Systematic revision and cladistic analysis of the Patagonian genus Platesthes

. The genus Platesthes Waterhouse, 1845 (Pimeliinae: Praocini), distributed in the Patagonian steppes in southern Argentina and Chile, is revised. A phylogeny of its 13 species is proposed, based on 48 morphological characters. The cladistic analysis provides one most parsimonious cladogram showing that three unambiguous synapomorphic characters of external morphology and male genitalia support the monophyly of Platesthes . This article includes a redescription of the genus, redescriptions of its species, an identification key, habitus photographs of the most representative species, illustrations of external morphology, genital features and metendosternites, a cladogram and distribution maps. A discussion of the biogeography and status of conservation of Platesthes in the Patagonian steppes and in Central Chile is presented. A new Platesthes species is described: P. neuquensis sp. n. and P. hirtipes Kulzer, 1962 stat. n. is elevated to species status. Other valid species of the genus are: P. depressa (Guérin-Ménéville, 1841), P. similis Kulzer, 1956, P. unicosta Kulzer, 1956, P. nigra Kulzer, 1956, P. pilosa Kulzer, 1956 , P. vidali Peña, 1986, P. burmeisteri Haag-Rutenberg, 1877, P. granulipennis Kulzer, 1956, P. kuscheli Kulzer, 1958, P. humeralis Kulzer, 1958 and P. silphoides Waterhouse, 1845 (type species), for which a lectotype is designated.

Body length was measured dorsally, along the midline, from anterior margin of labrum to elytral apex.For paraproct/coxite length the ratio proposed by Doyen (1993) was used; for basal lamina of tegmen/lateral styles length, and median lobe/tegmen length the ratios proposed by Flores (1996) were used.Dissection methods are those used by Tschinkel & Doyen (1980) for genital structures and by Flores (1997) for internal skeletal anatomy.Drawings were made with a camera lucida adapted to a stereoscopic microscope.Exact label data are cited only for the type material, and that on separate labels indicated in brackets.The distributions of the twelve species inhabiting the Patagonian steppes follow the biogeographic districts proposed by Morrone et al. (2002) within the Central Patagonia biogeographic province (Morrone, 2001).For Platesthes vidali Peña, 1986, which inhabits Central Chile, the entomofaunal regions proposed by Peña (1966a) were used.The method of cladistic analysis used is explained under the heading "Cladistic analysis".
Diagnosis.Recognized among other Praocini by the following combination of characters: maxillary palps with last segment axe-shaped; antennae longer in the male; length of antennomere 11 exceeding length of 10; pronotum with anterior angles rounded and anterior margin lacking edge, lateral margin simple and remote from disc; prosternum without apophysis, with edge on anterior margin; metasternum, mesepisternum and metepisternum with punctures; elytron with two straight, slightly raised carinae, surface punctate; epipleuron conspicuous in posterior 4/5; ventral femoral surface with setae arising from punctures; basal lamina of tegmen long (B/E > 1.0); lateral styles of tegmen with setae on ventral surface, lateral margins and dorsal surface; paraprocts very long (P/C > 3.0).
Redescription.  mm; habitus elongate to oval, flattened or convex; body glabrous or with short or long setae.Colour of body, antennae and legs black to dark brown.
Head.Prognathous; labrum with anterior margin not broadened; clypeus with round punctures, anterior margin concave, extending anterior to frontal process; frons with round or semicircular punctures; mentum subtrapezoidal, with setae; maxillary palps with last segment axe-shaped; eyes oval; antennae longer in the male; length of antennomere 11 exceeding length of 10; apical tomentose sensory patches on antennomere 9 in two areas subequal in size, on antennomere 10 in a semicircle, on antennomere 11 on distal third.
Thorax.Prothorax semi-mobile; pronotum without wrinkles, with round, semicircular or triangular punctures; anterior angles rounded, anterior margin concave, lacking edge, width of posterior margin exceeding width of anterior margin, lateral margin simple, slender, remote from disc, posterior margin not exceeding width of base of elytra, joined in central half to elytra; posterior angles not overlapping elytral humeri; prosternum without apophysis, not extended over mesosternum, with edge on anterior margin; proepisternum and prosternum with punctures; mesosternum inclined forward, separated from prosternum; mesosternum, metasternum, mesepisternum and metepisternum with punctures.
