selache

Selache is a term used in paleontology to refer to a group of extinct marine vertebrates that includes sharks, rays, and their relatives. The term is derived from the Greek words "selachos," meaning "saw," and "cheilos," meaning "lip," reflecting the saw-like teeth of many selachians. Selachians are characterized by their cartilaginous skeletons, which are lighter and more flexible than the bony skeletons of bony fish. They have a streamlined body shape, which is well-adapted for swimming and hunting in aquatic environments. Selachians have a diverse range of species, with some dating back over 400 million years. They have played a significant role in marine ecosystems throughout much of Earth's history, and their fossils provide valuable insights into the evolution of marine life. Today, selachians are represented by sharks, rays, and skates, which continue to inhabit the world's oceans.