Evolved from torquatocauda grandibucha which fed nearer the top, t. stilletoforma became better equipped for consuming living cells. The filter-mouth became smaller to reduce drag and increase swimming speed to catch swift cells, while the tail evolved duplicate 'fins' leading to an increase in swimming power and maneuverability. Eventually the mouth became a thrusting proboscis, suitable for penetrating cells such as those of carpotesta testagleba and even the large mancerxia majorsorbus. A small cluster of light-sensitive cells allows t. stilletiforma to stay in sunny areas where there is likely to be an abundant supply of prey.
