Cretaceous Period Essay Example

Cretaceous Period Essay Example Cretaceous Period Essay Cretaceous Period Essay The Cretaceous period was 144-65 million years ago. It was the last period of the Mesozoic era. The Cretaceous period was first defined by a Belgian geologist named Jean d’Omalius d’Halloy in 1882, using the strata in the Paris Basin and named for the extensive beds of chalk (calcium carbonate deposited by shells of marine invertebrates, principally coccoliths), found in the upper Cretaceous of Europe. The name Cretaceous was derived from latin creta, meaning chalk. The name of the island, Crete, has the same origin. The Cretaceous period had a relatively warm climate and high eustatic sea level. The oceans and seas were populated with now extinct marine reptiles and on the land, dinosaurs. And at the same time mammals, birds, and flowering plants appeared. Flowering plants spread during this period although they did not become predominant until the Campanian stage near the end of the epoch. Therid evolution was aided by the first appearance of bees. At the same time, some earlier Mesozoic gymnosperms like Conifers continued to thrive. On land, mammals were a small and still relatively minor component of the fauna. The fauna was dominated by the Archosaurian reptiles, especially dinosaurs which were the most diverse. Pterosaurs were common in the early and middle time of the period, but as the Cretaceous proceeded they faced growing competition from the radiation of birds, and by the end by the end of the period, only tow specialized families remained. During the Cretaceous, insects began to diversify, and the oldest known ants, termites, butterflies, moths, grasshoppers and wasps appeared. In the seas, rays, modern sharks and teleosts became common. Marine reptiles such as the ichthysosaurs were in the early to middle time of the Cretaceous, plesiosaurs throughout the entire period, and mososaurs in the late Cretaceous. There was a progressive decline in biodiversity during the Maastrichtian stage of the Cretaceous period prior to the suggested ecological crisis induced by the events of the mass extinction. Biodiversity required a substantial amount of time to recover from the events of the mass extinction, despite the probable extinction of many species. Despite the severity of this boundary event, there was a significant variability in the rate of extinction between and within different fossils. Species which depended on photosynthesis declined or became extinct due to the reduction of solar energy reaching the Earth’s surface because of atmospheric particles blocking the way of sunlight. Evidence suggests that herbivorous animals, which depended on plants as their food, died out because as their food sources became scarce. Consequently, top predators, such as the Tyrannosaurus Rex also perished.