Theromorph vertebrae: Dimetrodon and Sphenacodon, Samuel Wendell Williston, 1925
Illustration of dimetrodon and sphenacodon vertebrae from the osteology of the reptiles (1925). Date: 1925. The Osteology of the Reptiles p101 Fig-79
Author: Samuel Wendell Williston (1851–1918)Source: https://commons.wikimedia.org/Loading...