 The Boreidae (snow scorpionflies) are the sister clade to the Siphonaptera.Fossils of wingless "pre-fleas" with siphonate (sucking) mouthparts from the middle Jurassic to early Cretaceous have been found in northeastern China.These belonged to three proposed extinct families, the Pseudopulicidae, the Saurophthiridae, and the Tarwiniidae.