Ellesmeris sphenopteroides, gen. ET SP. NOV., a new zygopterid fern from the Upper Devonian (Frasnian) of Ellesmere, N.W.T., Arctic Canada

A new fern‐like fossil plant is described from the lower Upper Devonian of southern Ellesmere Island, Canadian Arctic Archipelago. The plant occurs in an Archaeopteris‐ dominated flora preserved in the Nordstrand Point Formation (Mid‐Late Frasnian) near Bird Fiord. The plant has a pinnate vegetative...

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Bibliographic Details
Published in:American Journal of Botany
Main Authors: Hill, Stewart A., Scheckler, Stephen E., Basinger, James F.
Other Authors: Natural Sciences and Engineering Research Council of Canada, National Science Foundation
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 1997
Subjects:
Arctic Archipelago
Canadian Arctic Archipelago
Ellesmere Island
Online Access:http://dx.doi.org/10.2307/2445886
https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2307%2F2445886
https://onlinelibrary.wiley.com/doi/pdf/10.2307/2445886
http://api.wiley.com/onlinelibrary/chorus/v1/articles/10.2307%2F2445886
Description
Summary:A new fern‐like fossil plant is described from the lower Upper Devonian of southern Ellesmere Island, Canadian Arctic Archipelago. The plant occurs in an Archaeopteris‐ dominated flora preserved in the Nordstrand Point Formation (Mid‐Late Frasnian) near Bird Fiord. The plant has a pinnate vegetative system with three branch orders and laminate sphenopteroid pinnules. Primary pinnae usually diverge from the main axis in distichous pairs (quadriseriate), but can depart singly (biseriate). Each primary pinna bears a basal catadromic aphlebia. Anatomically, the plant exhibits a mesarch, bipolar protostele that is ribbon‐ to clepsydropsoid‐shaped in the main axis. Primary pinna traces are also initially bipolar and crescent‐shaped, but may become four‐ribbed before dividing into a pair of bipolar traces. The morphology and anatomy of this plant are nongymnospermous and are most similar to Zygopteridales (particularly Rhacophytaceae and Zygopteridaceae). The Frasnian age of Ellesmeris shows that laminated foliage had evolved in some zygopterid ferns much earlier than previously recognized. The Sphenopteris‐ like pinnules of Ellesmeris indicate the need for caution when attributing such a convergent foliar design to other plant groups, such as the Devonian gymnosperms.

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