Strata is a comic science fiction novel by Terry Pratchett. Published in '81, it's one of his 1st novels & one of only two purely science fiction novels he's written, the other being The Dark Side of the Sun. Altho it takes place in a different fictional universe & is more science fiction than fantasy, it could be said to be a kind of prequel to the Discworld novels, as it also features a flat Earth similar to the Discworld. It has been called a "preconsideration" of Discworld, tho the plot and characters are modelled on (or parodies of) the novel Ringworld by Larry Niven. The Company builds planets. Kin Arad is a high-ranking official of the Company. After twenty-one decades of living, & with the help of memory surgery, she is at the top of her profession. Discovering two of her employees have placed a fossilized plesiosaur in the wrong stratum, not to mention the fact it's holding a placard which reads 'End Nuclear Testing Now', doesn't dismay the woman who built a mountain range in the shape of her initials during her own high-spirited youth. But then come a discovery of something which did intrigue Kin Arad. A flat earth was something new...