Bolyeria multocarinata, commonly known as the Round Island burrowing boa, was a species endemic to Round Island, a tiny landmass off the coast of Mauritius. Declared extinct in the late 20th century due to habitat destruction caused by introduced goats and rabbits, this snake held a remarkable position in evolutionary biology. It belonged to the family Bolyeriidae, which evolved an anatomical feature unique among all known land vertebrates: functional intramaxillary bones.
Unlike typical snakes whose upper jaw is a single solid bone, Bolyeria's maxilla was split into front and back segments connected by a flexible, movable joint. This structural adaptation allowed the front portion of the upper jaw to bend independently during prey capture. Evolutionary biologists believe this specialized hinged jaw evolved to help the snake grip slick, fast-moving skinks and geckos living in rocky crevices.
While modern pythons rely on flexible unfused mandibles at the chin, Bolyeria perfected a top-jaw hinge mechanism, providing an unprecedented evolutionary glimpse into skull kinetic diversification before its untimely extinction.