Chesterian (Carboniferous) Septopora (Order Fenestrida), eastern North America

The acanthocladid fenestrate bryozoan Septopora is widespread but only locally common in diverse Chesterian (Carboniferous; Upper Mississippian) quiet water carbonate platform and basin deposits in the eastern United States. The genus is characterized by colonies with fenestrate meshworks of main branches and short, fused pinnate, usually with two rows of auto zooecia per branch; and by hemispherical polymorphs (cyclozooecia) of unknown function opening on reverse sides of junctions of main and lateral branches and between auto zooecial apertures on frontal branch surfaces. Species characteristics include distance between branch centers, diameter of the distal tube (equivalent to apertura! diameter on the branch surface), apertural spacing along rows, fenestrule size, and size of cyclozooccia. S’. subquadrans Ulrich is the most abundant, widespread and apparently long-ranged species. Other species, including the type species, S. cestriensis Prout, are distinct but less abundant or temporally long-ranging, including the new species S gracilis .