I don’t know exactly when dinosaurs became extinct, but there are some clues.
There is an account of a man in the 1300s who was travelling down a
road in Medieval Europe when he encountered a giant lizard
(this may be in Morris’ commentary on Genesis).
The description of the lizard sounds very much like a stegeosaurus. He
killed it with his sword. The Komodo dragons can reach 15 feet or more, and
that is large enough for me to consider them dinosaurs. There have been
crocodiles reported that were 20 feet long. I consider that
big enough of a lizard to be a dinosaur. They may just have died
out gradually. There are a lot of mammals such as the giant
sloth, mammoths, and sabre toothed tigers that there are also
cave drawings of. Those large mammals are also extinct on
earth. Probably the earth’s climate would not support as large of a saurian
population as the much more benign ante-diluvian earth would. God will
replenish them when He regenerates the earth (Mt 19:28, Acts 3:21). They
apparently are being sustained in Paradise, because Enoch says that Gabriel,
one of the archangels, is over Paradise and the serpents and the Cherubim
There has been a lot of concern lately over the disappearance of smaller
varieties of reptiles such as the Texas horned toad. It appears that
reptiles are very sensitive to pollution in the ecosphere, and are subject
to a variety of contageous diseases. Maybe dinosaurs were wiped out by a
germ. Who knows?