ABSTRACT: Forty-nine new species of Neotropical Exosternini are described in this work, representing the newly recognized Phelister blairi species group, within the large, heterogeneous taxon Phelister. Eight previously described species are also assigned to this group. Relationships within are indicated with several informal subgroups: P. blairi subgroup: (P. blairi Hinton, 1935, P. erwini sp. nov., P. fimbriatus sp. nov., P. stellans sp. nov., P. sparsus sp. nov., P. pretiosus sp. nov., P. trigonisternus Marseul, 1889, P. globosus sp. nov., P. serratus sp. nov., P. geminus sp. nov., P. parana sp. nov., P. asperatus sp. nov., P. uniformis sp. nov., P. miscellus sp. nov., P. inbio sp. nov., P. sculpturatus Schmidt, 1893, P. tunki sp. nov., P. praedatoris Reichensperger, 1939, P. ifficus sp. nov., P. genieri sp. nov., P. marginatus sp. nov., P. vazdemelloi sp. nov., P. dilatatus sp. nov., P. spectabilis sp. nov., P. pervagatus sp. nov.); P. amazoniae subgroup: (P. morbidus sp. nov., P. annulatus sp. nov., P. sphaericus sp. nov., P. geijskesi Kanaar, 1997, P. fraternus sp. nov., P. conjunctus sp. nov., P. chabooae sp. nov., P. striatinotum Wenzel & Dybas, 1941, P. notandus Schmidt, 1893, P. amazoniae (Lewis, 1898) comb. nov., P. arcuatus sp. nov.); P. gregarius subgroup: (P. gregarius sp. nov., P. praecisus sp. nov., P. rudis sp. nov., P. incongruens sp. nov., P. congruens sp. nov., P. praesignis sp. nov.); P. umens subgroup: (P. umens sp. nov., P. almeidae sp. nov., P. chicomendesi sp. nov., P. microdens sp. nov., P. matatlantica sp. nov.); P. curvipes subgroup: (P. curvipes sp. nov., P. vilavelha sp. nov.); P. rio subgroup: (P. rio sp. nov., P. semotus sp. nov., P. uncinatus sp. nov., P. inscriptus sp. nov.); incertae sedis - unplaced to subgroup: (P. incertus sp. nov., P. okeefei sp. nov., P. blairoides sp. nov., P. pirana sp. nov.). Lectotypes are designated for the following species: P. trigonisternus Marseul, P. sculpturatus Schmidt, P. praedatoris Reichensperger, P. notandus Schmidt, and Discoscelis amazoniae Lewis. Preliminary phylogenetic analyses of the broader Neotropical Exosternini do not support the monophyly of the P. blairi group, nor of all of these subgroups, but the majority do fall within one large clade (which is potentially paraphyletic with respect to some other Neotropical exosternine genera). More work on the phylogeny and taxonomy of this diverse fauna is needed.
