Rare, symmetrical shark tooth from Ptychodus whipplei, an extinct dinosaur-era shark from the Cretaceous period of North Texas (Post Oak Creek in Sherman, Texas to be precise).The tooth is about .5 x .4 x .4 inches, in great condition with minimal weathering and no repair or restoration. Comes in a museum display case. Ptychodus whipplei is famous for its "rocket shaped" blunt teeth it used to crush shellfish. It grew to lengths of about 15 feet (4.5 meters) and lived throughout the North American Cretaceous interior seaway from 94 to 86 million years ago.