Schmeissneria: a missing link to angiosperms?

Area of Science:

• Paleobotany
• Evolutionary Biology
• Plant Systematics

Background:

• The evolutionary origin of angiosperms remains a long-standing debate.
• Pre-Cretaceous angiosperm fossils are controversial, with reliable records limited to the Cretaceous period.
• Molecular phylogenetics suggest angiosperm origins predate current fossil evidence.

Purpose of the Study:

• To investigate the potential for angiosperm origins during the Jurassic period.
• To analyze newly discovered fossils for angiospermous characteristics.
• To re-evaluate the systematic placement of early seed plants.

Main Methods:

• Scanning Electron Microscopy (SEM) and light microscopy of fossil specimens.
• Morphological analysis of female reproductive structures and associated leaves.
• Comparative analysis with known early Jurassic genera, including Schmeissneria.

Main Results:

• Discovery of Jurassic-aged fossils with distinct angiospermous traits from China.
• Detailed description of female structures with paired organs, central units, and closed apices.
• Morphological similarities suggest these fossils belong to Schmeissneria, previously classified within Ginkgoales.

Conclusions:

• The closed apex of the central unit is a key angiosperm feature, indicating potential angiospermy in Schmeissneria.
• These findings suggest either a Jurassic angiosperm or a novel seed plant lineage.
• If confirmed as angiosperms, this implies angiosperm origins in the Triassic, significantly impacting seed plant evolutionary history.