Transitional fossils are fossilized remains of organisms that exhibit traits common to both an ancestral group and its derived descendant group, effectively showing an intermediate state in evolutionary history. These fossils provide evidence of gradual evolutionary change by bridging morphological gaps between distinct groups of organisms
. For example, the fossil Tiktaalik, about 375 million years old, shows features of both fish and early four-legged land animals, illustrating the transition from aquatic to terrestrial life. Similarly, fossils like Pakicetus and Ambulocetus reveal stages in the evolution of whales from land mammals to fully aquatic forms. Another classic transitional fossil is Archaeopteryx, which displays characteristics of both non-avian dinosaurs and modern birds
. While transitional fossils often appear to form direct evolutionary links, due to the incompleteness of the fossil record, they are generally considered representatives of intermediate forms rather than direct ancestors. They highlight evolutionary trends and provide a continuum of morphological changes over time, supporting the theory of descent with modification through natural selection
. In summary, transitional fossils are crucial evidence for evolution, showing how major groups of organisms are related through intermediate forms that possess traits of both their ancestors and descendants.
