The hydroneustes eventually split from the hydroskimmer, although its territory stayed virtually the same. The mouth-tentacles have obtained small barbed hooks, in order to hold onto prey while it is being pushed into the mouth; they have also grown a small amount longer in order to aid in feeding. Hooks have also grown inside the mouth as makeshift small teeth, and are used mainly in helping to prevent potential prey from escaping back out of the mouth.
The body has elongated, creating another tentacle-like extension. This posterior tentacle drags behind the hydroneustes as it swims. It can either remain still while dragging or aid in swimming (albeit clumsily) by undulating a little. This slight increase in speed has created a need for vision, as well, and they have gained simple eyes.
Despite their advanced form, they have failed to fully replace the hydroskimmers, and both species continue to survive.