Reconstructing A 300-Million-Year-Old Cone Solves Paleobotanical Mystery

For example, some groups like the horsetail relatives have their spore-bearing bracts attached to the axis in whorls at nodes, whereas in others the spore-bearing bracts are attached alternately. The rare and enigmatic Pennsylvanian cone Tetraphyllostrobus was unique and conflictive as it externally resembled cones of Sphenophyllales (an extinct group related to the horsetails) except for its apparent decussate architecture (opposite bracts at a node are arranged at right angles), and has since been considered of uncertain affinity. In a new study published in the American Journal of Botany, Negaunee Postdoctoral Scientist Michael D’Antonio, Negaunee Assistant Curator of Paleobotany Fabiany Herrera, Research Associate Peter Crane (Oak Spring Garden Foundation), and collaborators Carol Hotton (Smithsonian Institution) and Selena Smith (University of Michigan) have reconstructed in 3D a cone specimen externally resembling Tetraphyllostrobus from the Field’s Mazon Creek Paleobotany Collection. Using a combination of advanced visualization techniques including X-ray micro-computed tomography, scanning electron microscopy, Airyscan confocal super-resolution microscopy, and optical microscopy, they determined that the cone had a whorled architecture and other anatomical characters specific to Sphenophyllales. They also analyzed in-situ spores which they determined to be of a type specific to Sphenophyllales. After detailed comparison to other small sphenophyll cones, they determined that the cone represented a new form and established Hexaphyllostrobus kostorhysii as a new genus and species. The fossil was named “kostorhysii” in honor of Jim Kostorhys, an enthusiastic Mazon Creek collector and the donor of the specimen to the Museum. These findings show the utility of state-of-the-art visualization techniques for Pennsylvanian plant systematics and suggests that as better-preserved Tetraphyllostrobus material becomes available, reconstructions of that cone, too, will likely indicate a whorled architecture.
April 26. 2024