Home / Introductions to both Fossil and Recent Plant Taxa / Cycads

! J. Asar et al. (2022): Early diversifications of angiosperms and their insect pollinators: were they unlinked? Free access. Trends in Plant Science, 27: 858-869. See also here.
Note figure 1: Emergence of crown angiosperms and insect pollinators.
Figure 2. Phylogeny of seed plants, depicting pollination modes of both extinct and extant lineages.

B.J. Axsmith et al. (2003): The enigmatic Paleozoic plants Spermopteris and Phasmatocycas reconsidered. Free access, American Journal of Botany, 90: 1585-1595.

M.R. Barone Lumaga et al. (2015): Epidermal micromorphology in Dioon: did volcanism constrain Dioon evolution? In PDF, Botanical Journal of the Linnean Society, 2015, 179: 236–254. See also here.

Phil and Jesse Bergman, Jungle Music Palms and Cycads, San Diego CA:
Cycads. Visit the
Cycad Photo Gallery. There are 437 pictures in the gallery.
Snapshot provided by the Internet Archive´s Wayback Machine.

Museum of Paleontology (UCMP), University of California, Berkeley: Introduction to the Cycads, Legacy of the Mesozoic. See also: Cycads: Fossil Record.

Blue Forest Safaris (Morne Fouche): Africa Cycads.

E.R. Bodor (2015): Plant reproductive organs from the Mecsek Coal Formation. Thesis, (abbreviated version?), ELTE Doctoral School of Earth Sciences, Budapest. In PDF.
Conclusion about "Dioonitocarpidium"(?).

! J.G. Bornemann (1856): Über organische Reste der Lettenkohlengruppe Thüringens. Ein Beitrag zur Fauna und Flora dieser Formation, besonders über fossile Cycadeen, nebst vergleichenden Untersuchungen über die Blattstruktur der jetztweltlichen Cycadeengattungen. In German, provided by Google books.
A pioneering depiction of dispersed fossil cuticles from the Triassic (Ladinian) of Germany.

E.D. Brenner et al. (2003): Cycads: evolutionary innovations and the role of plant-derived neurotoxins. In PDF, Trends in Plant Science, 8.

! Robert Buckley Trabuco Canyon, California, (Illustrations by Douglas Henderson, John Sibbick and Mark Hallet), The Palm & Cycad Societies of Florida (PACSOF): The Fossil Cycads. See also
! here (in PDF).
These expired links are now available through the Internet Archive´s Wayback Machine.

R. Buckley Trabuco Canyon, California: Inducing adventitious root growth in cycad leaves. Reprinted with permission from The Cycad Newsletter, Issue 1, 1999.
Still available through the Internet Archive´s Wayback Machine.

Robert Buckley, Trabuco Canyon, California, (Illustrations by Douglas Henderson, John Sibbick and Mark Hallet), The Palm & Cycad Societies of Florida (PACSOF):
The Fossil Cycads.
Reconstruction of the Carboniferous Period,
the leaves of the seed-fern Gigantopteris (Early Permian),
a reconstruction of Lyssoxylon grigsbyi (Triassic)
and a cycadeoid being enjoyed by Heterodontosaurus, the Pseudoctenis-type Cycadales, Early Jurassic,
a Pentoxylon reconstruction and a Nilsonia-type cycadale lived during the Jurassic,
Williamsonia, and belonging to the Bennettitales (Jurassic through Cretaceous).
These expired links are now available through the Internet Archive´s Wayback Machine.

Benjamin Burger, Utah State University, Vernal, Utah:
Why study fossil plants?
Invertebrate Paleontology and Paleobotany.
How did plants colonize the land, based on the fossil record?
How did the first seed plants (the Gymnosperms) evolve?
How did gymnosperms diversify during the early Mesozoic to become a modern dominate plant group?
! How good is the fossil record of Cycads?
What is the significance of the fossil record of Ginkgo?
What is the fossil record of Horsetails?
Fossil Algae.
What is an Angiosperm?
Video lectures.

! R.J. Butler et al. (2009): Testing co-evolutionary hypotheses over geological timescales: interactions between Mesozoic non-avian dinosaurs and cycads. PDF file, Biol. Rev., 84: 73-89. See also here (abstract).

! C. Cai et al. (2018): Beetle Pollination of Cycads in the Mesozoic. Abstract, Current Bialogy, 28: 2806-2812. See also here and there.

S.W. Carmichael (2019): Did Beetles Pollinate Ancient Plants? A review. Free access, MicroscopyToday, 27: 8-11

Bane Cheek, Polk Community College, Winter Haven, Florida: Cycads. Now provided by the Internet Archive´s Wayback Machine. See especially: An Introduction to Cycad Reproduction.

