Look at the herbarium sheets of Azolla and compare to fossils of from British Columbia. Since the text was published, an interesting aquatic fern has been described that has features of both Marsileales and Salvineales and suggests that these two orders are more closely related than was previously thought . See the paper on Hydropteris by Rothwell and Stockey. Below is a brief summary of each family and its fossil record. These plants are either dioecious or monoecious trees with opposite or spirally arranged leaves that are linear to broad.
Pollen is nonsaccate.
Araucarian conifers have a rich fossil record, extending from at least the Triassic, on the basis of reproductive structures. The genus Araucarites , in particular, represents fossil specimens of fused bract-scale complexes similar to those of extant Araucaria . As is discussed in the textbook, wood and leaf fossils with features similar to modern Araucariaceae may point to earlier origin but cannot be unequivocally placed in this group. Permineralized Jurassic cones are well known and contain young embryos. Although the araucarians are restricted today to the southern hemisphere, fossil evidence from the Mesozoic demonstrates that they were widespread throughout the world from the Triassic through the Cretaceous.