Crichton is backing and filling to try and make up for his earlier errors. Sir John Roxton is a character in the original Sir Arthur Conan Doyle The Lost World. And there’s no doubt in my mind that Crichton clearly meant to imply that the T. Rex motion-sensitive vision was derived from Frog DNA. Why make a point of using as unlikely a thing as frog DNA in reconstituting a dinosaur otherwise? And why (as we see from Darwin’s Finch’s quote) make a point of the T. Rex having frog DNA otherwise?