Reappraisal of the organic-walled microphytoplankton genus Maranhites: morphology, excystment, and speciation

Exceptionally well preserved material from the Upper Devonian of the Iberian Pyrite Belt, southwest Spain, provides new observations on the morphological variability of the organic-walled microphytoplankton genus Maranhites. This leads to a reassessment of the systematic status of the species hitherto attributed to the genus, the diagnosis of which is emended herein. Many of these species are considered to represent different ontogenetic stages of a single species, i.e., M. mosesii (also emended herein). This trend, also evidenced in other species of the genus, is principally manifested by the appearance, development, and final release of thin, translucent bladders, following equatorial rupture of the outer wall layer (perieilyma). The release of these bladders likely constitutes a potential excystment mechanism.