Phylum Protochordata, often referred to as the protochordates, encompasses a group of marine animals that are considered to be the closest relatives of vertebrates. This phylum includes three main subphyla: Urochordata (tunicates), Cephalochordata (lancelets), and the extinct group known as the Pikaia. Protochordates are characterized by the presence of notochords, dorsal nerve cords, and pharyngeal […]