Complex sentence: Common Eldarin evolved directly from the original speech of all Elves, Primitive Quendian (called "Quenderin" in Quenya), and was the language of all the Eldar--those Elves who decided to undertake the Great March to Valinor--before their divisions.
Split into simpler sentences: Common Eldarin evolved directly from the original speech of all Elves, Primitive Quendian (called "Quenderin" in Quenya). It was the language of all the Eldar--those Elves who decided to undertake the Great March to Valinor--before their divisions.