Fig. 1

The complete mitochondrial genome maps of Palea steindachneri (a) and Pelodiscus axenaria (b). The inner circle indicates the G-C content, whereas the outer circle illustrates the mitochondrial DNA structures of the two soft-shelled turtles. The exterior and interior sections of the outer circle correspond to the L- and H-strands, respectively. The grey arrows indicate the directions of gene transcription. The subsets in the top right were AT/GC skew values of different mitochondrial elements. − indicates the L-strand, + indicates the H-strand.