Dogs (Labrador Retrievers were used in this study) have roughly equivalent cellular ages to humans:
| Human Years | Dog Age Equivalent |
| 0 to 6 months | Juvenile |
| 6 months to 2 years | Adolescent |
| 2 to 7 years | Mature |
| 7 years and older | Senior |
I think the four stages roughly apply to all vertebrates. Divers familiar with Humann and DeLoach's field guide Reef Fish Identification quickly learn that the Juvenile and Mature phases of many tropical fish (e.g. many angelfish) are drastically different.
There’s obvious reason to suspect that the aging process in mice (which occurs over ~3 years) is just a different process than the aging process in humans (which occurs over 80+ years), which would obviously be a big problem for all the research into aging that relies on animal models. If dogs, one species with a very diverse set of phenotypes, could serve as a meta-model for how aging processes differ between short- and long-lived creatures, that would be very useful.