OK, here is what I don't get. You obviously believe that one aspect of the biblical creation story is suspect(6 days). But you can't see that the act of God creating all forms of animals and Man could have come about in different ways?
OK, I'll try to make this short, but....
You believe in an old universe, so I will assume you believe the general figure of around 15 billion years(+/- a couple billion). If you believe that figure , then you are also lending credence to the Big Bang theory. A single event from which the universe was created. Not only all matter, but time itself was created in the Big Bang(so the theory goes). By definition, there was no such thing as a place nor a time before the big bang. So following that, and your belief(mine too BTW) God exists in a way that we can not even begin to understand.
One last little mental experiment before I get to my conclusion.
Lets say you and God decide to go play a game of pool. You not wanting to offend God say, "You don't have to take it easy on my, play your best". Do you think God could sink every pool ball off the break? My guess would be yes. Now imagine that ability(beyond our understanding) several dozens of orders of magnitude more complex . One quick look on Google netted me a guestimate of 10^81 number of atoms in the universe.
What I am ultimatly trying to get at is that if believe in an old universe and God, then you must beleive he exists beyond our ability to comprehend. I bet you also believed he could sink all of the pool balls in one shot and has even greater abilities than that =) So Why is it soo far out the realm of possibility that God set the whole thing in motion at one point in time. And has interacted with the universe throughout it's existence (he created time you know).
I prefer that way of viewing creation than God floating around and snapping his fingers and saying "All T-Rex's come into existance right, now" Waiting a little while, "All T-Rex's die right now". Wash, Rinse, Repeat
We have barely scratched the surface of the fossil record. As someone correted me. Up until 1990 there were only 9 incomplete T-Rex skeletons ever found. Absence of proof is not proof of absence.