The frontoparietal is a unique feature of anurans, not only if this group is compared with other amphibians, but also with other vertebrates as well. It is often used as an important character in anuran systematics. However, little is still known about its evolutionary origin and significance. This is the reason why its state in Triadobatrachus and fossil anurans was examined, and compared with the condition in osteolepiforms and labyrinthodonts. Besides that also an information from the larval development was taken into consideration. It follows from all these data that the frontoparietal in adult anurans is a compound bone; the originally independent elements forming it (frontals, parietals, and some other ones) either coalesced with each other, or have disappeared during the course of evolution, often in convergent fashion. As the original state is better reflected in early developmental stages, one may suppose that larval condition also better reflects phylogenetic relations than the definitive bone complex of adults.