Tiktaalik is a lobe-finned bony fish from the Middle-Late Devonian of Canada. It was named in 2006 by Ted Daeschler, Neil Shubin, and Farish Jenkins. It was a truly remarkable fish, as it started the transition from water to land, and was one of the missing links between lobe-finned fish and amphibians.
Physiology
Tiktaalik was a unique lobe-finned fish. It had a streamlined body, fleshy, strong, lobe-like fins resembling tetrapod arms, a long tail similar to that of a tadpole, a big, flat head with big jaws, and eyes on the top of its head. Its body would have been covered in scaly skin.
Diet
Tiktaalik was a predator, preying on insects and smaller fish. Its teeth were small yet sharp, and were used to get a hold of struggling prey as the lobe-finned fish swallowed them whole.
Ecology
Tiktaalik was an evolutionary step-up from Eusthenopteron, as it had improved features that more resembled those of the tetrapods. For example, it had strong fins with a skeletal makeup very similar to those of tetrapod legs, allowing it to crawl out of the water and onto dry land (very much like a lungfish. As well as this, it had flexible neck bones (which allowed it to look around without turning its body) and a sturdy rib cage (which supported the lobe-finned fish and prevented it from being crushed by its own weight). It would have hunted very similarly to a crocodile, lying in wait near the surface (with its eyes just above the water), right before raising itself up and turning its head to capture its prey.
In popular culture
Tiktaalik was featured in the 1st episode of the 2013 documentary Rise of Animals: Triumph of the Vertebrates, where it is shown as the animal that made the transition from water to land. The scene which features it also takes a look at its fins, one of the features that made it more than capable of doing this task.