A Mysterious Thumb 0 Randall Gross ScienceDecember 2011Tuesday, December 27, 2011 at 12:29 pm PST • Views: 867 blogs.smithsonianmag.com Allosaurid Appendage Basal Iguanodontia Bony Spike Complete Iguanodon Dinosauria Dinosaurs Iguana-like Reptile Iguanodon Thumb Spike Lizards Peculiar False Thumb