and they sent their DNA here in a galaxy wide seeding operation?

There’s over a million viable alternatives to DNA as carriers of genetic data, so the odds are actually extremely low that something we could classify as saurian in convergent traits

And that’s before you get into even more exotic theorizes forms of life like gas clouds in the interstellar void that appear to form helical patterns when current runs through them, silicon based life in extremophile environments, and possible micro-time lifeforms that can only exist in the interior of different kinds of neutron stars.

Also, the lifeform which got the closest to converging on the great ape body plan, which thus far is the most efficient to be observed for complex use of tools, is actually pre-mezozoic, a Permian proto-mammal labelled Suminia, it even had opposable thumbs, although it is theorized to have primarily moved on all fours, so the thumbs were probably for branch clinging instead of hammer swinging.

Spread that doctrine, Saurian bro.

Panspermia

More likely to be arachnid’s. Would you like to know more?