Editing K-T Extinction
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Non-avian dinosaur fossils are found only below the [[K–T Boundary]], indicating that non-avian dinosaurs became extinct immediately before, or during the event. A very small number of dinosaur fossils have been found above the K–T boundary, but they have sometimes been explained as reworked, that is, fossils that have been eroded from their original locations then preserved in later sedimentary layers. Mosasaurs, plesiosaurs, pterosaurs and many species of plants and invertebrates also became extinct. Mammalian and bird clades passed through the boundary with few extinctions, and evolutionary radiation from those Maastrichtian clades occurred well past the boundary. Rates of extinction and radiation varied across different clades of organisms. | Non-avian dinosaur fossils are found only below the [[K–T Boundary]], indicating that non-avian dinosaurs became extinct immediately before, or during the event. A very small number of dinosaur fossils have been found above the K–T boundary, but they have sometimes been explained as reworked, that is, fossils that have been eroded from their original locations then preserved in later sedimentary layers. Mosasaurs, plesiosaurs, pterosaurs and many species of plants and invertebrates also became extinct. Mammalian and bird clades passed through the boundary with few extinctions, and evolutionary radiation from those Maastrichtian clades occurred well past the boundary. Rates of extinction and radiation varied across different clades of organisms. | ||
Scientists theorize that the K–T extinctions were caused by one or more catastrophic events, such as massive asteroid impacts (like the [[Chicxulub Crater|Chicxulub Impact]]), or increased volcanic activity. Several impact craters and massive volcanic activity, such as that in the Deccan traps, have been dated to the approximate time of the extinction event. These geological events may have reduced sunlight and hindered photosynthesis, leading to a massive disruption in Earth's ecology. Other researchers believe the extinction was more gradual, resulting from slower changes in sea level or climate. In 2010, a panel of scientists agreed that the Chicxulub Asteroid impact triggered the mass extinction. | Scientists theorize that the K–T extinctions were caused by one or more catastrophic events, such as massive asteroid impacts (like the [[Chicxulub Crater|Chicxulub Impact]]), or increased volcanic activity. Several impact craters and massive volcanic activity, such as that in the Deccan traps, have been dated to the approximate time of the extinction event. These geological events may have reduced sunlight and hindered photosynthesis, leading to a massive disruption in Earth's ecology. Other researchers believe the extinction was more gradual, resulting from slower changes in sea level or climate. In 2010, a panel of scientists agreed that the [[Chicxulub Asteroid]] impact triggered the mass extinction. | ||
This remained the undisputed cause of the extinction event until 2414, when the [[USS Rosenante]] and the [[USS Boudicca]] returned from an encounter with the Borg that had taken place in the [[Cretaceous Period]] of [[Earth|Earth's]] history. They reported that the Chicxulub Asteroid was in fact not an [[asteroid]] at all but an ancient [[Tkon]] ship known as a [[Tkon Nanosphere|Nanosphere]] which the [[Borg Collective]] had managed to assimilate during the Age of Makto, where they found it on the [[planet]] [[Dovek II]]. The two [[Federation]] [[starship]]s managed to prevent the Borg from seeding the Earth with [[Borg]] [[Nanoprobe]]s which would sit idle until [[Human]]ity arose to a point where the devices would begin to [[assimilation|assimilate]] it. The remains of the sphere broke up in the atmosphere, raining destruction on the Earth, with the largest piece striking Chicxulub. | This remained the undisputed cause of the extinction event until 2414, when the [[USS Rosenante]] and the [[USS Boudicca]] returned from an encounter with the Borg that had taken place in the [[Cretaceous Period]] of [[Earth|Earth's]] history. They reported that the Chicxulub Asteroid was in fact not an [[asteroid]] at all but an ancient [[Tkon]] ship known as a [[Tkon Nanosphere|Nanosphere]] which the [[Borg Collective]] had managed to assimilate during the Age of Makto, where they found it on the [[planet]] [[Dovek II]]. The two [[Federation]] [[starship]]s managed to prevent the Borg from seeding the Earth with [[Borg]] [[Nanoprobe]]s which would sit idle until [[Human]]ity arose to a point where the devices would begin to [[assimilation|assimilate]] it. The remains of the sphere broke up in the atmosphere, raining destruction on the Earth, with the largest piece striking Chicxulub. | ||
