One stream of thinking is that dinosaurs were already in decline prior to the asteroid impact at the end of the Cretaceous. An equally forceful point of view claims they were as plentiful as ever they were – right up to the iridium layer. The problem of course is the geological uniformitarian lens when looking at the sediments laid down by the asteroid strike. This was a major catastrophe and it must have laid down lots of sediments very quickly. However, to introduce such an idea would also mean accepting that at other periods in earth history, major catastrophes were responisble for lots of the sedimentary layers in the geological record. In fact, the geological record may only record major and minor catastrophes and the long periods of normality may be missing. In other words, we have a fragmented geological record rather than a continuous one. However, this is not to say that even in the present, local geology can record minor events such as flash floods or volcanic eruptions, and the like. No need to throw the baby out with the dish water.
At https://www.sciencedaily.com/releases/2025/04/250408121332.htm … an article which takes us to the root of the problem, the rocks. We are told the apparent decline is due to a poor fossil record. In other words, the Cretaceous rocks can be interpreted in two different ways. This of course relies on the Cretaceous spanning a very long period of time, rather than representing a series of catastrophic upheavals. We may suppose the decline in fossils has more to do with the sedimentary layering than with what organisms were thriving or not. Once you put on a catastrophic set of glasses – or lens, in a geological context. There is no reason to think in terms of decline, or not a decline. The fossil record becomes self apparent.
At the same time this is an interesting read. See the full Current Biology post at https://doi.org/10.1016/j.cub.2025.03.025 …