is it possible to use "would have" in place of "must have" or "may have"?

I am just a bit confused regarding the use of "WOULD HAVE".is it possible that "WOULD HAVE" can be used to suggest or show probability/possibility in the past? Something that may or may not have happened? For example this is an excerpt from a wikipedia article

"The Nimravidae are the oldest, entering the landscape around 42 mya and becoming extinct by 7.2 mya. Barbourofelidae entered around 16.9 mya and were extinct by 9 mya. These two WOULD HAVE shared some habitats."

http://en.wikipedia.org/wiki/Saber-toothed_cat

Now, I know that such a "WOULD HAVE" formation is used in "if clauses" for eg.

"If these species had lived together,they would have shared some habitats"

What i dont understand is that wikipedia excerpt does not use "if clause".So in the absense of "if clause" how should I interpret "WOULD HAVE SHARED"? Does that mean MAY/MIGHT HAVE SHARED? or MUST HAVE SHARED?
Really sorry for such an idiotic question but since i am not a native speaker of english, this question plagues me like hell.please help me understand it.thank you