What was the nature and role of Normapolles angiosperms? A case study from the earliest Cenozoic of Eastern Europe

The Normapolles were an extinct group of early angiosperms which dominated much of the northern hemisphere during the Cretaceous. Although a product of early angiosperm radiation, they persisted beyond the K–Pg boundary, representing a significant proportion of the earliest Palaeocene palynological assemblage recovered from the Boltysh meteorite crater in Ukraine. While it is likely that many forms represent an ancestral lineage to modern day Fagales, particularly the walnut family (Juglandaceae), clear trends in certain species indicate that separate ecological preferences relating to temperature existed amongst them. In the Boltysh record the most abundant taxa occur preferentially within the early Danian hyperthermal, indicating a warm environment. Allied to their co-association with pollen of modern affinity, this suggests that they were scrubby, sclerophyllous plants akin to those which thrive in winter-wet ecosystems today. During and subsequent to the recovery from the early Danian hyperthermal these species decline and are replaced by different types. The Boltysh record demonstrates that in the very earliest Cenozoic, the Normapolles were a considerably more resilient and complex group than they are often portrayed and potentially important palaeoecological indicators.