The University of Southampton
University of Southampton Institutional Repository

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 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
0031-0239
647-670
Marshall, John E.A.
cba178e3-91aa-49a2-b2ce-4b8d9d870b06
Hemsley, Alan R.
ea576ff3-8296-4817-a200-23156307c1f4
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), 647-670. (doi:10.1111/1475-4983.00314).

Record type: Article

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.

Full text not available from this repository.

More information

Published date: 2003
Keywords: seed-megaspore, devonian, greenland, functionally bisexual sporangium, heterospory, ovule evolution

Identifiers

Local EPrints ID: 2110
URI: https://eprints.soton.ac.uk/id/eprint/2110
ISSN: 0031-0239
PURE UUID: 1da3f05a-d61b-4d47-a56d-447e629f427d
ORCID for John E.A. Marshall: ORCID iD orcid.org/0000-0002-9242-3646

Catalogue record

Date deposited: 11 May 2004
Last modified: 06 Jun 2018 13:17

Export record

Altmetrics

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

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×