With insight provided in the key by G. Dellacasa et al. (2001) and a study of many New World taxa, this key was modified from Gordon and Skelley (2007) to include all presently recognized New World genus-level taxa. (as of summer 2007).

1.
.

 Scutellum large, triangularly elongate, 1/5 to 1/3 as long as elytron (Fig. 1)

.
2
 
1'.
.

 Scutellum small, triangular to pentagonal, l/6 or less length of elytron (Fig. 2)
.
7
Figure 1. Otophorus haemorrhoidalis.
Figure 2. Oscarinus odocoilis.
 
 
 

2(1).
.
.

 Metatibial apex fringed with distinctly unequal spinules, mixed short and long (Fig. 3). Elytral intervals often dulled

.
.
3
 
2'.
.
 Metatibial apex fringed with short spinules of equal length (Fig. 4). Elytral intervals shiny
.
5
diapterna hamata T. fossor
Figure 3.Diapterna hamata.
Figure 4. Teuchestes fossor.
 
 

3(2).
.
.
.
.
.

 Frontal suture lacking tubercles. Head and pronotum with punctures widely separated and unevenly distributed (Fig. 5). Elytron shiny or dull. Elytral humerus with fine or widely spaced moderate punctures

.
.
.
.

4
 
3'.
.
.
.
.
 Frontal suture with median tubercle, often weak. Head and pronotum evenly covered with punctures separated by 1‑2 diameters (Fig. 6). Elytron alutaceous. Elytral humerus with coarse, narrowly separated punctures
Figure 5. Diapterna hyperborea.
Figure 6. Colobopterus erraticus.
 
 
 

4(3).
.
.

 Superior metatibial spur shorter than basal metatarsal segment. Male with protibial spur and basal metatarsal segment unmodified. South America

.
Neodiapterna G. Dellacasa
 
4'.
.
.
.
 Superior metatibial spur longer than basal tarsal segment. Male with protibial spur and basal metatarsal segment greatly modified (Fig. 7-8). North America
Figure 7. Diapterna pinguella.
Figure 8. Diapterna pinguella.
 
 
 

5(2).
.
.

 Body large, longer than 10 mm. Scutellum weakly punctured near base, surface nearly impunctate (Fig. 9)

.
Teuchestes Mulsant
 
5'.
.
 Body less than 8 mm long. Scutellum coarsely punctured on surface (Fig. 10)
.
6
Figure 9. Teuchestes fossor.
Figure 10. Otophorus haemorrhoidalis.
 
 
 

6(5).
.
.

 Pronotum with mixed fine and coarse punctures evenly distributed, separated by 2‑3 diameters (Fig. 11). Elytron with red apex. North America and Mexico

.
Otophorus
Mulsant
 
6'.
.
.
.
.
 Pronotum with fine and very coarse punctures, coarse punctures unevenly distributed, widely scattered, separated by 3‑8 diameters (Fig. 12). Elytron unicolored, lacking red apex. Northeastern North America
Figure 11. Otophorus haemorrhoidalis.
Figure 12. Eupleurus subterraneus.
 
 

7(1).
.

 All elytral intervals distinctly carinate on disc OR elytra with distinct humeral tooth, often both (Fig. 13)

.
. 8

Figure 13. Dialytes ulkei.
7'.
.
.
 Elytral intervals variously modified, never carinate (except Xenoheptaulacus which is carinate on alternate intervals). Elytral humerus lacking tooth
.
.
26
 
 

8(7).
.

 Dorsal surface of protibia distinctly, densely punctured (Fig. 14)

.
9

Figure 14. Gonaphodiellus hoffmani, protibia.
8'.
 Dorsal surface of protibia impunctate
 
 
 

9(8).
.

 Elytral intervals and striae finely carinate. Brazil (?)
.

Pleuraphodius Schmidt
 
9'.
.
 Elytral intervals and striae not finely carinate. Mexico to South America
.
10
 
 
 

10(9).
.

 Elytral surface distinctly setose. Brazil (?)
.

Trichaphodius Schimidt (in part)
 
10'.
 Elytral surface glabrous. Mexico to South America
 
 

11(10).
.
.

 Head and pronotal disc glossy, impunctate (Fig. 15). Pronotum constricted laterally. Mexico
.

Imelda Dellacasa, Gordon and Dellacasa
 
11'.
.
.
 Head and pronotal disc distinctly punctured, often dull (Fig. 16). Pronotum emarginate at base, not constricted laterally. Mexico to South America
Figure 15. Imelda constricticollis.
Figure 16. Gonaphodiellus hoffmani.
 
