EurekaMag
+ Translate
+ Most Popular
The pigeon tick (Argas reflexus): its biology, ecology, and epidemiological aspects
Prevalence of hemoglobin abnormalities in Kebili (Tunisian South)
Lipogranuloma: a preventable complication of dacryocystorhinostomy
Value of basal plasma cortisol assays in the assessment of pituitary-adrenal insufficiency
Bees from the Belgian Congo. The acraensis group of Anthophora
Placing gingival retraction cord
Total serum IgE, allergy skin testing, and the radioallergosorbent test for the diagnosis of allergy in asthmatic children
Acariens plumicoles Analgesoidea parasites des oiseaux du Maroc
Injuries of terminal phalanges of the fingers in children
Biology of flowering and nectar production in pear (Pyrus communis)
Das Reliktvorkommen der Aspisviper (Vipera aspis L.) im Schwarzwald
Hydrological modelling of drained blanket peatland
Pathologic morphology and clinical significance of the anomalous origin of the left circumflex coronary artery from the right coronary artery. General review and autopsy analysis of 30 cases
Cyto genetic analyses of lymphocyte cultures after exposure to calcium cyclamate
Axelrodia riesei, a new characoid fish from Upper Rio Meta in Colombia With remarks concerning the genus Axelrodia and description of a similar, sympatric, Hyphessobrycon-species
Favorable evolution of a case of tuberculosis of pancreas under antibiotic action
RIFM fragrance ingredient safety assessment, Valencene, CAS Registry Number 4630-07-3
Parenteral microemulsions: an overview
Temperate pasture: management for grazing and conservation
Evaluation of a new coprocessed compound based on lactose and maize starch for tablet formulation
Thermal expansion and cracking of three confined water-saturated igneous rocks to 800C
Revision of the genera of the tribe Stigmoderini (Coleoptera: Buprestidae) a discussion of phylogenetic relationships
Anal tuberculosis. Report of a case
Gastric tuberculosis in the past and present
Adaptive responses of the cardiovascular system to prolonged spaceflight conditions: assessment with Holter monitoring

The fossil history and phylogeny of the cycadales


The fossil history and phylogeny of the cycadales



Geophytology 17(2): 125-162



Fossil remains attributed to the Cycadales include stems, leaves, scales, fructifications, seeds, pollen grains, and no exceptional plant fossil, Leptocycas gracilis, showing leaves, scales and a cone attached to a stem. A critical assessment of Palaeozoic fossils attributed to the groups suggests that all of them are doubtful and some, like Phasmatocycas, even appear to be based on erroneous reconstructions. The oldest undoubted cycads like Antarcticycas schopfii and Leptocycas gracilis and some others occur in the Lower and Upper Triassic. A few of these early cycads had compound leaves but other contemporaneous ones had simple leaves so that neither of the two kinds of leaves can be regarded as ancestral. Mesozoic cycads are generally referred to extinct genera but a few forms resembling Encephalartos (or Zamia) can be traced back to the Triassic and a Cretaceous leaf is actually referred to Encephalartos. Cycas-like leaf forms called Cycadites, Pseudocycas and Paracycas go back only to the Jurassic but the oldest Cycas-like megasporophylls called Cycadospadix are Triassic. Tertiary cycad leaves are mostly assigned to extant genera on the basis of the close similarity of their external form although in some cases even their cuticles are comparable. The only notable exceptions among Tertiary levels which have been lately referred to extinct genera are Dioonopsis nipponica, Eostangeria saxonica and two species of Pterostoma. The last mentioned species are assigned here to Macrozamia as M. zamioides (Hill) comb. nov. and M. anastomosans (Hill) comb. nov. due to the resemblance of their cuticle as well as their external form with those of Macrozamia. The contrasting distribution of living and fossil cycads show that while all the 11 genera of extant cycads are confined to the tropical and subtropical regions of the earth, the fossils of the group show a much wider geographical scatter where their distribution extends into the present temperate regions and even into areas near the north or the south poles. The author believes that this poleward distribution may particularly suggest subsequent drifts of the fossil localities instead indicating a capacity of past cycads for cold tolerance. Diverse views about the phylogeny and relationships of the group are reassessed. It is pointed out that even though the numerous similarities between cycads and preceding pteridosperms point towards their pteridospermous origin yet so far no particular pteridosperms can be regarded as ancestral to them. The similarities of cycads with other groups of gymnosperms are also discussed and it is concluded that none of them can presently be regarded as closely related to the cycads.

Please choose payment method:






(PDF emailed within 1 workday: $29.90)

Accession: 007902096

Download citation: RISBibTeXText

Related references

A new fossil genus and species of snakefly (Raphidioptera: Mesoraphidiidae) from Lower Cretaceous Lebanese amber, with a discussion of snakefly phylogeny and fossil history. Insect Systematics and Evolution 42(2): 221-236, 2011

Phylogeny, biogeography, and fossil history of the Otariidae. Journal of Vertebrate Paleontology 20(3 Suppl): 29A-30A, 25 September, 2000

Fossil Cycadales of Argentina. The Botanical Review 65(3): 9-38, 1999

The fossil history of branching Implications for the phylogeny of land plants. Hoch, P C , Stephenson, A G Monographs in Systematic Botany; Experimental and molecular approaches to plant biosystematics 71-86, 1995

New records of fossil Cycadales in Patagonia. Boletin de la Asociacion Latinoamericano de Paleobotanica y Palinologia 5): 13-16, 1978

Phylogeny, molecular and fossil dating, and biogeographic history of Annonaceae and Myristicaceae (Magnoliales). International Journal of Plant Sciences 165(4, Suppl S): S55-S67, 2004

The Gomphaeschninae (Odonata: Aeshnidae): new fossil genus, reconstructed phylogeny, and geographical history. Systematic Entomology 114: 505-522, 1986

Palaeontological history, phylogeny and the system of brachycleistogastromorphs and cynipomorphs with description of new fossil and recent families, subfamilies and genera. Entomologicheskoe Obozrenie 73(2): 385-426; 495, 1994

The complete chloroplast genome of Microcycas calocoma (Miq.) A. DC. (Zamiaceae, Cycadales) and evolution in Cycadales. Peerj 8: E8305, 2020

Numerical studies in cycadales part 1 present day cycadales systematics. Boletin de la Sociedad Argentina de Botanica 16(3): 231-247, 1975

A phylogeny of cycads (Cycadales) inferred from chloroplast matK gene, trnK intron, and nuclear rDNA ITS region. Molecular Phylogenetics and Evolution 37(1): 214-234, 2005

A fossil-calibrated phylogeny reveals the biogeographic history of the Cladrastis clade, an amphi-Pacific early-branching group in papilionoid legumes. Molecular Phylogenetics and Evolution 143: 106673, 2020

Presence of fossil pollens of Acacia albida Delile and Cycadales in the Pleistocene samples of Melka Konture (Ethiopia). Boissiera 4a 33-42, 1975

A note on the fossil flora of the Tico area, Santa Cruz Province Argentina; X, Two new species of Pseudoctenis, Cycadales. Ameghiniana 9(3): 241-257, 1972

Paleontological history, phylogeny, and systematics of brachycleistogastromorpha, Infraorder N, and cynipomorpha Infraorder N with descriptions of new fossil and recent families, subfamilies, and genera. Entomological Review 74(4): 105-147, 1995