Fossils of wingless "pre-fleas" with siphonate (sucking) mouthparts from the middle Jurassic to early Cretaceous have been found in northeastern China and Russia, belonging to the families Saurophthiridae and Pseudopulicidae, as well as "Tarwinia" from the Early Cretaceous of Australia. Most flea families formed after the end of the Cretaceous (in the Paleogene and onwards). Fleas probably arose in the southern continental area of Gondwana, and migrated rapidly northwards from there. They most likely evolved with mammal hosts, only later moving to birds.