Nicholas Hotton III, 78, a paleontologist who retired in 1993 as curator of fossil reptiles at the Museum of Natural History, died of colon cancer Nov. 29 at his Takoma Park home.

Dr. Hotton was an expert on the group of extinct reptiles that gave rise to mammals.

He wrote two popular books on fossils and evolution, "Dinosaurs" and "The Evidence of Evolution," and published dozens of scientific papers.

He spent nearly every spring collecting fossils at sites in west Texas and had done field research in South Africa, Antarctica and Wyoming, where he conducted educational dinosaur digs.

Dr. Hutton appeared on television and was interviewed for radio programs as an expert on paleontology.

His work included research into the specialized eating habits of early land animals. In recent years, he continued his work as research scientist emeritus at the museum.

Dr. Hotton was a native of Sault Sainte Marie, Mich., and a graduate of the University of Chicago, where he also received a doctorate in biology. He served in the Army in the Philippines and Okinawa during World War II.

He taught anatomy at the University of Kansas before joining the museum staff 40 years ago, and he also taught vertebrate paleontology at George Washington University.

He was a member of the Society of Vertebrate Paleontology and Sigma Chi research society. His other interests included Civil War history.

His wife of 43 years, Ruth Olmstead Hotton, who assisted in his field work, died in 1986.

Survivors include three children, Albert TenEyck Hotton of Silver Spring, Nicholas Hotton IV of Antwerp, N.Y., and Carol Louise Hotton of Takoma Park; and two granddaughters.