F.M. , Hueber .
Association of Prototaxites with the fungi has met with strong resistance based on the premise that just about anything dealing with the genus is speculative, including the hypothesis that it was a fungus. On first discovery, Prototaxites was described as fragmentary logs of fossilized gymnospermous trees. This continues to influence the interpretation of the habit of the genus as arborescent. It was the largest organism that accompanied herbaceous plants in the early colonization of terrestrial environments and persisted into the very Late Devonian. Apparent disappearance from the fossil record suggests its extinction at that time. It is worldwide in occurrence, from charcoalified fragments to immense silicified “logs”. Stratigraphy and preservation are the basis for the description and speculative classification of the genus. Critiques of the decision emphasize deficiencies in factual evidence which may be addressed here. The nature of the outer surface is unknown. The “trunks" were tapered; apices and basal structures were lost through fragmentation, therefore the morphology remains unknown. The habitat of the genus has perhaps been the most controversial. An aqueous habitat has been suspected on the basis of regular occurrence of specimens in continental, fluviatile deposits or very rarely in marine sediments associated with nearly the entire spectrum of land plants known in the Devonian. Association with small herbaceous species may suggest a marshland habitat. However, association with larger species suggests the “upland” habitat. "Growth rings” suggest perennial growth based on the number of concentric additions to the circumference of the “trunk”; one has 150 “increments”. Heterotrophic nutrition was deduced from the lack of evidence of an associated symbiont. Evidence of the occurrence and morphology of sporangia, though suggested, remains unconfirmed. Spore dispersal by winds or flushing of the surface by rains may be suggested by the morphology of the organism. If Prototaxites is a fungus that exceeds imagination, then, surely, is the illusion that it represents huge enrolled mats of liverworts even more excessive?
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1 - 529 School Lane, Rehoboth Beach, Deleware, 19971, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 555B/Convention Center
Date: Monday, August 2nd, 2010
Time: 2:00 PM