The interrelationships and phylogenetics of extinct Paleozoic and Early Mesozoic ray-finned fishes (Actinopterygii) are obscured by a low-quality fossil record and understudy of Late Paleozoic (Permo-Carboniferous) actinopterygians. To help address this issue, I describe a new species of ray-finned fish from the late Early Permian Minnekahta Limestone of South Dakota. This taxon is represented by two specimens, Field Museum of Natural History PF 3721 and Yale Peabody Museum 18649. PF 3721 is an exceptionally well-preserved partial three-dimensional head and trunk preserving the external anatomy of and some internal elements from the skull, paired fins, and scale cover. YPM 18649 is a partially articulated, laterally compressed individual with a heavily disarticulated skull. This fish has features of the paraphyletic "paleoniscoid" group, including an immobile maxilla with a narrow suborbital process and a broad postorbital expansion, a heterocercal caudal fin, and rhombic ganoid scales. I conducted an equally weighted maximum parsimony analysis in PAUP and a Bayesian analysis with the Mkv model of morphological evolution in MrBayes with 73 other taxa and 222 characters that placed this taxon in a polytomy with other Late Paleozoic and Early Mesozoic "paleoniscoids" in the respective consensus trees. I recommend the application of parsimony and Bayesian inference techniques in tandem to the problem of early actinopterygian interrelationships to provide necessary caution and direction to future work.
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