NEW YORK — Larry Agenbroad, a paleontologist who presided over the unearthing of scores of fossilized mammoths from a scrape of southwest South Dakota, helping it become an international research destination, died Oct. 31 in Hot Springs, S.D. He was 81.
His son Brett said the cause was complications of kidney failure.
In 1974, a construction worker clearing land for a housing subdivision on the edge of Hot Springs noticed unusual bones. Dr. Agenbroad, a paleontologist and professor at Chadron State College in Nebraska, about an hour away, was called in to study the site.
He initially suspected that the bones could come from at least six mammoths. But after further digging, he concluded that there were as many as 100, trapped more than 26,000 years ago in a sinkhole, whose warm pond, fed by an artesian spring, attracted them with water and vegetation but often would not let them escape. Other scientists helped Dr. Agenbroad determine that all of the mammoths were males and that most were relatively young.
“What is a hungry, newly independent mammoth most likely to do? Use its tusks to sweep three or four feet of snow off last year’s flattened grasses? Or clamber down a steep shale slope and go for the greens?” Dr. Agenbroad wrote in a 1997 article in Natural History magazine.
“The latter option was a one-way trip for foolhardy young males. As soon as their feet hit the shale, moistened just above the water level, they slipped into the pond. The slick walls of the sinkhole ranged from an incline of 60 degrees to vertical to overhanging, and the water, as suggested by mammoth footprints we have found in its sediments, was about 15 feet deep in some places. Although they were probably good swimmers, as elephants are, the hefty mammoths were unable to find a foothold and so were doomed.”
So far, 61 mammoths have been uncovered, the last about two years ago, and officials say the number will continue to climb, perhaps past 100. Most are Columbian mammoths, but a few woolly mammoths have also been uncovered, as have other animals, including a camel, a llama, wolves, and a short-faced giant bear, a beast that would dwarf a modern grizzly. Some might have died while feeding on dead mammoths.
The Mammoth Site, as the museum built there is called, is now in an 18,000-square-foot building where visitors can view the site from walkways and scientists continue to excavate fossils.
Dr. Agenbroad was site director and principal investigator for four decades, spending the academic year at Northern Arizona University and leading digs in Hot Springs in the summer. When he retired from the university in the early 2000s, he moved to Hot Springs full time.
“His work was more like his avocation,” Brett Agenbroad said. “That’s what he loved.”
Larry Delmar Agenbroad was born April 3, 1933, to Richard and Jenny Agenbroad on his family’s 160-acre farm south of Nampa, Idaho, about a mile from the Snake River. He received a bachelor’s degree in geologic engineering from the University of Arizona in 1959 and a doctorate in geology there in 1967.
Besides his son Brett, he leaves his wife of 65 years, the former Wanda Sommers; another son, Finn; seven grandchildren; a brother, Owen; and a sister, Lois Beebe.
Dr. Agenbroad became a prominent expert on mammoths and worked on many other sites where mammoths and other large mammals were found. In 1999, he was part of a team that helped excavate a woolly mammoth found in permafrost in the Taimyr Peninsula of Siberia, its hair and flesh intact. He supported a proposal to try to clone the mammoth by extracting DNA and letting it develop in the egg of an Asian elephant, mammoths’ closest living relative. The idea continues to intrigue some experts on mammoths.
“When people say, ‘Why clone a woolly mammoth?’ ” Dr. Agenbroad said at the time, “I say, ‘Why not?’ ”