The Isthmus of Panama contains an extremely rich fossil record that has enabled paleontologists to assemble a fascinating account of how the Isthmus formed, and what the environmental, ecological and evolutionary consequences of its formation were to life in the seas of Tropical America. In this paper we celebrate 20 years of the Panama Paleontology Project (PPP) with an account of marine paleontology on the Isthmus with the aim of stimulating interest in students and researchers into the currently understudied world of tropical paleontology. We summarize over 100 years of paleontological research on the Isthmus of Panama, present the most up-to-date model of Isthmus formation, and describe the origins of the Caribbean and Pacific environments that prevail today. We provide a short review of the history of paleontological research on the Isthmus, illustrate the significance of Isthmian paleontological research for understanding the origin of life in Tropical American seas today, and highlight the potentials for future research. We describe the most appropriate techniques for collecting marine fossils in the region and the best ways to manage collections. Finally, we present three geological formations (the Late Miocene Gatun formation, the Pliocene Cayo Agua formation and the Plio-Pleistocene Burica formation) that occur on the Caribbean and Pacific coasts of the Isthmus. For each formation the location of outcrops, their sedimentology and their ages are presented alongside geological and paleontological evidence that describes their depositional environment. For each formation, we list areas where fossils can easily be collected, illustrate those fossils commonly found and discuss their environmental, ecological and evolutionary significance.