! Curtis Clark, Biological Sciences Department California State Polytechnic University, Pomona: Plant Morphology. Resources, PDF files.
Website outdated. The link is to a version archived by the Internet Archive´s Wayback Machine.

Lynne M. Clos, Fossil News: Cycads: Living Fossils. See also: Field Adventures in Paleontology: Hunting For Fossil Cycads in Petrified Forest National Park, Arizona.
Still provided by the Internet Archive´s Wayback Machine.

! J.A.R. Clugston and G.J. Kenicer (2022): Sexing cycads—a potential saviour. In PDF, Nature Plants, 8: 326–327.
See also here.

M. Coiro and L.J. Seyfullah (2024): Disparity of cycad leaves dispels the living fossil metaphor. Open access, Communications Biology, 7.
"... Our analysis shows that the cycad leaf morphospace expanded up to the present, with numerous shifts in its general positioning, independently of sampling biases
[...] We also show that rates of evolution were constantly high up to the Early Cretaceous, and then experienced a slight decrease in the Paleogene, followed by a Neogene acceleration. These results show a much more dynamic history for cycads, and suggest that the ‘living fossil’ metaphor is actually a hindrance to our understanding of their macroevolution ..."

! M. Coiro et al. (2023): Reconciling fossils with phylogenies reveals the origin and macroevolutionary processes explaining the global cycad biodiversity. Open access, New Phytologist, doi: 10.1111/nph.19010.
Note figure 1: Global distribution of Cycadales.
! Figure 2: Bayesian total-evidence dated phylogeny of Cycadales.
! Figure 3: Ages of extant genera and fossil placements. Phylogenetic relationships for extant and extinct cycads.
! Figure 4: Historical biogeography of cycads.
"... Combining molecular data for extant species and leaf morphological data for extant and fossil species, we study the origin of cycad global biodiversity patterns through Bayesian total-evidence dating analyses.
[...] Cycads originated in the Carboniferous on the Laurasian landmass and expanded in Gondwana in the Jurassic.
[...] We show the benefits of integrating fossils into phylogenies to estimate ancestral areas of origin and to study evolutionary processes explaining the global distribution of present-day relict groups ..."

F.L. Condamine et al. (2015): Origin and diversification of living cycads: a cautionary tale on the impact of the branching process prior in Bayesian molecular dating. In PDF, BMC Evolutionary Biology.
Note figure 1: The node calibration procedure used for dating the cycads.
! Figure 2: Time-calibrated phylogeny of Cycadales.
! "... We also provide new insights into the history of cycad diversification because we found (i) periods of extinction along the long branches of the genera consistent with fossil data, and (ii) high diversification rates within the Miocene genus radiations. ..."

! N.R. Cúneo et al. (2010): Review of the Cycads and Bennettitaleans from the Mesozoic of Argentina. In PDF.

The Cycad Newsletter. Provided by the Cycad Society, a non-profit organization dedicated to the conservation of cycads through education and scientific research.

! The Cycad Society. A non-profit organization dedicated to the conservation of cycads through education and scientific research. Read examples of the interesting articles that have appeared in The Cycad Newsletter. Visit The Cycad Photo Gallery.

! The Cycad Society: Glossary of Cycad Terms. Consisting of two parts: Illustrated Glossary of Cycad Terms, and Expanded Glossary of Cycad Terms (PDF file).

Jose Manuel Sanchez de Lorenzo Cáceres, Palm & Cycad Societies of Florida, Inc.: The Cycads: Fossils of the Past.
Still available via Internet Archive Wayback Machine.

Paolo De Luca, Dipartimento di Biologia vegetale and Orto Botanico, Universita di Napoli, Italia: A Historical Perspective on Cycads from Antiquity to the Present. The historical aspects of the acquisitions of cycad collections in botanical gardens are outlined, and a brief survey of the history of cycads in various cultures. is given.
Website outdated. The link is to a version archived by the Internet Archive´s Wayback Machine.

The Cycad Society of South Africa.

V.M. Dörken and B. Rozynek (2013): Proliferated megasporangiate strobili of Zamia furfuracea (Zamiaceae, Cycadales) and its possible evolutionary implications for the origin of cycad-megasporophylls. In PDF, Palaeodiversity, 6: 135-147.

! C.C. Davis and H. Schaefer (2011): Plant Evolution: Pulses of Extinction and Speciation in Gymnosperm Diversity. See also here (abstract).

S. Deng et al. (2014): Pollen cones and associated leaves from the Lower Cretaceous of China and a re-evaluation of Mesozoic male cycad cones: In PDF, Journal of Systematic Palaeontology, 12.
Now recovered from the Internet Archive´s Wayback Machine.

