19. Unlike many previous, more fish-like transitional fossils, the "fins" of Tiktaalik have basic wrist bones and simple rays reminiscent of fingers. In fossils, what anatomical evidence indicates that gills were present? It is clear Pezosiren had 4 legs it used to walk on land, but it also had heavy ribs that could indicate it lived part time in water, much like a hippopotamus. They may have been weight-bearing. Describe how these two species differ anatomically and what that means about where they each lived. Like all modern tetrapods, it had rib bones, a mobile neck with a separate pectoral girdle, and lungs, though it had the gills… (However, many species of lobe-finned fishes that evolved during the Devonian period also had _____.) 8. The fossils are listed in series, showing the transition from one group to another, representing significant steps in the evolution of major features in various lineages. Explain why they are described as such and describe the environment in which they probably lived. This is a tentative partial list of transitional fossils (fossil remains of groups that exhibits both "primitive" and derived traits). Why is Tiktaalik such an important transitional fossil? -amphibian ("both ways of life") refers to life stages of many frog species that live first in H2O then land -larval stage of a frog, called a tadpole, is usually and aquatic herbivore w/ gills, a lateral line system resembling that of aquatic vertebrates, and a long, finned tail 6. Many transitional species had gills which means that they lived in _____. _____ 7. This species likely represents the transitional form of sea cows as it maintained the general body plan of a …