[1] Fossils give us a lot of evidence about the behaviour of extinct animals, reproduction and parental care. To discover dinosaur fossils, it’s important to find rocks of the right age. For example, in ancient rock exposures, we find only fossils of plants or marine organisms. In younger rocks, we find fossils of mammals, such as whales and horses. Palaeontologists can provide information on the exact age of rocks (225 to 65.6 million years old) that contain dinosaur fossils. [2] Important clues of dinosaur behaviour include fossilized eggs and nests. There is evidence that dinosaurs took care of their babies after hatching from the discovery of skeletons of the theropod dinosaur Citipati. These skeletons were found in brooding positions which suggests that these dinosaurs were protecting their eggs. Bones of older babies in nests of the duckbill dinosaur Maiasaura were also discovered, along with a fossil of an adult Psittacosaurus preserved wi...
[1] About 542 million years ago, a large diversity of animal phyla appeared. This spurt of evolution is called The Cambrian Explosion and is backed up by further fossil evidence. Over the course of the first 10 million years, marine animals developed the basic body forms now seen in modern groups. The record includes fossils of crustaceans, molluscs, sponges, algae, and starfish. However, animal fossils from the Precambrian era have been found, indicating that many animal phyla actually developed prior to the Cambrian explosion. In fact, plant fossils have been found dating back to 1400 million years ago in Montana, USA, and China. These fossils represent organisms that do not resemble any modern organism yet prove that animal life did exist. [2] The Cambrian Explosion lasted for about 20 to 25 million years, resulting in the divergence of most modern metazoan phyla. Prior to the Cambrian Explosion, many animals were unicellular organisms. Over the course of the e...