Onto the Land and Back to the Sea: The Amniotes 259(A)
(B)FIGURE 11.10. The evolutionary transition from small bipedal archosaurs like (A) Gracilisuchus, which has only
a few crocodilian features in its anatomy, and (B) Terrestrisuchus, which is more quadrupedal with a longer
snout, but still lightly built, to (C) Protosuchus, which has more typical crocodilian features, although it is still
smaller and much more lightly built than any living crocodilian. (From Carroll 1988: figs. 13-22, 13-24, and
13-25; courtesy R. L. Carroll)
(C)
the proper sister group or not, we can see that snakes once had legs and were descended
from some group of lizards that could walk.
We do not have space to talk about the transitional forms for many other fascinating
reptiles, and we will save the dinosaurs for the next chapter. But we should mention one
other surprising example: the origin of crocodilians. Today we think of crocodilians as huge,
armored, dangerous reptiles that haunt bodies of water, disguised at floating logs until