Amphioxus Head 15x (image) Marine Biological Laboratory Share Print E-Mail Caption This is the head of the marine invertebrate amphioxus (Branchiostoma floridae), magnified 15 times. Amphioxus are the most ancient of the chordates (animals whose features include a nerve cord), according to molecular analysis. They are important to the study of the origin of vertebrates. Credit Maria del Pilar Gomez/MBL Usage Restrictions Please use with proper credit. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.