1. Head strongly convex, clypeal surface rugosely punctate and distinctly setose
(Fig. 1) ................................. Argeremazus neuquen Stebnicka and Dellacasa

- Head flat to weakly convex; clypeal surface variable, smooth to tuberculate, finely to coarsely punctate, sometimes weakly setose, but never convex and distinctly setose (Figs. 2–5) ......................................................................................... 2

Fig. 1. Argeremazus neuquen, head; Fig. 2. Aegialia argentina head to elytral base; Fig. 3. Ataenius platensis head to elytral base; Fig. 4. Aphodius granarius head to elytral base; Fig. 5. Pleurophorus caesus head to elytral base. Scale line = 0.2 mm.

2. Labrum and mandibles not visible in antero-dorsal view, hidden beneath expanded clypeus (Figs. 3–5) ......................................................................... 3

- Labrum and mandibles visible in antero-dorsal view (Fig. 2) [Aegialiini] ................................................................................................................... 7
.

Fig. 2. Aegialia argentina head to elytral base; Fig. 3. Ataenius platensis head to elytral base; Fig. 4. Aphodius granarius head to elytral base; Fig. 5. Pleurophorus caesus head to elytral base. Scale line = 0.2 mm.

3. Elytral intervals margined at base (most visible toward the sides) (Figs. 3, 5, 12, 13); pygidium with basal longitudinal groove (Figs. 6, 11), usually eroded in apical half (Fig. 10); elytra with internal swelling along sutural margin that fits into the pygidial groove (Fig. 6) ................................................................................. 4

- Elytral intervals not margined at base (Figs. 2, 4), smoothly rounded (Figs. 35, 36, 39); pygidium entirely smooth (Fig. 9), unmodified, never eroded in apical half; elytral apex at suture not enlarged, sharply edged (Fig. 9) ................................ 5

Fig. 1. Argeremazus neuquen, head; Fig. 2. Aegialia argentina head to elytral base; Fig. 3. Ataenius platensis head to elytral base; Fig. 4. Aphodius granarius head to elytral base; Fig. 5. Pleurophorus caesus head to elytral base; Fig. 6. Ataenius picinus apex of abdomen and elytra; Fig. 9. Aidophus parcus apex of abdomen and elytra; Fig. 11. Ataenius platensis pygidium; Fig. 12. Bruchaphodius shannoni head to elytral base; Fig. 13. Parataenius simulator head to elytral base; Fig. 35. Aphodius granarius head to elytral base; Fig. 36. Aphodius pseudolividus head to elytral base. Fig. 39. Podotenus (Pseudopodotenus) fulviventris head to elytral base; Scale line = 0.2 mm.

4. Clypeus smooth, with transverse wrinkles or transverse ridges (Figs. 3, 12–15, 19–21); pronotum without grooves or rows of punctures; metafemur never greatly swollen, not larger than profemur [Eupariini] ................................................... 8

- Clypeus granulate or tuberculate, never with transverse ridges (Figs. 5, 28, 29, 31–33); pronotum usually with rows of punctures; metafemur usually enlarged (not in Pleurophorus), larger than profemur (Fig. 30) [Psammodiini] ........................ 18

Fig. 3. Ataenius platensis head to elytral base; Fig. 5. Pleurophorus caesus head to elytral base; Fig. 12. Bruchaphodius shannoni head to elytral base; Fig. 13. Parataenius simulator head to elytral base; Fig. 14. Ataenius gracilis head; Fig. 15. Ataenius chilensis head; Fig. 19. Ataenius opatroides head to elytral base; Fig. 20. Ataenius picinus head to elytral base; Fig. 21. Ataenius strigicaudus head to eltyral base; Fig. 28. Odontopsammodius cruentus head to elytral base; Fig. 29. Tesarius caelatus head to elytral base; Fig. 31. Leiopsammodius indefensus head to elytral base; Fig. 32. Leiopsammodius placidus (holotype) head to elytral base; Fig. 33. Platytomus micros head to elytral base. Scale line = 0.2 mm.

