Galápagos tortoise
Prior to his work on the Galapagos Islands, Baur was an assistant to Othniel Charles Marsh at Yale University from 1884 until 1890. Baur undertook an expedition to the Galápagos Islands in 1891, leaving New York on May 1, arriving in the Galápagos on June 9, and departing the islands on August 26 for Guayaquil, Panama, and the return to New York. Baur named several subspecies of Galápagos tortoise, including "Chelonoidis nigra guentheri" (Baur, 1889), and "Chelonoidis nigra galapagoensis" (Baur, 1889). Not all of Baur's tortoise taxa are still considered valid.