Legs.Procoxal separation equal to 1/3 procoxal width; mesocoxal and metacoxal separations not exceeding mesocoxal and metacoxal width; distance between mesoand metacoxae exceeding half mesocoxal length; metacoxal cavity closed laterally by metasternum and sternum 3. Ventral femoral surface with setae arising from punctures.External process of distal margin of protibiae equal to length of protarsomere 1; width of distal margin of protibiae equal to 1/4 or 1/5 protibial length.
Internal skeletal anatomy.Tentorium with medial straight bridge (Fig. 1).Proendosternite joined to posterior part of procoxal cavities, with posterior arms short, directed posterad and broadened in posterior margin.Mesendosternite with horizontal arms short, with long, slender dorsal arms three times as long as horizontal arms, extended about half distance to tergum.Metendosternite (Figs 2 -10) with arms long, extending beyond mesocoxal inflections about one third distance to tergum, stem not exceeding half metacoxal width, length of stem exceeding width, and stem narrow in basal part (Figs 3,4,6), or narrow in medial part (Figs 8,10), or stem with parallel sides (Figs 2,5,7,9), always wider in upper than basal part.Elytral-abdominal fusion accomplished by a ridge in the elytral epipleuron, which joins by a simple coaptation without interlocking with the abdominal sterna (Doyen, 1993: Fig. 205).
Pro-mesothoracic joint.Prothorax connected to mesothorax by two flexible membranes: the first one is thickened, short, connecting both apertures, pro-and mesothoracic; ventrally this membrane is attached also to the two apodemes formed internally by the mesosternalmesepisternal suture.The second membrane extends from the posterior arms of proendosternites attached to the mesocoxal inflections to the base of the horizontal arms of mesendosternite.
Habitat.Twelve species occur on the xerophilous cool steppes east to the Andes, in Central Patagonia biogeographic province (Morrone, 2001) from sea level to an altitude of 1300 m, where the annual rainfall ranges from 100 to 400 mm (Paruelo et al., 1998).Some of these species (P.unicosta, P. pilosa Kulzer, 1956, P. kuscheli Kulzer, 1958) live on the steppes and in the mesophylous forest of Nothofagus spp.(Fagaceae).Paula Sackmann (pers.comm.), using pitfall traps collected specimens of Platesthes pilosa near Bariloche, in Río Negro province (Argentina), at altitudes gradient between 813 to 1031 m, annual rainfall of from 600 to 1600 mm, on the steppes and in a mesophylous forest of Nothofagus pumilio.One species (Platesthes vidali) inhabits deciduous woodlands of Nothofagus obliqua, N. pumilio, N. antarctica, and N. alpina (Gajardo, 1994) in Central Chile west to the Andes between 1200 to 2400 m, in the Southern Andean Mountain range entomofaunal region (Peña, 1966a).
Redescription.Length 8.5-12.0mm.Body, antennae, and legs black to dark brown.Head.Labrum with anterior margin concave; clypeus with round punctures each with a central seta; clypeal suture not covered by frons, clypeus and frons at same level; frons with round punctures each with a central seta, separated by a distance much greater than diameter of one puncture; groove between eye and frons only on posterior half of dorsal margin of eye; antennae in the male reaching ¾ along lateral margin of pronotum, in the female reaching the middle of lateral margin of pronotum; antennomere 10 wider than long; width of antennomere 11 equal to width of 9 th.Thorax.Pronotum with round punctures each  [11][12][13][14]dorsal and ventral views. 11,13,, spiculum and internal female reproductive tract of P. silphoides (c -coxite; o -oviduct; p -paraproct; s -spermatheca; sag -spermathecal accesory gland; sp -spiculum; v -vagina).16,17: Elytra,. .Scales 1 mm.with a central seta and separated by a distance much greater than diameter of one puncture (Fig. 32); lateral margins raised, widest behind mid point; posterior angles obtuse (Fig. 20); disc of pronotum convex, higher than lateral margins; prosternum convex.Elytron flat, with two raised carinae reaching the end of elytron, more approximate to a lateral margin, external and internal of same length or external longer than internal (Fig. 36); round punctures with anterior margin not raised; pseudopleuron with sparse punctures; epipleuron smooth and glabrous, texture similar to that of elytron, anterior quarter twice as wide as posterior half.Legs.Ventral surface of trochanters, femora and tibiae with uniform pubescence; width of distal margin of protibiae equal to ¼ protibial length; ventral surface of tarsi bearing sparse setae.Male genitalia.Lateral styles of tegmen with proximal margin ventrally concave, widest at base, and not overlapping dorsally median lobe; base of basal lamina of tegmen concave.Female genitalia.Paraprocts glabrous; apicodorsal lobe of proctiger extending about ¼ length of coxite.
