Joseph Leidy
In 1852, Joseph Leidy had erected "Pontogeneus priscus" based on the centrum of a single cervical vertebra in the collections of the Academy of Natural Sciences in Philadelphia. Leidy noted that the centrum had been collected from exposures along the Washita River in Louisiana. synonymized these two taxa to form "Pontogeneus brachyspondylus" which he listed as "incertae sedis".