Bird Phylogeny: Neoaves

Part of a series of phylogenetic diagrams on crown-bird phylogeny. For the rest, see this folder. I suppose the first thing I should address is why I haven't drawn icons for all of the lineages shown. The reason is straightforward: the icons were drawn for a different project, and I've simply co-opted them for use here.

I've been fairly conservative in highlighting the known fossil record of bird groups, for most part only including time ranges for which we have reasonably high confidence. Many fragmentary fossil bird specimens have been historically assigned to modern groups without rigorous analysis; I have generally excluded these from the depicted time ranges. Material that has not yet been formally described in scientific literature is also excluded for now. That being said, I've still included some tentative records (as indicated by the thick dotted lines) where I've deemed appropriate.

Depicted divergence times are bare minima necessary to accommodate the depicted phylogeny while still allowing it to be readable, not based directly on rigorous estimates of divergence time. Thus, actual divergence dates could have potentially been older (likely in most cases) or younger (possibly in a few cases) than shown.

Few crown-bird clades have been given formal phylogenetic definitions; as such, I've largely applied them in a loose, flexible manner here. With some exceptions, I've used "order"-level clades (ending in "-iformes") that have extant representatives as total groups, including their living representatives as well as any extinct forms more closely related to them than their closest modern relatives are. "Family"-level clades (ending in "-idae") with extant representatives here should be interpreted as "anything more closely related to the modern group than to its next closest relative shown on the diagram".

Neoaves includes 95% of all modern bird species. It is probably fair to say that the interrelationships between neoavian groups remain the biggest unresolved question in crown-bird phylogenetics. As such, I have presented their relationships here as a polytomy. Nonetheless, most recent molecular studies consistently recover several major clades: Mirandornithes, Columbimorphae, Otidimorphae, Strisores, and a few others that I'll save for a different diagram.

Mirandornithes is the group that unites the diving Podicipediformes (grebes) and the long-legged, filter-feeding Phoenicopteriformes (flamingos). This group was one of the biggest surprises to come out of molecular studies of bird phylogeny in the early 2000s, but is now well accepted. The Oligocene–Pleistocene Palaelodidae exhibited many features that are morphologically intermediate between those of grebes and flamingos, having moderately long legs with greater specializations for swimming than modern flamingos, whereas the Eocene Juncitarsus appears to have been a stem-mirandornithean that evolved a specialized wading lifestyle independent of flamingos.

Columbimorphae includes Columbiformes (pigeons), Pterocliformes (sandgrouse), and Mesitornithiformes (mesites). Similarities between pigeons and sandgrouse have long been noted, but their affinities to the enigmatic mesites were a bit more surprising. The columbimorph fossil record is extremely poor, with the mesites in particular having no identified fossil record so far.

Otidimorphae includes Cuculiformes (cuckoos), Otidiformes (bustards), and Musophagiformes (turacos). Out of the major groups contributing to the neoavian polytomy here, this one is probably the most poorly supported, as some recent studies have found results in which either cuckoos or turacos don't form a clade with the other two. Otidimorphs also have a poor fossil record, though the unusual Eocene bird Foro has been identified as a stem-turaco. Foro had fairly long hindlimbs, suggesting that it spent more time on the ground than modern turacos (which are tree-dwelling fruit-eaters). This lends support to the hypothesis that neoavians were ancestrally terrestrial and evolved into arboreal niches several times independently, likely during the early Cenozoic. An enigmatic group of long-winged, probably terrestrial Eocene birds, the Perplexicervicidae (not shown in the diagram above), exhibits some anatomical similarities to bustards. Perplexicervicids had strange tubercles on their neck vertebrae, which are hypothesized to have functioned as armor protecting their necks from predators.

For Strisores, go here.

For the "other Neoaves", go here.

To return to the root of Neognathae, go here.