Distribution.Argentina (Santa Cruz and Tierra del Fuego provinces) and Chile (Region XII) (Fig. 41), in the Fuegian district within the Central Patagonia biogeographic province.Kulzer, 1956 (Figs 3, 21, 32, 40) Platesthes unicosta Kulzer 1956: 954.Redescription.Length 8.5-12.0mm.Body and legs black to dark brown, antennae dark brown.Head.Labrum with anterior margin concave; clypeus with round punctures each with a central seta; clypeal suture not covered by frons, clypeus and frons at same level; frons with round punctures each with a central seta and separated by a distance much greater than diameter of one puncture; groove between eye and frons only on posterior half of dorsal margin of eye; antennae in the male reaching ¾ along lateral margin of pronotum, in the female reaching the middle of lateral margin of pronotum; antennomere 10 wider than long; width of antennomere 11 equal to width of 9 th.Thorax.Pronotum with round punctures, each with a central seta and separated by a distance much greater than diameter of one puncture (Fig. 32); lateral margins not raised, widest at mid point; posterior angles obtuse (Fig. 21); disc of pronotum convex, higher than lateral margins; prosternum flat.Elytron arched, with one raised carina reaching the end of elytron, more approximate to a lateral margin; round punctures with anterior margin not raised; pseudopleuron with sparse punctures; epipleuron smooth and glabrous, texture similar to that of elytron, anterior quarter twice as wide as posterior half.Legs.Ventral surface of trochanters, femora and tibiae with uniform pubescence; width of distal margin of protibiae equal to ¼ protibial length; ventral surface of tarsi bearing sparse setae.Male genitalia.Lateral styles of tegmen with proximal margin ventrally bisinuate, widest at base and projecting dorsally over median lobe; base of basal lamina of tegmen concave.Female genitalia.Other material examined.ARGENTINA: Santa Cruz: Dpto.Lago Argentino: El Chaltén, Sendero Laguna Capri, 17.i.1998,G. Flores, 1 (IADIZA), Laguna Capri, 700 m, G. Flores, 19.i.1998, 4 (IADIZA), 1 (USNM), 1 (MACN), 1 (MLPA), El Chaltén, 450 m, 20.i.1998, G. Flores, 1 (IADIZA), 3 km SE El Chaltén, 400 m, 22.i.1998, G. Flores, 3 (IADIZA).

Platesthes similis
Redescription.Length 8.0-13.0mm.Body, antennae, and legs black to dark brown.Head.Labrum with anterior margin concave; clypeus with round punctures each with a central seta; clypeal suture not covered by frons, clypeus and frons at same level; frons with round punctures each with a central seta, separated by a distance much greater than diameter of one puncture; groove between eye and frons only on posterior half of dorsal margin of eye; antennae in the male reaching 3/4 along lateral margin of pronotum, in the female reaching the middle of lateral margin of pronotum; antennomere 10 wider than long; width of antennomere 11 equal to width of 9 th.Thorax.Pronotum with round punctures each with a central seta and separated by a distance much greater than diameter of one puncture (Fig. 32); lateral margins not raised, widest at mid point; posterior angles obtuse (Fig. 22); disc of pronotum convex, higher than lateral margins; prosternum convex.Elytron arched, with two raised carinae reaching the end of elytron, more approximate to a lateral margin, external and internal of same length or external longer than internal; round punctures with anterior margin not raised; pseudopleuron with sparse punctures; epipleuron smooth and glabrous, texture similar to that of elytron, anterior quarter twice as wide as posterior half.Legs.Ventral surface of trochanters, femora, and tibiae with uniform pubescence; width of distal margin of protibiae equal to ¼ protibial length; ventral surface of tarsi bearing sparse setae.Male genitalia.Lateral styles of tegmen with proximal margin ventrally bisinuate, widest at base, and not overlapping dorsally median lobe; base of basal lamina of tegmen concave.Female genitalia.Paraprocts glabrous; apicodorsal lobe of proctiger extending about ¼ length of coxite.Distribution.Argentina (Santa Cruz province) and Chile (Region XII) (Fig. 40), in the Fuegian district within the Central Patagonia biogeographic province.Kulzer, 1956 (Figs 6, 17, 23, 41) Platesthes nigra Kulzer 1956: 956;Kaszab, 1964: 358 (list); Peña, 1966b: 428 (cat.).

