Cephalochordates
Cephalochordates, also known as lancelets, are a group of small, filter-feeding marine animals characterized by their elongated bodies and notochords, which is a dorsal hollow rod that runs the length of their body. They lack a true brain and complex sensory organs but have a well-developed nervous system with a dorsal nerve cord and ganglia. Cephalochordates are considered to be the most basal group of chordates, providing important insights into the evolutionary history of vertebrates. They possess pharyngeal gill slits, a post-anal tail, and a muscular mouth used for capturing food particles from the water column. Cephalochordates are found in shallow coastal waters around the world and play an important role in marine food webs as primary consumers.