Mapes, Gene , Rothwell, Gar W. , Stockey, Ruth A. , Hilton, Jason .
The origin of modern conifer families; evidence from anatomically preserved Jurassic seed cones.
An ongoing reinvestigation of the famous Upper Jurassic Hugh Miller plant fossils from northeastern Scotland has revealed the presence of three species of conifer seed cones. Two of these, Conites juddii and a new genus, appear to represent basal taxodiaceous Cupressaceae, but the third has characters that are reminiscent of Sciadopityaceae and Pinaceae. The last of these fossil cones is more or less cylindrical, nearly 8 cm long and 3.3 cm wide, consisting of an axis ca. 1 cm wide from which bract/scale complexes diverge in a helical arrangement. Bracts and scales extend from the axis at an angle of 40-50o, and separate from each other at the level where two winged seeds are attached to the adaxial surface of the ovuliferous scale. Bracts and scales are each about 2.8 cm long, becoming wider and thinner distally. Ovuliferous scales become slightly wider (10 mm) than bracts (8 mm) before both terminate in rounded apices that are papery thin. Vascular tissue is weakly developed, with little wood in the axis. The pattern of trace divergence is unclear, but there is at least one small bundle in the bract and one in the ovuliferous scale. Seeds have prominent sclerotesta and a single lateral wing comprising parenchymatous scale tissue. There is no interseminal ridge. Several relatively small resin canals are present in the cortex of the cone axis, continuing distally as a single row in each of the bract and scale. Like the genus Pararaucaria, another morphotype of permineralized Jurassic conifer seed cones, this cone does not clearly conform to a family with living species. Rather, it displays a novel combination of characters of the type that make fossils vital for resolving deep nodes in the seed plant tree.
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1 - Ohio University, Department of Environmental & Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
2 - University of Alberta, Department of Biological Sciences, Biological Sciences Centre, Cw 405, Edmonton, Alberta, T6G 2E9, Canada
3 - University of Birmingham, School of Geography, Earth and Environmental Sciences, G5 Aston Webb Building, Edgbaston, Birmingham, B152TT, United Kingdom
Conifer seed cone
seed plant phylogeny.
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 9:15 AM