Fig. 8. (a) Dermal ridges and skin folds of a dolphin. Reproduced from ref. 3 with permission from IOP Publishing, copyright 2017. (b) Three-dimensional skin structure of a bottlenose dolphin. The surface of the skin is smooth and has no obvious bulges, and the traces of skin furrows and folds can be seen. Reproduced from ref. 62 with permission from the Royal Society, copyright 2019. (c) The distribution of dolphin fold skin throughout the body. Reproduced from ref. 3 with permission from IOP Publishing, copyright 2017. (d) Schematic picture of the internal imitation of a dolphin. Reproduced from ref. 56 with permission from IOP Publishing Ltd, copyright 2006.