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  • Cretaceous pollen cone with three‐dimensional preservation sheds light on the morphological evolution of cycads in deep time
Title: Cretaceous pollen cone with three‐dimensional preservation sheds light on the morphological evolution of cycads in deep time
Summary The Cycadales are an ancient and charismatic group of seed plants. However, their morphological evolution in deep time is poorly understood. While molecular divergence time analyses estimate a Cretaceous origin for most major living cycad clades, much of the extant diversity is inferred to be a result of Neogene diversifications. This leads to long branches throughout the cycadalean phylogeny that, with few exceptions, have yet to be rectified by unequivocal fossil cycads. We report a permineralized pollen cone from the Campanian Holz Shale located in Silverado Canyon, CA, USA ( c. 80 million yr ago). This fossil was studied via serial sectioning, SEM, 3D reconstruction and phylogenetic analyses. Microsporophyll and pollen morphology indicate this cone is assignable to Skyttegaardia , a recently described genus based on disarticulated lignitized microsporophylls from the Early Cretaceous of Denmark. Data from this new species, including a simple cone architecture, anatomical details and vasculature organization, indicate cycadalean affinities for Skyttegaardia . Phylogenetic analyses support this assignment and recover Skyttegaardia as crown‐group Cycadales, nested within Zamiaceae. Our findings support a Cretaceous diversification for crown‐group Zamiaceae, which included the evolution of morphological divergent extinct taxa with unique traits that have yet to be widely identified in the fossil record.  more » « less
Award ID(s):
1953993
PAR ID:
10463064
Author(s) / Creator(s):
;
Date Published:
Journal Name:
New Phytologist
Volume:
238
Issue:
4
ISSN:
0028-646X
Page Range / eLocation ID:
1695 to 1710
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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