Friday, August 25, 2017

Mapping the wing transition
Check out Figures 16.3 and 16.4 Pages 455 - 456.

This shows that feathers in basal Paraves are not exaptations.
Flight feathers are not variants of thermal insulating material, but structures that have evolved over a long period, enabling the span and aspect ratio of the wings to be progressively increased as they developed.
The structure of a flight feather is dedicated wholly to withstanding the bending and torsional moments caused by aerodynamic forces, and delivering these moments through the follicle to the wing skeleton.
The main features of the hypothetical patagial glider can still be seen, albeit much modified, in the modern bird wing, which has a patagium that joins the side of the body to the elbow joint, and continues as a narrow strip along the posterior side of the ulna, and of the reduced hand skeleton.

Dino to bird stories:
PRH, FS1, FS2, HOH, Thumbs Down, LSH.

Very recently Xu and Mackem (2013) introduced a digit reduction scheme called the
lateral shift hypothesis (LSH). Like the TDH, it follows the II, III, IV
identication of tetanuran digits, and values the positional criteria over the compositional ones. Unlike the TDH, however, it argues
that a (partial) homeotic anterior shift took place and that digit IV
was completely reevolved, following in both points the FSH

Also see:

1 comment:

  1. Persaonal communication:
    You have "initial arm flapping capability" as a characteristic of Pennaraptora.
    And "initial aerial locomotion" as a characteristic for Paraves (which is within Pennaraptora).
    So the basal Paraves were flapping their arms in aerial locomotion. In other words power flying.
    His response:
    yes, my feeling is that basal paravians probably get into air by a combination of gliding and flapping, with the former as the major compenont [sic]


    Dr. XU, Xing
    Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences,
    Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences
    142 Xiwai Street
    Beijing, 100044
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