FIGURE 10.8. Sketch of the skeletons of Acanthostega (top) and Ichthyostega (bottom), showing the mixture of
fishlike features (tail fins, lateral line systems, gill slits) and tetrapod features (robust limbs and shoulder and
hip bones, reduced back of skull, expansion of snout). (Drawing courtesy M. Coates)
FIGURE 10.7. The transformation of the pectoral fin of lobe fins into the hand and forelimb of primitive
tetrapods. Each bone of the lobed fin is homologous with one of the limb bones of the tetrapod, and the main
difference is modifications in shape and robustness and the loss of the fin rays, which are replaced by fingers.
(From Shubin et al. 2006; fig. 4; by permission of the Nature Publishing Group)
Glyptolepis Sauripterus Eusthenopteron Panderichthys Tiktaalik Acanthostega Tulerpeton
0.1 m0.1 m