Heterochrony and Early Left-Right Asymmetry in the Development of the Cardiorespiratory System of Snakes
Figure 1
Early lung development in Natrix natrix according to Schmalhausen.
Overview figure showing three subsequent stages of lung development in the snake Natrix natrix, a snake reported [12] to have a vestigial left lung. d: esophagus; l = left lung bud; r = right lung bud; tr = trachea. Adapted from Figures 5–7 in Ref. [15].