North America

Serratolamna

Serratolamna was a genus of prehistoric shark which lived from the late Cretaceous Period to the Eocene Epoch of the Paleogene Period, approximately 75-45 million years ago. The genus is currently divided into several species, of which the species S…. Read More ›

Didelphodon

Didelphodon, known largely from its appearance as a background character in the final episode of the 1999 BBC series Walking with Dinosaurs, was a large prehistoric mammal which lived in North America during the late Cretaceous Period 73-66 million years… Read More ›

Cimoliasaurus

Cimoliasaurus, meaning “chalk lizard” due to its fossils being found within layers of chalk, was a genus of elasmosaurid plesiosaur which lived at the end of the Cretaceous Period 70-66 million years ago, making it one of the last plesiosaurs… Read More ›

Mosasaurus

Mosasaurus was a genus of fully-aquatic marine lizards which lived throughout the world’s oceans during the late Cretaceous Period approximately 75-66 million years ago. Fossils of this animal were first discovered in 1764 within a chalk mine in the town… Read More ›

Siats

Introduction Siats, whose name is in reference to a monster from native Ute folklore, was a large meat-eating dinosaur which lived in Utah during the middle Cretaceous Period 98 million years ago. As far as we know, Siats was the… Read More ›

Gastonia

Introduction Gastonia was an armored dinosaur measuring approximately 16.5 feet long which lived in western North America during the early Cretaceous Period approximately 135-130 million years ago. The first specimens were found in eastern Utah in 1989, and more have… Read More ›

Thalassomedon

Thalassomedon, meaning “lord of the sea”, was a 38 foot long elasmosaurid plesiosaur which lived within the Mowry Sea, the shallow sea that covered North America during the middle of the Cretaceous Period 97-95 million years ago. In March 1939,… Read More ›

Edgarosaurus

Edgarosaurus was a 12 foot long short-necked plesiosaur which lived within the Mowry Sea during the middle Cretaceous Period 105-100 million years ago. In 1993, a well-preserved fossil specimen consisting of the skull, neck, and one front flipper (collection ID… Read More ›