Final answer:
Paleontologists use the outward appearance of fossils to make educated guesses about extinct animals' appearances. Studying the features of species from different periods in history helps paleontologists understand how species have evolved over time.
Step-by-step explanation:
Paleontologists use the outward appearance of fossils to make educated guesses about what extinct animals could have looked like. By studying the features of species from different periods in history, paleontologists compare the characteristics of extinct species with those of living organisms to understand how species have evolved over time. For example, highly detailed records of fossils have shown the evolution of humans and horses. Symmetry is also an important characteristic in identifying fossils, as it provides observable patterns in the external or internal structure of organisms.