Pacific Ocean, 175 million years hence
Nobody quite knows how feeding frenzies start. In the vast blueness of the open sea, it seemed that the odds would be against this particular school of forage fish leading to such a chaotic, energetic event. But due to some confluence of factors, this thousands-strong school, descended from catfish, proved tempting enough to all the nearby predators at this exact moment.
The first to arrive on the scene were the mermice. This species in question, the southern spear-toothed mermice (Pseudoeurhinus australis), bears forward-pointing spearlike incisors. The mermice are smart enough to not shoot right into the school - the fish would only maneuver around them. Instead they flanked the school, using their tusks to goad the fish closer together. Partially as a defense attempt and partially from the mermice’s prompting, the schooling fish began to swim in a tight spherical assemblage - a bait ball. And a bait ball is easier to eat from.
A squad of dartsquids were the next to show up. Built for speed, they began to dart in and out of the bait ball. Each squid impaled one fish at a time with their pointed external shells, curling inward to remove and eat the fish before moving on to the next one. The mermice drove the bait ball ever closer towards the surface of the ocean. This drew the notice of several nearby seabats, who circled near the commotion. They began to take advantage of the bait ball as well, dipping their long jaws into the water to catch the floundering fish. Several dartsquids shot above the surface of the water as they darted into the school.
All this splashing and activity caught the attention of one further predator: the giant sea crocodile Irwinbasileus. Being well over 10 meters in length, he could easily scoop up many fish at a time by lunge-feeding if he wanted to. But today had his eyes on a different prey item than the school. As one of the mermice shot into the school for more fish, the Irwinbasileus closed in from the other side. By now the milky cloud of blood obscured the remaining fish in the school. The dartsquids continued to jet in and out of the cloud, while the remaining mermice picked off those that left it.
Many predators left that day with full stomachs. Only a handful of fish survived.
