Horse Jaw Section | South Dakota chalcedony Their evolutionary history indicates a

Their evolutionary history indicates a close relationship with both marine ancestors and other freshwater-adapted crabs

and skeletal structure

hand selected polished orthoceras (Cephalopod) fossil specimen measuring approx

Cretaceous - Albian Stage (110 MYO) Ammonite fossils from Ambatolafia

Horse Jaw Section | South Dakota chalcedony Their evolutionary history indicates aMesohippus sp. Oligocene (33 30 MYO) Brule Formation White River Badlands South Dakota Specimen approx. size: 1. 25" x 1" x 0. 5" Mesohippus is a genus of extinct early horse that lived during the late Eocene to early Oligocene epochs, approximately 37 to 30 million years ago. Its fossils are primarily found in North America, particularly in the White River Formation of the western United States. As a transitional form in equid evolution, Mesohippus