The fifth extinction, delayed

I suppose it's that time of year we ask What If No Chicxulub.

The fabled Food-Chain consists of many herbivores for fewer carnivores. The herbivores as a result won't suffer the same genetic bottlenecks as the carnivores. The main herbivores at end-Cretaceous were hadrosaurs and 'ceratopes all doing just fine thankyouverymuch. Perhaps not so much tyrannosaurs by now split between more, smaller continents. (ARRRRGH 6/30/21: Pyrate!)

In our timeline the Caenozoic got hit by a Thermal Maximum 55 Mya. In its wake smaller, smarter, more muscular mammals pushed the (mammalian) top carneys off the top of the food-chain - becoming bears, wolverines, mongeese and of course cats n' dogs.

I propose that the Palaeocene / Eocene spike would still exist at about the same time, if Chicxulub had missed us. That, I think, would have put the big raptors out of our misery. It would have spared the herbivores. Reckon the primates would have been doing okay too. Our humanoid cousins-that-never-were would look back at 55 Mya as the Fifth Extinction to end the Mesozoic and, to be fair, I expect it would be doing more damage than it did in our timeline, simply having more brushwood to burn.

But I've said as much already before.

MODEL 12/21: 120 Mya. Few dinosaurs were harmed in this event.