Dinosaurs Were Destined To Become Extinct?

[Life]

New Study Shows That Dinosaurs Were Destined To Become Extinct

historyofyesterday.com/new-study-shows-that-dinosaurs-were-destined-to-become-extinct/

Dinosaurs Were Already on Their Way Out Before Asteroid Hit, Another Study Finds

www.sciencealert.com/dinosaurs-were-already-on-their-way-out-before-asteroid-hit-another-study-finds

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Discuss.

I will share my views as well.

[Infinity Blade]

I'm just going to outline my brief thoughts.

This is what Thomas R. Holtz said on his Twitter about the paper (link->).

Keep in mind the sampling in this paper, though. We have known since 2020 that only a few groups of dinosaurs seem to have easily preserved eggshell. Those are the same sorts represented at the end of the K in China, for which the data is only... eggshell.

So the supposed "decline" is really what happens when you go from more extensive data (skeletal plus eggshell) to a biased subsample (eggshell only).

Although to be fair, it isn't even really the S-L effect, either. That has to do with issues of random sampling and the statistics of small numbers. This paper is comparing apples (from the lower section) with oranges (from the upper).

This recent paper compares a time period from which we have more extensive data (skeletal and eggshell remains) to a later time period with a more limited sample of data (eggshell remains only). And then you remember that only a few groups of dinosaur actually had hard-shelled eggs that can reasonably be expected to fossilize (and these are the same sorts of groups represented by the end Cretaceous eggshells in China). What you end up with is a highly skewed view of dinosaur diversity through time.

Also, populations will always fluctuate over time. Even if dinosaur diversity went a bit down towards the end of the Cretaceous, that doesn't mean they were declining, as that could simply be reflective of population fluctuations.

Like so: