New fossil species and family from the insect group Ephemerida

Mickoleitia longimanus gen. et sp.n. is described from the Lower Cretaceous limestone of the Crato Formation in Brazil. It is attributed to a new family Mickoleitiidae and a new fossil insect order Coxoplectoptera within the palaeopterous Ephemerida, based on the presence of an elongated costal brace. This fossil insect exhibits a very peculiar combination of derived characters like specialized forelegs with strongly elongated, free coxae, single-clawed pretarsus, and distinctly skewed pterothorax as in dragonflies. Presence of several plesiomorphies exclude this taxon from modern Ephemeroptera (namely large hind wings with widened anal area and numerous cross veins that separate the elongate costal brace from the costal margin).
Fossil larvae described by Willmann (2007) as larval Cretereismatidae are herein attributed to Mickoleitiidae fam.n., based on the shared presence of broad hind wing buds with distinctly broadened anal area, wing bud venation similar to the adult holotype, and subchelate forelegs with elongate free coxae. These larvae (altogether 21 specimens from the same deposits from the Lower Cretaceous limestone of the Crato Formation in Brazil) are also highly autapomorphic in the structure of their abdominal gills and laterally flattened body with vertically oval section that is unique within all Ephemerida. A similar fossil larva from the Jurassic of Transbaikals was earlier described as Mesogenesia petersae and classified within modern mayflies. It is herein attributed to Mickoleitiidae fam.n. Coxoplectoptera are recognized as putative sister group of modern Ephemeroptera based on the shared presence of only 7 pairs of abdominal gills, while Permoplectoptera still have retained 9 pairs of gills.
The morphology of the larvae does not allow definite conclusions of their lifestyle, but with the limited information available we suggest that the larvae may have lived in subaquatic leaf litter, or on or in the ground of calm water habitats, or these larvae may have even been benthic organisms that were hiding with their thorax and abdomen in burrows, with antennae and forelegs stretched out into the water to catch small prey.
The phylogenetic reclassification of the mayfly stem group by Willmann (2007) is critically discussed and modified.

Staniczek A.H., Bechly G. and Godunko R.J. (2011) Coxoplectoptera, a new fossil order of Palaeoptera (Arthropoda: Insecta), with comments on the phylogeny of the stem group of mayflies (Ephemeroptera). Insect Systematics & Evolution 42: 101–138.