A focused search for ancient Mississippian Subperiod marine vertebrates during a paleontological resource inventory of Mammoth Cave National Park, Kentucky, has yielded a wealth of new fossil data, previously unrecognized at this park. To date, we have identified marine vertebrate fossils from four primary horizons at the park, two of which are the first records of marine vertebrate fossils occurring in those horizons. Mammoth Cave sites have produced more than 70 species of ancient fish, about 90% representing cartilaginous fishes (sharks and kin), including several new species. The paleontological resource inventory of Mammoth Cave demonstrates that this park is an important resource for providing data on how fish assemblages changed during the formation of the super-continent Pangea. The inventory data also can help correct antiquated information on fossil sharks found in the region (in some cases not updated since their publication in the late 19^th century).