TY - JOUR
T1 - Microsporangiophores from the Early Cretaceous (Berriasian) of Bornholm, Denmark, with comments on a pre-angiosperm xerophytic flora
AU - Friis, Else Marie
AU - Crane, Peter R.
AU - Pedersen, Kaj Raunsgaard
N1 - Publisher Copyright:
© 2021
PY - 2021/10
Y1 - 2021/10
N2 - 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.
AB - 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.
KW - Cycadales
KW - Cycadopites
KW - Monosulcites
KW - Skyttegård member
KW - SRXTM
KW - Synchrotron radiation x-ray microtomography
UR - http://www.scopus.com/inward/record.url?scp=85111048394&partnerID=8YFLogxK
U2 - 10.1016/j.revpalbo.2021.104487
DO - 10.1016/j.revpalbo.2021.104487
M3 - Journal article
AN - SCOPUS:85111048394
SN - 0034-6667
VL - 293
JO - Review of Palaeobotany and Palynology
JF - Review of Palaeobotany and Palynology
M1 - 104487
ER -