Even though people employ the concept of navel-gazing as a pejorative insult, I still find my belly buttons remarkably intriguing. Ever since my mother elucidated the reason behind my belly button as a youth, the deep poignancy around the mark has stuck with me forever. Call me sentimental all you want, but having a visual representation of the winding chain of feminine procreation that my mother engaged in to bring me to reality is pretty dope. It's like having a postage stamp and a return address from the primordial soup on the old breadbox.
Formerly, I assumed that only mammals, given our specific gestation process, had belly buttons, but reptiles have 'em too. And it turns out the grandmother of all reptiles, the dinosaur, bore belly buttons too. Thanks to fossils found in China, Paleontologists found evidence of a naval scar, which typically tends to vanish on animals that come from eggs, on a Psittacosaurus.
Modern egg-hatchers like snakes and birds lose their belly button scar within a few days or weeks after hatching. But other organisms keep the "umbilical scar" for the rest of their lives. While inside the egg, the embryo's abdomen is connected to the yolk sac, which provides the embryo with a food source for growing and developing. The scar appears when the embryo detaches from the yolk sac and other membranes, before or as it hatches from its egg. The scar, known as an umbilical scar, is a non-mammalian belly button, reports Gizmodo's Jeanne Timmons. The Psittacosaurus umbilical scar is similar to that of an adult alligator and is the first example of one in a non-avian dinosaur that predates the Cenozoic period, 66 million years ago, Science Alert reports.