A mid Devonian seed-megaspore from East Greenland and the origin of the seed plants
A mid Devonian seed-megaspore from East Greenland and the origin of the seed plants
A new species of late Mid Devonian seed-megaspore from East Greenland is described and named as Spermasporites allenii. The formerly monotypic genus Spermasporites is emended to accommodate this new species. Rare specimens of S. allenii, with near complete sporangial contents, occur together with specimens showing proximally adhering microspores. These demonstrate that S. allenii was contained within a sporangium exhibiting extreme anisospory, which is interpreted here as functionally bisexual. This is a key element in understanding its reproductive function. The megaspore was shed along with some attached microspores giving it potential for both cross- and self-fertilization. This confers the advantages of heterospory without recourse to separate micro- and megasporangia. This provides a more likely mechanism for seed plant origin than the archaeopteridalean sporangium reduction model. Ultrastructural study of the megaspore wall confirms the progymnosperm affinity of S. allenii. Comparable forms include the Frasnian Spermasporites devonicus and the Famennian seed-megaspores isolated from Archaeosperma arnoldii.
seed-megaspore, devonian, greenland, functionally bisexual sporangium, heterospory, ovule evolution
647-670
Marshall, John E.A.
cba178e3-91aa-49a2-b2ce-4b8d9d870b06
Hemsley, Alan R.
ea576ff3-8296-4817-a200-23156307c1f4
2003
Marshall, John E.A.
cba178e3-91aa-49a2-b2ce-4b8d9d870b06
Hemsley, Alan R.
ea576ff3-8296-4817-a200-23156307c1f4
Marshall, John E.A. and Hemsley, Alan R.
(2003)
A mid Devonian seed-megaspore from East Greenland and the origin of the seed plants.
Palaeontology, 46 (4), .
(doi:10.1111/1475-4983.00314).
Abstract
A new species of late Mid Devonian seed-megaspore from East Greenland is described and named as Spermasporites allenii. The formerly monotypic genus Spermasporites is emended to accommodate this new species. Rare specimens of S. allenii, with near complete sporangial contents, occur together with specimens showing proximally adhering microspores. These demonstrate that S. allenii was contained within a sporangium exhibiting extreme anisospory, which is interpreted here as functionally bisexual. This is a key element in understanding its reproductive function. The megaspore was shed along with some attached microspores giving it potential for both cross- and self-fertilization. This confers the advantages of heterospory without recourse to separate micro- and megasporangia. This provides a more likely mechanism for seed plant origin than the archaeopteridalean sporangium reduction model. Ultrastructural study of the megaspore wall confirms the progymnosperm affinity of S. allenii. Comparable forms include the Frasnian Spermasporites devonicus and the Famennian seed-megaspores isolated from Archaeosperma arnoldii.
This record has no associated files available for download.
More information
Published date: 2003
Keywords:
seed-megaspore, devonian, greenland, functionally bisexual sporangium, heterospory, ovule evolution
Identifiers
Local EPrints ID: 2110
URI: http://eprints.soton.ac.uk/id/eprint/2110
ISSN: 0031-0239
PURE UUID: 1da3f05a-d61b-4d47-a56d-447e629f427d
Catalogue record
Date deposited: 11 May 2004
Last modified: 16 Mar 2024 02:35
Export record
Altmetrics
Contributors
Author:
Alan R. Hemsley
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics
