Via @[1112395222:2048:Elizabeth Mammoth]. Wikipedia claims that the first mention of a dinosaur in a popular work was in Charles Dickens's 1853 novel Bleak House.
"Implacable November weather. As much mud in the streets as if the waters had but newly retired from the face of the earth, and it would not be wonderful to meet a Megalosaurus, forty feet long or so, waddling[b] like an elephantine lizard up Holborn Hill."
https://en.wikipedia.org/wiki/Crystal_Palace_Dinosaurs
"Implacable November weather. As much mud in the streets as if the waters had but newly retired from the face of the earth, and it would not be wonderful to meet a Megalosaurus, forty feet long or so, waddling[b] like an elephantine lizard up Holborn Hill."
https://en.wikipedia.org/wiki/Crystal_Palace_Dinosaurs