Anomalocaris is thought to have been a predator of the Early to mid Cambrian period. It propelled itself through the water by undulating the flexible lobes on the sides of its body. Each lobe sloped below the one more posterior to it, and this overlapping allowed the lobes on each side of the body to act as a single "fin", maximising the swimming efficiency. The construction of a remote-controlled model showed this mode of swimming to be intrinsically stable, meaning that Anomalocaris need not have had a complex brain to cope with balancing while swimming. The lateral lobes overlapped. The widest part of the body was on the third to fifth lobe; it narrowed towards its tail, and had at least 11 lobes in total. The more posterior lobes are difficult to discriminate, making a total count slightly difficult to reach. Anomalocaris had a large head, a single pair of large, possibly compound eyes, and an unusual, disk-like mouth. The mouth was composed of 32 overlapping plates, four large and 28 small, resembling a pineapple ring with the center replaced by a series of serrated prongs. The mouth could constrict to crush prey, but never completely close, and the tooth-like prongs continued down the walls of the gullet. Two large 'arms' (up to seven inches in length when extended) with barb-like spikes were positioned in front of the mouth. The tail was large and fan-shaped, and along with undulations of the lobes, was probably used to propel the creature through Cambrian waters. Stacked lamella of what were probably gills attached to the top of each lobe. For the time in which it lived Anomalocaris was a truly gigantic creature, reaching lengths of up to one meter.

Dimetrodon was a predatory synapsid ("Mammal-like reptile") genus that flourished during the Permian Period, living between 280–265 million years ago. It was more closely related to mammals than to true reptiles such as lizards. Dimetrodon was an apex predator, among the largest of its day. It grew to up to 3 metres (9.8 ft) in length. The name Dimetrodon means "two-measures of teeth", so named because it had a large skull with two different types of teeth (shearing teeth and sharp canine teeth), unlike reptiles. It walked on four side-sprawling legs and had a large tail. Dimetrodon may have moved in a manner similar to present-day lizards.

Dunkleosteus ("Dunkle's Bone") is a prehistoric fish, one of the largest arthrodire placoderms ever to have lived, existing during the Late Devonian period, about 380-360 million years ago. Due to its heavily armoured nature, Dunkleosteus was likely a relatively slow (albeit powerful) swimmer. It is presumed to have dwelled in diverse zones of inshore waters, although it is unknown whether or not it was also somewhat pelagic, that is, swimming freely in open ocean.

Edaphosaurus was a primitive herbivorous pelycosaur. Along with the Diadectidae, Edaphosaurus is one of the earliest known plant-eating tetrapods (land-living vertebrates). It had a remarkably small, short and shallow skull, a wide body and thick tail. On its back is a sail, different in shape to that of its contemporary Dimetrodon, the vertebral spines being shorter and heavier and bearing numerous small cross bars. The earliest known species are known from fragmentary remains of small animals from late Carboniferous. Successive species increased in size during the early Permian period, until they attained about 3.2 metres in length. These large species are distinguished by the cervical and anterior thoracic neural spines bearing large club-like sidebars.

Euparkeria was a small African reptile of the early Triassic period between 248-245 million years ago, close to the ancestry of the archosaurs. It had a light, lean body, long tail, and a small skull with tiny, needle-like teeth. It probably fed on insects and any other small animals that it could find on the forest floor, and would have periodically shed its teeth in order to keep them sharp. Euparkeria was one of the smaller reptiles of its time, with the adults reaching 60 centimetres (24 in); the size of a large lizard. Euparkeria had relatively long hind legs, and may have been semi-bipedal, able to move using only its hind legs when running quickly. This tendency towards bipedal locomotion makes Euparkeria one of the earliest reptiles to walk on two legs, a feature that would be retained in some dinosaurs and early Crurotarsi. Like many early archosaurs, it had a row of relatively light bony plates along its back and tail. Another means of defence that Euparkeria possessed was a sharp claw on its thumb, which could have been used as a weapon in close combat.

Helicoprion ("Spiral Saw") was a long-lived genus of shark-like cartilaginous fish that first arose in the oceans of the late Carboniferous 280 million years ago, survived the Permian-Triassic Extinction Event, and eventually went extinct during the early Triassic some 225 million years ago. The only fossils known are the teeth, which were arranged in a fantastic "tooth-whorl" strongly reminiscent of a circular saw. The individual teeth are serrated, and it's implied that Helicoprion was carnivorous. As there has yet to be an actual skull found, exactly how it captured or fed on its prey are subjected to a great deal of speculation. One hypothesis that it preyed on ammonites and that the teeth were specialized for the job of breaking into the ammonites' shells. Another idea was that the shark would swim into a school of fish and fling out the jaw, snagging prey on its many teeth.

Mawsonia is an extinct genus of prehistoric coelacanth fish which lived during the Cretaceous period (Albian stage, about 99 to 112 million years ago). Fossils have been found in Africa and South America. Mawsonia first described by British palaeontologist Arthur Smith Woodward in 1907.

Ophiacodon was a large synapsid pelycosaur. Its fossils were found in Joggins, Nova Scotia, Canada. Ophiacodon was at least two meters in length, and the largest species were up to 3.6 metres (12 ft). It is estimated to have weighed from 30 to 50 kilograms (66 to 110 lb). The size of the various species increased during the Early Permian epoch until its extinction. It was a specialized member of the ophiacodontid family. The skull was deep, with long jaws, and provided with sharp teeth. Ophiacodon may have eaten fishes in streams and ponds, although the high narrow skull would seem to argue against such a lifestyle. It was related to animals such as Archaeothyris, and its relatives seem to be ancestral to all synapsids, including mammals.

Postosuchus was a basal archosaur which lived in what is now North America during the middle through to the late Triassic period (228-202 million years ago). It was a rauisuchian, a cousin of crocodiles and came from the same ancestry as dinosaurs. Postosuchus was a quadrupedal reptile with a wide skull and a long tail. It was about 6 meters long, 2 meters tall, and was held up by columnar legs (a quite uncommon feature in reptiles). A crocodile-like snout, filled with many large-sized dagger-like teeth, was used to kill its prey. Rows of protective plates covering its back formed a defensive shield.