Philosophical discussion of homology (similarities due to shared descent) and homoplasy (similarities due to shared environment) has either focused on the homology's role in character delineation or the concepts' history. In this paper, I develop an account drawing on homology and homoplasy's use in biological inference and explanation - specifically recent debate around the microraptor Sinornithosaurus' purported venom. Biologists call on homology and homoplasy to infer character states, support adaptationist explanations, identify evolutionary novelties and hypothesize phylogenetic relationships. In these contexts, homology and homoplasy must be understood phylogenetically and kept separate: as they play divergent roles, overlap between them ought to be avoided. I use these considerations to criticize an otherwise attractive account defended by Gould, Hall, Ramsey & Peterson and Pearson. By this view, homology and homoplasy can only be identified qua some level of description, and some homoplasies (parallelisms) are homologous. I develop an account which retains the first but rejects the second aspect of that view, before characterizing parallel homoplasy in terms of its causal role.