! W.A. DiMichele et al. (2001): An Early Permian flora with Late Permian and Mesozoic affinities from north-central Texas. In PDF, Journal of Paleontology, 75: 449-460.
See also here.

dmoz, the Open Directory Project:
Science: Biology: Flora and Fauna: Plantae:
Cycadophyta. See also:
Earth Sciences: Paleontology: Paleobotany: Taxa.
These expired links are now available through the Internet Archive´s Wayback Machine.

V.M. Dörken and B. Rozynek (2013): Proliferated megasporangiate strobili of Zamia furfuracea (Zamiaceae, Cycadales) and its possible evolutionary implications for the origin of cycadmegasporophylls. In PDF, Palaeodiversity 6: 135-147.

B.L. Dorsey et al.(2018): Pleistocene diversification in an ancient lineage: a role for glacial cycles in the evolutionary history of Dioon Lindl. (Zamiaceae). Open access, American Journal of Botany 105(9): 1512–1530.

! Christopher J. Earle (server space has been provided by the Department of Botany, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany): The Gymnosperm Database. Currently the database provides basic information for all species and higher-ranked taxa of the gymnosperms, i.e., conifers, cycads, and their allies. You may navigate from the species list, alphabetized by binomial.

A. Elgorriagaa and B.A. Atkinson (2023): Cretaceous pollen cone with three-dimensional preservation sheds light on the morphological evolution of cycads in deep time. In PDF, New Phytologist, 238: 1695-1710.
See also here.
"... We report a permineralized pollen cone from the Campanian Holz Shale located in Silverado Canyon, CA, USA
[...] Our findings support a Cretaceous diversification for crown-group Zamiaceae ..."

B. Erdei et al. (2019): First cycad seedling foliage from the fossil record and inferences for the Cenozoic evolution of cycads. Free access, Biol. Lett., 15: 20190114.

! B. Erdei and S.R. Manchester (2015): Ctenis clarnoensis sp. n., an Unusual Cycadalean Foliage from the Eocene Clarno Formation, Oregon. In PDF, Int. J. Plant Sci., 176: 1–43.

Z. Feng et al.(2017): Leaf anatomy of a late Palaeozoic cycad. Biol. Lett., 13.

M.A. Flores-Barragan and M.P. Velasco-de Leon (2021): New records of Bjuvia and Nilssonia from the Permian of Mexico. In PDF, Palaeontologia Electronica, 24. See also here.

Debbie Folkerts, Auburn University, Auburn, Alabama: Kingdom Plantae: Gymnosperms. Powerpoint presentation.
The link is to a version archived by the Internet Archive´s Wayback Machine.

Palmengarten, Frankfurt am Main, Das Tor zur Welt der Pflanzen: Palmfarne - weder Palmen noch Farne (in German).
Website outdated. The link is to a version archived by the Internet Archive´s Wayback Machine.

! Florida Museum of Natural History, University of Florida, Gainesville:
Cycads and Ginkgo (Powerpoint presentatation).

A.V. Gomankov (2022): Cycads in the Permian of the Subangara Region. In PDF, Paleontological Journal, 56: 317–326.
See likewise here.
Note figure 2: General form of cladosperms of Dioonitocarpidium.
Figure 5: Scheme of presumed evolutionary development of cladosperms in the cycads.
"... The significance of Dioonitocarpidium as a possible initial form in the evolution of the Cycadales in the Mesozoic and Cenozoic is discussed ..."

R. Gorelick and K. Olson (2011): Is lack of cycad (Cycadales) diversity a result of a lack of polyploidy? Abstract, Botanical Journal of the Linnean Society, 165: 156-167.

David R. Greenwood, Victoria University of Technology, Melbourne (Palm and Cycad Societies of Australia, PACSOA): Cycad Articles, Australian Fossil Cycads. Provided by the Internet Archive´s Wayback Machine.

Guido Grimm, Department of Palaeobotany, Swedish Museum of Natural History, Stockholm: Cladistic analyses of fossil and recent Cycadales based on morphological and molecular data. See also:
The Best Tree Cladogram, and here (abstract), and there "Phylogenie der Cycadales" (in German).

! The Gymnosperm Database (edited by Christopher J. Earle). A premier source of information on conifers and their allies. Excellent!
If you have a specific question, use the search box (top of page at right). Alternatively you might also start with the Topics page.
Worth checking out: Essential Links.

T.M. Harris (1961): The fossil cycads. PDF file, Palaeontology, 4: 313-323.
Website outdated. The link is to a version archived by the Internet Archive´s Wayback Machine.
Note text. fig. 2: Reconstructions of Nilssonia tenuinervis, Androstrobus wonnacotti and Beania mamayi.

