Your "observers" aren't too observant. No one can tell if something drowned from only fossilized bones.
And God told Noah:Gen. 7:2 Take with you seven pairs of every kind of clean animal, a male and its mate, and one pair of every kind of unclean animal, a male and its mate, 3 and also seven pairs of every kind of bird, male and female, to keep their various kinds alive throughout the earth.
So, if there were then any dinos, they'd still be here !
You ignored
Genesis 3:14 And the LORD God said unto the serpent, Because thou hast done this, thou art cursed above all cattle, and above every beast of the field; upon thy belly shalt thou go, and dust shalt thou eat all the days of thy life:
After the fall the only serpents to be hatched crawed on their bellies. Before the fall they could stand on legs.