Paleobotanical data from fossil charcoal; an actualistic study of seed plant reproductive structures

• Published in: Palaios Vol. 10; no. 5; pp. 465 - 477
• Main Author: Lupia, Richard
• Format: Journal Article
• Language: English
• Published: Society of Economic Paleontologists and Mineralogists 01-10-1995; SEPM
• Subjects: accuracy; Angiospermae; Angiosperms; Carpels; Charcoal; coalification; experimental studies; Flowers; Fossils; fusain; Gymnospermae; interpretation; lithotypes; living taxa; macerals; modern analogs; Paleobotany; Petals; Plantae; Plants; preservation; Research Letters; Sample size; seeds; SEM data; Spermatophyta; Stamens; statistical analysis
• ISSN: 0883-1351; 1938-5323
• DOI: 10.2307/3515048

The exquisite preservation of fossil plant material achieved by charcoalification enables exceptionally detailed analyses. However, preservation by charcoal is not without bias. This study explores the bias introduced by non-uniform size change during charcoalification of the reproductive organs of seed plants. Carpels, stamens and petals from seven species of angiosperms, and ovulate structures from two species of gymnosperms, were experimentally charcoalified at 325-350° C for two hours and change in length, width or diameter recorded. Statistical tests using percent size reduction show that carpels underwent, with one exception, significantly less change relative to other structures of the same species (α = 0.05). Overall mean shrinkage varies between 14-32% for carpels, 19-41% for stamens, and 24-47% for petals. The ovulate structures of gymnosperms fall within the range of angiosperm carpels. Examination of observed change as a function of duration of charcoalification showed increasing shrinkage with time and no plateau after six hours. The results of the test for effect of flower-maturity could not rule out such an effect as contributing to variation in the results. Qualitative observations indicate that additional biases, including site-specific damage, also act on these structures prior to fossilization. Because non-uniform shrinkage of reproductive structures can be documented, the absolute sizes of charcoalified reproductive organs provide potentially misleading information for reconstructions or taxonomic studies, and it is unlikely that rescaling factors could be usefully applied. However, relative sizes of fossilized organs, in terms of one organ being larger than another, appear to record information more faithfully.