Sanders, Heather , Rothwell, Gar W. .
Reconstructing the frond of Buteoxylon gordonianum to understand the early evolution of seed plant fronds.
NEW specimens of Buteoxylon gordonianum from Oxroad Bay provide new insights into the ancestral morphology of spermatophyte fronds and illuminate the pattern of leaf evolution in seed plants. Leaves occur in a helical phyllotaxy, and shoots display regions of dense frond production and regions of no frond production. The base of the rachis displays a T-shaped vascular strand and branches equally and unequally. The distal portion of the frond consists of terete axes that dichotomize equally in a cruciate fashion to form a three dimensional organ. A cruciately forking system appears to be the ancestral architecture of the axes that gave rise to spermatophyte leaves. The morphological transition along the frond reveals a developmental transition between bilateral symmetry at the base and radial symmetry in the distal axes. Interpretations of such morphological variation increases understanding of the development of the most ancestral leaves. Comparisons with more derived leaf morphologies provide a framework for inferring the evolution of developmental patterning.[c.e.:srb]
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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:Papers for Sections
Date: Monday, July 31st, 2006
Time: 1:00 PM