Icon used to indicate a Subterranean Dragon egg in the game Dragonvale.
DragonVale is a simulation video game created by Backflip Studios for the iOS platform. It can be downloaded for free from the Apple App Store and played on the iPod Touch, iPhone, and iPad. It is also available via Google Play and the Amazon App Store for play on Android devices. It was released in September 2011 and uses the freemium business model.*
In the game, players create a theme park filled with dragon habitats, attracting virtual visitors and connecting with other players. Leveling up is achieved by breeding, raising and caring for dragons, and decorating your park by adding walkways, trees, decorations, and various buildings. The number of visitors is dependent on the type and level of dragons in the park and how well designed it is.*
There are hundreds of different types of dragons that can be bred in the game, and each species carries traits from one or more defining categories, or “Elements” as they are known. The Subterranean Dragon is one of a large group of dragons that are known as “Golden Hybrids”: Hybrid dragons are created by the breeding of any two dragons that share the appropriate Elemental characteristics. Many dragons from this group are known as “Regular Hybrids”, and while Golden Hybrids require the same specific Elemental matching as their cousins, they are produced less frequently and consequently tend to more valuable. Subterranean Dragons share the traits of both Earth and Dark Elements, and the icon representing their egg contains the brown background of Earth surrounded by the fangs of Dark, colored gold to distinguish them from Regular Hybrids.
*Information courtesy of http://dragonvale.wikia.com/wiki/DragonVale