North America

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 ›

Brachauchenius

Brachauchenius was a 15 foot long pliosaur which lived in the shallow sea that once covered the middle of North America during the middle Cretaceous Period 100-90 million years ago. Fossils of this animal were first found by Charles H…. Read More ›

Trinacromerum

Trinacromerum was a 12 foot long plesiosaur which lived within the Mowry Sea, the shallow sea that covered North America during the middle of the Cretaceous Period 95 million years ago. The holotype specimen was found in 1888 within the… Read More ›

Cimoliopterus

Introduction Cimoliopterus was pterosaur with a supposed wingspan of 16 feet or thereabouts, which inhabited Europe and North America during the middle of the Cretaceous Period approximately 100-94 million years ago. There are presently two species of this pterosaur genus:… Read More ›