The Terasquids are a group of cephalopods that are all terrestrial and come in many different shapes, sizes, habits, and species in 200 million AD, inhabiting much of Novopangea, in The Future is Wild.
About 450 million BC in the Ordovician, the first marine animals made the transition from ocean to land. The first animal colonists were the arthropods. They were able to move without the natural buoyancy of seawater using muscles within their hard exoskeletons. They had no need for lungs, taking oxygen from the air by diffusion, through pores in the cuticle. Next out of the sea were vertebrates, bony fish which had evolved primitive lungs. Over time, their fins would develop into the legs and arms of all tetrapods.
Despite their early emergence from the sea, invertebrates were not equipped to grow to any great size. They not only lacked the muscle power to support their weight, but diffusion was not an effective method of delivering oxygen into a large body. Vertebrates, with their strong internal skeletons and efficient lungs, had fewer restrictions on size. They dominated the land for 400 million years.
The last of the land vertebrates died away in the mass extinction, around 100 million AD. An important evolutionary niche had been vacated, and it was filled by cephalopods (starting with such forms as the earlier swampus).
To successfully colonize the land, cephalopods had to improve their land-living adaptations. Their tentacles became stronger, the muscle fibers forming a crisscrossing network that could contract to produce a solid support or extend into flexible appendages. Over time, most of the tentacles developed beneath the body as powerful columnar legs. Since these legs could support more weight, larger animals could evolve. Meanwhile, the cavity below the domed mantle developed into a type of lung. At last, many cephalopods (excepting such species as the rainbow squid) had discovered an efficient means of breathing air.
With such adaptations, a new group of land-living cephalopods, called the terasquids, evolved. They branched into many forms, from small hunters to the biggest land animals of the time.