Were Dinosaurs Dying Out Before The Asteroid Hit? New Study Adds to The Debate - ScienceAlert

While the Chicxulub asteroid and the consequences of its impact - which blocked the Sun's rays and triggered global climate cooling - are generally considered the prime candidates for the massive Cretaceous extinction event, some recent evidence suggests certain dinosaur species were already in decline tens of millions of years before that.

Gaps in dinosaur fossils and sampling biases mean we might be under sampling certain Cretaceous dinosaurs, while overestimating the presence of others.

Rather than simply counting the number of dinosaur species present at the time using fossil records, the team used statistical methods to look at the rate of speciation within dinosaur families. .

As such, the team says they are skeptical of the terminal extinction theory, instead suggesting that dinosaur diversity would have remained high throughout the Late Creataceous, even as species richness varied between branches.

"We may never know the true levels of speciation and extinction of Mesozoic dinosaurs," the authors of the new paper admit, "but an increased focus on filling gaps in the fossil record will be the primary way in which palaeontologists will continue to build a more accurate picture of past dinosaur diversity."