Early Paleogene
The Early Paleogene period is a significant chapter in Earth's history, representing the initial phase of the Paleogene Period. It spans from approximately 66 million years ago to 23 million years ago, and it marks the beginning of the Cenozoic Era, following the catastrophic Cretaceous–Paleogene extinction event. This extinction event saw the disappearance of around three-quarters of plant and animal species on Earth, including the non-avian dinosaurs.
Geological and Climate Changes
During the Early Paleogene, the Earth's configuration of continents and oceans was notably different from today. The Panama Isthmus had not yet formed, and Antarctica, Australia, and South America were more isolated from each other. This isolation allowed unique evolutionary pathways for flora and fauna. The period experienced significant volcanic activity, notably in the early Oligocene when flood basalts erupted across regions such as Ethiopia, northeast Sudan, and southwest Yemen as a result of the Afar mantle plume.
The climate was marked by significant fluctuations, including the Paleocene–Eocene Thermal Maximum, a brief period of intense warming that led to profound changes in ecosystems and the distribution of organisms.
Evolution and Biodiversity
The Early Paleogene is characterized by a rapid surge in biodiversity as surviving species from the Cretaceous–Paleogene extinction event adapted to new ecological niches. This era saw the rise of many modern groups of plants and animals. For instance, the diversification of mammals accelerated, with the emergence of early forms of primates, ungulates, and carnivorans. The extinct family Subparictidae, which were early Paleogene carnivorans endemic to North America, exemplifies the diversification of mammalian lineages during this time.
Marine environments also witnessed significant changes, with the evolution of modern fishes and the reduction of certain primitive marine reptiles. The Carangidae, for example, show a fossil record extending into the Early Paleogene, illustrating the continuity and evolution of marine life.
Geological Features
The Early Paleogene period contributed to the shaping of significant geological features. The Bering Land Bridge intermittently connected Asia and North America, facilitating the exchange of species between the continents. Geological formations from this period, such as those found in Dorset, UK, provide valuable insights into the ancient climate and ecosystems that prevailed during the Early Paleogene.