Dinosterol is one of many sterols that has been isolated from dinoflagellates, a genus of single-celled algae. Dinosterol was identified and named around 1978 when a Dutch group—the research team of organic chemist Jan de Leeuw at Delft University in the Netherlands— studied sterols in Black Sea sediments and another research team (Rhode Island group) analyzed natural products from marine algae that cause “red tides.”
The molecular structure of dinosterol is a biomarker in the paleontological studies of marine sediments. The book Echoes of Life  traces the history of the identification of such biomarker molecules. For the chemical compound dinosterol, it gives the following story:
One of its [the Dutch group's] first big successes came […] from a 5000-year-old layer of surface sediments in the Black Sea. Here the group found massive amounts of a sterol with a “peculiar” structure […]. The Black Sea sediments […] were also loaded with the distinctive fossils of dinoflagellates, a large, diverse genus of single-celled algae, and the Dutch group suspected this was the source of the sterol. In 1978, around the same time they determined its structure, a group of Rhode Island natural products chemists who were studying the toxin-producing algae [Gonyaulax tamarensis] responsible for the deadly “red tides” that periodically occur in coastal waters began isolating sterols from dinoflagellates and confirmed de Leeuw's suspicions: the most prevalent of the sterols, which they christened dinosterol, was none other than the Black Sea sterol, a hitherto unknown structure, with a methyl group attached to the A-ring, and and extra branch attached to its side chain.Synonyms for dinosterol (C30H52O), according to the Merck Index, are 4,23-dimethylergost-22-en-3-ol and—no surprise—Black Sea sterol.
Keywords: organic chemistry, sterols, algae, paleontology, history
 Susan M. Gaines, Geoffrey Eglington, and Jürgen Rullkötter: Echoes of Life • What Fossil Molecules Reveal about Earth History. Oxford University Press, New York, 2009; page 108.