Fig. 2
From: Oldest preserved umbilical scar reveals dinosaurs had ‘belly buttons’
Umbilical scars in modern reptiles, birds and Psittacosaurus. A Spiny-tailed lizard (Uromastix sp.), adult, snout-vent length (SNV) = 168 mm; B eastern brown snake (Pseudonaja textilis), hatchling, SNV = 239 mm; C thorny devil (Moloch horridus), adult, SNV = 95 mm; D freshwater crocodile (Crocodylus johnsoni), age unknown (photo: Ohmega1982/Shutterstock.com); E domestic chicken (Gallus gallus domesticus), 3-day-old chick (photo: A. Moss, used with permission); F freshwater crocodile (Crocodylus johnsoni) lacking umbilical scar, hatchling, SNV = 288 mm; G Psittacosaurus SMF R 4970. A–F Under white light and G under LSF. Abbreviations: cl, cloaca; in, incision made during dissection; ps, paired umbilical scales; um, umbilicus. Scale bars equal 5 mm (A–C) and 3 cm (D–E)