Elementary school arts and crafts would not be the same had it not been for the eating habits of dinosaurs.
Andrew Leslie, a postdoctoral paleobotanist at the Yale School of Forestry & Environmental Studies, has linked the hardness of present-day pinecones with the mass arrival of tall, herbivorous dinosaurs in the early-middle Jurassic period. The research, published online Feb. 23 in the Proceedings of the Royal Society B, found that the composition of the commonplace art-room pinecone was determined almost 200 million years ago.
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“I was collecting data for variables, and size and scope were two of most interesting ones,” Leslie said. “I noticed in the process of collecting data that there were these differences between early seed cones and modern ones, and took off from there.”
Leslie surveyed fossil samples of conifer pollen and seed cones — colloquially referred to by North Americans as pinecones — that spanned several hundreds of millions of years.
He noticed that there was a sudden spike in the average density and girth of conifer cones’ protective tissue in the Middle Jurassic period.
Around the same time, canopy-reaching herbivorous dinosaurs rose in number, and Leslie said this change in population could have altered the environment and caused the pinecones to adapt.
“If you’re a predator looking to get seeds, you’ll be fended off better by tougher cone tissue,” he explained.
Leslie also found that insect mouthparts underwent high diversification at this time, and this could have put additional evolutionary pressure on the seed-protecting cones.
But he said there could be other explanations. Some paleobotanists have suggested that climate change, for example, could have affected the evolution of conifer seed cones, he said.
Evolutionary scientists interviewed praised the study for its successful demonstration of a long-term coevolutionary relationship.
“One of the really big questions is how evolutionary lineages interacted on a broad scale,” David Jablonski, a professor of geophysical sciences at the University of Chicago, said. “It’s intriguing that there’s apparent evidence for an evolutionary response from conifers to dinosaurs because it’s remarkably difficult to demonstrate these types of interactions.”
Leslie said he plans to continue working with conifer cones, and to stay within the family Pinaceae, which contains cone-producing pine, spruce, and fir trees. This family is particularly fertile for research because contemporary botanists have a firm grasp of the relationship between the family’s cones and their modern-day predators, such as squirrels.
“I’m not done with pinecones just yet,” Leslie said.
Pinecones are the reproductive organs of pine trees.