I have an ex-JW friend who is still very religious. He says that the initial verses of the bible might be more accurately translated that the Earth "became without form". Implying that god wiped out whatever he created before. ie this might not have been the first creation. That the animals from millions of years ago (dinosaurs) were from some previous creation, prior to where Genesis picks up. One that he doesn't like, wipes out, and starts over.
EXCEPT, this is before god said "let there be light" and before he created the sun, moon, & stars on day 4. So whatever was there was living in total darkness in the coldness of absolute zero (-273 degrees Celcius). And not to mention that Exodus 20:11 says god made the earth as part of the 6 days. So there was no prior earth, prior to where Genesis starts.
Even if the WBTS does not state specificallly that dinosaurs were destroyed by the flood, other religious people do believe that their extinction event was the flood.
If the dinosaurs died off in the flood, that would mean Noah did not bring them on the ark. Which means he disobeyed Genesis 6:19-20 that tells him to bring 2 of every kind of thing that walks on the ground. But Genesis 6:9 describes Noah as righteous and faithful. That is why god is saving him, right?
Which is it? Was Noah faithful and brought the dinosaurs along? Or unfaithful and let them die off? And in turn, unfaithful and not deserving to survive?
If you believe Noah was faithful, then the dinosaurs did NOT die in the flood. They may have died off before. Or they may have died off after. But not as a cause of the flood.
Wikipedia shows the top 15 longest dinosaurs as being in the 100 foot range. Really, even if your ark is 450 feet long, how many of those can you fit? Really? Fitting all the species we have today would be impossible. Add in dinoaurs? Forget it.