[1] In the descriptive paper naming T. postnastae Manchester et al reported that radioisotope dating of plagioclase crystals collected by Robert Rosé from the fossiliferous horizon of the Moose Mountain flora had been performed.

Using crystals obtained from tuffaceous sandstones, Argon–argon dating provided an age of 14.91 ± 0.23 Ma placing the flora as Middle Miocene Langhian stage.

The etymology of the specific name postnastae is a reference to the older Ypresian age Trochodendron nastae which it resembles.

There are typically three to five sets of pinnate secondaries that are found in the upper portion of the leaves, branching from the midvein at 15–25° angles.

The higher order tertiary to quaternary veins form a reticulated polygonal mesh, with areoles that have freely ending veinlets.