On July 13, 1923, the party was the first in the world to discover dinosaur eggs. Initially thought to be eggs of a ceratopsian, Protoceratops, they were determined in 1995 actually to belong to the theropod Oviraptor. During that same expedition, Walter W. Granger discovered a skull from the Cretaceous period. In 1925, the museum sent a letter back informing the party that the skull was that of a mammal, and therefore even more rare and valuable; more were uncovered. Expeditions in the area stopped during 1926 and 1927. In 1928, the expedition's finds were seized by Chinese authorities but were eventually returned. The 1929 expedition was cancelled. In 1930, Andrews made one final trip and discovered some mastodon fossils. A cinematographer, James B. Shackelford, made filmed records of many of Andrews' expeditions. (Sixty years after Andrews' initial expedition, the American Museum of Natural History sent a new expedition to Mongolia on the invitation of its government to continue exploration.) Later that year, Andrews returned to the United States and divorced his wife, with whom he had two sons. He married his second wife, Wilhelmina Christmas, in 1935.