Sixty-five-million-year-old flowers bearing pollen of the extinct triprojectate complex—a Cretaceous-Tertiary boundary survivor

Abstract

Fossil flowers bearing pollen of Kurtzipites trispissatus Anderson have been recovered from the Paleocene Ravenscrag Formation, southwestern Saskatchewan, Canada. The flowers occur in clays about 7.0 m above the coal-zone associated with the Cretaceous-Tertiary boundary and represent a lineage that survived the Cretaceous-Tertiary boundary extinction event. Flowers are globular in shape, about 6.0 mm in diameter, and without an obvious perianth. All flowers are staminate and unisexual with numerous stamens inserted on a disk-shaped receptable. The stamens are long, narrow and basifixed; the filaments are short, the anthers are long ans slender and filled with K. trispissatus pollen. Pollen grains are tricolporate, about 20 μm in diameter, the exine tectate and scabrate, the endexine apparently restricted to the apertural region. This putatively anemophilous palynomorph is one of the few members of the mainly zoophilous triprojectate complex to survive the Cretaceous-Tertiary boundary event. Flower morphology supports the anemophilous reproductive strategy previously inferred for the plants producing Kurtzipites, suggesting that an anemophilous habit may have had selective advantage in the triprojectate complex, and perhaps other groups, at the Cretaceous-Tertiary boundary. The fossil flowers, hereassigned to Kurtziflora antherosa gen. et sp. nov., belong to a taxon that apparently became extinct during the Paleocene leaving no modern relatives.