Species

I think the Colonial Marines did just that but never encountered the Xanomorphs. 

"We Endanger Species" indeed.

Humans with the slogan "We Endanger Species" turned out as an interesting irony.

Back to OP, there were other species discussed in a joking fashion during the crew's breakfast- something about a certain species poontang if memory serves.

Yea, that's why I was interested in how many species the Corporation had encountered and why the xenomorph is so worth the trouble lol. 

The potential could get large with how the prequels could proceed.

But if we discount the prequels....

Then the Xenomorph was the first of its kind they had encountered,  the Bug Hunt likely refers to encountering a smaller less intelligent bug like species, and likely they are not that huge, if i remember the Last Supper Viral we had Rosenthal mention about Bugs the Size of Dogs.

Arcturian poontang seemed in reference to another world that could be interpreted as some kind of get away place for Marines, maybe much like a Space Las Vegas, its very ambiguous and did not have to indicate if those Arcturian's are Human, just that there is psychically not much difference between a Male and Female, i have not read any of the Books but it appears some of the Novels within the Franchise touched upon them more as the first Humanoid Alien Species that Mankind had first encountered.  Which is not the case since the Prequels we had contact with the Engineer.

It depends when we talk species if we can include all kinds of life, and i am sure there is bound to be many various species encountered within the Alien Time Line, but at the Time Line prior to Prometheus Mankind had only ever encountered Bacterial Life.

Who created the Arcturians ;) 

Well if they are going to ever cover this as Canon in the Franchise and reveal them as a actual Alien Species then who knows, the same beings who created Mankind could have created the Arcturians too, who knows if they could even play a part and be one of the 3-4 parties that Arrive on Origa-6?

Could you imagine if they are one of the 4 parties lol!? That would be some great fanboy writing. 

Who knows....

Aliens was a bit ambiguous to what they was... it could have been a Colony that became kind of a Space Bangkok or actually a Alien Species, i have not read the expanded universe Novels so i cant comment on that but some information had came about that the Arcturian's are the First Intelligent Species Mankind had discovered.... This is Prior to PROMETHEUS and the Engineers However. 

So who knows if they will be covered and what year they was actually discovered?

SO FAR all we can tell is the 3-4 Parties will consist of at LEAST One Company Ship/Mission and at LEAST One Engineer Ship.

The other 1-2 is uncertain.. it depends on if RS means incoming as in we can discount David, the Colonist and anything that arrives from his objectives (Xenomorphs) and also by virtue of him saying 3-4 maybe this means that 1-2 are closely related that its not a definite TWO separate Factions/Races.

This could mean anything though... and thats even if we read too much into the 3/4 being similar.. so it could be TWO Human Factions, TWO Engineers who knows. or even ONE Human ship has SYNTHETICS or ONE Engineer Ship has a different Race.

ALL WE KNOW for sure is ONE will be HUMAN the other ENGINEER the other 1/2 Parties is anyone's Guess.