Lizard anatomy is well studied/figured, but many of the resources are hidden in literature that may be unknown or inaccessible to artists. So my friend (and legendary creature artist) RJ Palmer (https://www.artstation.com/arvalis) comissioned me to create an idealised, artist-friendly ref for lizard muscles.
The main basis for the model is a Komodo Dragon (using a real CT-scanned skeleton), with the sculpted muscles representing a generalisation of the anatomy of varanids and other lizards. You can expect more views to be posted in due course, and can find further reading and major references here: https://docs.google.com/document/d/1BsaF53qG9lQCfqcNFB5RTrxnFV4o-Ut8/edit?usp=sharing&ouid=114245456272104399428&rtpof=true&sd=true

Multiview - full resolution here: https://www.dropbox.com/scl/fi/zxbh4a9i5pz1h1wvmvnpm/Komodo-multiview.png?rlkey=f4h123jakaob18zfe9k2ug0zn&st=sxq1ryjw&raw=1