A new cockroach (Blattodea, Rhipidoblattinidae) from the Toarcian (Lower Jurassic) of Alderton Hill, Gloucestershire, UK, and the earliest likely occurrence of aposematic colouration in cockroaches

We describe the seventh valid species of cockroach, Alderblattina simmsi gen. et sp. nov., from insect-rich strata recording the Toarcian Oceanic Anoxic Event (T-OAE). The T-OAE represents a period of extreme global warming and environmental change that drove palaeoecological pressures and evolutionary changes in marine and terrestrial ecosystems. Here, for the first time, we present evidence that this event may also be the driver for the evolution of aposematic colouration, a predator deterrent, in cockroaches. The specimen, an isolated compressed tegmen, was collected at Alderton Hill, Gloucestershire, UK, and is assigned to a new genus and species, based on the following unique combination of characteristics: small forewing; 15 branches of R and 11 branches of M + CuA; strong cross-vein between R and M; intercalaries; and two well-defined subspherical maculae (spots) and colouration at the wing tip. Alderblattina simmsi is assigned to the family Rhipidoblattinidae Rohdendorf, primarily based on its small size and the presence of branched anal veins in the clavus. The colouration present on A. simmsi represents the first recorded likely occurrence of aposematism in cockroaches, and provides evidence for the evolution of colour patterning in Blattodea.