Othniel Charles Marsh (right) and Edward Drinker Cope (left)
George Bird Grinnell and Marcus Benjamin, respectively
1910
Combination/derivative of <a href="//commons.wikimedia.org/wiki/File:OthnielCharlesMarsh1.jpg" title="File:OthnielCharlesMarsh1.jpg">Image:OthnielCharlesMarsh1.jpg</a> and <a href="//commons.wikimedia.org/wiki/File:Cope_Edward_Drinker_1840-1897.png" title="File:Cope Edward Drinker 1840-1897.png">Image:Cope Edward Drinker 1840-1897.png</a>