What is the most plausible ancestor for tool-using, sentient, bipedal reptilians?

A classical trope of fantasy is lizardfolk, or a similar species by another name (see for instance the Argonians of Elder Scrolls fame). In general, though, we're dealing with:

• Bipedal, often plantigrade but sometimes digitigrade
• Tool/weapon-using (albeit not particularly sophisticated), with opposable thumbs
• Human-sized (roughly) with often somewhat crocodilian or monitor-lizard-esque features
• Sentient, with a spoken language to their credit
• Oviparous i.e. egg-laying (although this topic is not often addressed) reptiles.

What would be the most logical/plausible evolutionary ancestor for such a species, given the wildlife available on Earth, past and present, to choose from? What sort of evolutionary path would lead to such a species? What sorts of environs would favor such an evolutionary path?

posted over 7 years ago

Shalvenay‭

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