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

Abstract

A new fossilized walchian (Voltziales) conifer plant from the Late Pennsylvanian Hamilton Quarry of Kansas, U.S.A. combines morphological characters of the morphogenus Walchia and the fossil plant genus Otovicia, with cuticular characters like those of the fossil plant genus Ernestiodendron, and seed cone morphology like that of the fossil plant genus Emporia. 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 conifers Hanskerpia 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.

Wetland-Dryland Vegetational Dynamics in the Pennsylvanian Ice Age Tropics

“…Studies of modern wind-pollinated plants subject to isolation in fragmented landscapes suggest high levels of gene flow created by pollen dispersal. Documentation of this pattern in conifers (Jørgensen et al 2002;Liepelt et al 2002;O'Connell et al 2007) may have the most applicability to the late Paleozoic, where the two dominant groups in seasonally dry habitats, cordaitaleans and conifers, are both coniferophytes in a broad evolutionary sense (Hernandez-Castillo et al 2001b;Rothwell et al 2005;Looy 2007). High gene flow might be expected to have kept speciation rates low in these groups, regardless of fluctuating climates.…”

Organic geochemistry of Upper Carboniferous bituminous coals and clastic sediments from the Lublin Coal Basin

“…Schultze and Michaelis 1990;Philp 1994;Fabiańska et al 2003;Rothwell et al 2005). The presence of compounds such as retene, cadalene or isohexylnaphthalenes can also suggest a genesis from the ancestors of conifers.…”

Stockeystrobusgen. nov. (Cupressaceae), and the evolutionary diversification of sequoioid conifer seed cones

“…Voltziacean seed cones typically are long narrow structures with a lax arrangement of bract-scale complexes, distinctive evidence of vegetative scales, one to three seeds per fertile short shoot or ovuliferous scale complex, and are much more ancient than the new cone described here (e.g., Florin 1938Florin -45, 1951Mapes and Rothwell 1984;1987;Clement-Westerhof 1988;Nishida et al 1991;Hernandez-Castillo et al 2001;Rothwell et al 2005;Looy 2007;Leslie 2011 Buchholz 1939;Sporne 1965). Among such species, only cones of Cupressaceae subfamily Sequoioideae and a few Cretaceous cupressaceous conifers of uncertain affinities (e.g., Cunninghamites lignitum [Sternberg] Kvaček) consist of cones with numerous helically arranged complexes that bear several inverted seeds adaxially attached to the underside of a peltate head (Hirmer 1936;Schulz and Stützel 2007).…”

“…Compact seed cones with large numbers of helically arranged bract-scale complexes are produced by conifers of the Voltziaceae, Cheirolepidiaceae, Pinaceae, Araucariaceae, Sciadopityaceae, Cupressaceae, and Podocarpaceae (i.e., Saxegothaea), but many taxa have only one or two seeds per bract-scale complex (i.e., species of Cheirolepidiaceae, Pinaceae, and Saxegothaea; Sporne 1965;Basinger 1984;Rothwell et al 2005;Escapa et al 2012;Leslie et al 2012), whereas Stockeystrobus has six to eight seeds. Voltziacean seed cones typically are long narrow structures with a lax arrangement of bract-scale complexes, distinctive evidence of vegetative scales, one to three seeds per fertile short shoot or ovuliferous scale complex, and are much more ancient than the new cone described here (e.g., Florin 1938Florin -45, 1951Mapes and Rothwell 1984;1987;Clement-Westerhof 1988;Nishida et al 1991;Hernandez-Castillo et al 2001;Rothwell et al 2005;Looy 2007;Leslie 2011 Buchholz 1939;Sporne 1965).…”

“…Krassilovia has five extremely distinctive spines at the margin of the peltate scale head that are reminiscent of those on the ovuliferous scale of Cryptomeria japonica and many Permian and Triassic species of Voltziaceae (Clement-Westerhof 1988;Rothwell et al 2005), but that interlock with adjacent scales in a unique fashion not known from any other fossil or living conifer (Herrera et al 2015). Moreover, seed cones of Krassilovia disaggregate at maturity to shed individual bract-scale complexes (Herrera et al 2015), as do some species of some taxodiaceous Cupressaceae (e.g., Taxodium disticum [L.] Rich.).…”