The Global Ocean is a complex environment supporting intricate food chains and highly-evolved species, quite unlike anything known from the Quaternary.
Consider the marine arthropods of previous times, namely crustaceans. They were all specialized, preferring a particular food source and habitat. However, their larval forms tended to be generalized, subsisting on diverse food sources and under almost any conditions. Arthropods were incredibly prolific throughout the oceans of the world and in some cases, despite generally being so small as to be invisible to the naked human eye, were effective predators. Versatile and hardy creatures such as these were ideally positioned to adapt and diversify in a time of crisis.
Immediately after the mass extinction, 100 million AD, marine crustaceans developed a new and crucial biological ability. They became able to reproduce while still in a juvenile, or larval, form (a phenomenon known as neoteny). Sidestepping the need to develop into cumbersome adults provided them with an evolutionary boost. It allowed them to evolve in diverse ways, filling many of the niches left by the now primarily extinct sea-dwelling bony fish (except for cod). Soon the oceans were repopulated with a whole clade of newly evolved animals. These crustaceans are called silverswimmers.There are almost as many different species of silverswimmers in the Global Ocean as there were bony fish in previous times. They all have a similar body plan - a lightweight armored head with bristly legs and antennae protruding from beneath, and a segmented tail that drives the animal through the water with an up-and-down motion. Like fish, they have branched out to take advantage of every habitat and opportunity. There are flat, bottom-dwelling silverswimmers; fierce, hunting silverswimmers; large plankton-feeding silverswimmers; and even silverswimmers that live as parasites on other silverswimmers (as well as on other animals). They range from the microscopic to those the size of a small whale. They are the success story of the Global Ocean that surrounds Novopangea.
Above the waves, flocks of ocean flish will follow the silverswimmer shoals as they skim through the rich green plankton. Silverswimmers can be caught by the flish, snatched out of the water by the vertebrate's jaws. At other times, ocean flish can be fooled by a rainbow squid mimicking the glitter of a silverswimmer shoal.