The Okapi and the giraffe had a common ancestor, it had lived for about 16 million years ago. The ancestor is also known as canthumeryx, and this ancestor had a enlarged neck. After the canthumeryx, there family tree has split into two ways. The side of the giraffe ancestor had their neck lenghted overtime.

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While the Okapi side has developed shorter necks, and now we can see that the okapi has shared a long-necked common ancestor with the giraffe , but after it had to develop in two different ways.