These are irregular isolated bones that can appear in addition to the usual centres of ossification of the skull and, although unusual, are not rare.

A large Wormian bone at lambda is often called an Inca bone (os incae),[3] due to the relatively high frequency of occurrence in Peruvian mummies.

[4] They tend to vary in size and can be found on either side of the skull.

His description of the extra-sutural bones contributed to the science of embryology.

Wormian bones have been documented to occur in nonhuman mammals representing diverse groups, including Marsupialia, Xenarthra, Eulipotyphla, Artiodactyla (including Cetacea), Carnivora, Pholidota, Rodentia, Lagomorpha, and Primates.