9. Elytral intervals flattened with 2 rows of distinct setae (Fig. 75) ............................................................. Bruchaphodius ovalipennis (Harold)
- Elytral intervals with distinct median ridge, lacking setae (Figs. 12, 76) ................................................................. Bruchaphodius shannoni (Bruch)

Fig. 12. Bruchaphodius shannoni head to elytral base. Fig. 75. Bruchaphodius ovalipennis habitus; Fig. 76. Bruchaphodius shannoni habitus. Scale line = 0.2 mm

10. Clypeal surface with distinct, strongly developed, transverse ridges (Figs. 13, 16); mesotibia strongly expanded at apex; metafemur swollen, nearly as large as profemur .................................................................................................... 11

- Clypeal surface variable, punctate, granulate, or with transverse wrinkles, never with distinct ridges (Figs. 14–15); mesotibia not strongly expanded at apex; metafemur not or weakly swollen, smaller than profemur ................................ 12

Fig. 13. Parataenius simulator head to elytral base; Fig. 14. Ataenius gracilis head; Fig. 15. Ataenius chilensis head; Fig. 16. Parataenius derbesis head to elytral base. Scale line = 0.2 mm

11. Coarse pronotal punctures restricted to postero-lateral third and base, very much larger than other punctures, rapidly decreasing in size anteriorly at middle (Fig. 13); punctures of elytral intervals fine and widely spaced (Fig. 17) ..................................................................... Parataenius simulator (Harold)

- Coarse pronotal punctures evenly distributed across surface, not as notably different from smaller punctures (Fig. 16); punctures of elytral intervals dense and restricted to central part of interval (Fig. 18)
.................... Parataenius derbesis (Solier) [see Erroneous Records section]

Fig. 13. Parataenius simulator head to elytral base; Fig. 16. Parataenius derbesis head to elytral base; Fig. 17. Parataenius simulator elytral base; Fig. 18. Parataenius derbesis elytral base. Scale line = 0.2 mm

15. Head smooth, apparently without punctures (Fig. 19); pronotum apparently lacking fine punctures, coarse punctures present laterally (Fig. 19); pronotum and elytra dull .................................................... Ataenius opatroides (Blanchard)

- Head with distinct punctation and often with transverse wrinkles (Figs. 3, 20–21); pronotum distinctly punctate throughout with dense fine punctures, coarse punctures also present laterally (Figs. 3, 20–21); pronotum and elytra shiny ...... 16

Fig. 3. Ataenius platensis head to elytral base; Fig. 19. Ataenius opatroides head to elytral base; Fig. 20. Ataenius picinus head to elytral base; Fig. 21. Ataenius strigicaudus head to eltyral base. Scale line = 0.2 mm

16. Elytral interval 9 (penultimate lateral interval) weakly punctate (Fig. 22), but not different from those of disc; pronotum with marginal setae near posterior angle spatulate (Fig. 3), flattened and widest near apex; meso and metatibial accessory spine near base of apical spurs short, at most as long as 4–6 apical spinules
...................................................................... Ataenius platensis (Blanchard)

- Elytral interval 9 (penultimate lateral interval) with puncture pattern differing from those of disc (Figs. 23–24); pronotum with marginal setae near posterior angle not notably spatulate, possibly flattened, but not widest near apex; meso and metatibial accessory spine near base of apical spurs longer than 4 apical spinules (Fig. 25) .. 17

Fig. 3. Ataenius platensis head to elytral base; Fig. 22. Ataenius platensis lateral elytron; Fig. 23. Ataenius picinus lateral elytron; Fig. 24. Ataenius strigicaudus lateral elytron; Fig. 25. Ataenius picinus apex of metatibia. Scale line = 0.2 mm.

