Cephalaspis lyelli

Cephalaspis (name meaning "Head Shield") is a genus of prehistoric, jawless, detritivorous primitive fish that originated during the Ordovician era and lived into the Devonian. The size of a modern trout, it was easy prey for the predators and super predators of its time, like the sea scorpions or even the Giant Orthocone.

Era & Discovery
Cephalaspis lived during the Ordovician and the Late Devonian period from 435-410 million years ago, living alongside Brontoscorpio, Cameroceras, Pterygotus, and other sea creatures. It was first discovered in 1835.

Physical Attributes
Being a primitive fish, Cephalaspis was small, about the size of a modern-day trout. Cephalaspis was a member of the Osteostraci, one of the most advanced sorts of Palaeozoic armored jawless fish. They were scavengers and bottom-feeder, unable to bite, instead feeding on worms, algae, and small shellfish on the sea-floor by sucking them into their jawless mouths utilizing water pressure; they would have also been prey for the large arthropods of her time, including the thunder-scorpion Brontoscorpio and sea "scorpions" (i.e., eurypterids).

Cephalaspis had a heavy, armored head, itch scales, and to escape from being eaten, these fish had evolved an early warning system: special sensors on their skin were very sensitive and could detect even the tiniest vibrations in the water - it would become the lateral line system in the modern fish. This survival mechanism also aided in avoiding predators like the sea scorpions Brontoscorpio and even an ambush predatory like Pterygotus. It was also jawless, with its mouth positioned at the bottom of its head facing the floor. It also had a powerful tail, perfect for propelling itself through the water. It had two, black eyes near the top of its head. But when Cephalaspis detected danger and were already swimming away from it, with their defensive headgear, they couldn't swim fast for long. They had to rest frequently, or they'd tire completely very quickly.

Their toughened head also possessed a vital weapon, one of the first complex brains, which is much more developed than their rivals, the sea scorpions, who had no memory at all. This brain allowed Cephalaspis and other early vertebrates to process the information surrounding them that they received from their senses (and the lateral line system) and to escape from dangerous predators, such as the giant Pterygotus. It's thanks to these primitive fish that we humans can think and solve problems today.

Behavior & Traits
Cephalaspis was a group animal that lived in shoals. They would often separate to individually find food. They were detritivorous, meaning that they fed on any small scraps of food on the sea floor. They practiced this lifestyle due to the fact that they were jawless fish so therefore, they couldn't effectively hunt.

Cephalaspis' head was heavily armored and was top heavy. Although being heavily defended, it also hindered its swimming abilities as its head couldn't be supported properly whilst swimming. So to combat this issue, Cephalaspis would constantly rest in small intervals. However, this too served as a handicap. In the time Cephalaspis would rest if it were being chased by a predator, the predator would easily be able to gain on the fish. However, if it detected a deadlier threat or needed to migrate, it would swim away quickly without resting.

Cephalaspis were anadromous fish. When breeding season came, Cephalaspis congregated to head for the one place they’d be safe from the sea scorpions: fresh water, inland, with their convoy plowing upriver, away from the sea. They returned to the spawning grounds where they hatched, using memory. Annually, vast amounts of pregnant females would swim to their spawning grounds and would then lay their eggs. However, the journey is often treacherous as predators like Brontoscorpio would often follow them there or would wait for them as it was an annual event.