A toothless mammal begging with an A is an Anteater/ Aardvark
edentata
The Echidna is toothless
panther
Dolphin
Toothless
nobody knows
toothless
Plankton
His dragon is called Toothless and there are several others mentioned in the books/film, but Toothless is Hiccup's only dragon in both.
Toothless
Because when he first sees him, he doesn't think he has teeth
a toothless watchdog is called Mohammod