Floristic survey and paleoecology of the Fayetteville Formation (Upper Mississippian) of northwestern Arkansas, United States.

摘要

Fossil plants have been known from the Fayetteville Formation since at least 1937, and since that time numerous individual taxa have been described, but no synopsis of the assemblage has been compiled. This report summarizes those previous reports and adds new data to produce a comprehensive floristic survey of this important fossil assemblage. The flora consists of 41 morphospecies: 19 permineralized species and 22 compression species that represent at least 15 whole plants. Lycopsid remains are the most numerous and pteridosperms are the most diverse. Sphenopsids are common but mono-generic, and ferns are rare. Lyginopteris royalii, Trivena arkansana, Megaloxylon wheelerae, Quaestora amplecta, Rhynchosperma quinnii, and Telangiopsis arkansanum are known only from these strata. The occurrences of Rhetinangium and Megaloxylon are the first reports of these genera in North America; the occurrence of Medullosa is the oldest unequivocal evidence for this genus anywhere in the world, and Rhetinangium the youngest.; Perhaps most importantly, the identification of two plant communities, nested within the landscape-level ecosystem provides a snapshot of the distribution of morphological and taxonomic diversity in the Euramerican floral province at Upper Mississippian time. The occurrence of recognizable spacial sub-units nested within a larger ecosystem unit has not been previously recognized in Mississippian terrestrial fossil assemblages and sheds new light on the evolution of terrestrial ecosystem structure.