Thunderclaw

"Thunderclaws ARE pretty cute. Feisty, but cute."

- Hiccup

The Thunderclaw is a medium-sized Tracker Class dragon that first appeared in How to Train Your Dragon 2.

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, Windgnasher and a few other Unknown Dragons.

Egg
Thunderclaw eggs are pear-shaped and are usually tan. They have a dark brown tip with wavy patterns that course down to the bottom of the egg. Occasionally, they come with leopard spots.

Hatchling to Adult
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 colorful spotted markings of varying colors. Some Thunderclaws even sport iridescent scales, as seen during the introduction to Valka's Bewilderbeast in How to Train Your Dragon 2.

Titan Wing
Titan winged Thunderclaws are yellowish green and have dark green spots on their bodies. The ledges on their snout become 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. According to To Berk and Beyond, Thunderclaws flick their tongues out in the air like snakes to 'taste' the air and as a result, frequently have their tongues lolling out.

Firepower
Thunderclaws can shoot either streams of green fire that is similar to the Scuttleclaws’, or streams of normal orange fire. Whilst breathing fire, their nasal horn seems to glow slightly from the inside as they emit flame.

Strength
Thunderclaws are strong dragons, which is shown when Sailback managed to carry Toothless all the way to Valka's Mountain, when several armored Thunderclaws were able to pull some of Drago's war machines, and when Bonesnarl carried Snotlout with the extra weight of a metal armor while running with minimal signs of struggle. They are also able to break through a metal roof with little to no effort.

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 stampede. Staying in groups allow the dragons to have safety in numbers from larger predators. As such, they prefer open plains for it allows them to gather freely in large numbers.

Weaknesses
It was revealed in The Serpent's Heir that Thunderclaws don't fly when they are panicking. This could make them easy to capture, which might explain why Drago had so many in his army.

Eret in To Berk and Beyond indicates that feeding a Thunderclaw a piece of yak butter gums up their teeth and tongue, distracting them and affecting their tracking ability.

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 appeared to disbelieve him. 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 and Drago's Army. Sailback later greeted Hiccup excitedly.

All the Thunderclaws from both Valka's mountain and Drago's army fought viciously against each other in the battle at Valka's mountain. After Drago's Bewilderbeast defeated Valka's, all the Thunderclaws bowed to their new Alpha. After they were freed by Toothless from the Bewilderbeast's control, they fought against the giant dragon. In the aftermath, they bowed to Toothless, acknowledging him as their new Alpha.

The Serpent's Heir
In The Serpent's Heir, Bonesnarl, one of Drago's armored Thunderclaws, has a main role in the beginning. He refuses to get his head armor casing removed. Later he gets the Scuttleclaw Hatchlings in line, after they run amok for Gobber.

Dragonvine
In Dragonvine, as well as 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. Its Titan Wing form, a battle form and the individuals Sailback and Rumpus were also made available.

Trivia

 * While the Thunderclaw first appeared in How to Train Your Dragon 2, its name was not revealed until its release in the game, Dragons: Rise of Berk.
 * 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.
 * It is the second dragon to have this name origin, with the first being the Thunderpede, although the latter doesn't form groups.
 * 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.