A key for the identification of cryptospores

ABSTRACT

Dispersed spores interpreted as deriving from the earliest land plants have complex configurations (e.g. permanent dyads and permanent tetrads) and are readily distinguished from the more familiar trilete spores that often dominate post-Late Silurian dispersed spore assemblages. These forms occur mainly from the Middle Ordovician to Early Devonian. They were first recognised in 1971, but it was not until 1979 that the process of formal description commenced. In 1984 they were included in a newly created higher taxonomic grouping called ‘cryptospores’, the term reflecting their complex morphology and then the ongoing debate regarding their affinities. Subsequently the exact definition of the term cryptospore has been debated, with some preferring a wide definition encompassing all non-marine palynomorphs produced by algae and early land plants, but others confining inclusion to spores deriving from early embryophytes. Since their recognition, numerous ‘cryptospore’ taxa have been described. However, their complex morphologies are difficult to interpret and numerous taxonomic debates have confused the delineation of genera and their classification into higher ranks. Here we present a key for the identification of ‘cryptospore’ taxa with the aim of clarifying some of this confusion.

KEYWORDS:

• Ordovician
• Silurian
• Devonian
• taxonomy
• cryptospores

Acknowledgements

This paper is dedicated to our friend and colleague Gordon Wood. We would like to thank T. Servais (Lille, France), M. Miller (Tulsa, Oklahoma) and J. Riding (Nottingham, UK) for their invaluable help in the writing of this paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

PS is a Senior Researcher of the Belgium National Fund for Scientific Research (NFSR). CHW's research is funded by NERC grant NE/N002067/1.

Notes on contributors

Philippe Steemans

Philippe Steemans is a senior researcher at the Belgium NFSR, Unit PPP (Paleobiogeology, Paleobotany, Paleopalynology), Liège University, Belgium. After a PhD thesis at University of Liège in 1986 on Lower Devonian miospores of the Western Europe, he received the title of Doctor. He is involved on palynology and its applications in the field of biostratigraphy, systematic, paleogeography etc. using miospores but also acritarchs and chitinozoans in collaboration with different specialists working in these research fields. He works on the Ordovician, Silurian and Devonian of many different regions like e.g. Saudi Arabia, North Africa, South America, China, Europe.

Charles H. Wellman

Charles H. Wellman is a professor of palaeobiology in the Deptartment of Animal and Plant Sciences, University of Sheffield. He received a BSc degree from the University of Southampton in 1987 and a PhD from Cardiff University in 1991. Charles' PhD research involved a study of early land plant microfossils from Scottish Silurian-Devonian ‘Lower Old Red Sandstone’ deposits. Subsequently Charles' research has diversified to investigate various aspects of the colonisation of the land, including work on both living and fossil material, and a consideration of what lived on the land before the land plants.