In the Quest of October, Johan van Arendonk gives explanation in an article on how to revive extinct animals. Johan explains in this article that this would be very difficult as DNA material will literally fall apart in the course of time. With DNA material from old bones you therefore often have a series of separate pieces of DNA. It is very difficult to turn these loose pieces without error together, into viable complete DNA.
Johan explains in this article the opportunities for cloning extinct animals, but also the problems that come with it. For example, for cloning you need, in addition to DNA, a suitable egg cell in which this old DNA can be placed. Preferably of the own kind, but since this is not an option in extinct animals you should look for a close relative. Because the egg cell is not of the same species and there is also a gap of many years of evolution between the DNA material and the egg cell, you can encounter a number of problems. For example, there is a big chance the prehistoric DNA does not communicate with the ‘new’ egg cell; the surrogate mother can reject the embryo and it's also the question whether the clone will resemble the extinct species since this also depends on other factors as, for example nutrients.
Once you have created an extinct animal it is doubtful whether he will survive in the present time. In fact, you put this extinct animal in a time machine, his ancient DNA is not yet adapted to the diseases of today. And if you want go a step further and want to breed with your clones, you would need both a male and a female clone, with both such different DNA material that they can have healthy offspring.
In short, it will still take a long time before we can clone prehistoric animals. Johan: "I don’t think I get the chance to experiences it, but it would be fantastic."