A new Pennsylvanian pollen organ from northwestern Missouri with affinities in the Lyginopteridales

• Identification of a new type of complex Lyginopterid fertile frond from the Upper Pennsylvanian
• Additional information on the diversity and architecture of pteridosperm pollen organs
• Expanding concepts on the evolution of seed fern diversity

An Upper Pennsylvanian locality (Bonner Springs Shale, Kansas City Group, Middle Missourian) in western Missouri contains a diverse and well-preserved fossil assemblage of both plants and arthropods. The plants are preserved as impressions and compressions, and include fertile and vegetative remains of various sphenopsids, lycopsids, ferns, seed ferns, cordaites and conifers. The discovery of a branching system with lyginopterid pollen organs, Parkvillia northcuttii, demonstrates that this group of Paleozoic seed ferns was more diverse and complex than previously known. The fertile structure is characterized by multiple levels of branching with the penultimate branches alternately arranged; ultimate rachises bearing 6–10 alternately arranged, slightly flattened, shield-shaped synangia. Synangia are approximately 5 mm in diameter and each consists of a cap with up to 18 sporangia attached to the abaxial surface. The radial and trilete pollen is ornamented by grana and coni. Also in the assemblage are small radially symmetrical ovules and sphenopterid foliage, suggesting that this assemblage contains multiple lyginopterid taxa. The orientation of sporangia and features of the synangia, together with the three-dimensional branching, indicate a morphological pattern that has not been recognized within the Lyginopteridaceae.