The Evolution of Reptiles

The Evolution of Reptiles — page 5
MASS EXTINCTION At the end of the Cretaceous all of the nonavian dinosaurs went extinct The avian dinosaurs continued to evolve into birds The dinosaurs weren't the only reptiles to be hit hard by this extinction event So were two groups of ocean predators mosasaurs and plesiosaurs Scientists don't agree on what caused this global extinction but they do know that it was something that changed the environment causing greenhouse gases to rise and temperatures around the world to heat up Some scientists believe this was caused by an asteroid striking Earth and throwing dust and dirt into the air Others believe debris was thrown into the air when volcanoes erupted Whatever the cause plants that needed a lot of sunlight died out Animals that ate these plants also died as did animals that preyed on them This mass extinction meant that other plants and animals had the opportunity to fill those niches leading to the evolution of many new species This period is sometimes known as the End Cretaceous Extinction or the Cretaceous Paleogene Extinction because the extinctions came between the Cretaceous and Paleogene 66-23 MYA periods period 145-66 MYA just before the majority of dinosaurs became extinct It was approximately the length of a school bus and weighed about as much as an African elephant Scientists know that it wasn't fully grown because its leg bones had not fully fused a process in which bones in a young animal grow together as the animal ages Its discovery was vitally important because very few fossils from the Cretaceous have been found in Africa It is difficult to find fossils in Africa because so much of the land is covered in vegetation Sallam and his crew made their find in the desert where the soil and rocks are visible Because so few African fossils have been found all discoveries like Sallam's are important This one is key because it also refutes a theory about the isolation of African dinosaurs