It is a small chasmosaurine ceratopsian which lived during the Late Cretaceous period (latest Maastrichtian stage) in what is now South Dakota.

It is known from a single partial skull which was collected from the Hell Creek Formation, dating to 66 million years ago.

Longrich suggested that Tatankaceratops appeared to possess a bizarre mix of characteristics from adult and juvenile Triceratops specimens; the animal's small size and short, slender brow horns are consistent with the animal being a juvenile, but the gnarled bone and fusion of skull elements to one another are typical of old adult ceratopsians.

[2] Other paleontologists, including Thomas R. Holtz, Jr., have written that they "strongly suspect" Tatankaceratops is merely a juvenile specimen of Triceratops.

[1] Protoceratops Zuniceratops Achelousaurus Pachyrhinosaurus Einiosaurus Centrosaurus Styracosaurus Avaceratops Anchiceratops Arrhinoceratops Nedoceratops Torosaurus Triceratops Chasmosaurus Pentaceratops Tatankaceratops