Fig. 4From: Heads or tails first? Evolution of fetal orientation in ichthyosaurs, with a scrutiny of the prevailing hypothesis Detail of the trunk of gravid Stenopterygius quadriscissus (MHH 1981/33) and interpretative drawing showing stage 4 fetuses with both head-first and tail-first in utero orientations. This suggests that both birth orientations were present in a single gravid female (An and Po denote maternal anterior and posterior)Back to article page