The article discusses the most interesting facts about the lives of ancient dinosaurs. They were the largest creatures ever to inhabit the land. During the Mesozoic era, these gigantic reptiles ruled the entire Earth. Later, they became completely extinct, and our ancestors — mammals — spread across the land. However, paleontologists continue to uncover more and more fossils of these famous reptiles. ...
Hemichordates are strictly marine benthic organisms. They are characterized by similar initial stages of embryonic development, the presence of a notochord (a dorsal outgrowth of the gut, also known as a stomochord), the unique structure of the secondary body cavity, and perforating budding. They first appeared in the early or middle Cambrian period. ...