! Jody L. Haynes (c/o Palm and Cycad Societies of Florida): Virtual Cycad Encyclopedia. Information about cycad taxonomy, biology, evolution, horticulture, conservation, etc.
Still available from the Internet Archive´s Wayback Machine.
Go to: "Jurassic Age" by Charles R. Knight.

! Jody L. Haynes: Expanded Glossary of Cycad Terms. In PDF, The Cycad Society.

M. Haworth et al. (2011): Cycads show no stomatal-density and index response to elevated carbon dioxide and subambient oxygen. Abstract, Australian Journal of Botany.

E.J. Hermsen et al. (2009): Morphology and ecology of the Antarcticycas plant. PDF file, Review of Palaeobotany and Palynology, 153: 108-123. Antarcticycas plant reconstruction on page 112.

E. Hermsen et al. (2007): Cycads from the Triassic of Antarctica: Permineralized cycad leaves. PDF file, Int. J. Plant Sci., 168: 1099-1112.
See also here.

! E.J. Hermsen et al. (2006): Cataphylls of the Middle Triassic cycad Antarcticycas schopfii and new insights into cycad evolution. Open access, American Journal of Botany, 93: 724-738.

R.S. Hill et al. (2019): New Macrofossils of the Australian Cycad Bowenia and Their Significance in Reconstructing the Past Morphological Range of the Genus. Free access, Int. J. Plant Sci., 180: 128–140.

K.E. Hill et al. (2019): Pinnule and Stomatal Size and Stomatal Density of Living and Fossil Bowenia and Eobowenia Specimens Give Insight into Physiology during Cretaceous and Eocene Paleoclimates. Free access, Int. J. Plant Sci., 180: 323–336.

! Ken D. Hill et al. (2004): The World List of Cycads. PDF file, The Botanical Review, 70: 274–298.
See likewise here.

! Ken D. Hill and D.W. Stevenson, Royal Botanic Gardens Sydney: The Cycad Pages. Botanical information and links, including identification and classification of cycads, ecology and conservation, cycad evolution and the fossil record, geography and distribution, as well as horticultural and general information. Excellent! Go to: John Hendricks, Ken D. Hill, Roy Osborne and Dennis Stevenson, Royal Botanic Gardens Sydney: The World List of Cycads. The lists as published gave the valid names of all known extant cycads.

M. Hrabovský (2021): Leaf evolution and classification. 3. Gymnospermopsida. In PDF, Acta Botanica Universitatis Comenianae, 57.
! Many black and white contour drawings.

Y. Hsiao et al. (2023): Museomics unveil systematics, diversity and evolution of Australian cycad-pollinating weevils. Open access, Proceedings of the Royal Society, B, 290: 20231385. https://doi.org/10.1098/rspb.2023.1385.
Note figure 1: Obligate pollination between Tranes weevils and Macrozamia cycads.
Figure 3: Fossil-calibrated chronogram for Australian cycad weevils.

L. Kessler, The New York Times: The Cult of the Cycads.

S.D. Klavins et al. (2005): Coprolites in a Middle Triassic cycad pollen cone: evidence for insect pollination in early cycads? PDF file, Evolutionary Ecology Research, 7: 479-488.
See also here.

S.D. Klavins et al. (2003): Gymnosperms from the Middle Triassic of Antarctica: the first structurally preserved cycad pollen cone. In PDF, Int. J. Plant Sci., 164: 1007-1020.
See also here.

E. Kustatscher and J.H.A. van Konijnenburg-van Cittert (2010): Seed ferns and Cycadophytes from the Triassic Flora of Thale (Germany). In PDF, Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, 258: 195–217. See also here.

Palm and Cycad Societies of Australia (PACSOA).

The Palm Haven. Palm Trees, Cycads, Bromeliads and other Tropical Plants. Go to: Cycads.

Conrad C. Labandeira et al. (2007): Pollination drops, pollen, and insect pollination of Mesozoic gymnosperms. PDF file, Taxon, 56:663-695.

M. Le Couls et al. (2016): Becklesia maulnyi sp. nov.: A new cycadean species from the Lower Oxfordian (Upper Jurassic) of Écommoy (Sarthe, NW France). Abstract, Annales de Paléontologie, 102: 95-101. See also here (in PDF).

Gerhard Leubner Lab, University Freiburg, Germany: Seed Evolution. Go to: Jurassic parc/Mesozoic era: Extinct gymnosperms and living ancient gymnosperms. Extant Cycadales and extinct Bennettitales.

! T. Linnell (1933); article started on PDF page 21: Zur Morphologie und Systematik triassischer Cycadophyten. II. Über Scytophyllum Bornemann, eine wenig bekannte Cycadophytengattung aus dem Keuper. In PDF, Svensk Botanisk Tidskrift 27: 310–331.
See also here and there.

