Bennettitales are large extinct fern-like plants that lived from the early Triassic to the Late Cretaceous. It is based off the real-life extinct genus Bennettitales. They are one of the few plants in the mod that don't still live today.
Punching a Bennettitales will not destroy it, unlike grass. Dinosaurs will not eat this plant.
Like most other things in the mod, it does not spawn naturally in the world.
The Bennettitales can only be obtained by putting a Plant Fossil in an Analyzer. There is a rare chance that the Analyzer will give back Fossilized Bennettitales Seeds, which you then must put in a Culture Vat. Unless the Culture Vat fails and spawns a Failure Plant, it will then turn the Fossilized Seeds into normal Bennettitales Seeds which can be planted.
To obtain the Tall Bennettitales, simply use bone meal on a regular Bennettitales.