Key to Bats of Greater El Paso Region


1. Nose leaf present; tail vertebrae not extending to edge of interfemoral membrane; no diastema in upper incisor series, bony palate complete in front: Family Phyllostomatidae, 2

1'. No nose leaf; tail extending at least to edge of interfemoral membrane; diastema in upper incisor row present; if absent, then tail extending well posterior to edge of interfemoral membrane: 3

2. Tail extremely reduced; zygomatic arch complete; two lower incisors on each side: Leptonycteris sanborni.

2'. Tail more than 10 mm: zygomatic arch incomplete; no lower incisors: Choeronycteris mexicana.

3. Tail extending conspicuously beyond free edge of interfemoral membrane: Family Molossidae, 4

3'. Tail extending at most a few mm beyond free edge of interfemoral membrane: Family Vespertilionidae, 7

4. Forearm more than 65 mm; upper lips without deep vertical grooves; palate without anterior emargination: Eumops perotis.

4'. Forearm less than 65 mm; upper lips with deep vertical grooves; palate with anterior emargination: 5

5. Forearm less than 45 mm; ears not united at base; second phalanx of fourth finger more than 5 mm; breadth of rostrum markedly greater than interorbital breadth: Tadarida brasiliensis.

5'. Forearm greater than 45 mm; ears united at base; second phalanx of fourth finger less than 5 mm; breadth of rostrum little more than interorbital breadth:6

6. Skull longer than 21 mm: Nyctinomops macrotis.

6'. Skull less than 21 mm: Nyctinomops femorosacca.

7. One upper incisor on each side: 8

7'. Two upper incisors on each side: 11

8. Total teeth, 28; ears long and naked; upper surface of interfemoral membrane largely naked: Antrozous pallidus.

8'. Total teeth, 30 to 32; ears short, rounded, and partly furred; upper surface of interfemoral membrane wholly or at least one-half furred: 9

9. One pair of upper premolars: Lasiurus ega.

9'. Two pairs of upper premolars (first of which is minute, medially displaced, and not visible in lateral view of tooth-row): 10

10. Skull longer than 15 mm: Lasiurus cinereus.

10'. Skull shorter than 15 mm: Lasiurus borealis.

11.Interfemoral membrane densely furred dorsally for more than one-half its length; fur black, tipped with white: Lasionycteris noctivagans.

11'. Interfemoral membrane furred for, at most, its basal one-third; fur not black tipped with white: 12

12. Cheek teeth (postcanine teeth) 6/6: (Myotis), 17

12'. Cheek teeth fewer than 6/6: 13

13. Length of ear more than 25 mm: 14

13'. Length of ear less than 25 mm: 16

14. Dorsal color black with three large white spots; postcanine teeth 5-5: Euderma maculatum.

14'. Dorsal color not as above; postcanine teeth 5/6: 15

15. A pair of anterior accessory lappets between base of ears: Idionycteris phyllotis.

15'. No anterior accessory lappets between bases of ears: Corynorhinus townsendii.

16. One pair of upper premolars: Eptesicus fuscus.

16'. Two pairs of upper premolars: Pipistrellus hesperus.

17. Calcar with well-marked keel: 18

17'. Calcar without well-marked keel: 20

18.Ventral surface of plagiopatagium furred to elbow: Myotis volans.

18'. Ventral surface of plagiopatagium not furred to elbow: 19

19. Rostral breadth less than 5.1 mm; skull length less than 13.5 mm: Myotis californicus.

19'. Rostral breadth more than 5.1 mm; skull length more than 13.5 mm: Myotis ciliolabrum.

20. Free edge of uropatagium with distinct fringeof macroscopically visible short hairs: Myotis thysanodes.

20'. Free edge of uropatagium without a distinct fringe of macroscopically visible hairs: 21

21. Well-developed sagittal crest present: Myotis velifer.

21'. No well-developed sagittal crest: 22

22. Ears more than 16 mm: 23

22'. Ears less than 16 mm: 24

23. Ears black: Myotis evotis.

23'. Ears brownish (may be dark, but not black): Myotis auriculus.

24.Dorsal fur usually with a slight sheen; mastoid breadth usually 7.5 mm or more: Myotis lucifugus.

24'. Dorsal fur usually lacking a sheen; mastoid breadth generally 7.4 mm or less: Myotis yumanensis.

Key modified from Findley et al. (1975).


Last Update: 4 Jan 2008