Platesthes nigra
Redescription.   tures each with a central seta; clypeal suture not covered by frons, clypeus and frons at same level; frons with round punctures each with a central seta and separated by a distance much greater than diameter of one puncture; groove between eye and frons only on posterior half of dorsal margin of eye; antennae in the male reaching ¾ f lateral margin of pronotum, in the female reaching the middle of lateral margin of pronotum; antennomere 10 wider than long; width of antennomere 11 equal to width of 9 th.Thorax.Pronotum with round punctures each with a central seta and separated by a distance much greater than diameter of one puncture (Fig. 32); lateral margins not raised, widest at mid point; posterior angles obtuse (Fig. 23); disc of pronotum convex, higher than lateral margins; prosternum convex.Elytron arched, with two inconspicouous carinae reaching to only half or ¾ the length of the elytron, more approximate to a lateral margin, external and internal of same length; round punctures with anterior margin not raised; pseudopleuron with sparse punctures; epipleuron smooth and glabrous, texture similar to that of elytron, anterior quarter twice as wide as posterior half.Legs.Ventral surface of trochanters, femora and tibiae with uniform pubescence; width of distal margin of protibiae equal to ¼ protibial length; ventral surface of tarsi bearing sparse setae.Male genitalia.Lateral styles of tegmen with proximal margin ventrally bisinuate, widest at base, and not overlapping dorsally median lobe; base of basal lamina of tegmen concave.Female genitalia.Paraprocts glabrous; apicodorsal lobe of proctiger extending about ¼ length of coxite.Distribution.Argentina (Santa Cruz province) and Chile (Region XII) (Fig. 41), in the Fuegian district within the Central Patagonia biogeographic province.Kulzer, 1956 (Figs 7, 24, 33, 41) Platesthes pilosa Kulzer 1956: 958;Kaszab, 1964: 358 (list).Platesthes pubescens Bruch (nomen nudum; description not published).

Platesthes pilosa
Redescription.  mm.Body and legs black to dark brown, antennae dark brown.Head.Labrum with anterior margin concave; clypeus with round punctures each with a central seta; clypeal suture covered by frons, clypeus lower than frons; frons with round punctures each with a central seta and separated by a distance much greater than diameter of one puncture; groove between eye and frons on entire dorsal margin of eye; antennae in the male reaching 3/4 along lateral margin of pronotum, in the female reaching the middle of lateral margin of pronotum; antennomere 10 wider than long; width of antennomere 11 equal to width of 9 th.Thorax.Pronotum with round punctures each with a setae on anterior margin and separated by a distance much greater than diameter of one puncture (Fig. 33); lateral margins not raised, widest at mid point; posterior angles obtuse (Fig. 24); disc of pronotum convex, higher than lateral margins; prosternum convex.Elytron arched, with two raised carinae reaching the end of elytron, equidistant between suture and lateral margin, internal longer than external; round punctures with anterior margin not raised; pseudopleuron with abundant punctures; epipleuron punctate and with setae, texture similar to that of elytron, anterior quarter twice as wide as posterior half.Legs.Ventral surface of trochanters with brush-like pubescence, ventral femoral and tibial surfaces densely setose throughout; width of distal margin of protibiae equal to ¼ protibial length; ventral surface of tarsi bearing abundant decumbent setae.Male genitalia.Lat-eral styles of tegmen with proximal margin ventrally bisinuate, widest at base, and not overlapping dorsally median lobe; base of basal lamina of tegmen concave.Female genitalia.Paraprocts glabrous; apicodorsal lobe of proctiger extending about ¼ length of coxite.Distribution.Argentina: Chubut, Neuquén, and Río Negro provinces (Fig. 41), in the Central district within the Central Patagonia biogeographic province.Peña, 1986 (Figs 8, 19, 25, 37, 40) Platesthes vidali Peña 1986: 62.
Distribution.Chile: Regions VII and VIII (Fig. 40), in the Southern Andean Mountain range entomofaunal region.
