What are Transitional Fossils?
Transitional fossils are the fossils of transitional forms of life representing an evolutionary bridge between two recognized groups. Transitional fossils are among the strongest evidence in favor of Darwin’s theory of evolution and natural selection, but they are insufficiently recognized. Many people believe there are more gaps in the transitional fossil record than there actually is. In reality, hundreds of important transitional forms are known. One of the first obvious transitional fossils is Pikaia gracilens, a simplistic lancelet-like organism found in the Burgess shale (505 million years ago) as well as the Flinders Ranges in Australia (560 million years ago). Pikakia is a transitional fossil between the invertebrates and the vertebrates (Chordata), displaying a primitive notochord, the precursor of a backbone. Pikakia averaged 1 1/2 inches (5 cm) in length, and swam above sea floor, where it likely ate microfauna and food particles. Pikakia fossilizes relatively poorly, with o
Fossils that show intermediate characteristics are generally called transitional fossils. Transitional fossils are fossils that have characteristics that are intermediate in nature to organisms that existed both prior to it and after it. As such, transitional fossils are strongly suggestive of evolution. There are many examples of transitional fossils in the fossil record. Examples include large-scale transitions such as from reptiles to birds (like the controversial archaeopteryx) and from reptiles to mammals, as well as more detailed transitions, such as those among the many hominids or the development of horses.
What are homologous morphologies? What is microevolution? 2. Concerning mass extinctions, compare and contrast the Permian and K/T extinction events, organisms most affected and causes. V. Paleozoic Life 1. Examples of PZ planktonic, nektonic, and benthic invertebrates; differences between PZ and MZ invertebrates 2. Vertebrate animals of the PZ: differences between fish, amphibians, and reptiles 3. How are the different reptile groups distinguished? When did reptiles evolve? VI. Plate Tectonics and Paleobiogeography 1. How do the latitudinal positions of continents, climate, and sea level change through time? 2. How are plate tectonics and glacial events related? How does this affect the distribution of organisms? 3. What does endemic vs. cosmopolitan distribution mean? VII. Mesozoic Life 1. Climate of the Mesozoic evidence from fossils 2. Ruling reptiles: dinosaurs. Know differences between theropod, sauropod, and ornithiscian dinosaurs, examples of each. 3. Dinosaur physiology: evide