17. Elytral interval 9 with fine, dense punctures covering entire surface (Fig. 23); metasternum lacking coarse punctures medially (Fig. 26) ................................................................................. Ataenius picinus Harold

- Elytral interval 9 with 2 rows of coarse punctures (Fig. 24); metasternum with group of coarse punctures near base of mesofemur (Fig. 27) ........................................................................... Ataenius strigicaudus Bates

Fig. 23. Ataenius picinus lateral elytron; Fig. 24. Ataenius strigicaudus lateral elytron; Fig. 26. Ataenius picinus metasternum; Fig. 27. Ataenius strigicaudus metasternum. Scale line = 0.2 mm.

18. Body elongate, cylindrical, parallel-sided for majority of length (Fig. 82); metafemur parallel-sided, not swollen ................. Pleurophorus caesus (Panzer)

- Body more robust, not elongate (Figs. 78–81, 83); metafemur swollen, at most weakly parallel-sided .................................................................................... 19

Fig. 78. Leiopsammodius indefensus habitus; Fig. 79. Leiopsammodius placidus habitus (holotype); Fig. 80. Odontopsammodius cruentus habitus; Fig. 81. Platytomus micros habitus; Fig. 82. Pleurophorus caesus habitus; Fig. 83. Tesarius caelatus habitus.

20. Metatibia with complete transverse ridge near middle (Fig. 30); eyes reduced (Fig. 29); flightless .............................................. Tesarius caelatus (LeConte)

- Metatibia lacking complete transverse ridge, possibly with transverse row of teeth; eyes normally developed (Figs. 31–32); flightless or not .................................. 21

Fig. 29. Tesarius caelatus head to elytral base; Fig. 30. Tesarius caelatus metafemur and tibia; Fig. 31. Leiopsammodius indefensus head to elytral base; Fig. 32. Leiopsammodius placidus (holotype) head to elytral base. Scale line = 0.2 mm.

21. Elytra lacking setae on lateral margin; base of head roughly punctate, lacking grooves (Figs. 32–33); pronotum grooves weak .............................................. 22

- Elytra with distinct, long setae on lateral margin (Fig. 78); base of head with angled grooves (Figs. 31, 78); pronotum with one longitudinal groove on midline and 2 transverse grooves on each side (Figs. 31, 78) ......................................................... Leiopsammodius indefensus (Schmidt)

Fig. 31. Leiopsammodius indefensus head to elytral base; Fig. 32. Leiopsammodius placidus (holotype) head to elytral base; Fig. 33. Platytomus micros head to elytral base. Scale line = 0.2 mm. Fig. 78. Leiopsammodius indefensus habitus.

22. Body more elongate, elytra parallel-sided (Fig. 81); clypeus rounded on each side of central emargination; pronotal lateral margin lacking fringe of setae (Fig. 33) ............................................................................ Platytomus micros (Bates)

- Body more globose, elytra not parallel-sided (Fig. 79); clypeus angulate on each side of central emargination; pronotal lateral margin with distinct fringe of setae (Fig. 32) ................................................ Leiopsammodius placidus (Schmidt)

Fig. 32. Leiopsammodius placidus (holotype) head to elytral base; Fig. 33. Platytomus micros head to elytral base. Scale line = 0.2 mm. Fig. 79. Leiopsammodius placidus habitus (holotype); Fig. 81. Platytomus micros habitus.

23. Scutellum narrowed at base, pentagonal (Fig. 34); head with tubercles on frontal suture (Figs. 35– 36) ........................................................................ 24

- Scutellum broadly triangular, not narrowed at base; head lacking tubercles on frontal suture (Figs. 39, 58– 62, 66–68) ........................................................ 25

Fig. 34. Aphodius granarius scutellum; Fig. 35. Aphodius granarius head to elytral base; Fig. 36. Aphodius pseudolividus head to elytral base; Fig. 39. Podotenus (Pseudopodotenus) fulviventris head to elytral base. Fig. 58. Orodaliscoides reflexus male habitus; Fig. 59. Orodaliscoides reflexus female habitus; Fig. 60. Orodaliscoides rugosiceps habitus; Fig. 61. Acanthaphodius bruchi habitus; Fig. 62. Symphodon anomalus habitus; Fig. 66. Podotenus (Paranimbus) sp. male habitus; Fig. 67. Podotenus fulviventris male habitus; Fig. 68. Podotenus fulviventris female habitus. Scale line = 0.2 mm.