Platesthes burmeisteri Haag-Rutenberg, 1877 (Figs 9,26,34,41) Platesthes burmeisteri Haag-Rutenberg, 1877: 156;Fairmaire, 1889: 121;Champion, 1895: 93;Kolbe, 1907: 86  Redescription.Length 9.0-13.5 mm.Body, antennae and legs black to dark brown.Head.Labrum with anterior margin concave; clypeus with round punctures each with a central seta; clypeal suture not covered by frons, clypeus lower than frons; frons with semicircular punctures each with a seta on posterior margin and separated by a distance much greater than diameter of one puncture; groove between eye and frons only on posterior half of dorsal margin of eye; antennae in the male reaching ¾ along lateral margin of pronotum, in the female reaching the middle of lateral margin of pronotum; antennomere 10 wider than long; width of antennomere 11 equal to width of 9. Thorax.Pronotum with semicircular punctures each with a seta on anterior margin and separated by a distance equal or less than diameter of one puncture (Fig. 34); lateral margins not raised, widest at mid point; posterior angles obtuse (Fig. 26); disc of pronotum convex, higher than lateral margins; prosternum convex.Elytron arched, with two raised carinae reaching the end of elytron, equidistant between suture and lateral margin, internal longer than external; round punctures with anterior margin raised, appearing as protuberances; pseudopleuron with abundant punctures; epipleuron punctate and with setae, texture similar to that of elytron, anterior quarter twice as wide as posterior half.Legs.Ventral surface of trochanters with brush-like pubescence or with uniform pubescence, ventral femoral and tibial surfaces densely setose throughout; width of distal margin of protibiae equal to ¼ protibial length; ventral surface of tarsi bearing abundant decumbent setae.Male genitalia.Lateral styles of tegmen with proximal margin ventrally concave, widest at base, and not overlapping dorsally median lobe; base of basal lamina of tegmen concave.Female genitalia.Paraprocts with setae; apicodorsal lobe of proctiger extending about ½ length of coxite.(MLPA), 1 (IADIZA), 1 (FMNH), 1 (NHMB).CHILE: Region XI: General Carrera: Chile Chico, 1-11.ii.1983, G. Arriagada, 3 (MNNC).

Platesthes granulipennis
Distribution.Argentina: Chubut and Santa Cruz provinces (Fig. 40), in the Central district within the Central Patagonia biogeographic province.Kulzer, 1958 (Figs 38, 41) Platesthes humeralis Kulzer 1958: 9. Redescription.Length 13.0-14.0mm.Body and legs black, antennae dark brown.Head.Labrum with anterior margin "V"-shaped; clypeus with round punctures, each with a seta on posterior margin; clypeal suture covered by frons, clypeus lower than frons; frons with semicircular punctures each with a seta on posterior margin and separated by a distance much greater than diameter of one puncture; groove between eye and frons on entire dorsal margin of eye; antennae in the male reaching ¾ of lateral margin of pronotum, in the female reaching the middle of lateral margin of pronotum; antennomere 10 wider than long; width of antennomere 11 equal to width of 9. Thorax.Pronotum with triangular punctures each with a seta on anterior margin and separated by a distance equal or less than diameter of one puncture (Fig. 35); lateral margins raised, widest behind mid point; posterior angles obtuse (Fig. 38); disc of pronotum convex, higher than lateral margins; prosternum convex.Elytron arched, with two raised carinae reaching the end of elytron, equidistant between suture and lateral margin, internal longer than external (Fig. 38); round punctures with anterior margin not raised; elytral humeri very expanded and raised (Fig. 38), forming a deep depression in lateral intercostal space; pseudopleuron with abundant punctures; epipleuron punctate and with setae, texture similar to that of elytron, anterior quarter twice as wide as posterior half.Legs.Ventral surface of trochanters, femora and tibiae with uniform pubescence; width of distal margin of protibiae equal to ¼ protibial length; ventral surface of tarsi bearing abundant decumbent setae.Male genitalia.Lateral styles of tegmen with proximal margin ventrally bisinuate, widest at base and not overlapping dorsally median lobe; base of basal lamina of tegmen concave.Distribution.Argentina: Chubut province (Fig. 41), in the Central district within the Central Patagonia biogeographic province.Kulzer, 1958 (Figs 1, 2, 28, 35, 40) Platesthes kuscheli Kulzer 1958: 10;Peña, 1966b: 428 (cat.).
Distribution.Argentina (Chubut, Río Negro, and Santa Cruz provinces) and Chile (Region XI) (Fig. 40), in the Central district within the Central Patagonia biogeographic province.
