This blog isn’t written from the standpoint of whether or not we should bring back extinct species (we should not). 
Nor will it weigh in on the conservation effects this de-extinction would have on currently existing species on Earth (complete disaster). It will, however, speak (pun intended) to what conversations we might have with species who have gone extinct. Now that I think about it, it would be no different really, than a medium session. Wherein the consciousness of beings not in physical form anymore is revealed to those who are still in physical form. Like you, dear reader, and me.
There are so many to choose from! Exciting – or depressing, depending on your perspective. And according to the 2012 Marine Census that came up with a new approach to census projections most species become extinct before humans “discover” them. I put this last part in quotes because it’s the height of human arrogance to perceive that something doesn’t exist until we say it does.
So which one would be your favorite species to speak with? And what question(s) would you want to ask them? You might think that T-Rex and/or Brontosaurus wouldn’t be capable of higher thought or math for that matter. At least according to science and brain size measurements. That’s where they’ve got it all wrong, IMHO. Brain is merely one component of consciousness among the brain/body fusion. Neither is separate from the other and they operate together. I have a hunch if T-Rex was your choice that they’d be remarkably similar to snakes and lizards of today. Definitely Earth-element connected and deeply grounded.
The same would apply to Mastodons yet they’d also have the overlay of today’s Elephants. Deep emotional connection to herd and highly functioning sentient being qualities no different than humans at all. Their grieving over bones left behind by ancestors is well known among animal behaviorists and yet we still can’t make that leap to Sentient, capital “S”.
Perhaps you’d like to fly with a Pterodactyl, the likely distant ancestor of today’s Bat. Birds of today weren’t descended from this flying reptile and the winged fingertips more closely resemble those of Bat. The ever-present and renewing element of Air would give the same loft and glide that transcends Earth’s gravity then as now.
Whatever your particular choice, the questions might be the same. What happened to your species? Were there other species involved in your extinction like there are today? What would you like to say to your relatives that are descended from your DNA? Do you want to come back to live on Earth again?
I’m already hearing answers in my head which may differ from yours. “It was simply our time to leave” and “we moved aside to make way for others.” Most definitely the feeling I get from a majority of them is oh hell, no – I do NOT want to come back to Earth. They say they wouldn’t know what to do, how to interact with other species. And they know well that even in their time of what we might say was “pre-historic” that it was all about the delicate balance of Nature. Something that’s been disrupted mightily on Earth and by our species.
As we weren’t around then in the time of T-rex, pterodactyl and the like, it’s hard to say whether or not their species would have been as impacted by our actions as today’s animal species are. And we might even ask if today’s species who are going extinct might want to come back to Earth at some point as well. My hunch is that like their long ago relatives of a different kind they’ll pass. Not because they didn’t enjoy their life on Earth. It’s more that they know when to say when and when enough is enough. Something humans still haven’t gotten right.