A study of 19 fossilized dinosaurs have found that one species had teeth when young, but lost them in adulthood. The species involved was related to modern birds, and may help unravel the origins of the beak.
Dr Shuo Wang of the Capital Normal University in China has been examining a collection of theropod dinosaurs with the marvelous name Limusaurus inextricabilis.
Wang began studying juvenile L. inextricabilis fossils 15 years ago. When he first came upon adult specimens, he didn't recognize them as the same species. “Initially, we believed that we found two different ceratosaurian dinosaurs from the Wucaiwan Area, one toothed and the other toothless, and we even started to describe them separately,” he said in a statement.
In the course of detailed examination, however, Wang and his colleagues noticed that, teeth aside, these animals looked remarkably similar. Another 77 developmental differences have been identified between the adults and their young, Wang reports in Current Biology, but they nevertheless come from a single species that did not grow new teeth after losing their childhood ones.
Unfortunately for the L. inextricabilis, their habitat in northwestern China in the Upper Jurassic contained muddy traps in which animals of all ages became stuck. Wang has found L. inextricabilis specimens in three deposits, two from roughly the same time and the other from somewhat later. He has found fossils at six stages of development, from hatchlings and juveniles to subadults and adults. The paper describes this as “one of the best-documented growth series for an extinct theropod species.”