Sanders, Heather , Rothwell, Gar W. .
The frond architecture of the Lower Carboniferous seed fern Buteoxylon gordonianum.
Lower Carboniferous seed ferns, with overlapping ranges of morphology, from Oxroad Bay, Scotland have been described as Buteoxylon gordonianum, Triradiaoxylon primaevum, Tristichia ovensii, Calathopteris heterophylla and Oxroadopteris parvus. The frond consists of terete axes that dichotomize equally in a cruciate fashion to form a three dimensional organ that resembles above ground axes of Psilotum nudum. The entire frond is variable in length with the rachis ranging from 2-13 mm in diameter and up to 12cm in length before branching. The dichotomizing axes diverge at a ca. 30o angle on the distal portion of the frond. This architecture is also reflected in the fronds of the earliest seed plant, Elkinsia polymorpha and later spermatophytes such as plants belonging to the genus Pitus. The basic architecture of seed plant fronds is similar to that of the aneurophytalean progymnosperms, Proteokalon petryi and Triloboxylon ashlandicum, supporting the hypothesis of a close relationship between seed plants and the Aneurophytales. A cruciately forking system appears to be the ancestral architecture of the axes that gave rise to spermatophyte leaves.
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1 - Ohio University, Department of Environmental & Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
Presentation Type: Oral Paper
Location: Salon G - Austin Grand Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 3:15 PM