Fiction novel involving time traveling dinosaurs that then destroy humanity

Question

I am trying to recall the title a fiction novel that involves a race of sentient dinosaurs that travel from the past into the future to when humanity is living underground, possibly due to apocalyptic events.

I recall it being mentioned that the reason the dinosaurs disappeared from the fossil record is that that is when they time traveled. Once in the same time as humanity, several of the underground cities are attacked with a metal corroding gas.

Two of the main characters are survivors of one of these attacks and the novel is mostly their life afterwards where they find dinosaurs on the surface as well as other humans who never lived underground. Additionally on the surface are cities built by the dinosaurs where they raise other dinosaurs such as triceratops and hadrosours much as humans do cattle.

Some other details: The dinosaur cities were described with walls made from a plastic. One of other humans stated his age in moons (i.e., 268 moons for about 22 years).

I had read this book at least 10 years ago. Any help is appreciated.

Answer 1

Books are by Gary Gentile:

• A Time for Dragons
• Dragons Past
• No Future for Dragons

The Goodreads summary of the first book:

One hundred years have passed since the dragons took over the world, while dwindling tribes of humans struggle to survive. But a few of the very bravest of men are willing to challenge the ruling dragons--for possession of the future itself.

Also released as a trilogy, The Time Dragons Trilogy. Here is an excerpt from a summary on Amazon:

The dragons of the titles are actually intelligent, meat-eating reptiles from Earth’s distant past. They are bent on dominating the planet for all time by exterminating mankind in the present. After dragon death bombs destroy nearly all vestige of human civilization, small bands of survivors are all that remain of a population that numbered in the billions. These isolated pockets of humanity subsist by stealth for more than a century. The dragons slowly reform the planet by planting vegetation from their home time, and by populating the land with species of herbivorous dinosaurs that constitute their food supply - herds of dinosaurian meat on the hoof. Modern-day Earth soon resembles the Cretaceous. When the dragons renew their efforts to stamp out the few surviving humans, a handful of freedom fighters meet and join forces. They plan a courageous campaign against entrenched dragon rule. This small resistance organization first snipes at dragons in the newly-formed jungles, then attacks the dragon outpost with whatever weapons they can muster. Thus begins the saga of human retaliation, as a small but dedicated guerrilla outfit seeks to eradicate the dragons, and reclaim the planet that is rightfully theirs. This fast-paced, action-packed story is quite literally never-ending. Battles rage in the past, present, and future; on land, in the air, and under the ice. From gun fights with dragons to hand-to-hand combat with a Tyranosaurus rex, the intrepid heroes and heroines never give up in their war against alien tyranny. The grand design of the Time Dragons trilogy is sweeping in its concepts and paradoxes in time. From its inspired beginning to its climactic conclusion, the reader is kept entranced by the brilliant dialogue of engaging characters as well as measured action sequences. Read the Time Dragons trilogy now, or again. Read the ultimate conclusion that has never been revealed: an ending that is not endless, but fundamentally satisfying in all its mind-bending nuances.

Answer 2

Could it be "The Dinosaur's Descendants" by Mark Ellsbery?

The Dinosaur’s Descendants is a science-fiction thriller in the tradition of Michael Crichton. Having recently discovered time travel, the government sends a team of researchers sixty-six million years into the past. They arrive to discover a monumental surprise: not only are dinosaurs technologically sophisticated, but they are planning an invasion of the twenty-first century. As dinosaur agents sow chaos in the present, Team T-REX must fight to save the future of humanity.