Digit wrote:
I would rather have a clear idea of why they died out than outlandish theories.
Anything that we have not witnessed for ourselves tends to sound like 'outlandish theories' to our ears, Dig. That's "the box" which is most people's limited scope. It pays to think "outside the box".
Why did birds survive? Why some Crocodilians? Why some Turtles, and why, conversely did some not.
The 50 Kg dividing line as proposed by some seems as porous as a piece of net!
The 65 KTA event caused "nuclear winter" on earth. 80% of land flora, and 95% of sea flora, died off. For
years! Probably
decades! No more food for big vegetarians ("dino cows"). They went extinct. So also no more food for big predators. They went extinct.
Birds survived, because a) they were much smaller, so needed much less food (quantity wise), and b) they could cover vast distances in search of food. Land-dino's could not!
Crocodilians survived because crocodilians burrow (like the mammals that survived did too). Example: in the far west of the Sahara desert, 3,000 bone-dry sandy miles from Egypt, there survives a population – today! – of a few thousand Nile crocodiles. They survive in the middle of the desert around very rare water holes that dry up for 6 months each year by burrowing in the dry(est) season (it's all bone dry of course, but still there are seasonal differences). And they burrow deep! I've seen them burrowed 100/150 feet deep!
Until very recently the local human population knew about their existence, but not about how they survived the dry seasons, so they regarded those crocs-that-no-one-sees-for-6-months-each-year as spirits, gods.
Those crocs are the survivors of the time when the Sahara was green and wet. When the Sahara dried up, I'm guessing between 7,000 and 4,000 BC, they were cut off from the 'rest' of the Nile crocs. Nevertheless: they adapted to new conditions and managed to survive at least 6,000 years!
Why some Turtles, and why, conversely did some not.
I'm guessing the cause was some turtle species ate specialized flora (like Koalas eat only Eucalyptus, or Pandas only Bamboo), which was wiped out by the KTA event, while other turtle species were less picky.
