I think it's time to give some in-world context to Qutrussan and where it is spoken. I have changed where it is spoken, so the previous maps are obsolete now. I will hopefully update this with a new image at some point, but it is just words for now I'm afraid...!
Qutrussan - A Brief Introduction
Qutrussan is the name of the main and official language spoken on the large island of Qutrus. In Qutrussan, the language is referred to variously as Qutrussă Gilga (language of Qutrus), Gilga s-Qutrus (language of Qutrus), Galaithíma (the High Speech), Thímasnu (Our Speech), or simply Qutrussán (Qutrussan).
Confusingly, Qutrus can refer to: the entire island, a province, and the capital city of that province. The island itself is roughly the size of Spain and France combined, between the latitudes of 20-40. The southernmost part of the island is flat with a semi-arid steppe climate approaching desert conditions in parts. Moving northwards, the climate becomes more temperate reaching a mediterranean-like climate. A moderately high mountain range runs through the centre of the island, tapering off towards the South-West.
The Island of Qutrus is divided into 7 provinces, with the Province of Qutrus being the governmental, administrative, economic and military centre:
Qutrus - Located on the eastern most tip of the island, facing the Āos Continent.
Qashrus - Located below Qutrus, its climate is slightly harsher but is considered more or less the islands 'second' province and together with Qutrus is often known as 'Greater Qutrus'.
Stias - Located on the southern tip of the island. Very arid, and partly desert.
Yarthas - Located across the mountain across in the west.
Sadram - Similar, but above Yarthas.
Hutuppu - Located in the north-west, noted for its mild mediterranean-like climate and the highest mountain ranges.
Móri - The northern-most province.
The island is technically administered entirely by Qutrus, although each province has a high level of autonomy. The capital city, or Qutrussă Naggia, is of course, located in Qutrus Province.
In terms of language, Qutrussan is believed to find its origins somewhere in the Greater Qutrus region. The Qutrussan language(s) are believed to have arrived on the island from the main continent of Āos approximately 3,000 years ago, supplanting pre-existing languages. A precise glottochronology is difficult, but it probably looks something like:
Proto-Āos: Spoken in the western part of the large (largest?) continent Āos, which lies to the East of Qutrus.
Proto-Western-Āos, Proto-Eastern-Āos: A split occurs as one group appears to move north-eastwards.
At this point, it is assumed that Āossian languages dominated the Western plains and coastal region of Āos, but nearly all have now disappeared. There are rumours of small isolated groups still speaking languages which could well be Āossian, but most of this area now speaks languages from another family.
A branch of Proto-Western-Āos migrated to the island of Qutrus, becoming Proto-Qutrussan approximately 3,000 years ago. It is assumed that proto-Qutrussan split into several languages which diverged for approximately 1,000 years throughout the island.
Around 2,000 years ago, Ancient Qutrussan emerges somewhere around Qutrus-Qashrus. Old Qutrussan is established by 1,000 years ago and begins to dominate the entire island. Classical Qutrussan, the variety here, is codified by about 500 years ago and is now the main language of the entire island, having supplanted the other previously-spoken Qutrussan languages.
There are also two other known groups of languages which are not Qutrussan, and also probably not Āossian. The majority of the speakers live in isolated communities in the highlands in Hutuppu and Móri. They consider themselves ethnically and culturally distinct.
Since the spread of Classical Qutrussan, various 'Low Qutrussan' dialects/languages have arisen in the various provinces. The Western varieties are generally more divergent. The situation is probably similar to Latin & Vulgar Latin, but Classical Qutrussan still has a strong place as a spoken and written language, especially in Qutrus & Qashrus.
My main issue is the naming of the continent Āos - this doesn't fit Qutrussan phonology, and I don't have an etymology for it but I named it this early on and it has stuck. I am also unsure how aware Qutrussan scholars will be of the history of their language. Also, since Qutrussan is more or less the only surviving branch of the family, it will make it hard for me to create a protolanguage. Perhaps some Āossian languages will have survived on the continent.
I am also unsure about how much time should elapse between each language/stage of a language. At the minute, I am using roughly 1000 year intervals per stage.