====== Dinosaur extinction ======

>__The question why non-avian dinosaurs went extinct 66 million years ago (Ma) remains unresolved because of the coarseness of the fossil record__. A sudden extinction caused by an asteroid is the most accepted hypothesis but it is debated whether dinosaurs were in decline or not before the impact.
>\\ [source below]

The evidence for a catastrophic asteroid impact at the end of the Cretaceous period - the //Chicxulub// (K/Pg or K-T) event -  is now considered indisputable. However, the widely accepted theory that the impact put an almost immediate end to the (non-avian *) dinosaurs has recently been questioned.

An open-access 2021 report published in //Nature Communications//, which analysed fossil records of more than 200 dinosaur species, suggests that they had begun substantially and progressively declining in numbers about 10 million years// before //the Chicxulub impact. The authors speculate that the decline may have been driven by global climate cooling and herbivorous diversity drop.

See :  [[https://www.nature.com/articles/s41467-021-23754-0|Dinosaur biodiversity declined well before the asteroid impact, influenced by ecological and environmental pressures]] //Nat Commun// **12, **3833 (2021) {{:oa_padlock_grn.png?16&nolink|Open Access}}

* //Note : //Although all the non-avian (i.e. not birdlike) dinosaurs were forced into extinction, the avian (birdlike) species did somehow survive. The reasons for their survival are unknown. See : [[content:life_sciences:zoology:avian_kt_survival]]