Thrashing Seaswimmer

The thrashing seaswimmer has split from the the speartooth seaswimmer. Akin to other descendants of the speartooth seaswimmer, it is now fully aquatic, as it now rests one half of its brain at a time in the water, in addition to giving birth in the water. Stemming from this transition, it has now assumed an actively pelagic lifestyle, both in hunting fast-moving prey and in charging into shoals of small prey items in the sunlit zone up to 20 cm or smaller in length. In addition to an increasingly fusiform body, its caudal fin became heart-shaped, increasing propulsion. Two dermal ridges evolved on the lower sides, acting as keels for stability. Further enhancing its speed is the flattening of the stalked nostrils, as well as as of the two pairs of smaller dorsal eyes, reducing drag.

This species owes its name to a novel hunting strategy it employs. First, it looks out for groups or congregations of organisms like diamond pumpgills, krillpedes or miniswarmers with its large lateral eyes as it swims. Then, moving towards the targeted group, it charges into it, thrashing about, wielding a long, pointy tooth that stuns, shears or impales prey. The incapacitated prey is then suctioned into its mouth.

It must be noted, however, that this strategy is only utilized by males, for only they have the prodigiously long tooth for it. Further, ram-feeding unsuspecting lone prey is still a viable strategy to get by, and is, in fact, what females, lacking this long tooth, do. The vestigial canine teeth are useful for restraining ensnared prey when this method of feeding is employed, especially larger prey.

They retain monogamy from their ancestor, and these creatures typically live in pairs. The female stands to greatly benefit from her partnership with her mate, as her prosperity and thus fertility is highly dependent on his ability to hunt, which can be measured by the length of his tooth. Competition is also fierce; males will joust for their right to a female, who will move along with the victor, while the loser, if he doesn't have a broken tooth from this, will just have to find another female or wrest one from another male.