I think the prehistoric animals became extinct during the form and void...they was actualy frozen during that period, wouldnt that be apart of the ending of the first heaven and earth..that is how they where able to be preserved..I know in history of archeological finds, a elephant was found with a living plant still preserved in his intestines, the plant was bittersweet,If I remember correctly.Just some things I have stumbled upon that makes more sence.