! Y. Liu et al. (2022): The Cycas genome and the early evolution of seed plants. Open access, Nature Plants, 8: 389–401.
"... Although the major cycad lineages are ancient, modern cycad species emerged from several relatively recent diversifications ..."

J. Liu et al. (2022): Not that young: combining plastid phylogenomic, plate tectonic and fossil evidence indicates a Palaeogene diversification of Cycadaceae. Open access, Annals of Botany, 29: 217–230.

Y. Lu et al. (2014): Phylogeny and divergence times of gymnosperms inferred from single-copy nuclear genes. PloS one.

! L. Luthardt et al. (2023): Cycadodendron galtieri gen. nov. et sp. nov.: An Early Permian Gymnosperm Stem with Cycadalean Affinity. Free access, International Journal of Plant Sciences, 184.
Note figure 10: Details of cycad-specific stem-anatomical features.
"... Cycadodendron galtieri gen. nov. et sp. nov. represents a petrified cycad stem of early Permian age providing the oldest-known evidence of cycad anatomy.
[...] The broad anatomical similarities of C. galtieri with other fossil and extant cycads demonstrate the early evolution of various cycad-specific anatomical features in the lower Permian ..."

Yuandan MA et al. (2009): Carbon storage of cycad and other gymnosperm ecosystems in China: implications to evolutionary trends. PDF file, Polish Journal of Ecology, 57: 635-646.
This expired link is available through the Internet Archive´s Wayback Machine.

Department of Botany, University of Wisconsin, Madison: Plant Systematics Collection. This web site provides structured access to a teaching collection of plant images representing over 250 families and 1000 genera of vascular plants. Go to: Phylum Cycadophyta The Cycads).
Websites outdated. The link is to versions archived by the Internet Archive´s Wayback Machine.

SERGIUS H. MAMAY, DAN S. CHANEY, AND WILLIAM A. DIMICHELE: A Mesozoic-type flora from the Lower Permian of Texas. Abstract, 1998 Annual Meeting of the Botanical Society of America, 2-6 August, 1998 Baltimore, MD. Specimens of Dioonitocarpidium! Provided by the Internet Archive´s Wayback Machine.

! S.H. Mamay (1976): Paleozoic Origin of the Cycads. In PDF, Geological Survey Professional Paper, 934. See also here.

L.C.A. Martínez et al. (2017): A new Encephalarteae trunk (Cycadales) from the Cretaceous of Patagonia (Mata Amarilla Formation, Austral Basin), Argentina. In PDF, Cretaceous Research, 72: 81-94. See also here.

L.C.A. Martínez et al. (2012): A new cycad stem from the Cretaceous in Argentina and its phylogenetic relationships with other Cycadales. Free access, Botanical Journal of the Linnean Society, 3: 436–458.

! S. McLoughlin (2021): Gymnosperms: History of Life: Plants: Gymnosperms. PDF file, in: Elias, S. and Alderton, D. (eds): Encyclopedia of Geology. See also here.

! Y. Miao et al. (2017): Fossil and Living Cycads Say "No More Megasporophylls". J. Morphol. Anat., 1: 107. See also here and there (in PDF).

John M. Miller (gigantopteroid.org), University of California, Berkeley: Origin of Angiosperms. See also here or navigate from essay contents.
These expired links are now available through the Internet Archive´s Wayback Machine.

G.E. Mustoe (2007): Coevolution of cycads and dinosaurs. Cycad Newsletter.

! Palaeobotanical Research Group, Münster, Westfälische Wilhelms University, Münster, Germany. History of Palaeozoic Forests, CYCADS. Link list page with rankings and brief explanations. Images of modern cycads.

! N.S. Nagalingum et al. (2011): Recent Synchronous Radiation of a Living Fossil. Abstract.
"Using fossil-calibrated molecular phylogenies, we show that cycads underwent a near synchronous global rediversification beginning in the late Miocene, followed by a slowdown toward the Recent. Although the cycad lineage is ancient, our timetrees indicate that living cycad species are not much older than ~12 million years". See also here. In PDF, Science 334.

netfirms: The Cool Tropics, Research Cycads. A directory.
Snapshot provided by the Internet Archive´s Wayback Machine.

Paläontologische Museum Nierstein:
Image of Dioonitocarpidium pennaeforme (website in German).
Still available via Internet Archive Wayback Machine.

S. Nigris et al. (2021): Fleshy Structures Associated with Ovule Protection and Seed Dispersal in Gymnosperms: A Systematic and Evolutionary Overview. Open access, Critical Reviews in Plant Sciences, 40.

