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Abstract PremiseDetecting clear tissue‐ and organ‐specific patterns of gene expression is key to understanding the genetic mechanisms that control plant development. In situ hybridization (ISH) of mRNA is one of the most precise, yet most challenging approaches to gene expression assays. Methods and ResultsDetection of histone H4 expression in reproductive tissues ofMimulus lewisii, a model angiosperm, was optimized using the RNAscope ISH assay. The optimized protocol was used to detect histone H4 expression in reproductive tissues of two gymnosperm species,Taxodium distichumandJuniperus virginiana, without further need for species‐specific optimization. Additionally, the optimized protocol was used to detect expression ofCYCLOIDEAtranscription factors inM. lewisiireproductive tissues without further optimization and with results similar to those previously reported. ConclusionsThe RNAscope assay can quickly and sensitively generate high‐quality ISH results in reproductive tissues across a breadth of plant species. 

Characterization and phylogenetic integration of fossil angiosperms with uncertain affinities is relatively limited, which may obscure the diversity of extinct higher taxa in the flowering plant tree of life. The order Cornales contains a diversity of extinct taxa with uncertain familial affinities that make it an ideal group for studying turnover in angiosperms. Here, we describe a new extinct genus of Cornales unassignable to an extant family and conduct a series of phylogenetic analyses to reconstruct relationships of fossils across the order. Two permineralized endocarps were collected from the Cedar District Formation (Campanian, 82–80 Ma) of Sucia Island, State of Washington, United States. Fossils were sectioned with the cellulose acetate peel technique and incorporated into a morphological dataset. To assess the utility of this dataset to accurately place taxa in their respective clades, we used a series of phylogenetic pseudofossilization analyses. We then conducted a total‐evidence analysis and a scaffold‐based approach to determine relationships of fossils. Based on their unique combination of characters, the fossils represent a new genus, Fenestracarpa washingtonensis gen. nov. et sp. nov. Pseudofossilization analyses indicate that our morphological dataset can be used to accurately recover taxa at the major clade to family level, generally with moderate to high support. The total‐evidence and scaffold‐based analyses recoveredFenestracarpaand other fossil genera in an entirely extinct clade within Cornales. Our findings increase the reported diversity of extinct Cornales and indicate that the order's initial radiation likely included the divergence of an extinct higher clade that endured the end‐Cretaceous Mass extinction but perished during the Cenozoic.