Over many decades ago, reproduction is believed to be between related animals and any mating between unrelated animals can't produce children (offspring/progeny). Although it was accepted back then that mating do and can take place between animals that are not of the same components/species, but their bringing forth offspring wasn't accepted. Over time, this has been proved wrong. Many different species of animal have crossbred and young ones have been born which will be revealed in this article. https://img.esteem.ws/ch3xppnkga.jpg ^{CC0 Creative Commons.

Following much evidence that separate species of animals can mate and have offspring, it was later accepted and resolved thus, that those offspring would be sterile. Meaning that they won't have the ability to reproduce and have their own children.

Well, this is true for some animals but for some, reproduction is possible in their females because they are fertile but not the males.

Sometimes, this also depends on which animal is the mother and which is the father and vice versa. When a female horse mate with a male donkey their offspring(mule) is infertile but when a male horse and a female donkey mate their female offspring(hinny/jennet) is fertile.

The reason for infertility is differences in the structure of the chromosomes inherited from their parent, thereby inhibiting their production of fertile eggs or sperm.

Below are examples of crosses between different species of animals .

Tigon

Tigon is the offspring of the cross between a male tiger and a female lion. This is just an opposite of Liger but they aren't as common as ligers. They are never bigger than their parents. A second generation hybrid can occur when a lioness mates with a Tigon to produce a litigon and a female tigon with a male tiger produces a Titigon.

Liger

The liger is the largest cat in the world which is a cross between tigeress and lion. They grow larger than either parent (tigers or lions). Male ligers are infertile while the females are fertile. They can further mate with either of their parents to produce offsprings (li-ligers/ ti-ligers). They are sociable like the lion and a good swimmer like the tigers.

Mule

A mule is the product of mating between a male donkey and a female horse. A mule is obtained more often than a hinny when they mate. Hinny is the child of a male horse and a female donkey. Mules are generally infertile except in few females. A female mule that can reproduce is sometimes called a Molly Mule. It does not sound like a donkey or a horse totally but a mixture of both distinctively.

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Charles Darwin wrote: >quote"The mule always appears to me a most surprising animal. That a hybrid should possess more reason, memory, obstinacy, social affection, powers of muscular endurance, and length of life, than either of its parents, seems to indicate that art has here outdone nature.">quote

Zebroid

A zebroid is the product of a cross between a zebra and any equine, in which the zebra is most times the father (sire). When a male donkey and a female zebra mate the give birth to a zebra hinny are usually infertile. A zorse or zebrula is the offspring of a male zebra and a female horse. It is sterile. A zebra-donkey or a zonkey is the product of a cross between a zebra and a donkey
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Wholphin

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A wholphin or wolphin is an extremely rare cross which is believed to have existed in the wild occur as a result of the mating of a female dolphin and a male whale.

Grolar bear

A Grolar bear is the offspring of grizzly and the polar bear hybrid.

Cama

A cama is born when a male dromedary camel mates with a female llama.

Dzo

A Dzo or dzomo are offspring of a yak and a cattle. Dzo (male) are sterile while Dzomo (female) are fertile. They are bigger and stronger than their parents.

Beefalo

Beefalo is the offspring of domestic cattle And bison (buffalo). They are fertile and thus, can reproduce.

For further reading, visit
https://en.m.wikipedia.org/wiki/List_of_genetic_hybrids

Reference
https://en.m.wikipedia.org/wiki/Mule

https://twistedsifter.com/2012/01/10-bizarre-hybrid-animals/

https://www.quora.com/Can-two-different-animals-or-species-mate-to-give-birth-to-a-different-species-which-never-existed

http://m.discoverwildlife.com/animals/why-do-animals-interbreed

https://www.theguardian.com/notesandqueries/query/0,5753,-22904,00.html

https://en.m.wikipedia.org/wiki/Crossbreed

https://en.m.wikipedia.org/wiki/List_of_genetic_hybrids}}}