! Y. Ogura, Department of Botany, Faculty of Science, University of Tokyo, Tokyo, Japan, (page hosted by Botany online, The Internet Hypertextbook, Biological Classics in the Internet): HISTORY OF DISCOVERY OF SPERMATOZOIDS IN GINKGO BILOBA AND CYCAS REVOLUTA. PHYTOMORPHOLOGY, Vol 17, 109 - 114 (1967).
Website outdated, download a version archived by the Internet Archive´s Wayback Machine.

The Palm and Cycad Societies of Australia (PACSOA): PACSOA is a group of affiliated, semi-autonomous, regional Palm and/or Cycad Societies, based in Brisbane, Queensland.

Palm & Cycad Societies of Florida, Inc. (PACSOF): The fossil Cycads. With paintings and reconstructions of Douglas Henderson, John Sibbick, and Mark Hallett.
Go to: Jurassic Cycadales. Pentoxylon, Nilsonnia.
See also the pair of diplodoci make their way across a floodplain dotted with cycadeoid- type plants.
These expired links are now available through the Internet Archive´s Wayback Machine.

The Palm & Cycad Societies of Florida (PACSOF): Virtual Cycad Encyclopedia. Worth to visit: Chapter 4: Cycad evolution.

Bill Parker, Arizona: Chinleana. Discussion of Late Triassic paleontology and other assorted topics. Go to:
Discovery of an Entire Fossil Cycad from the Late Triassic of China (September 07, 2009).

Joe & Karen Perner, Katherine, Northern Territory, Australia: Cycad International. A Cycad Gardens Nursery. Go to: What are Cycads, or visit the Cycads Gallery.
Snapshot provided by the Internet Archive´s Wayback Machine.

! Kathleen B. Pigg, Department of Plant Biology, Arizona State University: Laboratory. Go to: The Cycads, Cycadeoids (Bennettitales) and Ginkgophytes.

C. Pott (2019): The cycadalean megasporophyll Dioonitocarpidium in the Carnian (Late Triassic) flora of Lunz am See, Austria. Abstract, PalZ.

C. Pott and A. Launis (2015): Taeniopteris novomundensis sp. nov. – "cycadophyte" foliage from the Carnian of Switzerland and Svalbard reconsidered: How to use Taeniopteris? Abstract, Neues Jahrbuch für Geologie und Paläontologie, 275.
See also here (in PDF).

! Christian Pott and Michael Krings (2010): Gymnosperm Foliage from the Upper Triassic of Lunz, Lower Austria: an annotated check list and identifiation key. PDF file, Geo.Alp, 7: 19-38.

! C. Pott et al. (2012): Baikalophyllum lobatum and Rehezamites anisolobus: Two Seed Plants with "Cycadophyte" Foliage from the Early Cretaceous of Eastern Asia. In PDF, International Journal of Plant Sciences, 173: 192-208.
See likewise here.
Paper awarded with the Remy and Remy Award 2012, Botanical Society of America.

! C. Pott et al. (2010): Late Palaeozoic foliage from China displays affinities to Cycadales rather than to Bennettitales necessitating a re-evaluation of the Palaeozoic Pterophyllum species. PDF file, Acta Palaeontol. Pol., 55: 57-168.

C. Pott et al. (2007): Pseudoctenis cornelii nov. spec. (cycadalean foliage) from the Carnian (Upper Triassic) of Lunz, Lower Austria. PDF file, Ann. Naturhist. Mus. Wien, 109 A: 1-17.

! S.E. Pratt (2014): Benchmarks: September 1, 1957: Fossil Cycad National Monument is dissolved. Earth, September 01, 2014.
See also here (National Fossil Day).
These expired links are now available through the Internet Archive´s Wayback Machine.

A. Prado (2011): The Cycad Herbivores. PDF file, Bulletin de la Société d´entomologie du Québec, Antennae, 18.

Mary Ann Reihman, Biological Sciences, Natural Sciences and Mathematics, California State University, Sacramento: Biology lecture notes. Go to: Comparison of Cycadophyte Misc. Gymnosperms (Bennettitales).

Bernard Renault, 1881-1885 (provided by Gallica): Cours de botanique fossile fait au Muséum d'histoire naturelle.- Première année (1881). Cycadées, zamiées, cycadoxylées, cordaïtées, poroxylées, sigillariées, stigmariées.

! S. Renner (2009): Gymnosperms. Provided by the Internet Archive´s Wayback Machine. PDF file, In: S.B. Hedges and S. Kumar (eds.): The Timetree of Life (see here).

G.W. Rothwell et al. (2022): Large Permineralized Seeds in the Jurassic of Haida Gwaii, Western Canada: Exploring the Mode and Tempo of Cycad Evolution. Abstract, International Journal of Plant Sciences.
"... Fossil seed specimens are studied from external morphology and serially sectioned by the classic cellulose acetate peel technique ..."
! "... Results suggest that modern pollination and postpollination biology and the two contrasting modes of cycad seed germination evolved during the Mesozoic but that crown group cycad species may not have appeared until the Cenozoic. ..."

