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Archaenthus: An Early Angiosperm From the Cenomanian of the Western Interior of North America

David L. Dilcher and Peter R. Crane
Annals of the Missouri Botanical Garden
Vol. 71, No. 2, Historical Perspectives of Angiosperm Evolution (1984), pp. 351-383
DOI: 10.2307/2399030
Stable URL: http://www.jstor.org/stable/2399030
Page Count: 33
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Archaenthus: An Early Angiosperm From the Cenomanian of the Western Interior of North America
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Abstract

Archaeanthus linnenbergeri Dilcher & Crane, gen. et sp. nov., a multifollicular angiosperm fruit, is described from the mid-Cretaceous (uppermost Albian-mid-Cenomanian) Dakota Formation of central Kansas. Clusters of follicles were borne terminally at the apex of a stout branch with helically arranged leaves. Each cluster comprised 100-130 helically arranged follicles on an elongated receptacle. The follicles were stalked with a short, rounded tip and dehisced along a single adaxial suture. Ovules were numerous and borne along either side of the suture; 10-18 seeds matured in each follicle. The receptacle below the gynoecium shows three groups of scars, an upper group of numerous small scars interpreted as those of stamens with six to nine larger scars immediately below, interpreted as those of inner perianth parts. The flower is delimited at the base by three large, narrowly elliptical scars interpreted as those of outer perianth parts. A prominent scar below the base of the flower is thought to mark the position of floral bud-scales. Archaeanthus is linked with perianth parts (Archaepetala beekeri Dilcher & Crane, gen. et sp. nov. and Archaepetala obscura Dilcher & Crane, sp. nov.), bud scales (Kalymmanthus walkeri Dilcher & Crane, gen. et sp. nov.), and leaves (Liriophyllum kansense Dilcher & Crane, sp. nov.) on the basis of association evidence and structural agreement in the presence of distinctive resin-bodies. Liriophyllum populoides Lesq. is shown to be a separate species. The reconstructed Archaeanthus plant is most closely related to Recent Magnoliidae and in some features comes close to the hypothetical angiosperm archetype predicted by magnoliid floral theory; it demonstrates that many of the characters interpreted as primitive from neontological evidence are also ancient. Archaeanthus does not predate other kinds of angiosperm reproductive structure in the fossil record but conclusively demonstrates the existence of magnoliid-like plants and flowers early in angiosperm evolution.

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