Platesthes hirtipes Kulzer, 1962 stat.n. (Figs 18,29,41) Platesthes silphoides hirtipes Kulzer 1962: 86.Redescription.Length 14.0-17.5 mm.Body black, elytral carinae and legs black to dark brown, antennae dark brown.Head.Labrum with anterior margin concave; clypeus with round punctures each with a central seta; clypeal suture covered by frons, clypeus lower than frons; frons with round punctures each with a seta on posterior margin and separated by a distance much greater than diameter of one puncture; groove between eye and frons on entire dorsal margin of eye; antennae in the male reaching ¾ along lateral margin of pronotum, in the female reaching the middle of lateral margin of pronotum; antennomere 10 wider than long; width of antennomere 11 exceeding width of 9 (Fig. 18).Thorax.Pronotum with triangular punctures each with a seta on anterior margin, separated by a distance equal or less than diameter of one puncture (Fig. 35); lateral margins raised, widest behind mid point; posterior angles obtuse (Fig. 29); disc of pronotum convex, higher than lateral margins; prosternum convex.Elytron arched, with two raised carinae reaching the end of elytron, equidistant between suture and lateral margin, internal longer than external; round punctures with anterior margin not raised; pseudopleuron with abundant punctures; epipleuron punctate and with setae, texture similar to that of elytron, anterior quarter twice as wide as posterior half.Legs.Ventral surface of trochanters with brush-like pubescence, ventral femoral and tibial surfaces densely setose throughout; width of distal margin of protibiae equal to ¼ protibial length; ventral surface of tarsi bearing abundant decumbent setae.Male genitalia.Lateral styles of tegmen with proximal margin ventrally concave, widest at base and not overlapping dorsally median lobe; base of basal lamina of tegmen straight.Female genitalia.Paraprocts glabrous; apicodorsal lobe of proctiger extending about ¼ length of coxite.Other material examined.ARGENTINA: Chubut: Dpto.Languiñeo: Sierra Tepuel (Tecka), 11.iii.1961, L.E. Peña, 1 (FMNH).
Distribution.Argentina: Chubut province (Fig. 41), in the Central district within the Central Patagonia biogeographic province.
Distribution.Argentina: Chubut and Santa Cruz provinces (Fig. 40), in the Central district within the Central Patagonia biogeographic province.
Platesthes neuquensis sp.n. (Figs 31,39,40) Diagnosis.Pronotum with triangular punctures each with a setae on anterior margin, separated by a distance equal or less than diameter of one puncture; clypeal suture covered by frons, clypeus lower than frons; frons with round punctures each with a seta on posterior margin; lateral margins of pronotum raised, widest behind mid point; elytra with two raised carinae equidistant between suture and lateral margin.
Description.Length 12.0-15.0mm.Body and legs black to dark brown, antennae dark brown.Head.Labrum with anterior margin concave; clypeus with round punctures each with a central seta; clypeal suture covered by frons, clypeus lower than frons; frons with round punctures each with a seta on posterior margin and separated by a distance much greater than diameter of one puncture; groove between eye and frons on entire dorsal margin of eye; antennae in the male reaching ¾ along lateral margin of pronotum, in the female reaching the middle of lateral margin of pronotum; antennomere 10 wider than long; width of antennomere 11 equal to width of 9. Thorax.Pronotum with triangular punctures each with a setae on anterior margin and separated by a distance equal or less than diameter of one puncture (Fig. 35); lateral margins raised, widest behind mid point; posterior angles obtuse (Fig. 31); disc of pronotum convex, higher than lateral margins; prosternum convex.Elytron arched, with two raised carinae reaching the end of elytron, equidistant between suture and lateral margin, internal longer than external (Fig. 39); round punctures with anterior margin not raised; pseudopleuron with abundant punctures; epipleuron punctate and with setae, texture similar to that of elytron, anterior quarter twice as wide as posterior half.Legs.Ventral surface of trochanters, femora and tibiae with uniform pubescence; width of distal margin of protibiae equal to ¼ protibial length; ventral surface of tarsi bearing abundant decumbent setae.Male genitalia.Lateral styles of tegmen with proximal margin ventrally bisinuate, widest at base and not overlapping dorsally median lobe; base of basal lamina of tegmen straight.Female genitalia.Paraprocts glabrous; apicodorsal lobe of proctiger extending about ¼ length of coxite.

