41a. The Carnegie Apatosaurus Mount, 1936
The photograph at the right shows Apatosaurus lousiae as it was mounted in the Carnegie Museum in Pittsburgh (Apatosaurus is on the right, the famous Carnegie Diplodocus is at the left). If you look closely, or better yet, if you look at the enlarged detail below, you will see that Apatosaurus has two heads, one mounted on the neck, and one in a case below. The one on the skeleton is in fact a cast of the one in the case, and it is a cast because Charles Gilmore was not at all sure that it belonged on the skeleton. The man who supervised the reconstruction, William J. Holland, was not sure either. In fact, Holland leaned toward a Diplodocus-like skull that had been found in the Carnegie quarry, rather than the Camarasaurus-like skull that the American Museum in New York, and the Peabody Museum in New Haven, had installed on their skeletons. Holland had written a paper in 1915 in which he gave good reasons why the Diplodocus-like skull should be preferred. But he never mounted that skull on the skeleton; he either lacked the courage of his convictions, or he was not allowed to install the skull of his choice. So the Carnegie Apatosaurus stood for twenty years without a skull, until finally a cast of the conventional Camarasaurus-like skull was put in place.
As it turns out, of course, Holland was right, and the wrong skull had been installed. The situation was not corrected until the 1980s.
Gilmore, Charles W. "Osteology of Apatosaurus, with special reference to specimens in the Carnegie Museum," in: Memoirs of the Carnegie Museum, vol. 11, no. 4 (1936), pp. 175-300. This work was on display in the original exhibition as item 41.