 
 

12(8).
.

 Protibia with apical tooth close to tarsal insertion, projecting forward with tarsus (Fig. 17)

.
13
 
12'.
.
 Protibia with apical tooth removed from tarsal insertion and projecting away from tarsus (Fig. 18)
.
14
Figure 17. Dialytes ulkei.
Figure 18. Calamosternus granarius, male
 
 
 

13(12).
.

 Protibia slender, spur lacking (Fig. 19). Elytra distinctly bicolored. Chile

Acanthaphodius Schmidt
 
13'.
.
 Protibia broad, spur distinct (Fig. 20). Elytra unicolor, dark. Eastern North America
Figure 19. Acanthaphodius bruchi, female.
Figure 20. Dialytes striatulus.
 
 

14(12).

 Elytron carinate (Fig. 21-22)

15
 
14'.
.
 Elytron not carinate, intervals flat, convex or possibly tectiform, narrowly raised in middle (Fig. 23)
.
16
Figure 21. Oxyomus sylvestris.
Figure 22. Strigodius robinsoni.
Figure 23.Dialytodius decipiens.
 
 

15(14).
.
.

 Elytral striae with punctures as wide as carinate intervals (Fig. 24). Clypeal margin rounded. North America and Mexico

.
Oxyomus
 Dejean
 
15'.
.
.
.
.
.
 Elytral striae with punctures much narrower than interval (Fig. 25); intervals with row of punctures on each side of middle carina same size as strial punctures, giving each interval a tri‑carinate appearance obscuring striae. Clypeal margin distinctly dentate. Eastern North America
Figure 24. Oxyomus sylvestris.
Figure 25. Strigodius robinsoni.
 
 

16(14).
.
.
.

 Elytral intervals strongly and irregularly punctured, with scattered setae, dull appearing (Fig. 26). Pronotal base usually lacking marginal groove. Southwestern US and Mexico

.
.
.
17
 
16'.
.
.
.
 Elytral intervals weakly punctured or punctures in two regular rows, rarely with setae, most with glossy intervals (Fig. 27). Pronotal base rarely lacking marginal groove. Widespread
.
.
.
19
Figure 26. Neotrichonotulus inurbanus.
Figure 27. Dialytellus dialytoides.
 
 

17(16).
.
.

 Elytra short, laterally curved, not parallel-sided. Metatarsus distinctly pubescent; apical segments about as wide as long. Mexico

Jalisco Dellacasa, Gordon and Dellacasa

 
17'.
.
.
.
 Elytra normal length, parallel-sided laterally. Metatarsus not pubescent, with few scattered setae; apical segments distinctly longer than wide. Mexico, southern Arizona
.
.
.
18
 
 

18(17).
.
.

 Anterior angles of pronotum not explanate (Fig. 28). Mexico, southern Arizona
.

Neotrichonotulus Dellacasa, Gordon and Dellacasa
 
18'.
.
 Anterior angles of pronotum narrowly explanate (Fig. 29). Mexico
Figure 28. Neotrichonotulus inurbanus.
Figure 29. Trichonotuloides glyptus.
 
 

19(16).
.
.
.

 Pronotum with base narrower than apex and lacking distinct posterior angles (Fig. 30), or base distinctly sinuate (Fig. 31). Body of most longer than 7 mm, some western members 5 mm. North America

.
.
Stenotothorax Schmidt (in part)
 
19'.
.
.
.
 Pronotum with distinct posterior angles, lateral base not narrower than apex, base lobed or straight but not sinuate (Fig. 32). Body length usually less than 5 mm, except rare individuals
.
.
.
20
Figure 21. Oxyomus sylvestris.
Figure 22. Strigodius robinsoni.
Figure 23.Dialytodius decipiens.
 
 

20(19).
.
.
.

 Elytra distinctly mottled black and yellowish. Body wedge-shaped in lateral view (Fig. 33), head and pronotum somewhat flattened, elytra with greatest height near apical third. Mexico

.
Pseudogonaphodiellus Dellacasa, Gordon and Dellacasa
 
20'.
.
.
 Elytra not distinctly mottled, some bicolored. Body not flattened (Fig. 34), approximately same height as elytra
.
.
21
Figure 21. Pseudogonaphodiellus zdzslawae, male.
Figure 22. Dialytellus dialytoides.