Pseudoeuhinus australis
All modern groups of marine mammals are extinct 175 million years in the future. By this time, new clades of marine organisms have evolved to fill the seas. Descended from common murids, the Nereomyoidea are nicknamed mermice. They have four paddlelike limbs and a flattened tail, used to swim with a dolphinlike vertical motion. Unusually for marine mammals, mermice are primarily visually-oriented creatures and retain color vision, fine-tuned to discern different shades underwater.
The southern spear-toothed mermouse can be found in the southern portion of the now-widening Pacific Ocean. It grows around 4 meters in length, approximately the size of a dolphin. Although the cheek teeth are all conical and identical, mermice retain a distinct pair of incisors on each jaw. In different lineages, these may be specialized for different purposes. In the case of Pseudoeurhinus, the upper incisors project straight anteriorly from the snout. These incisors are used to corral, batter, and stun prey, similarly to the modern swordfish.