The origins of the arrow worms have long been obscure, but molecular studies are finally bringing the true evolutionary position of these beautiful marine predators into sharper focus. In the 160 ...

A study on the development of priapulids or ‘penis’ worms throws doubt on a feature that has been thought for more than 100 years to define the largest branch of the animal tree of life. Members of ...

Lynn Margulis classified the Chaetognaths, known as arrow worms, as deuterostomes. Deuterostomy is characterized by several developmental characteristics including radial, indeterminate cleavage, a ...