5 Sea Monsters That Once Swam Over America (Documentary)

There is a layer of white chalk under the wheat fields of Kansas, and it is made from the shells of animals that lived in open ocean water. For roughly thirty million years a shallow sea ran straight through the middle of North America, from the Arctic down to the Gulf of Mexico, and it split the continent in two. This full documentary counts down five sea monsters that swam over ground that is now the United States, from the smallest to the largest. A turtle the size of a car, pulled out of South Dakota and now standing in a museum in Vienna. A fish that died because it swallowed something half its own length, still preserved inside it. A reptile with more neck bones than any animal that has ever lived, and the fossil that caused the most famous error in American science. A fifty foot marine lizard that is now an official state fossil. And a shark that was rebuilt from scratch by researchers in 2025 and turned out to be a completely different shape from the one everyone pictures. Four of these five shared the same inland sea and vanished together sixty-six million years ago. The fifth arrives fifty million years later, in a different ocean, on what is now the American coastline. This is not one lost world. It is two, stacked under the same country. You can watch the full documentary about any of these animals here:    • America's Prehistoric Animals Documentaries   CHAPTERS 0:00 When Kansas Was an Ocean 1:01 The Turtle the Size of a Car 6:03 The Fish Inside a Fish 10:42 The Neck That Broke the Record 16:02 The Lizard That Went to Sea 20:42 The Shark That Was the Wrong Shape 26:36 Two Lost Oceans, One Country SOURCES & FURTHER READING Natural History Museum Vienna and Black Hills Institute — Archelon specimen Brigitta, South Dakota 1992: circa 460 cm head to tail, 400 cm flipper to flipper, over 2,200 kg Wieland 1895 — Archelon holotype, Pierre Shale, South Dakota; later material from Wyoming, North Dakota and Kansas Recent protostegid phylogenetic work — Archelon placed in a separate basal lineage originating in the Late Jurassic, not ancestral to modern sea turtles Leidy 1870 — Xiphactinus audax first described from Kansas material; largest known bony fish Sternberg collection, Sternberg Museum of Natural History, Hays, Kansas — the fish-within-a-fish specimen; at least a dozen Xiphactinus preserve large undigested contents Sachs and Kear 2013 — Elasmosaurus platyurus circa 10.3 m; neck circa 70 percent of body length with roughly 72 cervical vertebrae Cope 1868 and Leidy's correction — skull placed on the tail end; used against Cope by Marsh during the Bone Wars O'Keefe and Chiappe 2011, Science — live birth in plesiosaurs; Kansas polycotylid preserving a single large fetus Kansas Historical Society — Tylosaurus proriger circa 15 m; declared Kansas state marine fossil on 4 April 2014 Mosasaur neonate material from open-ocean Niobrara Chalk, previously assigned to birds — indicates birth at sea rather than in coastal nurseries Shimada et al. 2025, Palaeontologia Electronica — megalodon body proportions from 145 modern and 20 extinct shark species; Belgian 11 m vertebral column gives circa 16.4 m; Danish vertebrae push the maximum credible estimate to 24.3 m and circa 94 tonnes Same study — slender lemon-shark-like body form rather than a scaled-up great white; newborns estimated at 3.6–3.9 m Wroe et al. 2008, Journal of Zoology — megalodon bite force estimated at 108,514–182,201 N, the highest modelled for any animal Western Australian Museum summary — megalodon range circa 16 to 3.5 million years ago; teeth from Florida, Calvert Cliffs Maryland, the Carolinas and Sharktooth Hill California #Megalodon #Prehistoric #Paleontology #SeaMonsters #NaturalHistory