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, and was later confirmed by an official source too.

Official 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. The free-spirited Thunderclaw is all business when it's time to face opponents on the field of battle."

- Dragons: Rise of Berk

Development
The Thunderclaw was created using a modular system to mix and match preset body parts onto different dragons. It was created from the same base that was used for the Snafflefang, Snifflehunch, Shovelhelm, and three other unknown dragons.

Physical Appearance
Thunderclaws 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. Thunderclaws are a squat dragon with large bodies and short but strong legs. They are for the most part bipedal but can rest on their forelimbs when necessary. They have a large nose horn and an elongated chin. Their hides have colourful spotted markings of varying colours. Some Thunderclaws even sport iridescence!

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.

Sense of Smell
Thunderclaws have an acute sense of smell which allows them to track and locate items easily. This ability has allowed Vikings to classify them into the Tracker Class. They prefer to use their tongues to aid them in smelling, like snakes or lizards.

Fire
These dragons shoot a greenish fire similar to Scuttleclaws. Whilst breathing fire, the nasal horn seems to glow slighty from the inside as they emit flame.

Behavior and Personality
This dragon usually lives on the ground, although it can fly when it needs to. They tend to live in packs, and have a tendency to make stampedes. The numbers allow them to have safety in numbers from larger predators. As such, they prefer open plains for it allows them to gather freely in large numbers.

How to Train Your Dragon 2
The Thunderclaw was first seen in Stoick's recount of his experience with Drago Bludvist, who had arrived at a chief meeting. He told the present chiefs that he could control the dragons, but the audience seemed unamused. Furious, he summoned armored Thunderclaws, which destroyed the hall, killing everyone but Stoick.

Later, a Thunderclaw named Sailback helped Valka lift Toothless up from the water after he was saved by the Seashockers. Numerous Thunderclaws can be seen in Valka's Sanctuary. Sailback later greeted Hiccup excitedly. ,

Comics
In Burning Midnight, a herd of Thunderclaws are seen chasing Snotlout in his recount, later to be saved by Stoick.

Dragons: Rise of Berk
The Thunderclaw's name was revealed in this game. It's titan form and the individuals Sailback and Rumpus were also made available.

Trivia

 * The Thunderclaw is the third dragon with "thunder" in its name, although all of these dragons are in different classes.
 * The "Thunder" in the name "Thunderclaw" was meant to represent the creature's tendencies to stampede in a group, causing the ground to rumble and to even potentially defeat it's enemies.
 * During the introduction to Valka's Bewilderbeast, a Thunderclaw is seen that appears to have iridescent scales, like a Stormcutter.
 * 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, probably because they are not well taken care of.
 * A Thunderclaw's fire blasted off Drago Bludvist's prosthetic arm. Ironically enough, it was one of his armored Thunderclaws who shot the blast.