Mallomonas schumachii sp. nov., a fossil Synurophyte bearing large scales described from an Eocene maar lake in Northern Canada

A new, and presumably extinct, species representing the genus Mallomonas, M. schumachii, is described from an Eocene maar lake situated near the Arctic Circle in northern Canada. The new species bears bristles and possesses three types of scales. Body scales are large, square-shaped, with a posterior rim encircling approximately half of the perimeter, a thick secondary layer of closely spaced hexagonal chambers covering the anterior 2/3 of the base plate, a small and shallow dome, and a base plate bearing two sizes of pores. This species also had large triangular-shaped scales bearing short forward-projecting spines, and small obovate scales lacking domes, that possibly surrounded the flagellar pore and posterior end of the cell, respectively. Bristles are of the craspedodont type, with an open slit running the length of the shaft, an expanded and flat foot, and a ring of small teeth lining the apex of the shaft. The surface area of M. schumachii scales is over twice as large, and estimated to be larger than scales from any known modern species. The large scale size may have posed disadvantageous to the cell and resulted in the extinction of M. schumachii. Based on the remains of organisms found in association with M. schumachii, this species is believed to have thrived in acidic to slightly acidic environments that were high in humic content.