In graph theory, a planar graph is a graph that can be embedded in the plane, i.e., it can be drawn on the plane in such a way that its edges intersect only at their endpoints.
A graph is said to k-regular if all the vertices of the graph has dgree k.
The Green sea turtle or Chelonia mydas has a dorsoventrally flattened body. Its carapace is composed of five central scutes flanked by four pairs of lateral scutes. The resulting planner graph is 3-regular with 24 vertices and 36 edges.