CLADISTIC ANALYSIS
Methods.Outgroups.Character polarity was determined by the outgroup comparison method (Nixon & Carpenter, 1993).Outgroups were used to provide a root for the cladogram and to test the monophyly of Platesthes, not to explore the sister group relationships of Platesthes.Since there is no phylogeny for the genera of Praocini, the outgroups chosen within Praocini were the genera Praocis, Antofagapraocis Flores, 2000, Falsopraocis Kulzer, 1958and Platyholmus Solier, 1840.The present analysis was based on 17 terminal units: 13 species of Platesthes plus the following outgroup species: Praocis rufipes Eschscholtz, 1829 (type species), Antofagapraocis subnudus Flores, 2000, Falsopraocis ricardae (Solier, 1851) (type species) and Platyholmus uspallatensis Fairmaire, 1883.
Characters.Of the 48 characters used 41 were features of external morphology, five of male genitalia and two of female genitalia (Appendix 1).The distribution of states among the terminal taxa is indicated in the data matrix (Appendix 2).Multistate characters 7, 9, 16, 19, 22, 27, 29, 30, 34, 37, 39, 42 and 44 were treated as non-additive because it was not possible to make a correlation between apomorphic states.Multistate characters 6, 11, 12, 14, 15, 33 and 40 were treated as additive and coded according to Strong & Lipscomb (1999).The rule for ordering, in which conditions are arranged in a graded linear sequence from one to another through intermediates, is called the method of intermediates (Wilkinson, 1992); it assumes that small changes in a character are more likely to occur than large changes.In characters 6 (punctures on the frons) and 15 (punctures on the pronotum) the states absent (0) and round with a central seta (Fig. 32) (6.1, 15.1) are present in other genera of Praocini (the last also in four species of Platesthes), while the states round with a seta on anterior (pronotum)/posterior (frons) margin (Fig. 33) (6.2, 15.2), semicircular with a seta on anterior (pronotum)/posterior (frons) margin (Fig. 34) (6.3, 15.3) and triangular with a seta on anterior margin (Fig. 35) (15.4) are unique to species of Platesthes within Praocini.I considered the absence of punctures plesiomorphic for Praocini and that the states 2, 3 and 4 evolved in sequence from the state 1.For the different states exhibited by the elytral carinae (characters 22-24), the absence of carinae was coded only once in the character 22 to avoid repeating this state three times and the consequent heavy weighting of this character state.In characters 23 and 24 the absence of carinae was coded as inapplicable (-) for the species Praocis rufipes, Antofagapraocis subnudus and Platyholmus uspallatensis.The same for the character state "absence of punctures" on frons and pronotum, which was coded only once in the character 6 (punctures on frons) and character 15 (punctures on pronotum) and coded as inapplicable (-) in characters 7 and 16 for the species Platyholmus uspallatensis.
Results.The analysis of the data matrix (Appendix 2) produced one most parsimonious cladogram (Fig. 42) 109 steps long, with a consistency index (CI) of 0.65 and a retention index (RI) of 0.72.Excluding autapomorphies the consistency index (CI) is 0.63.The monophyly of Platesthes is established by three unambiguous synapomorphies (Fig. 42): antennae longer in the male (10.1), epipleuron conspicuous in posterior 4/5 (31.1) and setae of lateral styles of tegmen on ventral surface, lateral margins and dorsal surface (44.2).The cladogram shows three other character states (22.2, 32.1 and 48.1) that support the monophyly of Platesthes (Fig. 42), from which 22.2 (elytra with two main carinae, internal longer than external) evolves to state 3 (elytra with two main carinae, external and internal of same length) in the clade Platesthes depressa, P. similis, P. unicosta and P. nigra and then evolves to state 1 (elytra with one main carina) in P. unicosta; the character state 32.1 (epipleuron texture similar to that of elytron) shows a reversal to plesiomorphic state 0 (epipleuron texture different from that of elytron), in P. granulipennis; and the character state 48.1 (apicodorsal lobe of coxite extending about ¼ length of coxite) shows a reversal to plesiomorphic state 0 (apicodorsal lobe of coxite extending about ½ length of coxite) in the clade P. burmeisteri and P. granulipennis.
Examination of the morphology of species from the remaining genera of Praocini not used as outgroups in this analysis, revealed that the character states epipleuron conspicuous in posterior 4/5 (31.1) and setae of lateral styles of tegmen on ventral surface, lateral margins and dorsal surface (44.2) are unique to Platesthes.
