Lacertan

I would like to move on now to the Lacertan, the precursors of what is referred to as either the lizardkin or dragonkin, depending on who you want to offend. It is well known that some groups are quick to denounce claims of kinship with the others in the family, the evidence is quite clear on the matter. The major species in the family are the dragonborn, lizardfolk, kobolds, tortles, troglodytes, and yuan-ti.
These six species were not evolved in the way the various sub-species of elves, for example, came to be. Each were intentionally created through various experiments conducted by several lost civilizations. While we cannot show it conclusively, it is most likely that the experiments were conducted by dragons engaged in biological warfare.
The Lacertan have traits in common with each of the current species to a greater or lesser degree. The yuan-ti and tortle are the most divergent from the original stock, while the dragonborn are the closest. The dragonborn share the lacertan's tall, powerful build, although they lack the prehensile tails of the lacertan and tend more towards horns than the ridges the lacertan exhibited. The lizardfolk come closest in that regard, although their crests are often more pronounced than what would be expected on lacertans. Kobold muzzles and tails are similar to the lacertan, although the kobolds have longer and narrower snouts. Troglodytes start to diverge significantly, with scales and claws the only truly close relations, and the tortles and yuan-ti share almost no visible physical traits.

— Charlemagne Darnath, Dean of Anthropology
Koleran University, Sulae, 861 Af.