Some species of pipefish have prehensile tails, as in seahorses. Included in Syngnathidae are seahorses, the pipefish, and the weedy and leafy sea dragons. Molecular dating finds that pipefish and seahorses diverged during the Late Oligocene. Included in Syngnathidae are seahorses, the pipefish, and the weedy and leafy seadragons. They are related to the pipefish and seahorses. In seahorses and pipefish, it is the male that becomes pregnant. Forty-nine species of pipefish and nine species of seahorse have been recorded. In the Black Sea, their diet contains sprats, anchovies, and pipefish. These disturbances cause a decrease in seagrasses and eelgrasses that are vital in pipefish habitats. The common seadragon is in the subfamily Syngnathinae, which contains all pipefish. Sea horses, pipefish and adult sturgeon have no teeth of any type. Pair bonding varies wildly between different species of pipefish. Some pipefish species display classical polyandry because of this unique situation. Courtship between male and female pipefish involves lengthy and complicated shows of display. The snake pipefish is occasionally eaten, but it has poor nutritional value.