Petrified Arborescent Horsetail-Calamites Arthropithys by sysadmin | Feb 1, 2016 | BlogPetrified Arborescent Horsetail-Calamites Arthropithys- Northern Tocantins Petrified Forest, State of Tocantins, Brazil. Permian period 6.25″ across. Horsetails (sphenopsids) are closely related to ferns.
