The architecture of Permian glossopterid ovuliferous reproductive organs

Abstract

McLoughlin, S. & Prevec, R. 20 September 2019. The architecture of Permian glossopterid ovuliferous reproductive organs. Alcheringa XX, xxx–xxx. ISSN 0311-5518

A historical account of research on glossopterid ovuliferous reproductive structures reveals starkly contrasting interpretations of their architecture and homologies from the earliest investigations. The diversity of interpretations has led to the establishment of a multitude of genera for these fossil organs, many of the taxa being synonymous. We identify a need for taxonomic revision of these genera to clearly demarcate taxa before they can be used effectively as palaeobiogeographic or biostratigraphic indices. Our assessment of fructification features based on extensive studies of adpression and permineralized fossils reveals that many of the character states for glossopterids used in previous phylogenetic analyses are erroneous. We interpret glossopterid fertiligers to have been borne in loose strobili in which individual polysperms represent fertile cladodes of diverse morphologies subtended by a vegetative leaf or bract. Polysperms within the group are variously branched or condensed with ovule placement ranging from marginal to abaxial, in some cases occurring on recurved branchlets or in cupule-like structures. Glossopterid polysperms of all types are fringed by one or two ranks of wing-like structures that may represent the remnants of megasporophylls that were, ancestrally, developed on the fertile axillary shoot. Glossopterid fertiligers have similarities to the condensed bract/ovuliferous scale complexes of conifer cones, but comparisons with Mesozoic seed-ferns are hindered by insufficient data on the arrangement and homologies of the ovule-bearing organs of the latter group. Nevertheless, glossopterid polysperms differ from the ovuliferous organs of Mesozoic seed-ferns by longitudinal versus transverse folding, respectively.

Stephen McLoughlin* [[email protected]], Department of Palaeobiology, Swedish Museum of Natural History, Box 50007, 104 05 Stockholm, Sweden; Rose Prevec [[email protected]], Department of Earth Sciences, Albany Museum, 40 Somerset Street, Makhanda, 6139, Eastern Cape, South Africa, and Department of Botany, Rhodes University, PO Box 94, Makhanda, 6140, Eastern Cape, South Africa.

Key words:

• Glossopteris
• fructifications
• reproductive biology
• Gondwana
• plant anatomy
• phylogeny.

Acknowledgements

Some of the material presented here contributed towards the PhD degree of RP at the University of the Witwatersrand (Adendorff 2005). We thank the curators and collection managers of the many institutions hosting glossopterid fossils that assisted us in locating and photographing relevant specimens. We thank Pollyanna von Knorring for preparing the reconstruction of glossopterid fertiligers in Fig. 14. We thank three reviewers and the assistant editor (Chris Mays) for their constructive critiques of the manuscript. Finally, we thank the Chief Editor for his invitation to prepare this paper as a contribution to the Nelly Ludbrook review series.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

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Additional information

Funding

Financial support from the following organizations is gratefully acknowledged: to SM—Swedish Research Council [VR grants 2014-5234, 2018-04527] and National Science Foundation [project #1636625]; to RP—University of the Witwatersrand, Rhodes University, the DST-NRF Centre of Excellence in Palaeosciences and the NRF African Origins Platform [UID: 98822].