I highly recommend The Sixth Extinction: An Unnatural History by Elizabeth Kolbert if you like this topic. A great read that tells you about the extinction-level event that we are currently part of and, is most likely, caused by us (i.e., humans).

Another recommended read (which I’m in the middle of right now) is The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth's Past Mass Extinctions by Peter Brannen.

Coincidentally I’ve just reached the Permian mass extinction event, where the author discusses how the ammonites clocked out in a later mass extinction. A related species, Nautiluses, have survived till today and are now at risk of extinction because humans prize their beautiful shells.

We humans are atoms in the scope of geological time, but time will tell if we prove to be atoms of Uranium in Little Boy...

I have a nit to pick with the title.

The intentional wrong tense makes it seem more immediate (and thus perhaps more urgent and interesting).

Ammonites have not gone. They went a long time ago. Where did they all go?

That's a good use of the present perfect, actually. There is nothing immediate or even remotely future-implied about "they have gone." That tense is used to show something that happened in the past and is completed, like the ammonites 66 million years ago.

If I may shift to the subjunctive voice, what would you prefer here? The pluperfect, "they had gone," might imply they'd since returned. The imperfect, "they went" seems awkward.

Side note: for urgency and immediacy, use the imperative voice!

Young girls picked them, every one.

Where Have All the Flowers Gone is a famous folk song, written by Pete Seeger.

The song asks "Where have all the X gone?" for a chain of values of X, each being consumed by some thing which then becomes the subsequent X. The first question is "Where have all the flowers gone" and the answer is "Young girls picked them, every one."

The song is a commentary about how we send generation after generation of our children off to war and death--figuratively consuming our children.

Kinda like the ammonites of yore devouring their own offspring.

>That may have proved a problem for ammonites, which routinely fed on their own offspring.

How can we possibly know that about species extinct for over 60 million years??

Edit: nice down vote without a comment, stay classy

Probably because many fossils have been found showing partially digested juvenile ammonites inside adults, I expect. That’s how they found out placoderms (which went extinct 360 million ya) gave birth to live offspring.