Neoagnostus dilatus was named by Hohensee and Stitt (1989) [Questionably assigned to genus]. Its type specimen is UMC 16670a, a cephalon/head, and it is a 3D body fossil. Its type locality is Ouachita Mountains collecting locality J, which is in a Furongian deep subtidal shelf grainstone in the Collier Shale Formation of Arkansas.