The wings before the bird: an evaluation of flapping-based locomotory hypotheses in bird antecedents
- Published
- Accepted
- Subject Areas
- Evolutionary Studies, Paleontology
- Keywords
- flight, WAIR, Maniraptora, Macroevolution, Theropoda, flap running, flight stroke
- Copyright
- © 2016 Dececchi et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ PrePrints) and either DOI or URL of the article must be cited.
- Cite this article
- 2016. The wings before the bird: an evaluation of flapping-based locomotory hypotheses in bird antecedents. PeerJ PrePrints 4:e1676v1 https://doi.org/10.7287/peerj.preprints.1676v1
Abstract
Background. Powered flight is implicated as a major driver for the success of birds. Here we examine the effectiveness of three hypothesized pathways for the evolution of the flight stroke, the forelimb motion that powers aerial locomotion, in a terrestrial setting across a range of stem and basal avians: flap running, Wing Assisted Incline Running (WAIR), and wing-assisted leaping. Methods. Using biomechanical mathematical models based on known aerodynamic principals and in vivo experiments and ground trothed using extant avians we seek to test if an incipient flight stroke may have contributed sufficient force to permit flap running, WAIR, or leaping takeoff along the phylogenetic lineage from Coelurosauria to birds. Results. None of these behaviours were found to meet the biomechancial threshold requirements before Paraves. Neither was there a continuous trend of refinement for any of these biomechanical performances across phylogeny nor a signal of universal applicability near the origin of birds. None of these flap-based locomotory models appear to have been a major influence on pre-flight character acquisition such as pennaceous feathers, suggesting non-locomotory behaviours, and less stringent locomotory behaviours such as balancing and braking, played a role in the evolution of the maniraptoran wing and nascent flight stroke. We find no support for widespread prevalence of WAIR in non-avian theropods, but can’t reject its presence in large winged, small-bodied taxa like Microraptor and Archaeopteryx. Discussion. Using our first principles approach we find that “near flight” locomotor behaviors are most sensitive to wing area, and that non-locomotory related selection regimes likely expanded wing area well before WAIR and other such behaviors were possible in derived avians. These results suggest that investigations of the drivers for wing expansion and feather elongation in theropods need not be intrinsically linked to locomotory adaptations, and this separation is critical for our understanding of the origin of powered flight and avian evolution.
Author Comment
This is a submission to PeerJ for review.
Supplemental Information
Theropod mapping
Data S1- Mapping of W.A.I.R. values across theropod and early avian phylogeny. Topology based on Dececchi and Larsson 2013.
Extant avian nexus
Nexus file for the Modified flapping rate regression. Nodal dates form Jetz et al. 2012. Taxa and measurements from Askew et al. 2001 and Jackson 2009
Calculations
Spreadsheet for WAIR and leaping height calculations.
Equation description and justifications
Explanation for equations used.
Measurement data
Measurement data for non-avian and avian theropods used in this analysis.
Humerus percentage of forelimb
Humerus percentage of forelimb calculation compared to bodysize in avian and non-avian theropods.
Body width estimation
Furcula width for Deinonychosaurians and early avians used to calculate body width estimate.
WAIR calculation using ALL flapping rate
WAIR values using flap rate from regression from Jackson 2009 all taxa.
WAIR calculation using GF flapping rate
WAIR values using flap rate from regression of ground foraging birds from Jackson 2009.
WAIR calculation using MOD flapping rate
WAIR values using flap rate from regression based on modified dataset adding galliform birds form Askew et al. 2001 and Jackson 2009.
Flap running
Increased in velocity after 10 iterations for flap running analysis.
modelling passerine bird take off
Take off calculations for passerine birds from Jackson 2009.
Vertical jumping
Height gain due to flap based thrust for non-avian theropods and Archaeopteryx.
HOrixontal jumping
Horizontal distance gain due to flap based thrust for non-avian theropods and Archaeopteryx.
Leaping take off values using ALL
Body weight support values for ground based take off with a leaping speeds of 3.8, 4.1 and 5.1 m/s. using flap rate from regression from Jackson 2009 all taxa.
Leaping take off values using GF
Body weight support values for ground based take off with a leaping speeds of 3.8, 4.1 and 5.1 m/s. using flap rate from regression of ground foraging birds from Jackson 2009.
Leaping take off values using MOD
Body weight support values for ground based take off with a leaping speeds of 3.8, 4.1 and 5.1 m/s. using flap rate from regression based on modified dataset adding galliform birds form Askew et al. 2001 and Jackson 2009.
WAIR and leaping takeoff based on previous models of Microraptor, Archaeopteryx, Caudipteryx and Protoarchaeopteryx
WAIR and leaping takeoff values for models taken from the literature. Data for Archaeopteryx from Yalden 1984, Microraptor specimens from: Chatterjee and Templin 2007, Alexander et al. 2010 and Dyke et al. 2013. Caudipteryx and Protoarchaeopteryx from Nudds and Dyke 2009.