From fish to tetrapod

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The development of ancestral tetrapods from the fish involves physical changes.

1.The loss of several bones from the skull. This isolated the head from the shoulders and produced a recognizable neck.

2.The loss of bones that support internal gills. The gills themselves may have been retained in some genera.

3.The development of a backbone of strong vertebrae as the main organ of support, rather than a notochord – a rigid rod of gristle – and the subsequently reduced notochord not reaching into the skull.

4.The development of muscular limbs with separate fingers and toes.

5.The formation of a bony connection between the backbone and the hips (the sacrum). This is a weight­bearing adaptation.

6.The loss of the fin rays – structures that would get in the way on land.

7.The first feet did not have the standard five-toed pattern.

Animatronic Dinosaur