Definition: The term "cladoselachian" is a term used in the field of paleontology to describe a type of fossil that contains bones from an animal species that lived during the Cambrian period, approximately 540 million years ago. This type of fossil is known as an "ancient fossil," and it provides valuable information about the evolution and distribution of animals during this time. The term "cladoselachian" comes from the Greek word "clados" which means