Article (Scientific journals)
An exceptional specimen of the early land plant Cooksonia paranensis, and a hypothesis on the life cycle of the earliest eutracheophytes
Gerrienne, Philippe; Dilcher, D. L.; Bergamaschi, Sergio et al.
2006In Review of Palaeobotany and Palynology, 142 (3-4), p. 123-130
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Keywords :
Cooksonia; early land plant; Early Devonian; heteromorphic life cycle; eutracheophytes
Abstract :
[en] An exceptionally large specimen of the early land plant Cooksonia paranensis Gerrienne et al. has been discovered from the type locality (Jackson de Figueiredo, Parana Basin, Brazil; early Lochkovian, Early Devonian). This nearly complete specimen consists of five dichotomous axes attached at their base to a small thalloid(?) structure. Each terminal axis segment ends in an expanded, cup-like, empty tip. Three interpretations of the specimen are proposed. (1) The whole specimen is a gametophyte of the Sciadopkyton-type, with a central area from which five axes depart; under this interpretation, the terminal cups are gametangiophores. (2) The basal structure represents the remains of a rhizome bearing five upright aerial axes, in which case the whole plant is a sporophyte. (3; our favoured hypothesis) The specimen is a cluster of five individual sporophytes still attached to the remains of a small female or bisexual gametophyte. In the latter case, this fossil is evidence that reduced thalloid gametophytes and branched axial sporophytes are plesiomorphic among the earliest eutracheophytes. We suggest that a major difference in life cycle defines a basal dichotomy in tracheophytes. Eutracheophyta, including all living vascular plants, have a heteromorphic, sporophyte dominant alternation of generations, whereas their extinct sister-group Rhymopsida (renamed here Paratracheophyta) is characterised by a more or less isomorphic alternations of generations. (c) 2006 Elsevier B.V. All rights reserved.
Disciplines :
Earth sciences & physical geography
Phytobiology (plant sciences, forestry, mycology...)
Author, co-author :
Gerrienne, Philippe ;  Université de Liège - ULiège > Département de géologie > Paléobotanique - Paléopalynologie - Micropaléontologie (PPM)
Dilcher, D. L.
Bergamaschi, Sergio
Milagres, Ingrid
Pereira, Egberto
Rodrigues, M. A. C.
Language :
English
Title :
An exceptional specimen of the early land plant Cooksonia paranensis, and a hypothesis on the life cycle of the earliest eutracheophytes
Publication date :
December 2006
Journal title :
Review of Palaeobotany and Palynology
ISSN :
0034-6667
eISSN :
1879-0615
Publisher :
Elsevier Science Bv, Amsterdam, Netherlands
Volume :
142
Issue :
3-4
Pages :
123-130
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 07 November 2011

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