“For example,” said Michael Foote, a former student of Dr. Raup’s and a paleontologist at the University of Chicago, if biodiversity has not increased, “that tells us that there are some factors that are controlling diversity, perhaps some kind of competition among species or physical perturbations to the biosphere.”

Image As an author and theorist, Dr. Raup raised questions about extinction patterns and biodiversity.

Dr. Raup’s most famous contribution to the field may have been the revelation in 1983, after a six-year study of marine organisms he conducted with J. John Sepkoski Jr., that over the last 250 million years, extinctions of species spiked at regular intervals of about 26 million years.

Extinction periodicity, as it is known, enlivened the study of huge volcanic eruptions and of changes in the earth’s magnetic field that may have coincided with periods of mass extinction. It has also given rise to numerous theories regarding the history of life, including that the evolution of myriad species has been interrupted by nonterrestrial agents from the solar system or the galaxy.

One prominent hypothesis involved an undiscovered companion to the sun — it was christened Nemesis — that every so often swung close enough to the solar system that it redirected comets toward the earth.

Extinction periodicity remains unproven — further published analyses of the Raup-Sepkoski data have been divided on their original conclusions — and Dr. Raup was open about the fact that the data could lead him only so far. (“I believe they really are periodic,” he said of mass extinctions in a 1997 interview published online, “but I can’t prove it.”) But throughout his career, it was the questions that arose because of his work that established him as among paleontology’s most creative thinkers.

“Throughout their careers, most scientists are lucky if they can come up with one idea considered so insightful by their peers that it significantly alters the research agendas of a large number of colleagues,” Arnold I. Miller, a paleontologist at the University of Cincinnati, wrote in an email. “By rough count, Dave Raup did this at least five times in a research career spanning some 40 years.”