Sorry esshup, that picture shows darker coloring since photoed in the shade and you are correct, in real life they are mottled brown/green and not black. The large 'fuselage' and the small straight tail indicates bullfrog tadpole.
I am not sure how many other frogs take longer to develop probably not all frogs but specific to bullfrog they spend longer in the tadpole stage.
As far as I know, in N. America the bullfrog is the only frog that takes more than a year to get from hatching to an adult frog. I've seen where it is said that they can get to an adult in one year, but I am assuming that they mean 365 days and not one "season" as a year.