Gar W. Rothwell, Department of Environmental and Plant Biology, Ohio University, Athens, OH: Vascular Plant Morphology. Now provided by the Internet Archive´s Wayback Machine.
This course covers the structure, development, reproductive biology and relationships of vascular plants. The course is structured to emphasize the evolutionary changes that led to the diversity of modern tracheophytes. Go to: Cycads (PDF file).

B. Rozynek (2008): Schozachia donaea n. gen., n. sp., a new cycad megasporophyll from the Middle Triassic (Ladinian) of Southern Germany. PDF file, PALAEODIVERSITY 1: 1-18.

! D.E. Salas-Leiva et al. (2013): Phylogeny of the cycads based on multiple single-copy nuclear genes: congruence of concatenated parsimony, likelihood and species tree inference methods. In PDF, Annals of Botany, 112: 1263–1278. See also here (abstract).

A. Salt (2022): Cycads studied to reconcile fossil and molecular evidence for evolutionary timescales. Botany One.
Article written with the aid of GPT-3, open.ai’s text generator!

! S. Salzman et al. (2024): New insights on cycad biology and evolution. In PDF. See likewise here.
"... we present the most recent advances in cycad research on land plant evolution, the evolution and mechanisms of insect pollination and herbivory, the biochemical basis of symbiosis, microbial symbionts, and plant genomics ..."

S. Salzman et al. (2020): An ancient push-pull pollination mechanism in cycads. In PDF, Sci. Adv., 6: eaay6169. See also here.
Note fig. 4: Time line and plant behaviors responsible for push-pull pollination.

V.L. Santucci et al. (2023): The price of neglect: Revisiting Fossil Cycad National Monument (1922–1957). Free access, Parks Stewardship Forum, 40.
"... Previously unknown records continue to emerge, helping to expand and reshape the understanding of the monument’s unfortunate history, and also raising new questions. Some of the newly uncovered information is presented here ..."

Vincent L. Santucci, National Park Service, Kemmerer, WY, and Marikka Hughes, Peabody Museum of Natural History, Paleobotany Division, New Haven: Fossil Cycad National Monument: A Case of Paleontological Resource Mismanagement. This expired link is available through the Internet Archive´s Wayback Machine.

D. Schneider et al. (2002): Cycads: their evolution, toxins, herbivores and insect pollinators. PDF file.

! J. Schuster (1932):
Das Pflanzenreich, IV, Cycadaceae. In German, Verlag Wilhelm Engelmann, Leipzig.

K.P. Sharanya, Department of Botany, NSS College Pandalam:
Cycads. Lecture notes, Powerpoint presentation.

Scott Singleton, Houston Gem and Mineral Society (2006): Cycad Anatomy and Fossil Occurrences in Texas. PDF file.

! A.R.T. Spencer et al. (2017): New insights into Mesozoic cycad evolution: an exploration of anatomically preserved Cycadaceae seeds from the Jurassic Oxford Clay biota. PeerJ 5.
Description of a new genus of anatomically preserved gymnosperm seed from the Callovian–Oxfordian (Jurassic) Oxford Clay Formation (UK), using a combination of traditional sectioning and synchrotron radiation X-ray micro-tomography (SRXMT).

R. Spiekermann et al. (2021): Not a lycopsid but a cycad-like plant: Iratinia australis gen. nov. et sp. nov. from the Irati Formation, Kungurian of the Paraná Basin, Brazil. Abstract, Review of Palaeobotany and Palynology, 289. See also:
Scientists Find a Fossilized Ancestor of 'Dinosaur Food' (The New York Times).

R. Stockey and G.W. Rothwell (2001): Permineralized cycad seeds from the Jurassic of British Columbia, Canada. Abstract. Botany 2001, August 12 - 16, 2001; Albuquerque, New Mexico.
Available via Internet Archive Wayback Machine.

Ralph E. Taggart, Department of Botany and Plant Pathology/Department of Geological Sciences at Michigan State University, East Lansing:
! BOT335 Lecture Schedule. Some interesting chapters in terms of palaeobotany, e.g.
The First Vascular Land Plants;
Carboniferous Forests;
Arborescent Lycopods;
Psaronius: a Carboniferous tree-fern;
Carboniferous Horsetails;
Carboniferous Seed Ferns;
The Evolution of Conifers;
Cycadophytes, the True Cycads;
Mesozoic Cycadeoids;
Ginkgophytes;
North American Redwoods, Past and Present.
These expired links are available through the Internet Archive´s Wayback Machine.

! T.N. Taylor (1969): Cycads: Evidence from the Upper Pennsylvanian. In PDF, Nature 164.

