Hanskerpiagen. nov. and phylogenetic relationships among the most ancient conifers (Voltziales)

Abstract

AbstractA new fossilized walchian (Voltziales) conifer plant from the Late Pennsylvanian Hamilton Quarry of Kansas, U.S.A. combines morphological characters of the morphogenusWalchiaand the fossil plant genusOtovicia, with cuticular characters like those of the fossil plant genusErnestiodendron, and seed cone morphology like that of the fossil plant genusEmporia. Internal anatomical characters are basically similar to the other walchian genera for which such features are known, but some are taxonomically informative. Numerical cladistic analysis reveals that this novel combination of characters defines a new fossil plant genus and species of walchian conifersHanskerpia hamiltonensis. This analysis provides a test of hypotheses for relationships among walchian and other ancient conifers. Results of this analysis support some previously proposed relationships among the most primitive conifers and other Paleozoic coniferophytes. However, the analysis also calls to question the validity of all previously proposed familial circumscriptions for walchian conifers, and highlights the perplexing systematic challenges posed by the most ancient fossil conifers. The unexpected species richness of voltzialean conifers is interpreted as having resulted from the evolutionary ecology of unstable environments.