What Animals Developed from the Armored Fish?

Do you have any idea what animals developed from the armored fish? You have seen the way in which the early fish had a spine made of cartilage, and the bone plates served to protect them. They probably needed to be armored because they could not swim particularly well. As they became more mobile, however, the need for the protective armor was reduced.

The bone cells slow began to move inwards, changing the cartilage into bone. Thus, the first fish with a true backbone evolved. It is  interesting  to note that  modern sharks still have a spinal  column which is made of cartilage because  the ossification, as the change to  the bone, is known, has not occurred in this group.

What animals developed from the armored fish?

The first bony fish appeared during early Devonian times, that is, about 380 million years ago. At the end of Devonian times, about 350 million years ago, the bony fish began to evolve very  rapidly indeed and divided into two  groups. The groups are the modern bony fish, which  account  for about 95 percent  of all  modern fish,  and the remaining five percent are  a group known as  lungfish.

What Animals Developed from the Armored Fish?

What Animals Developed from the Armored Fish?

The modern bony fish form a group in which there is just one single line of evolution. This  evolution  takes place as a  gradual loss of  the heavily  armored scales  together  with changes in the structure of  the jaw.  The change in the jaw structure  is mainly  concerned with  the way in which  the  mouth opens, but it is  rather complicated  and it is  enough to say that  modern fish  are able  to open  their  mouths far  wider  than  their early  ancestors.

This ability has obvious advantages when it comes to feeding. There are still lungfish living today. They differ from more familiar fish in two main respects.  Firstly, they have internal nostrils rather than gills, and equally important, the structure of the fins is different.

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A specimen of a living coelacanth was found off the South African coast in 1939. This and a number of other examples that have been found since show that this fish has existed for as much as seventy million years.

In the true fish, the fins are formed on rays which extend from the body they are usually referred to as ray-finned.  In the case of the lungfish, however, the fin rays enter an extension of the body tissue itself they are known as lobe-finned. This means that the fins of the lungfish eventually led to their ability to move on to land because of their development into legs.

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Just a few of the primitive fishes that were living during Devonian times.

Modern lungfish are able to survive for long periods when ponds dry out. They burrow into the mud at the bottom of ponds, only to emerge when the pond fills with water once again.

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This diagram shows how the various groups of reptiles (some of which have very complicated names that need not concern us here) are related to one another throughout the fossil record. It also shows how the birds evolved from reptiles.

During  Devonian  times, the widespread  desert climate tended to encourage  the development  of animals  which  were  able to  survive on  land as well as in water. These animals were the amphibians. They first appeared in Greenland, which was furthest away from the return of the sea during carboniferous times some 300 to 350 million years ago.

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