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 sp...
Published in: | Palaeontology |
---|---|
Main Authors: | , |
Format: | Article in Journal/Newspaper |
Language: | unknown |
Published: |
2003
|
Subjects: | |
Online Access: | https://eprints.soton.ac.uk/2110/ |
id |
ftsouthampton:oai:eprints.soton.ac.uk:2110 |
---|---|
record_format |
openpolar |
spelling |
ftsouthampton:oai:eprints.soton.ac.uk:2110 2023-07-30T04:03:14+02:00 A mid Devonian seed-megaspore from East Greenland and the origin of the seed plants Marshall, John E.A. Hemsley, Alan R. 2003 https://eprints.soton.ac.uk/2110/ unknown 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), 647-670. (doi:10.1111/1475-4983.00314 <http://dx.doi.org/10.1111/1475-4983.00314>). Article PeerReviewed 2003 ftsouthampton https://doi.org/10.1111/1475-4983.00314 2023-07-09T20:28:54Z 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. Article in Journal/Newspaper East Greenland Greenland University of Southampton: e-Prints Soton Greenland Palaeontology 46 4 647 670 |
institution |
Open Polar |
collection |
University of Southampton: e-Prints Soton |
op_collection_id |
ftsouthampton |
language |
unknown |
description |
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. |
format |
Article in Journal/Newspaper |
author |
Marshall, John E.A. Hemsley, Alan R. |
spellingShingle |
Marshall, John E.A. Hemsley, Alan R. A mid Devonian seed-megaspore from East Greenland and the origin of the seed plants |
author_facet |
Marshall, John E.A. Hemsley, Alan R. |
author_sort |
Marshall, John E.A. |
title |
A mid Devonian seed-megaspore from East Greenland and the origin of the seed plants |
title_short |
A mid Devonian seed-megaspore from East Greenland and the origin of the seed plants |
title_full |
A mid Devonian seed-megaspore from East Greenland and the origin of the seed plants |
title_fullStr |
A mid Devonian seed-megaspore from East Greenland and the origin of the seed plants |
title_full_unstemmed |
A mid Devonian seed-megaspore from East Greenland and the origin of the seed plants |
title_sort |
mid devonian seed-megaspore from east greenland and the origin of the seed plants |
publishDate |
2003 |
url |
https://eprints.soton.ac.uk/2110/ |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
East Greenland Greenland |
genre_facet |
East Greenland Greenland |
op_relation |
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), 647-670. (doi:10.1111/1475-4983.00314 <http://dx.doi.org/10.1111/1475-4983.00314>). |
op_doi |
https://doi.org/10.1111/1475-4983.00314 |
container_title |
Palaeontology |
container_volume |
46 |
container_issue |
4 |
container_start_page |
647 |
op_container_end_page |
670 |
_version_ |
1772814188091015168 |