Did Planetary Cooling Make Dinosaurs Vulnerable? 


The ongoing argument over the theories of dinosaur disappearance all too often ignore that dinosaur populations had already been in decline for tens of millions of years before the impact and, or, volcanic events which caused their brutal demise.

The obvious cause for a dinosaur and sea reptile decline would be cooling of the planet, giving an advantage to animals capable of regulating their internal temperature, in particular by staying warm enough where it mattered: birds and mammals, but also some fishes (tuna, sharks, which can keep their major swim muscles as warm as if they were mammals).

This is a very rough picture, but notice the cooling towards the end of the Cretaceous. Whatever happen next, and massive volcanism and a huge impact certainly happened, drastic cooling would have happen (‘nuclear winter”) for weeks, months, or years…

Indeed dinosaurs and their fellow in the air and the seas, although immensely advanced and efficient in many ways, which enabled them to evolve absolutely gigantic forms in the air or on land, had one Achilles’ heel: they were mesotherms, neither too cold nor too warm, depending a lot of the balmy climate which ruled the planet, all the way to the poles. That does not mean the cold killed them directly. The cold, plus the comparative advantage it gave to small hot and nasty mammals would have, as I have argued in my quasi-extinction theory I also use to explain the quasi disappearance of homo Neanderthalis.

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Our results highlight that dinosaurs showed a marked reduction in their ability to replace extinct species with new ones, making them vulnerable to extinction and unable to respond quickly to and recover from the final catastrophic event 66 Mya.

– from research article “Dinosaurs in decline tens of millions of years before their final extinction” published in the Proceedings of the National Academy of Sciences

https://www.pnas.org/content/early/2016/04/13/1521478113

It’s a bit as with the decline of Rome: dinosaurs could evolve new species, but not a whole new method of staying warm enough to avoid being eaten! Similarly Rome could not change its entire systems of thought and moods, as they all considered slavery the core of civilization! When you are too far in, being wiped out is the only outcome…

Patrice Ayme

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The paper admits that some herbivore dinosaurs species were not in decline… But I gave the reason above for the overall decline.

“Whether dinosaurs were in a long-term decline or whether they were reigning strong right up to their final disappearance at the Cretaceous–Paleogene (K-Pg) mass extinction event 66 Mya has been debated for decades with no clear resolution. The dispute has continued unresolved because of a lack of statistical rigor and appropriate evolutionary framework. Here, for the first time to our knowledge, we apply a Bayesian phylogenetic approach to model the evolutionary dynamics of speciation and extinction through time in Mesozoic dinosaurs, properly taking account of previously ignored statistical violations. We find overwhelming support for a long-term decline across all dinosaurs and within all three dinosaurian subclades (Ornithischia, Sauropodomorpha, and Theropoda), where speciation rate slowed down through time and was ultimately exceeded by extinction rate tens of millions of years before the K-Pg boundary. The only exceptions to this general pattern are the morphologically specialized herbivores, the Hadrosauriformes and Ceratopsidae, which show rapid species proliferations throughout the Late Cretaceous instead. Our results highlight that, despite some heterogeneity in speciation dynamics, dinosaurs showed a marked reduction in their ability to replace extinct species with new ones, making them vulnerable to extinction and unable to respond quickly to and recover from the final catastrophic event.”

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2 Responses to “Did Planetary Cooling Make Dinosaurs Vulnerable? ”

  1. ianmillerblog Says:

    I don’t think there is any doubt cooling would lead to trouble. The dinosaurs were too specialised, and while they could easily survive the cooler temperatures, plant growth would slow and the giant herbivores would have needed a huge food supply. As they run into food problems, so do the carnivores. The mere strategy of laying fewer eggs would have led to an obvious population decline. The evidence is the smaller theropods could develop more feathers to keep warm, but food would stress them, and of course there was a massive upset through a meteor and the Deccan traps. Some therapods did survive – now as birds, but there were biggish birdlike creatures a couple of million years later.

    Like

    • Patrice Ayme Says:

      Birds have higher temperature than even mammals… The cooling and waning of most dinosaur genus, millions of years before Geccan and bolide is striking… There used to be dinosaurs in Antarctica… when it was balmy…

      Like

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