Both the Gek and Tethys in my eyes look like lizards to me. Nobody, even new players, who I’ve ever played with has ever said “that frog guy” in relation to Tethys or “that frog species” in relation to the Gek. Every new player is always like “Oh yeah those lizard guys I have to raise my standing with” or “that lizard guy on the Anomaly” or “How do I get that appearance to make me look like the lizard guy(s) (in regards to both Tethys and Gek)” ect ect ect… Unfortunately, despite that, I’m still extremely doubtful of the theory they’re connected, because it isn’t that there is a lack of evidence in the game that directly says they aren’t connected in at least some way, but the issue more lies with the fact that there’s evidence to support the ancient Gek looked exactly like they do now. You really don’t even have to go that far to find such evidence. I could cite a couple things, but the Rubble of the First Spawn is the strongest argument, which is an object that, as you might expect, depicts a visual representation of ancient Gek. For those who aren’t aware, you can find Rubble of the First Spawn randomly while flying through space. It may be possible to use the Anomaly Detectors to find it as well, but I haven’t found it yet that way myself. In defense of CptBartRoberts, the Gek may have looked both like Tethys AND like modern Gek “back in the day.” The Tethys-like version of the Gek may have simply been mostly wiped clean, with a lack of visual record to show they existed alongside the modern looking Gek, but the Rubble of the First Spawn remains a strong obstacle to your theory nonetheless without more information on Tethys’ species. It unfortunately boils down to the whole “anything is possible without proper evidence to the contrary, but is it PLAUSIBLE” thing. I’m sure I’ve probably missed some things, but being that I’m not really a super fan of NMS lore (for now). I just wanted to throw my hat into the ring until I have a chance to research more.