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Else Marie Friis

Microsporangiophores from the Early Cretaceous (Berriasian) of Bornholm, Denmark, with comments on a pre-angiosperm xerophytic flora

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A new taxon, Skyttegaardia galtieri, is described based on microsporangiophores with Monosulcites/Cycadopites pollen isolated from clays collected at the Skyttegård locality, island of Bornholm, Denmark, which are of earliest Cretaceous (Berriasian) age. Each microsporangiophore consists of a short, massive proximal fertile stalk-like portion with a truncate base, and a long sterile distal extension. A cavity on each side of the median line of the stalk-like portion, partially encloses a sporangium that dehisces by a longitudinal slit. The long distal extension tapers to a slender point and is curved toward the inferred adaxial side. The extension is irregularly angular in cross-section and the cuticle is thick with deep stomatal pits. The organization of the microsporangiophore, the in situ pollen and stomatal features suggest relationship with extant Cycadales. However, in all extant and fossil cycads there are usually many more sporangia per microsporangiophore, typically in groups of two to five, and they are borne on the surface of the proximal stalk-like portion rather than embedded in its tissues. These differences preclude secure inclusion of Skyttegaardia in Cycadales and open the possibility that these microsporangiophores were produced by a group of extinct plants, the other parts of which remain to be identified. The thick cuticle and sunken stomata of Skyttegaardia, together with the embedded sporangia, suggest adaptation to water stress, which is also consistent with the xeromorphic traits seen among the leaf fragments in the Skyttegaard flora and the arid conditions inferred from geological–geochemical proxies.

OriginalsprogEngelsk
Artikelnummer104487
TidsskriftReview of Palaeobotany and Palynology
Vol/bind293
ISSN0034-6667
DOI
StatusUdgivet - okt. 2021

Bibliografisk note

Funding Information:
We thank the Paul Scherrer Institut, Villigen, Switzerland, for provision of synchrotron radiation beamtime at the TOMCAT beamline X02DA of the Swiss Light Source and Federica Marone for her help at the beamline. We are also grateful to Anna Lindstr?m for help with the SRXTM analyses. Financial support was provided by the Swiss Light Source (projects 20110963 and 20160140) and by the Swedish Research Council (Vetenskapsr?det 2014-5228 to E. M. Friis). We also thank the Oak Spring Garden Foundation for support during the preparation of this paper.

Funding Information:
We thank the Paul Scherrer Institut, Villigen, Switzerland, for provision of synchrotron radiation beamtime at the TOMCAT beamline X02DA of the Swiss Light Source and Federica Marone for her help at the beamline. We are also grateful to Anna Lindström for help with the SRXTM analyses. Financial support was provided by the Swiss Light Source (projects 20110963 and 20160140 ) and by the Swedish Research Council (Vetenskapsrådet 2014-5228 to E. M. Friis). We also thank the Oak Spring Garden Foundation for support during the preparation of this paper.

Publisher Copyright:
© 2021

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