The Hauterivian is a stage in the geological time scale that occurred during the Early Cretaceous period, approximately 135 to 130 million years ago. It follows the Barremian stage and precedes the Aptian stage. This period is characterized by significant geological and biological changes, including the diversification of dinosaurs and the emergence of flowering plants. During the Hauterivian, the Earth's climate was generally warm, and sea levels were high, leading to widespread shallow marine environments. Fossil evidence from this time includes various marine organisms, such as ammonites and bivalves, which provide insights into the ecological conditions of the era.