Runcaria, a middle Devonian seed plant precursor

[en] The emergence of the seed habit in the Middle Pateozoic was a decisive evolutionary breakthrough. Today, seed plants are the most successful plant lineage, with more than 250,000 living species. We have identified a middle Givetian (385 million years ago) seed precursor from Belgium predating the earliest seeds by about 20 million years. Runcaria is a small, radially symmetrical, integumented megasporangium surrounded by a cupule. The megasporangium bears an unopened distal extension protruding above the multilobed integument. This extension is assumed to be involved in anemophilous pollination. Runcaria sheds new light on the sequence of character acquisition leading to the seed.

Disciplines :

Earth sciences & physical geography

Author, co-author :

Gerrienne, Philippe ; Université de Liège - ULiège > Département de géologie > Paléobotanique - Paléopalynologie - Micropaléontologie (PPM)

Meyer-Berthaud, B.

Fairon-Demaret, Muriel ; Université de Liège - ULiège > Services généraux (Faculté des sciences) > Relations académiques et scientifiques (Sciences)

Streel, Maurice ; Université de Liège - ULiège > Département de géologie

Steemans, Philippe ; Université de Liège - ULiège > Département de géologie > Paléobotanique - Paléopalynologie - Micropaléontologie (PPM)

Language :

English

Title :

Runcaria, a middle Devonian seed plant precursor

Publication date :

29 October 2004

Journal title :

Science

ISSN :

0036-8075

eISSN :

1095-9203

Publisher :

Amer Assoc Advancement Science, Washington, United States - Washington

Volume :

306

Issue :

5697

Pages :

856-858

Peer reviewed :

Peer Reviewed verified by ORBi

Available on ORBi :

since 25 May 2009

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Bibliography

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Runcaria heinzelinii Stockmans, 1968. Holotype (fig. S4): specimen number IRSnB104,866, housed at the Institut Royal des Sciences Naturelles de Belgique (Brussels, Belgium). Emended diagnosis, descriptio generico-specifica: Cupules borne in pairs, each on a short stalk up to 3 mm in length and 0.4 mm in diameter. Stalks resulting from a ∼70° isotomy of the fertile axis. Cupule containing one 6.5- to 8-mm-long integumented indehiscent megasporangium. Cupule comprising four segments free from each other, 1.6 to 3 mm long and 1.1 to 1.7 mm wide, curved outward and separated distally in two bluntly pointed tips. Lateral edges of cupule segments decurrent along the stalk. Megasporangium radially symmetrical, surrounded by a 4.7- to 5.2-mm-long divided integument. Megasporangium comprising a sessile oval body 1.4 to 2 mm long and 0.9 to 1.3 mm wide, bearing a distal extension, 4 to 5.2 mm long and 0.2 to 0.4 mm wide, emerging above the integument. Tip of megasporangial extension unopened and enlarged, up to 470 μm wide and 780 μm long. Integument separated into a minimum of 16 lobes free from each other and from the megasporangium down to their base. Integument lobes 75 to 100 μm wide, comprising elongate thickened cells and separated by intervals up to 100 μm wide; lobes converging distally around the columnar extension at about four-fifths of its length.
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We thank N. Rowe, B. Kaufmann, and D. Dilcher for critical reading of the manuscript and F. Damblon for the loan of the specimen. P.G. and P.S. are Fonds National par la Recherche Scientifique (FNRS) research associates. B.M-B. is a Centre National de la Recherche Scientifique (CNRS) researcher.