Peronosporomycetes (Oomycota) from a Middle Permian Permineralised Peat within the Bainmedart Coal Measures, Prince Charles Mountains, Antarctica

Abstract

The fossil record of Peronosporomycetes (water moulds) is rather sparse, though their distinctive ornamentation means they are probably better reported than some true fungal groups. Here we describe a rare Palaeozoic occurrence of this group from a Guadalupian (Middle Permian) silicified peat deposit in the Bainmedart Coal Measures, Prince Charles Mountains, Antarctica. Specimens are numerous and comprise two morphologically distinct kinds of ornamented oogonia, of which some are attached to hyphae by a septum. Combresomyces caespitosus sp. nov. consists of spherical oogonia bearing densely spaced, long, hollow, slender, conical papillae with multiple sharply pointed, strongly divergent, apical branches that commonly form a pseudoreticulate pattern under optical microscopy. The oogonia are attached to a parental hypha by a short truncated stalk with a single septum. Combresomyces rarus sp. nov. consists of spherical oogonia bearing widely spaced, hollow, broad, conical papillae that terminate in a single bifurcation producing a pair of acutely divergent sharply pointed branches. The oogonium bears a short truncate extension where it attaches to the parental hypha. We propose that similarities in oogonium shape, size, spine morphology and hyphal attachment between the Permian forms from the Prince Charles Mountains and other reported Peronosporomycetes from Devonian to Triassic strata at widely separated localities elsewhere in the world delimit an extinct but once cosmopolitan Palaeozoic to early Mesozoic branch of the peronosporomycete clade. We name this order Combresomycetales and note that it played an important role in late Palaeozoic and early Mesozoic peatland ecosystems worldwide.

Biota and palaeoenvironment of a high middle-latitude Late Triassic peat-forming ecosystem from Hopen, Svalbard archipelago

“…The specimens have not been found attached to hyphae: however, an intriguing feature is the common occurrence of an inner circular body, which has been interpreted as an oosphere or oospore in Combresomyces (Dotzler et al 2008;Strullu-Derrien et al 2011). If these structures are Peronosporomycetes oogonia, then they differ in architecture from any established forms and would represent a second Triassic record for that group (Schwendemann et al 2009;Slater et al 2013).…”

“…Williamson (1883) argued that the name Zygosporites was superfluous and suggested that the genus be deleted from the record (Taylor et al 2015). The multi-furcate spinose ornamentation of the Hopen specimens closely resembles that of the oogonia of Combresomyces, a peronosporomycete (oomycete) widely dispersed in peat-forming communities from the Carboniferous to Triassic (Krings et al 2007(Krings et al , 2011Dotzler et al 2008;Schwendemann et al 2009;Strullu-Derrien et al 2011;Slater et al 2013). However, the Hopen specimens are more oblong compared to the globose form of most Combresomyces oogonia, the site of attachment is generally broader (although proportionally similar to that illustrated in at least some specimens of Galtierella biscalithecae from the Pennsylvanian of France: Krings et al 2011, fig.…”

Structurally preserved fungi from Antarctica: diversity and interactions in late Palaeozoic and Mesozoic polar forest ecosystems

“…Two species of Combresomyces have been described by Slater et al (2013) from the Permian of the Prince Charles Mountains, including C. caespitosus B.J. Slater, S. McLoughlin et J. Hilton, characterized by long, hollow, slender, conical papillae with at least two orders of apical branches (Fig.…”

The record of Australian Jurassic plant–arthropod interactions

“…true fungi and Peronosporomycetes; Slater et al, 2013). Moreover, permineralized driftwood of this age preserved in marine environments may yield important evidence for the global development of xylic-boring teredinid and pholadid bivalves, which arose in the Jurassic (Savrda, 1991;Vahldiek and Schweigert, 2007).…”