Thunderclaw

The Thunderclaw is a Tracker Class dragon introduced in How to Train Your Dragon 2. It's name was first revealed in the game Dragons: Rise of Berk.

Description
Members of this Tracker Class breed form running, rumbling herds very easily. Talk about safety in numbers... unless you are in their way during a stampede.

Thunderclaws have an acute sense of taste, and they use their tongues to guide them to whatever they are tracking.

Appearance
Thunderslaws have a ledge on their chin and a large sail on their back. Their bodies have large spots or stripes as patterns and they have a thick, fat tail.

Titan Wing
Source: Dragons: Rise of Berk

Titan winged Thunderclaws are yellowish green and have dark green spots on their bodies.The ledges on their snout becomes dark green, along with the spines along its back. The sail on their backs has grown into a sharp spike. Titan Thunderclaws develop spikes under their chin and two prominent canines on their lower jaws.

Trivia

 * Like Scuttleclaws, some Thunderclaws shoot green fire.
 * Before it's name was officially revealed, fans called it the Sailback.
 * The Thunderclaw is the third dragon with "thunder" in its name, although all of these dragons are in different classes.
 * Thunderclaws are shown to have multiple differences in color, the common one is mostly purple, but a mostly green variation exists.
 * While breathing fire, the nasal horns of the Thunderclaws appear to be glowing internally.
 * The Thunderclaw appears to have iridiscent scales like the Stormcutter.
 * The Thunderclaw shares the same body with the Snafflefang and an unknown dragon. This is because it was created using a modular system to mix and match preset body parts onto different dragons.
 * Despite this, the Rise of Berk Thunderclaw is actually thinner than the Snafflefang, probably to differentiate the two in the game.
 * The Thunderclaws in Valka's Sanctuary are lighter and more vivid in color, while the ones in Drago's army are darker and duller in color.