Early seed plants in the Southern Hemisphere: I. Associated ovulate and microsporangiate organs from the carboniferous of Peru

A new type of pteridosperm ovulate fructification has been recovered from Carboniferous sediments on the Paracas peninsula of Peru, South America. Co-occurring in a monospecific assemblage with the ovulate fructification are fragments of microsporangiate branch systems that display a progymnosperm-like grade of organization. The ovulate branch system together with hundreds of dispersed seeds are described and named Oclloa cesariana gen. et sp. nov/ Oclloa ovules are acupulate, up to 11.0 mm long, 4.0 mm wide, and borne singly on the slender forked ultimate branchlets of primary laterals that are alternately arranged along a central axis. The integumentary lobes are fused laterally and to the nucellus in the basal one-half to two-thirds of the seed. At levels just below the pollen chamber, the integument separates distally into a whorl of 5–9 free, tentacle-like lobes. Minute projections line the margins and possibly inner surfaces of the free apical lobes. Internally, megasporangia display a pollen chamber, short lagenostome, and remnants of the central column; all features indicative of hydrasperman reproduction. Morphologically, Oclloa closely resembles the genus Physostoma, but our observations of the acupulate nature and other structural features distinguish it from this taxon. Oclloa is the first well documented acupulate lagenostomalean seed found outside of tropical Euramerica. Moreover, it provides the first positive evidence that not all ovules modified for hydrasperman reproduction were produced by cupulate branch systems. Found exclusively associated with Oclloa are microsporangiate branch systems that bear groups of 2–4 unfused, banana-shaped sporangia that are similar to Zimmermannitheca. However, based on differences in shape and number of sporangia per cluster, cluster symmetry, and branch system morphology, the specimens are assigned to the new taxon Obandotheca laminensis gen. et sp. nov.