North Dakota Stratigraphy Tusoteuthis longa ROCK ROCK UNIT COLUMN PERIOD EPOCH AGES MILLIONS OF YEARS AGO Common Name: Holocene Oahe .01 Giant squid Coleharbor Pleistocene QUATERNARY Classification: 1.8 Pliocene Unnamed 5 Miocene Class: Cephalopoda 25 Arikaree Order: Teuthida Family: Kelaenidae Brule Oligocene 38 South Heart Chadron Chalky Buttes Camels Butte Eocene Golden 55 Valley Bear Den Pen (hard support structure) of the giant squid, Tuseteuthis, Sentinel Butte superimposed on a sketch of the squid. Pen is 2 meters long. TERTIARY Cretaceous Pierre Shale. Cavalier County. North Dakota State Fossil Collection. Bullion Paleocene Creek Description: Tusoteuthis longa was a giant squid that inhabited the Pierre Sea Slope that covered North Dakota about 80 million years ago. These Cannonball ancient squids had a rigid support structure in their body called a Ludlow pen or gladius. The pen was in many ways similar to a back bone 65 but made of shelly material and not bone. The pens are found as Hell Creek fossils. Some of these squids grew to lengths of 15 feet or more. They lived in the Pierre Sea with sharks, mosasaurs, and many Fox Hills other animals. ACEOUS Pierre CRET 84 Niobrara Carlile Carbonate Calcareous Shale Claystone/Shale Siltstone Sandstone Sand & Gravel Mudstone Lignite Glacial Drift Giant squid, Tusoteuthis, battleing a mosasaur. Image from the Morden Museum, Morden, Manitoba Locations where fossils have been found ND State Fossil Collection Prehistoric Life of ND Map North Dakota Geological Survey Home Page.