Independent origins of powered flight in paravian dinosaurs?

• Published in: Current biology 2021-04, Vol.31 (8), p.R370-R372
• Main Authors: Serrano, Francisco J., Chiappe, Luis M.
• Format: Article
• Language: English
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2021.03.058

Feathered dinosaurs discovered during the last decades have illuminated the transition from land to air in these animals, underscoring a significant degree of experimentation in wing-assisted locomotion around the origin of birds. Such evolutionary experimentation led to lineages achieving either wing-assisted running, four-winged gliding, or membrane-winged gliding. Birds are widely accepted as the only dinosaur lineage that achieved powered flight, a key innovation for their evolutionary success. However, in a recent paper in Current Biology, Pei and colleagues1 disputed this view. They concluded that three other lineages of paravian dinosaurs (those more closely related to birds than to oviraptorosaurs) — Unenlagiinae, Microraptorinae and Anchiornithinae — could have evolved powered flight independently. While we praise the detailed phylogenetic framework of Pei and colleagues1 and welcome a new attempt to understand the onset of flight in dinosaurs, we here expose a set of arguments that significantly weaken their evidence supporting a multiple origin of powered flight. Specifically, we maintain that the two proxies used by Pei and colleagues1 to assess powered flight potential in non-avian paravians — wing loading and specific lift — fail to discriminate between powered flight (thrust generated by flapping) and passive flight (gliding). Francisco Serrano and Luis Chiappe critique a recent study in Current Biology by Pei and colleagues on independent origins of flight in paravians.