Willem Kolvoort / Limestone plateau with about 2500 footprints of dinosaurs from about 150 million years ago. The footprints in this picture might be of the Iguanodon, Megalosaurus or Thyrannosaurus. Kugitang Tau Range...

Willem Kolvoort / Dinosaur footprint, possibly Iguanodon, megalosaurus or Tyrannosaurus. From limestone plateau with about 2500 footprints of dinosaurs from about 150 million ago. Kugitang Tau Range, Turkmenistan 1990...

Willem Kolvoort / Dinosaur footprints, Kugitang Tau Range, Turkmenistan, 1990. The footprints in this photo might be of the Iguanodon, megalosaurus or Tyrannosaurus.

Willem Kolvoort / Dinosaur footprints, Kugitang Tau Range, Turkmenistan, 1990. The footprints in this photo might be of the Iguanodon, megalosaurus or Tyrannosaurus.

Willem Kolvoort / Dinosaur footprints, Kugitang Tau Range, Turkmenistan, 1990. The footprints in this photo might be of the Iguanodon, megalosaurus or Tyrannosaurus.

John Cancalosi / Dinosaur bone, cross section, fossilized

Paul D Stewart / Lithograph of the Moody Footmark Quarry in South Hadley, where Pliny Moody discovered the very first fossil tracks in 1802. From Hitchcock, Edward. Ichnology of New England. A Report on the Sandstone...

Paul D Stewart / Lithograph of a slab with multiple dinosaur trackways. From 'Ichnology of New England. A Report on the Sandstone of the Connecticut Valley, especially its Fossil Footmarks'. Boston: William White, 185...

Paul D Stewart / Lithograph of a dinosaur track from 'Ichnology of New England. A Report on the Sandstone of the Connecticut Valley, especially its Fossil Footmarks'. Boston: William White, 1858. The prints were first...

Robin Chittenden / Fossil Iguanodon dinosaurs foot cast on beach, Isle of Wight, Hampshire UK August 2015

Kevin Schafer / Dinosaur (Lambeosaurus sp) fossil, Royal Tyrrell Museum, Drumheller, Alberta, Canada

Tim Fitzharris / Whirlpool Canyon, Green River, Dinosaur National Monument, Colorado