1-2) are an extinct order of seed plants known from fossils collected throughout the Mesozoic Era, around 252 to 66 million years ago.

[9] It is likely that Caytoniales flourished in wetland areas, because they are often found with other moisture-loving plants such as horsetails in waterlogged paleosols.

[5] The woody nature of associated stalks and preserved short shoots are evidence that Caytoniales were seasonally deciduous, shrubs and trees.

The extra protection of the reproductive organs gave rise to the idea that Caytoniales were predecessors to angiosperms, which have completely enclosed seeds.

The size of the pollen grains supports the idea that they were wind-pollinated, and their bisaccate wings may have enabled entry into the seed by a pollination drop mechanism.

This theory was disproved 1933 by Thomas's student Tom Harris, who studied the same reproductive organs and found different results.

"Most of the fruits were obtained by dissolving in hydrofluoric acid a single very small fragment of shale collected from Cape Stewart," he wrote.

[1] While Thomas's original idea led many scientists to believe that Caytoniales may have been angiosperms, Harris's further research disproved this theory.

The enclosure of ovules in Caytoniales has nevertheless been considered an early stage in evolution of the angiosperm double integument, and the carpels formed from an elaboration of their stalk (Fig.