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Key to Bats of the Greater El Paso Region

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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 femorosaccus.


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

thumbnail of ventral view of Antrozous skull

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 fringe of 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).

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Last Update: 20 Jul 2005