1.
.
.
 Anterior angles of clypeus small, hidden below the external tubercles of the frons. Clypeus hidden below frons (fig. 1), if slightly visible then clypeus is nearly vertical. Frons frequently punctate (tribe Passalini)
.
.
2
 

1'.
.
.
.
.
.

 Anterior angles of clypeus well developed and visible, when not very visible (some Pseudacanthus), then frontal-clypeal suture is obvious at least in anterior view (figs. 21, 22). Clypeus usually exposed, visible dorsally, at times separated from the frons by a suture (figs. 18, 19, 20, 23, 26, 28, 29, 31, 34, 35). When suture not present, the frons-clypeus lacks punctures (figs.15, 24, 25, 30) (tribe Proculini)

.
.
.
.
.
11
Heads of:
Figure 1. Passalus
(Pertinax) sp.
Figure 15. Verres
hageni
Figure 18. Petrejoides sp.
Figure 19. Popilius eclipticus
Figure 20. Undulifer incisus
.
Figure 21. Vindex sculptilis
.
Figure 22. Pseudacanthus subopacus
Figure 23. Spurius bicornis
.
Figure 24. Veturius sp.
.
.
Figure 25. Publius sp.
. .
.
Figure 26. Chondrocephalus purulensis
Figure 28. Odontotaenius striatopunctatus
.
Figure 29. Oileus
sargi
Figure 30. Pseudoarrox karreni
Figure 31. Gen. nov. 2
.
Figure 34. Heliscus yucatanus
Figure 35. Coniger ridiculus
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2(1). Apex of maxillary lacinia unidentate. Antenna with 5 lamellae
3
 

2'.
.

Apex of maxillary lacinia bidentate. Antenna with 3 lamellae, rarely 4 or 5

.
5
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3(2).
.
.
.
.
. 		Anterior border of ligula tridentate (fig. 2). Median Frontal Structure (MFS=area in center of head usually with some form of horn or protuberance) similar to that of P. interstitialis (fig. 11) or P. punctatostriatus (fig. 1). Frontal ridges and internal tubercles present, if not, and MFS is “striatopunctatus” type, then central horn reaches anterior border of head
.
.
..
0
.
4
 
3'.
.
.
.
 Anterior border of ligula unidentate (fig. 3). MFS similar to that of Passalus plicatus (fig. 14), without lateral tubercles, central horn does not reach anterior border of head. Frontal ridges and internal tubercles absent

.
.
.
Passipassalus

Figure 2. Ligula of Paxillus leachi
.
Figure 3. Ligula of Passipassalus buhrnheimi
Figure 11.Head of Passalus (Passalus) interstitialis “Neleus” group
Figure 14. Passalus (Passalus) plicatus “Petrejus” group
.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4(3).
.
.
. 		Prosternellum pentagonal, with posterior border of pentagon longer than half of the maximum width of prosternelum (fig. 4). Humeral angles of elytra glabrous or pubescent. Anterior femur without marginal groove ventrally on anterior border


.
Paxillus
 

4'.
.
.
.
.

Prosternellum rhomboidal, if appears pentagonal, then posterior border is narrower than half the maximum width of Prosternellum (fig. 5). Humeral angles of elytra always glabrous. Anterior femur with marginal groove ventrally on anterior border (Antilles, South America)
.
.
.
.
Spasalus
Fig. 4: Prosternellum of Paxillus
Fig. 5: Prosternellum of Spasalus
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5(2).
.
.
.
.
.
.
.
Anterior tibia as wide at apex than at base (fig. 6), with transverse striae on ventral face. Anterior border of labrum concave with an obtuse central projection (fig. 8). Mandibular apex bidentate with superior tooth large and inferior tooth small, rarely with the superior tooth divided or, in South America, tridentate. All tarsi usually short, less than half the length of the tibia (Arizona to South America)

..

.
.
.
.
Ptichopus
 

5'.
.
.
.
.

 Anterior tibia nearly parallel-sided, apex less than twice as wide as base (fig. 7) usually without transverse striae on ventral face. Anterior border of labrum straight, slightly concave or bi-emarginate (figs. 1, 9). Mandibular apex with 3 sub-equal teeth, if 2, then clypeus vertical and easy to see. All tarsi long, length greater than half the length of tibia
.
.
.
6
Figure 1. Head of Passalus
(Pertinax) sp.
Figure 6. Anterior tibia of Ptichopus angulatus
Figure 7. Anterior tibia of Passalus sp.
Figure 8. Head of Ptichopus angulatus
Figure 9. Head of Gen.
nov. 1
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6(5).
.
. 		Mandibular apex tridentate. Clypeus below frons, not exposed, difficult to see even from front (Mexico, Central America, South America, and Antilles)
.
Passalus
7
 

6'.
.
.

