Credit: Dorling Kindersley Anyone who's raised a child or a pet will know just how fast and how steady their growth seems to be. You leave for a few days on a work trip and when you come home the child seems to have grown 10cm! That's all well and good for the modern household, but how did dinosaurs grow up? Did they, too, surprise their parents with their non-stop growth? A new study lead by Dr Kimberley Chapelle of the American Museum of Natural History in New York City and Honorary Research Fellow at the University of the Witwatersrand suggests NOT. At least for one iconic southern African dinosaur species. By looking at the fossil thigh bones under a microscope, researchers can count growth lines, like those of a tree. This allows them to study how much the individuals grew each year. By looking at growth rings in the bones of Massospondylus carinatus, Dr Chapelle was able to show that its growth varied season-to-season, more like a tree than a puppy or a baby human.