Tullimonstrum gregarium - DLD 3640 (Pit 15) de6fc62da0a6084df77cadbc8665a7bf Devonian period: 395 m

Devonian period: 395 m

Optical Calcite is a birefringent crystal

Along with its massive size Edmontosaurus had an extremely long and heavy tail

Onyx is a banded variety of chalcedony

calcite and other minerals

Tullimonstrum gregarium - DLD 3640 (Pit 15) de6fc62da0a6084df77cadbc8665a7bf Devonian period: 395 mTullimonstrum gregarium, popularly known as The Tully Monster, is the Illinois State Fossil & is perhaps one of the most mysterious fossils ever unearthed Age of the Tully Monster During the Pennsylvanian Period (roughly 307 million years ago), the land that is now Illinois lay near Earth's equator. Dense swamps, forested with primitive plants, covered much of western and central Illinois. In shallow seas nearby, the Tully monster swam along with