Egg tooth
Egg tooth as a structure is referred to, which is used by young animals, to break up the hatching egg shell from the inside. In lizards and snakes it involves a modified tooth on Zwischenkieferbein. Geckos often have a double egg tooth.
In birds, turtles, crocodiles and monotremes same function is performed by a highly keratinized survey on the beak or the tip of the snout. This is also referred to as Eischwiele, to distinguish them from the real Eizähnen.
Eizähne or Eischwielen are usually dropped or re-formed shortly after hatching.
Even in insects, especially in dragonflies, are structures with which to free them from the eggs referred to in analogy with the egg tooth of the birds as the egg tooth. With them, however, is serrated Sagitalkämme on the head of the larvae.