The species of Platesthes are grouped in two clades (Fig. 42), the first includes four species in an unresolved politomy.The second clade includes the remaining nine species of Platesthes, in which the relationships are resolved and some of its subclades are supported by the character states punctures on the frons (6.2, 6.3) and pronotum (15.2, 15.3, and 15.4), which are unique within the Praocini.

DISCUSSION
The first clade of species of Platesthes includes P. depressa, P. similis, P. unicosta and P. nigra (Fig. 42), which occur from south of the Santa Cruz River to north of Tierra del Fuego island (Figs 40,41) (with the exception of P. unicosta, which occurs northwest of the source of the Santa Cruz River).The remaining nine species of Platesthes in the second clade are distributed from north of the Santa Cruz River to Neuquén in Argentina and reach Region VII in Central Chile (Figs 40,41) (with the exception of P. granulipennis, which occurs on both sides of the Santa Cruz River).The valley of the Santa Cruz River was covered by ice repeatedly, during the Pliocene and Pleistocene glaciations (Mercer, 1976), which could have acted as a vicariant event separating populations to the north and south of the valley.The Santa Cruz River is a biogeographic barrier as is shown by the distribution of other genera of Tenebrionidae, such as Psectrascelis Solier, 1836 (Peña, 1985) and Patagonogenius Flores, 1999(Flores, 1999), which do not occur south of the Santa Cruz River.
The distribution of the species of the two clades of Platesthes coincides approximately with the boundaries of the three districts recognized by Morrone et al. (2002) for the Central Patagonia biogeographic province: the four species of the first clade (Platesthes depressa, P. similis, P. unicosta and P. nigra) inhabit the Fuegian district (Figs 40,41), while the species of the second clade inhabit the Payunia district (P.neuquensis) and the Central district (the remaining species) (Figs 40,41), reaching also to the Region VII in Central Chile (P.vidali).
From a biodiversity conservation perspective, the distribution of Platesthes in the Patagonian steppes is subject to threats from livestock grazing and mining, which lead to habitat destruction (Flores, 1998).The distribution of Platesthes in the Patagonian steppes includes 16 protected zones (Table 1), which represent less than 1% of the total area of distribution of the genus in this area.This percentage is low, because a biome is poorly represented when less than 3% of it is protected and adequately represented when it is more than 10% (Roig-Juñent & Claver, 1999).These protected zones fall in the area of distribution of 10 of the 12 species of Platesthes.There are no protected zones for species with small areas of distribution such as P. humeralis and P. hirtipes.On the Patagonian steppes, most of the reserves are isolated and remote (Flores & Roig Juñent, 2001), and are as biological islands within modified ecosystems (Halffter & Ezcurra, 1992).The distribution of Platesthes vidali in Central Chile falls within the Southern Andean Mountain range entomofaunal region (Peña, 1966a).This area has been ranked by Flores & Vidal (2000) as the first for conservation priority of the areas of endemism of the tenebrionid genus Callyntra Solier, 1836 using the cladistic indices of Vane-Wright et al. (1991).These authors emphasized the necessity for creating more reserves in this area, which has only four protected areas (Table 1) and specimens of P. vidali have been collected in three of these.

CONCLUSIONS
A cladistic analysis of Platesthes reveals that this genus is a monophyletic group defined by three synapomorphies of external morphology and male genitalia.Other character states, such as the punctures on frons and pronotum are unique to Platesthes among the Praocini and support subclades of species.Phylogenetic analysis indicates that the species of Platesthes are arranged in two monophyletic groups, which allows the proposal of a biogeographic evolutionary scenario.
Preliminary observations on the status of conservation of Platesthes in its area of distribution indicates that species of this genus are inadequately protected.Further studies of the taxa inhabiting mainly the Patagonian steppes are required to identify additional areas in need of conservation.
ACKNOWLEDGEMENTS.I gratefully acknowledge curators for the loan of material; S. Roig Juñent, C.A. Triplehorn and two anonymous reviewers for suggestions for improving this paper; S. Roig Juñent for the use of NONA, K.C. Nixon for the use of Clados; O. Merkl for providing helpful information about the location of the types of Kulzer, P. Sackmann for sending information on the habitat of Platesthes pilosa, O. Villegas for taking the photographs and my wife Claudía Vergara for help in preparation of artwork and help in the field trip to Santa Cruz province in 1998.This study was supported by a re-entry fellowship of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina, and a re-entry grant of the Antorchas Foundation, Argentina.