Boulder Class

Boulder Class dragons are tough and associated with the earth.

They can eat rocks, which many of them melt within their stomachs and regurgitate as lava blasts.

Although they have small wings compared to their body size, they are able to fly as fast and as high as most other dragons can.

The dragon species included are:

Catastrophic Quaken

Crimson Goregutter

Eruptodon

Grapple Grounder

Groncicle

Gronckle

Hotburple

Sentinel

Shovelhelm

Snafflefang

Thunderpede

Whispering Death

Screaming Death

Mystery Class

Little is known about the Mystery Class dragons, due to their stealthy and sneaky nature.

This Class tends to include the most diverse and interesting range of dragons out of all, most of which exhibit extremely rare and unique traits.

The dragon species included are:

Armorwing

Boneknapper

Buffalord

Cavern Crasher

Changewing

Death Song

Dramillion

Flightmare

Foreverwing

Hideous Zippleback

Hobgobbler

Prickleboggle

Sandbuster

Silkspanner

Slithersong

Slitherwing

Smothering Smokebreath

Snaptrapper

Sweet Death

Sword Stealer

Sharp Class

Sharp Class dragons are vain and prideful, and all of them possess sharp body parts.

Most of these dragons can fire extremely sharp and poisonous projectiles from their bodies, which can quickly be regenerated.

The dragon species included in this class are:

Devilish Dervish

Egg Biter

Grim Gnasher

Hackatoo

Raincutter

Razorwhip

Scuttleclaw

Shivertooth

Speed Stinger

Stormcutter

Thornridge

Timberjack

Windstriker

Stoker Class

Stoker Class dragons are hot-headed fire breathers.

A notable characteristic of these dragons is their high shot limit and firepower.

Some of them are capable of setting themselves, or a part of their body on fire.

The dragon species included are:

Fireworm

Flame Whipper

Gobsucker

Green Death

Hobblegrunt

Hobgobbler

Large Shadow Wing

Monstrous Nightmare

Night Terror

Red Death

Silver Phantom

Singetail

Small Shadow Wing

Terrible Terror

Threadtail

Typhoomerang

Strike Class

Strike Class dragons are characterized by their extreme speed, high jaw strength, and superior intelligence.

Some members of this Class possess pinpoint accuracy and unique abilities that allow them to navigate in their respective environment/atmosphere.

The dragon species included are:

Deathgripper

Light Fury

Night Fury

Skrill

Songwing

Snow Wraith

Triple Stryke

Woolly Howl

Tidal Class

Almost all Tidal Class dragons live in ocean, although some of them have amphibian biology allowing them to survive on land.

Dragons of this class are generally larger than those of other classes.

Tidal Class dragons don't react well to signs of aggression.

The dragon species included are:

Bewilderbeast

Fathomfin

Luminous Krayfin

Purple Death

Ripwrecker

Sand Wraith

Scauldron

Seashocker

Shellfire

Shockjaw

Sliquifier

Submaripper

Thunderdrum

Tide Glider

Windwalker

Tracker Class

Tracker Class are the newest class of dragons.

Natural born hunters, Tracker Class dragons have a highly acute sense of smell and taste that enables them to effortlessly track down and find anything.

The dragon species included are:

Common Rockstomper

Deadly Nadder

Mudraker

Rumblehorn

Snifflehunch

Submaripper

Thunderclaw

Windgnasher

I found this information online so it's not mine but you can look up more for the classes.