Ancient marine turtles - Archelon ischyros

Giant Cretaceous Sea Turtle (70 million years) Archelon ischyros, a cast Replica
Courtesy of Black Hills Institute of Geological Research, Inc
The original skeleton is on display at The National Museum of Natural History in Vienna, Austria.

Bones of giant sea turtle found in South Dakota

Rapid City, S.D. Sept 30 1996 (Reuter)
The fossilized remains of one of the largest known sea turtles - probably 20 feet (6 metres) wide has been found in South Dakota.
The South Dakota School of Mines and Technology said the skeleton was found near the city of Pierre in a shale bank last month.
The animal, called Archelon, had a shell 12 feet (3.6 metres) across and from tips of its flippers could have been 20 feet wide and more than double the weight of today's sea turtles, the announcement said.

The turtle roamed the region toward the end of the age of the dinosaurs, about 70 million years ago, when much of the area was covered by water.
The fossilized bones are not the first Archelon found in the state but compromise one of the most complete remains yet uncovered, the school said.
The skeleton eventually will be put on display at the school's geology museum.