Do we know long dinosaurs lived?

In a thread on dinosaurs and dragons, it’s speculated that people couldn’t have known that dinos had short (relative to dragons) lifespans. I wonder how long dinosaurs’ lifespans were, whether we have any means of distinguishing one dino species from another in terms of lifespan, and whether this is speculation or if there a method for knowing (approximately) how long they lived. Is there some lucid reason that T-rex couldn’t have lived typically for six years or six hundred, and how would we know?

It is my understanding that a lot of this is just educated guesswork, but by comparing dinosaurs to their closest living relatives (like alligators), scientists estimate they lived between 50 and 100 years on average, depending on the species.

Some dinosaur bones would grow in layers and thus would show growth rings if you cut them in half. One dinosaur was judged to have been 70 years old when it died using this method.

Dilettante answering.

Lifespan in modern animals is highly correlated to size and metabolism (higher metabolism = lower lifespan).

The first one makes intuitive sense.

The second makes sense if you think about entropy being positively correlated with activity - active cells being more susceptible to entropy - more reproduction, more burning of ATP in the mitochondria - basically more *transactions *that can contribute to wear and tear on the cells themselves and on their DNA.

If a species was cold-blooded and huge, it may have lived hundreds of years. This would be more apt to be Triassic and early Jurassic species, and some people may say they weren’t dinosaurs. Whatever. Dimetrodon can call itself anything it wants to.

If a species was warm-blooded (Jurassic/Cretaceous), lifespans would probably be similar to similarly-sized mammals. Elephants live 60 years, give or take. Big dinos could have been older.

Cool! My thread [del]spawned[/del] inspired another thread. :slight_smile: