kosmos: Impact event

Evidence: 61 • authority: 72

The Paleogene Period (IPA: PAY-lee-ə-jeen, -⁠lee-oh-, PAL-ee-; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 Ma (million years ago) to the beginning of the Neogene Period 23.04 Ma. It is the first period of the Cenozoic Era, the tenth period of the Phanerozoic and is divided into the Paleocene, Eocene, and Oligocene epochs. The earlier term Tertiary Period was used to define the time now covered by the Paleogene and subsequent Neogene periods; despite no longer being recognized as a formal stratigraphic term, Tertiary sometimes remains in informal use. Paleogene is often abbreviated Pg, although the…

Evidence: 61 • authority: 72

The Cretaceous–Paleogene (K–Pg) extinction event, formerly known as the Cretaceous–Tertiary (K–T) extinction event, was a major mass extinction of three-quarters (75%) of the plant and animal species on Earth which occurred around 66 million years ago. The event caused the extinction of all the non-avian dinosaurs and most other tetrapods weighing more than 25 kg (55 lb), excepting some ectothermic species such as sea turtles and crocodilians. It marked the ends of both the Cretaceous period and the Mesozoic era, and logged the beginning of the current geological era, the Cenozoic era. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary or K…

Evidence: 43 • authority: 72

Since the 19th century, a significant amount of research has been conducted on the Cretaceous–Paleogene extinction event, the mass extinction that ended the dinosaur-dominated Mesozoic Era and set the stage for the Age of Mammals, or Cenozoic Era. A chronology of this research is presented here. Paleontologists have recognized since at least the 1820s that a significant transition occurred between the Mesozoic and Cenozoic eras. Around this time dinosaur fossils were first being described in the scientific literature. Nevertheless, so few dinosaurs were known that the significance of their extinction went unrecognized, and little scientific effort was exerted toward finding an explanation.…

Evidence: 33 • authority: 92

Rise of modern marine fishes captured in an early Paleocene Lagerstätte.. The Cretaceous-Paleogene (K-Pg) extinction reshaped Earth's biodiversity, yet its impact on marine fishes remains debated due to gaps in the Paleocene record. Here, we report a paleotropical assemblage from the early Paleocene (Danian) of Egypt that provides a window into this transition. The Qreiya 3 Lagerstätte [62.2 million years ago (Ma)] reveals an offshore marine ecosystem with at least 21 actinopterygian taxa across nine orders, exceeding the diversity of all other Danian skeletal assemblages combined. Most fishes are percomorphs and include the oldest skeleton-based records for at least six ecologically diverg…

Evidence: 33 • authority: 92

Two major extinction events in the evolutionary history of turtles: one caused by a meteorite, the other by hominins. ABSTRACT We live in a time of highly accelerated extinction, which has the potential to mirror past mass extinction events. However, the rarity of these events and the restructuring of diversity that they cause complicate direct comparisons between the current extinction crisis and earlier mass extinctions. Among animals, turtles (Testudinata) are one of few groups which both have a sufficient fossil record and a sufficiently stable ecological importance to enable meaningful comparisons between the end Cretaceous mass extinction and the ongoing extinction event. In this pape…

Evidence: 33 • authority: 92

The stepwise rise of angiosperm-dominated terrestrial ecosystems.. Angiosperms are the most diverse and abundant plant taxon today and dominate the majority of Earth's terrestrial ecosystems. They underwent rapid divergence and biogeographic expansion from the early to the middle Cretaceous. Yet, transformative ecosystem change brought about by the increased ecological dominance of angiosperms unfolded progressively until the Late Cretaceous. After the Cretaceous-Paleogene (K-Pg) boundary, angiosperms restructured terrestrial ecosystems towards a modern form. By the Neogene, crown groups that make up modern terrestrial angiosperm biodiversity radiated, and regional floristic distinctions we…

Evidence: 28 • authority: 92

No phylogenetic evidence for angiosperm mass extinction at the Cretaceous-Palaeogene (K-Pg) boundary.. The Cretaceous-Palaeogene mass extinction event (K-Pg) witnessed upwards of 75% of animal species going extinct, most notably among these are the non-avian dinosaurs. A major question in macroevolution is whether this extinction event influenced the rise of flowering plants (angiosperms). The fossil record suggests that the K-Pg event had a strong regional impact on angiosperms with up to 75% species extinctions, but only had a minor impact on the extinction rates of major lineages (families and orders). Phylogenetic evidence for angiosperm extinction dynamics through time remains unexplor…

Evidence: 28 • authority: 92

Fructose metabolism as a common evolutionary pathway of survival associated with climate change, food shortage and droughts.. Mass extinctions occur frequently in natural history. While studies of animals that became extinct can be informative, it is the survivors that provide clues for mechanisms of adaptation when conditions are adverse. Here, we describe a survival pathway used by many species as a means for providing adequate fuel and water, while also providing protection from a decrease in oxygen availability. Fructose, whether supplied in the diet (primarily fruits and honey), or endogenously (via activation of the polyol pathway), preferentially shifts the organism towards the stori…

Evidence: 28 • authority: 92

Human cancer, the naked mole rat and faunal turnovers.. We argue that the human evolutionary heritage with frequent adaptations through geological time to environmental change has affected a trade-off between offspring variability and cancer resistance, and thus favored cancer-prone individuals. We turn the attention to a factor setting the highly cancer-resistant naked mole rat apart from most other mammals: it has remained phenotypically largely unchanged since 30-50 million years ago. Research focusing on DNA stability mechanisms in 'living fossil' animals may help us find tools for cancer prevention and treatment.. Authors: Bredberg A, Schmitz B.. Journal: Cancer medicine. Year: 2019

Evidence: 24 • authority: 88

The Cretaceous–Tertiary Mass Extinction. Abstract The Cretaceous–Tertiary boundary (KTB) mass extinction is primarily known for the demise of the dinosaurs, the Chicxulub impact, and the frequently rancorous thirty-years-old controversy over the cause of this mass extinction. Since 1980 the impact hypothesis has steadily gained support, which culminated in 1990 with the discovery of the Chicxulub crater on Yucatán claimed as the KTB impact site and “smoking gun” that virtually proved this hypothesis. In a perverse twist of fate, this discovery also began the decline of the impact hypothesis, because for the first time it could be tested directly based on the impact crater and impact ejecta…

Evidence: 24 • authority: 72

An impact event is a collision between astronomical objects causing measurable effects. Impact events have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effect. When large objects impact terrestrial planets such as the Earth, there can be significant physical and biospheric consequences, as the impacting body is usually traveling at several kilometres per second (km/s). The minimum impact speed for bodies striking Earth is 11.2 km/s (25,054 mph; 40,320 km/h), the Escape velocity of the Earth. While planetary atmospheres can mitigate some of these impacts through the effects of atmospheric entry, many lar…