page_title: Paleontology in the United States
section_title: Official fossils
hierarchical_section_title: Paleontology in the United States / Official symbols / Official fossils
caption_attribution_description: English: Woolly mammoths (Mammuthus primigenius) in a late Pleistocene landscape in northern Spain. (Information according to the caption of the same image in Alan Turner (2004) National Geographic Prehistoric Mammals, Washington, D.C.&#58; &#32;National Geographic ISBN 9780792271345, ISBN 9780792269977)
context_page_description: Paleontology in the United States refers to paleontological research occurring within or conducted by people from the United States. Paleontologists have found that at the start of the Paleozoic era, what is now "North" America was actually in the southern hemisphere. Marine life flourished in the country's many seas. Later the seas were largely replaced by swamps, home to amphibians and early reptiles. When the continents had assembled into Pangaea drier conditions prevailed. The evolutionary precursors to mammals dominated the country until a mass extinction event ended their reign.
  The Mesozoic era followed and the dinosaurs began their rise to dominance, spreading into the country before Pangaea split up. During the latter Jurassic Morrison Formation dinosaurs lived in the western states. During the Cretaceous, the Gulf of Mexico expanded until it split North America in half. Plesiosaurs and mosasaurs swam in its waters. Later it began to withdraw and the western states were home to the Hell Creek dinosaurs. Another mass extinction ended the reign of the dinosaurs.
  The Cenozoic era began afterward.
context_section_description: Alabama: Basilosaurus cetoides
  Alaska: Woolly mammoth
  Arizona: Araucarioxylon arizonicum
  California: Saber-toothed cat
  Colorado: Stegosaurus armatus
  Connecticut: Eubrontes giganteus
  Delaware: Belemnitella americana
  Georgia: Shark teeth
  Idaho: Hagerman horse
  Illinois: Tully monster
  Kentucky: Brachiopods
  Louisiana: Petrified palmwood
  Maine: Pertica quadrifaria
  Maryland: Murex snail
  Massachusetts: Dinosaur tracks
  Michigan: American mastodon
  Mississippi: Basilosaurus cetoides and Zygorhiza kochii
  Missouri: Delocrinus missouriensis
  Montana: Maiasaura peeblesorum
  Nebraska: Wooly mammoth, Columbian mammoth, and Imperial mammoth.
   
  Nevada: Shonisaurus popularis
  New Jersey: Hadrosaurus foulkii
  New Mexico: Coelophysis bauri
  New York: Eurypterus remipes
  North Dakota: Shipworm-bored petrified wood
  Ohio: Isotelus maximus
  Oklahoma: Saurophaganax maximus
  Oregon: Metasequoia glyptostroboides
  Pennsylvania: Phacops rana
  South Dakota: Triceratops horridus
  Tennessee: Pterotrigonia thoracica
  Texas: Pleurocoelus nanus
  Utah: Allosaurus fragilis
  Vermont: Beluga whale
  Virginia: Chesapecten jeffersonius
  Washington: Columbian mammoth
  West Virginia: Jefferson's ground sloth
  Wisconsin: Calymene celebra
  Wyoming: Knightia
caption: The Pleistocene wooly mammoth.
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