Tarwinia australis (Siphonaptera: Tarwiniidae) from the Lower Cretaceous Koonwarra fossil bed: Morphological revision and analysis of its evolutionary relationship

Tarwinia australis, from the Lower Cretaceous Koonwarra fossil bed, Victoria, South Australia, is the first described Mesozoic flea. It was suggested to have a unique morphology that differs from all other known Mesozoic giant fleas by having a laterally-flattened body and peculiar tibial ctenidia. It represents an extinct family, Tarwiniidae, among the three major Mesozoic monster flea groups. Re-examination of the holotype reveals that this Southern Hemisphere ferocious bloodsucker bears different morphological details from those described previously. Tarwinia australis definitely bears elongate siphonate mouthparts and a relatively compact antenna with 15 flagellomeres. Its legs are slender, elongate, and armed with pseudocombs-like ctenidia on all tibiae. The abdomen is covered with posteriorly-directed setal rows, and with a posteriorly-located pygidium and exposed male genitalia. It differs from pseudopulicids mainly on the basis of characters of tibial ctenidia that probably indicate a very different host association.