was defined by Illiger 1811 as Chiroptera (bats) + Dermoptera (colugos). Wikipedia authors consider this clade obsolete and polphyletic. The large reptile tree (LRT, 1233 taxa) nests these two taxa together in a monophyletic clade that also includes the pangolins and their closest ancestors (e.g. Zhangheotherium). We looked at their traditionally overlooked relationships a few days earlier here.
Szalay and Lucas 1996 reported, “We find support for the Volitantia in the nature of the shared derived similarities (and phyletically significant differences as well) in the elbow complex, and in Leche’s (1886) suggestion of the synapomorphus and unique presence (in non aquatic mammals) of an interdigital membrane of the hand in bats and colugos. They studied Chriacus and Mixodectes (not yet tested), not pangolins.
Like another clade traditionally considered obsolete,
Enaliosauria, that was resurrected by the LRT, Volitantia is likewise resurrected as a monophyletic clade, but it now includes the Pholidota (pangolins) according to LRT results.
The putative clade ‘Ferae‘ (pangolins + carnivorans) is not supported by the LRT because pangolins nest within the Volitantia.
As long-time readers know,
many traditional relationships between placental clades are not supported by the LRT, which continues to document a gradual accumulation of derived traits at every node in nearly full resolution for a wide gamut of tetrapod taxa.
Many arboreal mammals were experimenting with gliding
(e.g. Volaticotherium and Maiopatagaium), but only one clade, bats, experimented with flapping. This was, perhaps not coincidentally, during the Middle to Late Jurassic (Oxordian, 160 mya). Remember, these membranes were all extensions of the infant nursery found in colugos and other volatantians, not far from the basalmost placental, Monodelphis. It is possible that all basalmost mammals had these membrane extensions and most of their ancestors lost them.
Illiger C 1811. Prodromus systematis mammalium et nivium additis terminis zoograhicis utriudque classis. Berlin: C. Salfeld.
Szalay F and Lucas SG 1996. The postcranial morphology of Paleocene Chriacus and Mixodectes and the phylogenetic relationships of archontan mammals. Bulletin of the New Mexico Museum of Natural History and Science 7: 47 pp.