A new species of Joffrichthys (Teleostei : Osteoglossidae) from the Sentinel Butte Formation, (Paleocene) of North Dakota, USA

Joffrichthys triangulpterus, sp. nov, is a new species of the family Osteog lossidae, and is described based on two nearly complete, and two partial, a rticulated specimens from the Sentinel Butte Formation in the Fort Union Gr oup (Paleocene) of central North Dakota, USA. The familial placement is bas ed on three diagnostic characters: uroneurals absent, six hypurals; and a k idney shaped opercle. The generic placement into Joffrichthys is based on t wo diagnostic characters and eight similar morphologies and meristics share d between the new species and previously described J. symmetropterus: two c omplete or partial neural spines present on preural 2; one spine or no spin es present on ural 1; similar shapes of the maxillary, dentary, preopercle, opercle, and frontal; a similar body silhouette; and a similar vertebral a nd supraneural count. The specimens are identified as a new species by nine diagnostic characteristics distinguishing it From J. symmetropterus, the m ost closely related taxon: more posteriorly-placed pelvic fins; a greater d orsal fin ray count (30 total); a triangular dorsal and anal fin; asymmetri cally positioned dorsal and anal fins (anterior pterygiophore insertions se parated by 8 to 9 vertebrae); the third dorsal and fifth anal pterygiophore s being the longest; and two complete spines on preural 2. The North Dakota fish is important because it represents a new species of Joffrichthys and represents the most southern occurrence of the genus to date.