|
Ediacarans |
1 Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario, Canada K7L 3N6 (e-mail: laflamme{at}geoladm.geol.queensu.ca)
2 1-249 Macdonnell Street, Kingston, Ontario K7L 4C4
3 53 Sterling Crescent, St. John's Newfoundland A1A 4J9
The Ediacaran frond Charnia, known mainly from fragmentary leaf-like fronds from around the world, is represented by completely preserved specimens with holdfasts in the Mistaken Point biota of Newfoundland. Previous reconstructions of Charnia from two-dimensional impressions were significantly oversimplified, resulting in three-dimensional reconstructions which highlighted a sheet-like morphology. Overlapping relationships and internal structures are rarely (if ever) preserved, and only through detailed photography together with both landmark and traditional morphometric analyses of numerous complete Charnia specimens can the preservational biases be removed. Charnia is reinterpreted here as having a series of individual overlapping primary branches attached to an internal central stalk, and with individual branches constrained by an internal, organic skeleton and/or attachments between adjacent branches. Three species, C. masoniFord 1958, C. wardi Narbonne & Gehling 2003, and C. antecedens sp. nov. can be distinguished on the basis of length/width ratios and the degree of attachment of adjacent branches. Morphological, taphonomical, and ecological studies at Mistaken Point imply that Charnia was a sessile, epibenthic frond that fed from suspension in this deep-water volcaniclastic setting. Evolution of more rigorous connections between the primary branches allowed Charnia to migrate into more turbulent, shallower-water habitats by the late Ediacaran.
