Primeval 19 – Paleocene Epoch

 

The K-Pg Extinction event marked a change from the Cretaceous to Paleogene Period, and also marked the beginning of the Paleocene epoch. The Paleogene is a geologic period that began 66 and ended 23 million years ago and consists of the Paleocene, Eocene, and Oligocene Epochs. The Paleocene is a geologic epoch that lasted from about 66 to 56 million years ago. As with many geologic periods, the strata that define the epoch’s beginning and end are well identified, but the exact ages remain uncertain.

Earth 50 Million Years Ago

Earth 50 Million Years Ago

The Paleocene Epoch is bracketed by two major events in Earth’s history. It started with the mass extinction event at the end of the Cretaceous, known as the Cretaceous-Paleogene (K-Pg) boundary. It ended with the Paleocene-Eocene Thermal Maximum, which was a 200,000 year long interval characterized by extreme changes in climate and carbon cycling.

The early Paleocene was cooler and dryer than the preceding Cretaceous, though temperatures rose sharply during the Paleocene–Eocene Thermal Maximum. The climate became warm and humid worldwide towards the Eocene boundary, with subtropical vegetation growing in Greenland and Patagonia, crocodiles swimming off the coast of Greenland, and early primates living in tropical palm forests of northern Wyoming.(1)Elisabeth Nadin (2003) “Global Fever” UCSC Science Notes 2003 The Earth’s equatorial areas were hot and tropical similar to today, however the temperate zones were generally hot and arid, and the polar regions would have been temperate.

Champsosaur Hunting a Turtle

Champsosaur Hunting a Turtle

Terrestrial Paleocene strata immediately above the K–Pg boundary is often marked by a “fern spike”, a bed especially rich in fern fossils.(2)Vivi Vajda (2003) “Global Disruption of Vegetation at the Cretaceous-Tertiary Boundary – A Comparison Between the Northern and Southern Hemisphere Palynological Signals” The Geological Society of America Ferns are often the first species to colonize areas damaged by forest fires, therefore the fern spike may have been one of the first plants to thrive in the post-Chicxulub devastation. In general, the Paleocene is marked by the appearance of several modern plant species including cacti and palm trees. Paleocene and later plant fossils are generally similar to modern families of plants. The warm temperatures worldwide gave rise to thick tropical, sub-tropical and deciduous forest cover around the globe, including the first recognizably modern tropical rain forests, with ice-free polar regions covered with coniferous and deciduous trees.(3)J. J. Hooker (2005) “Tertiary to Present: Paleocene” in Richard C. Selley et al. (Editors) Encyclopedia of Geology Volume 5 Pages 459-465 With no large grazing dinosaurs to thin them, the Paleocene forests were probably denser than those of the Cretaceous.(4)Stephen Jay Gould (1993) The Book of Life Page 182 Flowering plants, first seen in the Cretaceous, continued to develop and proliferate, and along with them co-evolved the insects that fed on these plants and pollinated them.

terror_birds

Terror Bird in South America

Fossil evidence from the Paleocene is scarce, and there is relatively little known about mammals of the time. Because of their small size until late in the epoch early mammal bones are not well preserved in the fossil record, and most of what we know comes from fossil teeth, and only a few skeletons. The brain to body mass ratios of these archaic mammals were quite low.(5)M. Alan Kazlev (2002) “The Paleocene” Palaeos Cenozoic

Due to the climatic conditions of the Paleocene, reptiles were more widely distributed over the globe than at present. The sub-tropical reptiles found in North America during this epoch include the champsosaurs, crocodiles, turtles, snakes, and lizards. Examples of champsosaurs of the Paleocene include Champsosaurus gigas, the largest champsosaur ever discovered. This creature was unusual among Paleocene reptiles in that Champsosaurus gigas became larger than its known Mesozoic ancestors. Champsosaurus gigas were more than twice the length of the largest Cretaceous specimens, at 3 meters long. Reptiles as a whole decreased in size after the K-Pg event. Champsosaurs declined towards the end of the Paleocene and became extinct during the Miocene. Birds began to re-diversify during the epoch, occupying new niches. Large flightless birds have been found in late Paleocene deposits, including the herbivorous Gastornis in Europe, and carnivorous Terror Birds in South America. In the late Paleocene, early owl types appeared, such as Ogygoptynx in the United States and Berruornis in France.

References   [ + ]

1. Elisabeth Nadin (2003) “Global Fever” UCSC Science Notes 2003
2. Vivi Vajda (2003) “Global Disruption of Vegetation at the Cretaceous-Tertiary Boundary – A Comparison Between the Northern and Southern Hemisphere Palynological Signals” The Geological Society of America
3. J. J. Hooker (2005) “Tertiary to Present: Paleocene” in Richard C. Selley et al. (Editors) Encyclopedia of Geology Volume 5 Pages 459-465
4. Stephen Jay Gould (1993) The Book of Life Page 182
5. M. Alan Kazlev (2002) “The Paleocene” Palaeos Cenozoic