P.B. Tomlinson et al. (2018): Cracking the omega code: hydraulic architecture of the cycad leaf axis. Free access, Annals of Botany, 121: 483–488.

! J.H.A. van Konijnenburg-van Cittert et al. (2017): Differentiation of the fossil leaves assigned to Taeniopteris, Nilssoniopteris and Nilssonia with a comparison to similar genera. Abstract, Review of Palaeobotany and Palynology, 237: 100–106. See also here (in PDF).

! T. Walters and R. Osborne (eds., 2004): Cycad Classification: Concepts and Recommendations. 288 pages. Provided by CABI Publishing through the Google Print Publisher Program. Registration procedure required. Use "More results from this book" or "Search this book" to navigate. Unfortunately, you can view two pages around your search result, but you can search again! Use Google Book Search to search the full text of books.
Note: The table of contents.
See also here Book review, in PDF, South African Journal of Botany 2004.

Shi-Jun Wang et al. (2011): Cycad Wood from the Lopingian (Late Permian) of Southern China: Shuichengoxylon tianii gen. et sp. nov. PDF file, Int. J. Plant Sci., 172: 725-734.

X. Wang et al. (2009): The discovery of whole-plant fossil cycad from the Upper Triassic in western Liaoning and its significance. Chinese Science Bulletin, 54: 3116–3119.
See also here. (in PDF).
Also worth checking out: Discovery of an Entire Fossil Cycad from the Late Triassic of China (by Bill Parker, September 07, 2009).

George Reber Wieland, (photograph). Go to: Vincent L. Santucci, National Park Service, Kemmerer, WY, and Marikka Hughes, Peabody Museum of Natural History, Paleobotany Division, New Haven: Fossil Cycad National Monument: A Case of Paleontological Resource Mismanagement. See also here.

Wikipedia, the free-content encyclopedia:
Spermatophyte.
! Cycadophyta.
Fossil Cycad National Monument.

! P. Wilf et al. (2016): The last Patagonian cycad, Austrozamia stockeyi gen. et sp. nov., early Eocene of Laguna del Hunco, Chubut, Argentina. In PDF, Botany, 94: 817-829. See also here.

Y. Xu et al. (2023): How similar are the venation and cuticular characters of Glossopteris, Sagenopteris and Anthrophyopsis? In PDF, Review of Palaeobotany and Palynology, 316.
See likewise here.
Note figure 1: Geologic ranges of some representative reticulate taxa.
"... Considering the putatively close relationship of glossopterids (Glossopteris), Caytoniales (Sagenopteris) and Bennettitales (here encompassing Anthrophyopsis) resolved as members of the ‘glossophyte’ clade in some past phylogenetic studies, cuticular features suggest that these groups are not closely related. In addition, anastomosing venation, superficially similar to that of Glossopteris, Sagenopteris and Anthrophyopsis appears to have arisen independently in numerous other plant groups ..."

J.M. Zgurski et al. (2008): How well do we understand the overall backbone of cycad phylogeny? New insights from a large, multigene plastid data set. PDF file, Molecular Phylogenetics and Evolution.
Now recovered from the Internet Archive´s Wayback Machine.

! J.-W. Zhang et al. 2010): A new species of Leptocycas (Zamiaceae) from the Upper Triassic sediments of Liaoning Province, China. Abstract, Journal of Systematics and Evolution, 48: 286–301. See also here (in PDF).
See fig. 9: Reconstruction of Leptocycas yangcaogouensis, resembling like that of Dioon edule.

! Y.J. Zhang et al. (2015): Extending the generality of leaf economic design principles in the cycads, an ancient lineage. Free access, New Phytologist, 206: 817–829.

! X. Zhang (2019): Ovule development in Cycads: observation on anatomy and nucellus morphology in Zamia and Cycas. In PDF, bioRxiv. See also here.

! G. Zhifeng and B.A. Thomas (1989): A review of fossil cycad megasporophylls, with new evidence of Crossozamia Pomel and its associated leaves from the Lower Permian of Taiyuan, China. In PDF, Review of Palaeobotany and Palynology,60: 205-223.
See also here.
! Note fig. l: Proposed evolutionary pathways of cycad megasporophylls.

G. Zijlstra et al. (2016): (2438–2439) Proposal to conserve the names Taeniopteris and T. vittata with a conserved type (fossil Tracheophyta: "Taeniopterides"). In PDF, Taxon, 65: 399-400.

! The World List of Cycads (produced under the auspices of the IUCN/SSC Cycad Specialist Group (CSG) and sponsored by Montgomery Botanical Center).
The World List of Cycads is a working list of known cycad species names with the primary goal of providing reliable information on the taxonomy of cycads.
! Don't miss the extensive Cycad Literature List.