This new and significantly updated authored dictionary is a unique glossary of paleontological terms, taxa, localities, and concepts. It focuses primarily on identifying the most significant groups of fossil animals and plants in relation to their evolution and phylogeny. It also focuses on mass extinctions, on taxa that are problematic in some significant way, on the principal fossil-Lagerstätten of the world, and on historical turning points marked by index fossils. Although there are many current resources on the subject, none contains an accurate representation of the paleontological lexicon. Although well aware that the fast-changing field of paleontology will always defy any attempt at complete description, the author has attempted to provide an accurate and comprehensive set of about 4,000 entries that will be useful to professionals as well as to general readers of scientific literature without a background in paleontology.