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The end-Cretaceous event is the only mass extinction definitively known to be associated with an impact, and other large extraterrestrial impacts, such as the Manicouagan Reservoir impact, do not coincide with any noticeable extinction events. [249]
But the end-Cretaceous extinction is the only one reliably associated with an asteroid, according to Benton. ... The causes of these extinctions are varied — land-use change, habitat loss ...
In this mass extinction, many commonly recognized groups such as non-avian dinosaurs, plesiosaurs and mosasaurs, as well as many other lesser-known groups, died out. The cause of the extinction is most commonly linked to an asteroid about 10 to 15 kilometres (6.2 to 9.3 mi) wide [4] [5] colliding with Earth, ending the Cretaceous.
The end-Cretaceous mass extinction removed the non-avian dinosaurs and made it possible for mammals to expand into the large terrestrial vertebrate niches. The dinosaurs themselves had been beneficiaries of a previous mass extinction, the end-Triassic, which eliminated most of their chief rivals, the crurotarsans.
By the time the Cretaceous-Paleogene, or K/Pg, extinction event was over, about three-quarters of species alive at the time of impact had disappeared forever.
Proposals for an extraterrestrial cause of the end-Cretaceous mass extinction were rejected by all of attendees but Jan Smit and Walter Alvarez. These became close friends based on their shared support for extraterrestrial hypotheses, although Smit was still more sympathetic to the supernova hypothesis. [38]
But, such birds are exceptionally rare before the end-Cretaceous extinction event and this study is the first with a nearly complete skull. The skull has preserved its powerful jaw muscles, unlike ...
Luis Walter Alvarez, left, and his son Walter, right, at the K–T Boundary in Gubbio, Italy, 1981. The Alvarez hypothesis posits that the mass extinction of the non-avian dinosaurs and many other living things during the Cretaceous–Paleogene extinction event was caused by the impact of a large asteroid on the Earth.