Unrooted maximum likelihood phylogeny of photoprotein and photoprotein-like proteins showing clusters of major groupings. Five major groups were reconstructed: ctenophoran, Nematostella, hydromedusan, and Amphimedon photoproteins, as well as closely related coelenterazine-binding proteins from Renilla (an anthozoan cnidarian). Sarcoplasmic calcium binding proteins (SARCs) and calmodulins (CAMs) from a variety of taxa branch outside of these five major groups. Bayesian methods reconstructed a tree with the same topology. Bootstrap support values greater than 50% are denoted. Bayesian posterior probabilities are shown as colored circles at nodes. Red circles indicate 100% support, blue circles indicate >96% support, and black circles indicate >65% support. Species are abbreviated as follows: Ac = Aequorea coerulescens; Am = Amphimedon macrodactyla; Ap = A. parva; Aque = A. queenslandica; Av = A. victoria; Ba = Beroe abyssicola; Bi = Bolinopsis infundibulum; Bl = Branchiostoma lanceolatum; Co = Capsaspora owczarzaki; Dm = Drosophila melanogaster; Hm = Hydra magnipapillata; Hs = Homo sapiens; Mb = Monosiga brevicollis; Mc = Mitrocoma cellularia; Mlei = Mnemiopsis leidyi; Nd = Nereis diversicolor; Nvec = Nematostella vectensis; Og = Obelia geniculata; Ol = O. longissima; Psp = Penaeus sp.; Rm = Renilla mulleri; Rr = R. reniformis; Sr = Salpingoeca rosetta; Ta = Trichoplax adhaerens.