Williamsonia (plant)

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Williamsonia
Temporal range: Early Jurassic–Late Cretaceous[1]
Williamsonia ovulate cone.jpg
Fossil seed cone of Williamsonia from the Jurassic period
Scientific classification
Kingdom: Plantae
Superdivision: Spermatophyta
Division: Cycadophyta
Class: Spermatopsida
Order: Bennettitales †
Family: Williamsoniaceae
Genus: Williamsonia
Carruth., 1870[2]
Type species
Williamsonia gigas
Carruth., 1870[2]
Williamsonia finds.png
  Areas where Williamsonia has been found

Williamsonia is an extinct genus of plant belonging to Bennettitales, an order of seed plants which bore a resemblance to cycads. Fossilized specimens of Williamsonia have been discovered worldwide.[1][3]

Taxonomy[edit]

Williamsonia was originally described as Zamia gigas by William Crawford Williamson.[4] William Carruthers proposed the name Williamsonia in an 1870 paper of his, with the type species being W. gigas.[2]

Biology[edit]

Williamsonia possessed a sturdy stem and had multiple fern-like leaves. The plant did not live in groups. The stamens of Williamsonia curved inward and upward.[3]

Williamsonia produced flowers up to 4 inches (10 cm) in length.[1] Its stalked seeds would have grown from a central receptacle, and the entire flower of Williamsonia would have been surrounded by protective bracts (which are often the only part of the plant to undergo fossilization).[1] The cones of Williamsonia were monosporangiate. They were "cup shaped" and could be up to 15 centimetres (5.9 in) in diameter. As many as 25-50 ovules could be present in each cone.[5] The development of the ovules appears to be similar to that of Cycadeoidea.[5]

Fossil sites[edit]

An anatomically preserved cone of Williamsonia has been discovered in Campanian rocks of Vancouver Island. This was the first reproductive structure of Williamsoniaceae to be recovered from western North America.[6] Bennettitalean cones (8 centimetres (3.1 in) in length and 6 centimetres (2.4 in) in diameter) from the Crato Formation of Brazil may belong to Williamsonia,[7] as well as finds from the Gristhorpe Beds of Cayton, England (in this case the specific species W. leckenbyi).[8] In addition, W. harrisiana has been described from the Rajmahal Hills of India,[9] as well as W. nizhoniamcdouldsd from the Chinle Formation of New Mexico.[10]

In Brazil, it was found Williamsonia in Paleorrota geopark that were in the Santa Maria Formation, dating from Carnian, Upper Triassic.[11][12]

References[edit]

  1. ^ a b c d Palmer, Douglas; et al. (2009). Prehistoric Life: The Definitive Visual History of Life on Earth (1st American ed.). New York: Dorling Kindersley. p. 230. ISBN 978-0-7566-5573-0. 
  2. ^ a b c Seward, A. C. (2011). Fossil Plants: A Text-Book for Students of Botany and Geology. Cambridge, New York: Cambridge University Press. p. 421. ISBN 1-108-01597-2. Retrieved February 7, 2012. 
  3. ^ a b Firefly Guide to Fossils (illustrated ed.). Firefly Books. 2003. p. 174. ISBN 1-55297-812-5. Retrieved February 8, 2012. 
  4. ^ Reddy, S. M.; Chary, S. J. (2003). University Botany 2: Gymnosperms, Plant Anatomy, Genetics, Ecology 2. New Delhi: New Age International. p. 12. ISBN 978-81-224-1477-6. Retrieved February 8, 2012. 
  5. ^ a b Taylor, Thomas N.; Taylor, Edith L.; Krings, Michael (2009). "Cycadophytes". Paleobotany: The Biology and Evolution of Fossil Plants (2nd ed.). Amsterdam: Academic Press. p. 734. ISBN 0-12-373972-1. Retrieved February 8, 2012. 
  6. ^ Stockey, Ruth A.; Rothwell, Gar W. (March 2003). "Anatomically Preserved Williamsonia (Williamsoniaceae): Evidence for Bennettitalean Reproduction in the Late Cretaceous of Western North America". International Journal of Plant Sciences (The University of Chicago Press) 164 (2): 251–262. doi:10.1086/346166. Retrieved February 8, 2012. 
  7. ^ Martill, David M.; Bechly, Günter; Loveridge, Robert F. (2007). The Crato Fossil Beds of Brazil: Window into an Ancient World (illustrated ed.). Cambridge University Press. p. 542. ISBN 0-521-85867-4. Retrieved February 8, 2012. 
  8. ^ Crane, Peter R.; Herendeen, Patrick S. (January 2009). "Bennettitales from the Grisethorpe Bed (Middle Jurassic) at Cayton Bay, Yorkshire, UK". American Journal of Botany 96 (1): 284–295. doi:10.3732/ajb.0800193. Retrieved February 9, 2012. 
  9. ^ Bose, M. N. (July 1968). "A new species of Williamsonia from the Rajmahal Hills, India". Journal of the Linnean Society of London, Botany 61 (384): 121–127. doi:10.1111/j.1095-8339.1968.tb00109.x. Retrieved February 9, 2012. 
  10. ^ Ash, Sidney R. (July 1968). "A new species of Williamsonia from the Upper Triassic Chinle Formation of New Mexico". Journal of the Linnean Society of London, Botany 61 (384): 113–120. doi:10.1111/j.1095-8339.1968.tb00108.x. Retrieved February 9, 2012. 
  11. ^ Passo das Tropas, Santa Maria, RS. Marco bioestratigráfico triássico na evolução paleoflorística do Gondwana na Bacia do Paraná
  12. ^ PRESENÇA DE BENETTITALES NO TRIÁSSICO SUL RIOGRANDENSE: O GÊNERO WILLIAMSONIA CARRUTHERS