Rinistachya hilleri gen. et sp. nov. (Sphenophyllales), from the upper Devonian of South Africa
A rich and diverse plant assemblage has been excavated from latest Devonian (Famennian) black shales of the Witpoort Formation (Witteberg Group) at Waterloo Farm, close to the city of Grahamstown (South Africa). Several specimens of a new sphenopsid have been collected. The description of this as a new taxon, here named Rinistachya hilleri, gen. et sp. nov., provides an important addition to the scarce early record of the group. Rinistachya hilleri presents a novel architecture that include apparently plesiomorphic characters, reminiscent of the organisation of the Iridopteridales (including the production of two types of laterals at one node, the location of fertile parts in loose whorls on lateral branches and an organisation of the fertile parts in which they branch several times before bearing distally elongate sporangia). Other characters unambiguously nest Rinistachya within the Sphenopsida (including presence of planate and slightly webbed ultimate appendages and lateral strobili made of successive whorls of fertile leaves with fertile parts located at their axil). This provides strong support for a close relationship between Sphenopsida and Iridopteridales. Rinistachya furthermore represents the first record of a Devonian sphenopsid from Gondwana and extends the known distribution of the Sphenopsida from the tropics to very high palaeolatitudes. It is a new sphenopsid with a peculiar organisation. The new taxon allows better characterization of the initial evolutionary radiation at the base of the group.
KeywordsSphenopsid Famennian Devonian Biogeography Gondwana Witpoort formation
The South African National Roads Agency is thanked for their support in the rescue of shale during roadworks and construction of storage sheds therefore. Chris Harris is thanked for his assistance in drafting Fig. 2a, b. We would like to thank two anonymous reviewers for their useful comments that greatly improved the manuscript.
Financial support was provided to CP by a BELSPO Brain (ColdCase) grant for a joint project led by Pascal Godefroit. A travel grant for a short research stay in South Africa was also granted to CP by the FNRS (Belgium). Research support by the South African NRF-DST Centre of Excellence in Palaeosciences (CoE in Palaeosciences) and support by the South African Millennian Trust were granted by RG.
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