 Mandibular apex bidentate. Clypeus vertical, exposed, in dorsal view slightly visible but easy to see from the front (Northern Mexico to Nicaragua) (fig. 9)
.
Gen. Nov. 1
Figure 9. Head of Gen. nov. 1
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7(6).
.
. 		Anterior border of head generally straight, without secondary tubercles, with or without a central concavity (fig. 1) (Mexico to South America)
.
Passalus
(Pertinax)
 

7'.
.
.

Anterior border of head with 1 or 2 secondary tubercles (figs. 10, 11) or, if without tubercles, then horn “broken”, with vertical base then bent forward abruptly (fig. 12)
.

. .
8
Figure 1. Head of Passalus
(Pertinax) sp.
.
.
Figure 10. Head of Passalus (Mitrorhinus) lunaris
.
.
.
Figure 11.Head of Passalus (Passalus) interstitialis “Neleus” group
.
.
Figure 12. Horn of Passalus (Passalus) plicatus ("Neleus" group) – lateral view. Anterior at left
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
8(7).
. 		Anterior border of head with a single, medial, secondary tubercle (fig. 10) (South America)
Passalus (Mitrorhinus)
 

8'.
.
.

 Anterior border of head with 2 partially or completely separated secondary tubercles (fig 11) (Arizona to South America, Antilles)
Passalus (Passalus)
9
Figure 10. Head of Passalus (Mitrorhinus) lunaris
Figure 11. Head of Passalus (Passalus) interstitialis “Neleus” group
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

9(8). .
.

Secondary tubercles contiguous at base (fig. 13)
10
.
 
9'.
. 		Secondary tubercles more or less separated (fig. 11) (Arizona to South America)
Passalus (Passalus) “Neleus” group
Figure 11. Passalus (Passalus) interstitialis “Neleus” group
Figure 13. Passalus (Passalus) jansoni “Phoroneus” group
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
10(9).
. 		Apex of central tubercle (horn) of MFS not free or almost not free (fig. 13) (Guatemala to South America)
Passalus (Passalus) “Phoroneus” group
 

10'.
.

 Apex of horn very free; horn with vertical base, then curves forward horizontally (fig. 14) (South America)
Passalus (Passalus) “Petrejus” group
Figure 13. Passalus (Passalus) jansoni “Phoroneus” group
Figure 14. Passalus (Passalus) plicatus “Petrejus” group
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
11(1).
.
.
.
. 		Anterior margin of labrum deeply concave, with a “scooped out” excavation in labrum behind concavity of margin (fig. 15). Frontoclypeal suture absent (weak in Verres n. sp.). Antenna with short lamellae (fig. 16) (Mexico to South America)

.
.
.
.
Verres
 

11'.
.
.

Anterior margin of labrum straight, slightly concave, or convex (figs. 20, 21); if strongly concave, then frontoclypeal suture present
.
.
12
Figure 15. Verres hageni
Figure 16. Antenna of Verres hageni
Figure 20. Undulifer incisus
Figure 21. Vindex sculptilis
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
12(11).
.
.
.
. 		Anterior border of clypeus strongly convex in center. Frontoclypeal suture triarcuate and prolonged laterally toward supraocular ridge. Frontal ridges absent (fig. 20). Meso- and metasternon pubescent. Body length approximately 30mm (Mexico)


.
. .
.
Undulifer

Figure 20. Head of Undulifer incisus

12'.
.
.
.
.

Anterior border of clypeus slightly convex in center or with an obvious triangular protusion. Frontoclypeal suture not triarcuate, usually more or less straight. Frontal ridges present or absent. Meso- and metasternon pubescent or not. Body length variable

.
.
.
.
13
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
13(12).
.
. 		Internal tubercles of head extend anteriorly more or less the same distance as the external tubercles (fig. 21, 22), projecting beyond frontoclypeal suture when it is present
.
.
14
 

13'.
.
.

 Internal tubercles of head absent or, if present, not extending anteriorly to the level of the external tubercles (fig. 23), not projecting beyond frontoclypeal suture when it is present
.
.
15

Figure 21. Head of Vindex sculptilis
Figure 22. Head of Pseudacanthus subopacus
Figure 23. Head of Spurius bicornis
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
14(13).
.
.
. 		Apex of horn not free, clypeus vertical or almost vertical (45 degrees). Body usually flattened; length 20-30mm (fig. 21). (Mexico to Honduras and El Salvador)
.
.
.
Vindex
 

14'.
.
.

 Apex of horn free, clypeus usually horizontal. Body rounded; length 23-46mm (fig. 22 ). (Mexico to Guatemala)
.
.
Pseudacanthus

Figure 21. Vindex sculptilis
Figure 22. Pseudacanthus subopacus
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
15(13).
. 		Center of face flat, without central horn, only a tubercle on each side. Body length 17-23mm (fig. 23)
.
Spurius

Figure 23. Spurius bicornis

15'.
.

Center of face with protuberances or horn. Body length variable
.
16