Fig. 4

The cortical growth pattern of Serpianosaurus mirigiolensis (a, b), Neusticosaurus edwardsii (c, d) from Monte San Giorgio and Nothosaurus (e, f) from the Germanic Basin. All show lamellar-zonal bone tissue type (lzb) with a varying growth pattern. The bone matrix of the cortex of S. mirigiolensis comprises lamellar bone (lb) with simple vascular canals (svc). N. edwardsii shows parallel-fibred (pfb) and lamellar bone (lb) with the same vascularisation like S. mirigiolensis, whereas the cortex of Nothosaurus is classified as lamellar-zonal bone (lzb), which is irregularly interrupted by bands of fibrolamellar bone (flb). The vascularisation comprises primary (po) and secondary osteons (so)