Tuesday 3 December 2013

Angiosperm-like pollen from the Middle Triassic of Switzerland.

Angiosperms (Flowering Plants) are the most successful and diverse groups of plants today, but do not have a particularly long fossil record, with both plant and pollen fossils appearing abruptly in the Early Cretaceous, followed by the group rapidly diversifying and assuming a dominant role in many ecosystems. It has long been thought that the origins of the group are probably much older than this, with various sources proposing dates from the Late Permian to the Early Jurassic. A number of fossils of possible Flowering Plants or pollen from this period have been described, but none of these is universally accepted.

In a paper published in the October 2013 edition of the journal Frontiers in Plant SciencePeter Hochuli of the Palaeontological Institute and Museum of the University of Zürich and Susanne Feist-Burkhardt of Dr. Susanne Feist-Burkhardt Geological Consulting & Services, describe a series of pollen grains from the Middle Triassic of the Germanic Basin in Northern Switzerland.

Hochuli and Feist-Burkhardt suggest that these pollen grains should be considered to belong to stem-group Angiosperms, which is to say not actually Flowering Plants as such, but ancestral to the Flowering Plants and more closely related to Flowering Plants than any other exiting plant group.

Possible stem-group Angiosperm pollen from the Triassic of northern Switzerland; (1) light microscope image and (2) confocal laser scanning microscopy image. Scale bars are 10 μm. Hochuli & Feist-Burkhardt (2013).

Hochuli and Feist-Burkhardt recognize six separate forms of Angiosperm-like pollen from the locality, suggesting that the plants had some diversity. In addition they describe some pollen which they assign to the genus Afropollis, which has previously been suggested as Angiosperm pollen, but which is currently regarded as being Angiosperm-like pollen produced by an unknown plant of uncertain affinities. Afropollis has previously only been described from Cretaceous deposits. A number of pollen grains are also assigned to the genus Eucommiidites, which is widespread in the Jurassic and Cretaceous, and again produced by an unknown plant of uncertain affinities.

Afropollis pollen from the Triassic of northern Switzerland; (7) confocal laser scanning microscopy image and (8) light microscope image. Scale bars are 10 μm (7) and 20 μm (8). Hochuli & Feist-Burkhardt (2013).

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