I read this issue a quarter of a century ago, and reading it again today...was like reading a brand-new comic, it wasn't super-memorable. From 1991, Armageddon: the Alien Agenda #1, "Days of Thunder Lizards" Written by Jonathan Peterson, pencils by Dan Jurgens, inks by Steve Leialoha.
After the conclusion of Armageddon 2001, Hawk, Dove, and Captain Atom are all presumed dead. Out of those three, Dove is the only dead one; murdered by her partner Hawk, who become the time-travelling despot Monarch. Monarch and Cap end up thrown back in time to the Paleozoic Era...or some time with dinosaurs: Captain Atom's not a scientist, he doesn't know for sure. Still, his powers aren't at full, Monarch's still trying to kill him, and oh yeah, there's aliens. Maybe more than one group...
Good things about this issue: it does dial back a lot of Captain Atom's recent angst from the end of his series and his almost heel-turn to Monarch. For his part, Hawk-Monarch is a whiny, useless bully; which I think he would remain in any of his later appearances. Losing his mask doesn't help; he has a somewhat thick head and shaggy haircut. Oh, and Jurgens draws dinosaurs pretty well! (He did in his Warlord days too.) Almost makes up for this issue's title.
We glanced at another Armageddon mini about a million years ago, Armageddon: Inferno, which I think brought back the Justice Society. I think the Captain got at least another mini-series out of being lost in time; before probably getting shoved over to Extreme Justice or something.