Voltzian Conifers of the South Ash Pasture Flora (Guadalupian, Texas): Johniphyllum multinerve gen. et sp. nov., Pseudovoltzia sapflorensis sp. nov., and Wantus acaulis gen. et sp. nov.

Premise of research. The earliest occurrences of several characteristic late Permian and early Mesozoic plant groups have been described from Euramerican floras of Pennsylvanian and early Permian age. The basinal deposits in which such early representatives occur are generally associated with short-lived drier conditions or with a gradual shift toward a drier climate. In this article, we provide formal descriptions of voltzian conifer fossils (voltzian Voltziales) from a middle Permian flora based on the macromorphological characteristics of ovuliferous cones and isolated dwarf shoots and the epidermal characteristics of broad, parallel-veined leaves. Methodology. The fossils were examined using light and scanning electron microscopy. Pivotal results. The discovery of the three new conifer taxa described here is important for four reasons. First, Pseudovoltzia sapflorensis (Majonicaceae) cones are the oldest-known members of this genus in western Euramerica. Second, the morphology of the ovuliferous dwarf shoot Wantus acaulis is unlike any of the other late Paleozoic or early Mesozoic voltzian conifer taxa and thus represents a new Paleozoic voltzian conifer lineage. Third, the broad, parallel-veined leaves of Johniphyllum multinerve have a macromorphology that is predominantly known from Mesozoic voltzian conifer lineages, but their epidermal features are comparable with those of late Paleozoic conifer taxa. Fourth, the swollen leaf bases of J. multinerve suggest that the leaves were actively abscised, a functional trait that is unusual in Paleozoic conifers. Conclusions. Together, these three new taxa increase both the taxonomic diversity and the morphological disparity among both reproductive and vegetative structures in late Paleozoic voltzian conifers and once more illustrate that structural evolution, innovation, and diversification in this conifer group took place in more extrabasinal environments, where chances of preservation are unlikely. The migration of these conifers to the basinal lowlands, and thus into the window of preservation, seems to have been facilitated by the increasingly drier climate.