The spectacularly preserved fruit was found in 2018 and measures 6-1/2" round. Here you can see both the part and counterpart in fine detail. There is another spectacular specimen from Fossil Butte National Monument also collected last year. Nelumbo is a genus of aquatic plants in the order Proteales found living in freshwater ponds. You'll recognize them as the Lotus emblem of India, Vietnam and many wellness centres.
Interestingly, these lovelies can thermoregulate, producing heat. Nelumbo use the alternative oxidase pathway (AOX) to exchange electrons. Instead of using the typical cytochrome complex pathway most plants use to power mitochondria, they instead use their cyanide-resistant alternative. This is perhaps to generate a wee bit more scent in their blooms and attract more pollinators.
The use of this thermogenic feature would have also allowed thermo-sensitive pollinators to seek out the plants at night and possibly use the cover of darkness to linger and mate. So they functioned a bit little like a romantic meeting spot for lovers and like the scent diffuser in your home. This lovely has an old lineage with fossil species in Eurasia and North America going back to the Cretaceous and represented in the Paleogene and Neogene.
Photo credit: Doug Miller of Green River Stone