I like the design, color, and shading.
"broken off" should be "broken-off".
"their thagomizer" should be "their thagomizers".
Consider the following:
"One should beware the Romans for their well-organized armies and long sword." Romans would not all possess a single sword among them; they would have multiple swords. Do they outlive their poison reserves, or does it accumulate within their bodies practically indefinitely?
"notable larger" should be "notably larger".
"both are adults are" Did you mean "both are adults who are" or "both adults are"?
You mentioned "almost no natural predators". Are you suggesting that there would probably be a few predators in the near future, or that they already have predators which eat the young before they're sufficiently poisonous? If so, could you point out a few?