Complex sentence: Over time, these groups developed a new dialect of their ancestral language and came to regard themselves as a distinct population, the Tsimshian-proper, while still sharing all the rights and customs of the Gitxsan, their kin on the upper Skeena.
Split into simpler sentences: Over time, these groups developed a new dialect of their ancestral language and came to regard themselves as a distinct population, the Tsimshian-proper. They continued to share the rights and customs of those who are known as the Gitxsan, their kin on the upper Skeena.