The mixing of DNA (genes) of fallen angles and animals produced dinosaurs and other monstrous things. God told us in Geneses that “all” animals had corrupted their way on the Earth (Gen 6:12). This happened with people as well as animals. We have God’s own testimony as to this abomination.
Gen 6:4 There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.
Jasher (Historical Book-Not Bible)
Gives a little more insight as to why animals were corrupted.
18 And their judges and rulers went to the daughters of men and took their wives by force from their husbands according to their choice, and the sons of men in those days took from the cattle of the earth, the beasts of the field and the fowls of the air, and taught the mixture of animals of one species with the other, in order therewith to provoke the Lord; and God saw the whole earth and it was corrupt, for all flesh had corrupted its ways upon earth, all men and all animals.
Today, science acknowledges that the T-Rex shares strong physiological similarities to birds. Scientists have discovered well preserved blood vessels and collagen fibers in a recovered T-rex fossil. The discovery of 68-million-year-old soft tissue from the bones of a Tyrannosaurus rex was found in 2013. How could both of these things be? Well first of all, the T-Rex came into existence when the Nephilim giants or the fallen angels began mixing bird DNA with that of other animals and themselves producing monsters.
Annunaki = Fallen Angels (Just for one who doesn’t know)