Penguins are a group of aquatic flightless birds.
The largest living species is the emperor penguin.
The smallest penguin species is the little blue penguin also known as the
fairy penguin.
Depending on which authority is followed, penguin biodiversity varies
between 17 and 20 living species. (Wikipedia)
Here, you can see 18 different species.
Guess the species name and hover below the picture to see if
you're right.