24. Pronotum with distinct, complete basal margin (Figs. 35, 55–56); body black
......................................... Aphodius (Calamosternus) granarius (Linnaeus)

- Pronotum lacking basal margin (Fig. 36); body bicolored (Fig. 57) .............................................. Aphodius (Labarrus) pseudolividus Balthasar

Fig. 35. Aphodius granarius head to elytral base; Fig. 36. Aphodius pseudolividus head to elytral base. Scale line = 0.2 mm. Fig. 55. Aphodius granarius male habitus; Fig. 56. Aphodius granarius female habitus; Fig. 57. Aphodius pseudolividus habitus.

25. Small, less than 5 mm; protibia with apical most tooth projecting forward (Fig. 37); elytra with distinct color pattern (Fig. 61); male metafemur with distinct medial peg (Fig. 38) ................................................ Acanthaphodius bruchi Schmidt

- Larger, greater than 6 mm; protibia with apical most tooth projecting laterally (Figs. 40–42, 63–65); elytra unicolorous, or with paler apex only; male metafemur lacking peg ............................................................................................... 26

Fig. 37. Acanthaphodius bruchi protibia; Fig. 38. Acanthaphodius bruchi metafemur male; Fig. 40. Orodaliscoides reflexus protibia; Fig. 41. Orodaliscoides rugosiceps protibia; Fig. 42. Symphodon anomalus protibia; Fig. 61. Acanthaphodius bruchi habitus; Fig. 63. Podotenus fulviventris female protibia; Fig. 64. Podotenus fulviventris male protibia; Fig. 65. Podotenus (Paranimbus) sp. male protibia. Scale line = 0.2 mm.

26. Body stout, head convex, clypeal margin strongly reflexed (Figs. 58–60); elytra evenly rounded apically, without apical umbone (Fig. 3) .................................. 27

- Body and head flattened (Figs. 39, 62, 66–68); elytra with apical umbone (Figs. 44–45) ...................................................................................................... 28

Fig. 3. Ataenius platensis head to elytral base; Fig. 39. Podotenus (Pseudopodotenus) fulviventris head to elytral base; Fig. 44. Podotenus fulviventris lateral apex of elytron; Fig. 45. Symphodon anomalus lateral apex of elytron; Fig. 58. Orodaliscoides reflexus male habitus; Fig. 59. Orodaliscoides reflexus female habitus; Fig. 60. Orodaliscoides rugosiceps habitus; Fig. 62. Symphodon anomalus habitus; Fig. 66. Podotenus (Paranimbus) sp. male habitus; Fig. 67. Podotenus fulviventris male habitus; Fig. 68. Podotenus fulviventris female habitus. Scale line = 0.2 mm.

27. Protibia with teeth equally separated (Fig. 40); Argentina ................................................................ Orodaliscoides reflexus (Schmidt)
- Protibia with apical 2 teeth (1+2) closer than next pair (2+3) (Fig. 41); Chile
.............................................................. Orodaliscoides rugosiceps (Harold)

Fig. 40. Orodaliscoides reflexus protibia; Fig. 41. Orodaliscoides rugosiceps protibia. Scale line = 0.2 mm.

28. Protibial apex modified, bluntly expanded, apical teeth not large (Fig. 42); body dark tan to light brown, abdomen not orange .... Symphodon anomalus (Harold)

- Protibial apex not modified, not bluntly expanded, apical teeth normally developed (Figs. 63–64); body black with orange abdomen
........... Podotenus (Pseudopodotenus) fulviventris (Fairmaire and Germain)

Fig. 42. Symphodon anomalus protibia; Fig. 63. Podotenus fulviventris female protibia; Fig. 64. Podotenus fulviventris male protibia. Scale line = 0.2 mm.