Imagine getting a visit from the tooth fairy every night. Some species of the long-necked, herbivorous dinosaur clan known as sauropods came close, a new study suggests. Researchers examined the well-preserved fossils of Camarasaurus and Diplodocus, two sauropods that lived in the same region of western North America about 150 million years ago. By counting tiny features in the fossilized dentin inside those creatures' teeth (left, each line presumed to represent one day's growth), the team could estimate the number of days that it took for a single tooth to form. Then, dividing that number by the number of teeth in line to replace the most mature tooth in its row, the researchers could estimate how often each tooth fell out and was replaced. On average, Camarasaurus' broad-crowned teeth were replaced every 62 days, and Diplodocus' narrow-crowned, peglike teeth were each replaced every 35 days, the researchers report today in PLOS ONE. Considering the number of teeth in each creature's mouth (Diplodocus, center and right), that means that the adults of these species lost a tooth's worth of material—either through the normal wear and tear of eating tough vegetation or by actually shedding a tooth—on average, every 1 or 2 days . The researchers contend that differences between these dinosaurs' tooth shape and replacement rate probably represent differences in their diet or feeding habits, which, in turn, may have allowed both of these large species to share the same ecosystem without directly competing against each other.