Techinically… it’s not quite extinct…
Me, I’m sort of torn between the Carolina Parakeet, or the ivory-billed woodpecker a.k.a. “The Lord God Bird”, the Neanderthals, one of the trilobite species…
There is just so much to choose from.
But today I’ll say Carolina Parakeet.
In one of Arthur C Clarke’s books, I forget which one, people in the future have brought back the passenger pigeon, and then find themselves annoyed by the noise of the flocks. Bit I’d revive them anyway.
This.
How would we interact with this new ethnic group? Well, we would learn a lot about them that we don’t know.
There’s a suggestion their language skills didn’t match ours… but they lived at a time when no humans had writing, so how can we possibly know that?
I dont think we have the huge hardwood forest habitat for them anymore.
Yes, sea scorpions! Then I’ll finally be able to figure out if they are edible.
Oil is thought to mainly be zooplankton and algae. You might be thinking of coal. And the plants didn’t form coal beds due to any great CO2 sequestering capability, but because a) the climate and geography was such that great forested swamps covered huge areas, with plants and trees dropping into the swamp and not decaying due to anoxic conditions and b) bacteria not immediately catching up to evolve the ability to digest the newly evolved substancef “wood”.
I say bring back baluchitheriums. Because elephants have been pretty arrogant and need to be taken down a notch.
Yeah this. Or, a milder version, we need to be reminded we aren’t so big.
Passenger pigeon. Given the op’s rules, that’d be a truly insanely large number of birds. There is, sadly, not enough habitat for all of them. So, capitalism will provide the answer: I will open KFPP, a chain of restaurants which will apply 11 secrets herbs and spices to passenger pigeons, until numbers are down to a stable population.
Megalodon is a bad idea. It would lend credibility to the Discovery Channel, and from there it’s a small step to all the other cable nonsense.
Bring back some good old fashioned terror birds.
This is my boring answer.
My wildly irresponsible answer would be Megalania. Because modern Australia isn’t deadly enough.
If I was going for a trilobite I suppose I would pick Terataspis grandis. An ammonite, maybe Diplomoceras maximum or Parapuzosia seppenradensis.
Another vote from me, for the old “Tiger” – a creature I’ve always thought delightful. Very sadly, I have the impression that general opinion is: that the possibility of its still being with us, is truly infinitesimally small. Tasmania just isn’t that big – if thylacines had survived to the present day, they’d have been rediscovered by now.
One of the island mini-elephant species, probably Palaeoloxodon falconeri. Have people in place in Sicily and Malta to round them up when they first appear, and make a killing in the exotic pet market. 1m high elephants - they’ll sell like hotcakes.
Ooh, there was a one-meter elephant? Okay, that’s my choice.
I’m most intrigued by one of the extinct versions of human, but the downside is so high, as they would be likely to be enslaved or slaughtered again.
It could be that the most delicious fowl became extinct just because it was so delicious. I’d vote that one back now that we have the know-how to farm them.
I think we should use this once-in-history opportunity to solve some real mystery. Like, what the heck was Cothurnocystis? Echinoderm, chordate or something equally close to both?
Seriously, that’s one weird looking creature! Cothurnocystis - Wikipedia
You think that’s weird, when we have all the Burgess fauna to mine for weirdness in all its 5-stalk-eyed glory?
If the OP didn’t have that “must survive in current environment” caveat, that’s where I’d be looking.
As I understood him, there’s no such caveat; species will simply die off if environment doesn’t suit them. As long as we could get some specimens before the seagulls, I don’t mind them being dead. Might actually prefer it that way; won’t upset the ecosystem! 
