Late Mississippian and earliest Pennsylvanian trilobite faunas of North America are dominated by thePaladinandKaskiaclades. Phylogenetic analysis of middle Carboniferous species of these clades demonstrates the close ancestral relationship between these groups. TheKaskiaclade consists of eight species:K. chesterensisWeller, 1936,K. osagensis(Cisne, 1967),K. longispina(Strong, 1872),K. wilsoni(Walter, 1924),K. genevievensis(Walter, 1924),K. rosei(Cisne, 1967),K. gersnain. sp., andK. rollinsin. sp.KaskiaWeller, 1936 ranges from late Osagean to middle Chesterian (early Visean-early Serpukhovian) and is restricted to cyclothemic shelf and nearshore deposits. Species ofKaskiaappear to have evolved in areas of shallow water and high environmental stress. ThePaladinclade consists of 12 species including previously named speciesP. morrowensis(Mather, 1915),P. girtyianusHahn and Hahn, 1970,P. rarusWhittington, 1954,P. helmsensisWhittington, 1954, andP. moorei(Branson, 1937). New species belonging to this clade arePaladin moorefieldensisn. sp.,P. pleisiomorphusn. sp.,P. imoensisn. sp.,P. mangerin. sp., andP. wapanukaensisn. sp. This group ranges from the early Chesterian to early Morrowan (late Viseanlate Bashkirian). Species ofPaladinappear to be confined to outer shelf shelf-edge and off-shelf facies where presumably deeper water environments existed. This is manifested in their paleogeographic distribution, which is paleoenvironmentally controlled.