Abridged History of the 10th Age
While most sages believe that troglodytes are descended from the Wyrms in the same way that Lizard Men are, their relationship (if any) is unclear. They do not speak a derivative of Wyrmish, but rather their own language. They are more common in the Golden Belt of the north than the Lizard Men are, and dwell primarily in dry dark places. It is said that troglodyte caves sometimes form beneath major cities, for they can feed on the refuse and cast-aways of the city above quite happily.
However, Troglodytes are creatures of the Upper Underdark, and you shall not see them venturing deep into the bowels of the world. They stay near the surface, probably to raid and hunt and to avoid the eye of the more terrifying races of the underground.