Fig. 1

Umbilical scar in Psittacosaurus SMF R 4970 under LSF. A Cropped image of Psittacosaurus sp. (SMF R 4970) showing just the skeleton and soft tissue outlines, with the umbilical scar highlighted by the dashed yellow line. B Close up of boxed region in (A) with the maximal anteroposterior extent of the umbilical scar indicated by arrowheads. Wrinkling forming irregular wavy creases in the integument can be seen on the far right on this image where the abdomen meets the inner thigh; C, D Close up of boxed region in (B) showing paired quadrangular scales (blue outline in D) delimiting the umbilicus. Transverse banding is visible in the remaining abdominal scales (black outlines in D). E Close up of paired quadrangular scales (ps). A clear line of interstitial tissue, delimiting the former scar, can be seen between the paired scales. Anterior is towards the top in (B–E). Scale bars equal 5 mm (B–D) and 2 mm (E)