Reproductive Biology of the Arborescent Seed-Fern Linopteris obliqua: Implications for Taxonomy (Medullosales, Late Pennsylvanian Sydney Coalfield, Canada)

A shaley slab (65 x 45 x 7 cm) from the Sydney Coalfield, Canada, Cantabrian age, on splitting apart revealed 2 – 3 layers each entombing thousands of abscised pinnules of Linopteris obliqua and eight dispersed compound-synangial structures. The campanulary-ventral-sporal micromorphology of the best preserved structure of these compares sufficiently well with previously reported structures from the Sydney Coalfield named Potoniea krisiae. Earlier studies involving larger sampling suites furthermore contributed to the observation that Hexagonocarpus sp. (female organ) and P. krisiae (male organ) usually co-occur with abscised L. obliqua pinnules; however, these two organs do not co-occur on isochronous bedding planes. In the absence of confirmatory organic attachments, the presented data provide as yet the strongest support for the hypothesis of the organs’ connectivity, but whether female-male trees existed or not, and the mode of attachment of the organs remain unknown. Hypothesized for the latter is pinnate attachment.