Othniel Charles Marsh still retains a reputation as an "armchair paleontologist," too busy to work in the field, who owed his high standing not to genius, but to luck and to his family's money. It is true that his contributions to geology were not of particularly high quality, and that his paleontological work was sometimes slipshod. Whereas his great rival Edward Drinker Cope went into the field throughout his career, Marsh himself spent only four seasons in the field, between 1870 and 1873. It is also true that the chair of paleontology that Marsh occupied at Yale was endowed for him by his wealthy uncle, who further endowed the Peabody Museum of Natural History where Marsh's collections remain to this day. Marsh's ambitious, possessive, and sometimes unscrupulous and egotistical nature also made him a rather difficult person to work with. Yet for all that, his contributions to paleontology and evolution were formidable. He remains one of the great figures in American paleontology.

Marsh's enormous collection of fossils enabled him to fill in a number of the gaps in the fossil record that were troublesome for supporters of Darwinian evolution. His descriptions in the 1870s of Cretaceous toothed birds such as Ichthyornis and Hesperornis, coming right on the heels of the discovery of Archaeopteryx, filled in a major gap in the early history of birds. In 1877, Marsh proposed the theory that birds were descended from dinosaurs, following Thomas Henry Huxley. Later, in 1881, Marsh suggested a close affinity between birds and coelurosaurs (small carnivorous dinosaurs):

This theory of birds evolving from dinosaur ancestors was revived in the 1960s, and is now by far the most widely accepted theory of the origin of birds. For more information, see the DinoBuzz website, from which this information was gleaned: www.ucmp.berkeley.edu/diapsids/avians.html.