Tanystropheus reptiles. Illustration of a pair of long-necked six-metre-long reptiles of the genus Tanystropheus swimming in an ocean bay 230 million years ago in the Triassic in what is today China. These animals weigh around 140 kilograms. On the shore (far left) are a pair of two-metre-long bipedal basal saurischian dinosaurs. Beyond them, on the horizon, are 18-metre-tall araucarians, an ancient family of coniferous trees. Horsetails and ferns are flourishing near the water.