No timeline could properly chart the Xenomorph's changes because we have never seen the original creature in its native environment! Even changes in the creature over the course of the series only reflect the creature as it has taken on new genetic materials wherever it is.
We know the Predators have been bringing them to Earth since before recorded history. Building pyramids at the South pole is a good clue of how long ago this had to have been. We know that the Engineers have had them for at least 2,000 years. But we have no idea of the relationships between the sources of the two creatures and how much evolution has occurred between their different source Xenomorphs.
I don't see the Xenomorph's rapid genetic changes as evolution. I see this as a form of rapid genetic mutation/manipulation where the creature is adapting/mutating depending on the wildlife from which they swap genes with in order to spawn in the local environment.
With such a mutable genetic structure, it would be difficult to determine purely from an appearance point of view, what creature started off as the parent species, or if we have ever seen a genetically pure one.
It would require a genetic scan from a creature that has never left its first home environment to differentiate which form was the original and which features were from the native planet. As I have stated in previous StackExchange conversations on the Xenomorph:
The most damning evidence as a sign of their engineered heritage is their uncanny ability to gestate from a variety of host organisms and the speed of their growth. They do not need to take more than a day or two to reach full adulthood. They are born knowing how to hunt, track and prepare their prey for implantation. We know for certain that they can develop in humans and the Predator species. We have also seen them gestate in dogs, creating functional if not attractive xenomorphs. Taking human and Predator DNA into account, that is three completely different species who are genetically compatible enough to produce viable offspring. In genetic terms, this would be highly unlikely, on the order of nearly impossible without an advanced technology making it possible. --Scifi.StackExchange > What purpose is acidic blood to a Xenomorph?
I believe in their native environment, wherever that is, they are all very similar or have a default genetic structure they attempt to return to if the conditions allow it. As a variety of aliens come to their world and use them in other environments, the new spawn may resemble less of their original genetic heritage but the potential for the original genes may always be there. Indeed, the creatures may possess the ability to reset their genetic structure as they adapt to a new environment and return to their previous physical shape, keeping the genes necessary for survival and only the external changes necessary for the environment.
Since we have also seen the Xenomorph take the characteristics of the creatures it hosts within (taking on the Predator characteristics for example in AVP and AVP: Requium) this implies an intelligence behind the design of the creature to build an organism able to gestate in a variety of organisms of different genetic structures, from different planets and to produce viable offspring of sufficient strength, speed, coordination, and intelligence to work cooperatively, telepathically (assuming a queen is available), or using a very fast other means of interacting that seems like telepathy and be able to quickly take over an area as effectively as these creatures do.
Dark Horse gives us a look at the creatures on a planet where there are two warring factions of the Xenomorphs, Aliens: Genocide, 1997, but one faction is red, the other classic black. We are not told if this is the homeworld or just another world long conquered by the species. All we can be sure of is they are not good at sharing a planet. Both groups tend to resemble what is considered the classic form of the creatures, as we have come to know them.
Aliens: Genocide, Dark Horse Comics, 1997