When, in 1970, palaeontologist Lambert Beverley Halstead pointed out that Scrotum is a scientifically valid name and the first ever proposed for a dinosaur, a shudder went through the normally stolid taxonomic community. Things may not have been helped by the fact that Halstead seems to have been obsessed with dinosaur sex. His most memorable work is an illustrated compendium of dinosaurian copulatory positions--a sort of reptilian Kama Sutra--that includes a 'leg over' manoeuvre by the sauropods, the largest dinosaurs of all--that many consider highly dubious. On at least two occasions Halstead took to the stage, where, with his wife, he demonstrated some of the more arcane postures.*