Dorsal Vertebra of the Hylonomus Small 320×157 Medium 640×314 Large 1024×502 Download Tiff Original 2400×1176 | (314.9 KB) Description Hylonomus was an early reptile. It lived 315 Ma (million years ago) during the Carboniferous period. Pictured here is the dorsal vertebra Keywords dinosaur, dorsal vertebra, hylonomus, repitle Galleries Reptile Anatomy Source: Encyclopaedia Britannica (11th ed., vol. 3) (New York, NY: The Encyclopaedia Britannica Company, 1910)