Horsetails

I haven't tried it, but Horsetails can be used for polishing metals and wood to a fine sheen because of their silicate content. This quality may also have been good for dental  hygiene of the herbivorous dinosaurs of the Jurassic - natural toothbrushes. 
These are growing by the shady ponds below Hallgarth and with a bit of imagination a smallish dinosaur (with very white teeth) might be seen there bathing and browsing and stirring up the mud.