Anya, you are referring to is Differential escape, one of three different, well-known YEC arguments against the fossil record, the other two being Ecological Zonation and Hydrological Sorting.
I've already dealt with Ecological Zonation
What you are describing is Differential Escape. It fails to explain the fossil record as we see it.
Here's just one reason:
"Fossils are not sorted according to their ability to escape rising floodwaters. If they were, we would expect to see slow-moving species like sloths and tortoises and every low-elevation plant at the bottom of the fossil record, while fast-moving species, such as velociraptors, pterosaurs, and giant dragonflies, would be at the top. But this is nothing like what we actually observe; in many cases we find just the opposite. For example, in undisturbed strata there has not been a single sloth fossil found below even the highest velociraptor remains, and flowering plants do not appear in the fossil record until after winged insects and reptiles."
You didn't "deal" with anything. Just hand-waving. These are YEC puzzles. The Evolution model has plenty of puzzles.
We don't find whales with plesiosaurs. So what? There may be several different factors concerning the behavior and physiology of those extinct aquatic reptiles that differentiate them from mammals.
The same goes for dinosaurs being separate from mammals in general. So what? They may have occupied significantly different habitats. Some dinosaurs may be very fast moving but have significantly lower stamina than mammals, not to mention intelligence. Crocodiles/Alligators can movevery fast for a short distance, yet will tire easily.
Mammals are substantially different than reptiles in almost every regard. Try and grasp that.
Evolution doesn't explain anything about mammals or dinosaurs. Why do the big sauropods suddenly appear all over the world in the Mesozoic?
Oh they just do. Why do dinosaurs go extinct at the K/T?
Oh they just do. Why do most modern mammal body plans suddenly appear at the Paleocene/Eocene with virtually no record of any ancestral transitional forms?
Oh they just do. Why does an 'advanced' semi-aquatic mammal, essentially a mix between a platypus and a beaver (Castorocauda) appear in the middle of the Jurassic 100 million years before evolutionists thought aquatically adapted mammals "evolved" ?
Oh it just does. Why is there a 15 million year gap of tetrapod/lobe-finned fish as soon 'Stega crawled up on land? And on the other side of "Romer's Gap", essentially modern reptiles are running around?
Oh there just is. Why is the fossil record virtually devoid of any Evolution?
Uh, Punctuated Equilibrium, yea... we predicted it all along.
[Insert ad-hoc evolutionary storytelling ad infinitum]
Saying that a type of animal "evolved" or "went extinct" at a certain period as an explanation for its fossil record is no more an explanation than anything else.
If you actually study paleontology and biogeography literature there are innumerable puzzles and enigmas with Evolutionary explanations.
I will keep repeating this: if you turned even a percentage of these critical standards to Evolution, your theory would be left in shambles. You will strain at any gnat when it comes to YEC, but swallow any camel when it comes to Evolution.