 on a transversal axis of the skull. I2 and C1 separated by a small gap, C1 with two slightly concave faces on the lingual region, and one slightly concave face on the labial region. P1 well developed, reaching half of C1 in height; P1 in contact with C1 and molars. M1 and M2 about the same size, almost square shaped, with W-shaped cusps. M3 reduced, triangular, with only 3 cusps. I1-I3 reduced, trilobed, and occupying the whole space between canines. P2 about three times P1 in height. Molars have well-developed cusps and decrease in size from M1 to M3.

Comparisons.

Histiotus alienus most resembles H. colombiae Thomas, 1916, H. magellanicus (Philippi, 1866), and H. velatus (I. Geoffroy St.-Hilaire, 1824), from which it can be differentiated based on a series of characters. From H. colombiae , H. alienus differs in the size of the ears (>30 mm in H. colombiae and ~ 27 mm in H. alienus ), development of the membrane between pinnae (poorly developed in H. colombiae and about 2 mm high at the edges and vestigial at the center in H. alienus ), and length of the dorsal fur (>13 mm in H. colombiae and ~11.5 mm in H. alienus ). From H. magellanicus , H. alienus differs in the size of the ears (>27 mm in H. magellanicus , usually close to 23 mm, and ~27 mm in H. alienus ), width of medial lobe of ear (~3 mm in H. magellanicus and ~4.5 mm in H. alienus ), shape of ears (oval in H. magellanicus and slightly triangular in H. alienus ), development of the membrane between pinnae (almost absent in H. magellanicus , and about 2 mm high at the edges and vestigial at the center in H. alienus ). From H. velatus , H. alienus differs in the width of medial lobe of the ears (>6 mm in H. velatus and ~4.5 mm in H. alienus ), development of the membrane between pinnae (~3 mm high throughout its extent in H. velatus , and about 2 mm high at the edges and vestigial at the center in H. alienus ), the shape of the ears (noticeably triangular in H. velatus and slightly triangular in H. alienus ), and the length of the dorsal fur (~10 mm in H. velatus and ~11.5 mm in H. alienus ). From H. humboldti Handley, 1996, H. alienus differs in the lateral profile of the skull (sharply dished in H. humboldti and flat in H. alienus ), development of the membrane between pinnae (~2 mm high throughout its extent in H. humboldti , and about 2 mm high at the edges and vestigial at the center in H. alienus ), and color (orangish-brown dorsal fur and light-yellowish ventral fur in H. humboldti , and dark-brown dorsal fur and slightly lighter ventral fur in H. alienus ). From H. mochica Velazco et al., 2021, H. alienus can be easily differentiated by the pelage color and banding pattern (unicolored dorsal fur in H. mochica and bicolored in H. alienus ), width of medial lobe of the ears (>9 mm in H. mochica and ~4.5 mm in H. alienus ), development of the membrane between pinnae (~4.5 mm high throughout its extent in H. mochica , and about 2 mm high at the edges and vestigial at the center in H. alienus ), shape of ears (noticeably triangular in H. mochica and slightly triangular in H. alienus ). From H. cadenai , H. alienus differs in the size of the ears (>31 mm in H. cadenai and ~27 mm in H. alienus ), development of the membrane between pinnae (poorly developed in H. cadenai , and about 2 mm high at the edges and vestigial at the center in H. alienus ), shape of the ears (noticeably triangular in H. cadenai and slightly triangular in H. alienus ), and color (yellowish general color in H. cadenai and dark-brown general color in H. alienus ). From H. diaphanopterus Feijó, Rocha & Althoff, 2015, H. laephotis Thomas, 1916, H. macrotus (Poeppig, 1835), and H. montanus (Philippi & Landbeck, 1861), H. alienus differs in color, with general color dark brown in H. alienus and much lighter in the other species, and with nearly white ventral fur in H. diaphanopterus , H. laephotis , H. macrotus , and H. montanus .

Morphometric analysis.

In the CVA, the first canonical variate CV1 accounts for 41.3% of the variation and is influenced by size, as observed in the loadings of all variables, which are all uniformly negative (Figs 5 , 6 ). The plots along the axis of CV1 also reflect the differences in skull size among the species analyzed. Histiotus alienus is recovered as intermediate in size among its congeners, overlapping only with H. montanus . Histiotus magellanicus , H. macrotus , and H. colombiae have the largest skull sizes, with H. magellanicus and H. macrotus extensively overlapping in the morphospace. The smaller H. laephotis , H. humboldti , and H. velatus also extensively overlap along CV1. Along CV2 (20.2% of the variation), which has a greater influence of the shape of the skull, almost all species overlap in the morphospace; this highlights the resemblance of skull shapes among Histiotus species. Considering the correlations of CV2 (Fig. 6 ), there is an evident contrast between the POB, WFH, and BCB subset of measurements with the remaining measurements, indicating some degree of differentiation in the shape of the skull between these taxa despite the overall resemblance. Histiotus alienus is recovered as most similar to H. montanus in the morphometric analysis, which considers skull shape and size; however, these species are strikingly different in their external morphology and easily distinguished.

Figures

Figure 4. Dorsal, ventral, and lateral views of the skull of the holotype of Histiotus alienus Thomas, 1916 (BM 9.11.19.1).

Figure 5. Plot of multivariate individual scores of craniometric characters in the first two canonical variates. Analyses were performed using 16 craniodental measurements.

Figure 6. Plot of vector correlations of craniometric characters in the first two canonical variates. Analyses were performed using 16 craniodental measurements.