Crocodile

Crocodiles are large reptiles mentioned in the How to Train Your Dragon Book series.

Description
Crocodiles are large reptiles belonging to the Family Crocodylidae. All crocodile species occur in tropical locations around the globe and are very sensitive to cold temperatures. Crocodiles are long and low to the ground, with four legs positioned at their sides and webbed feet. Their tail is thick and strong, used mostly to propel the crocodile through water. Crocodiles are not choosy about their food - they eat a range of other creatures from various mammals, birds, other reptiles, fish, and even invertebrates.

Function
In the Book series, crocodiles are used as a metaphor to describe dragons physically and behaviorally.

In real life, crocodiles are eaten by humans, hunted as trophies, and killed for their hides.

How to Train Your Dragon
Toothless is compared to a crocodile for his ruthlessness as a dragon.

"However, you only had to look into his big, innocent, heavily lashed eyes to realize that he was totally without morals. The eyes were ancient, the eyes of a killer. You might as well ask a crocodile or a shark to be your friend."

- Book 1