A Macroneuropteris scheuchzeri tree preserved in growth position in the Middle Pennsylvanian Sydney Mines Formation, Nova Scotia, Canada

Fossil plants preserved in growth position provide important insights into the architecture and ecology of ancient plants. Here I describe an upright tree of Macroneuropteris scheuchzeri rooted above the Point Aconi Coal in the Middle Pennsylvanian Sydney Mines Formation of Nova Scotia - the first example of an autochthonous pteridosperm described in the literature. The fossil tree has a sharply tapering trunk surrounded in its lower part by a large number of downward-recurved senescent petioles, which form a skirt. Petioles borne in an upright or horizontal position, interpreted as fronds that were still photosynthetically active when buried, are confined to the uppermost preserved part of the tree. Adapted to growth in rapidly aggrading coastal wetlands, the skirt of Macroneuropteris scheuchzeri probably acted to prop up the trunk while additionally trapping large mounds of mud around the base of the tree and stabilizing coastal wetlands. The tree had a sprawling habit and a maximum height of about 2 m. Similar, but smaller, trees found in adjacent beds probably represent juvenile specimens of the same species.