Re: Theropod pre-avian aerial behavior

On 10/28/24 12:18 PM, Pandora wrote:

Op 27-10-2024 om 14:32 schreef John Harshman:
 

On 10/27/24 1:37 AM, Pandora wrote:

Theropod trackways as indirect evidence of pre-avian aerial behavior
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Open access:
https://www.pnas.org/doi/10.1073/pnas.2413810121
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Abstract
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Body fossils set limits on feasible reconstructions of functional capacity and behavior in theropod dinosaurs, but do not document in- life behaviors. In contrast, trace fossils such as footprints preserve in-life behaviors that can potentially test and enhance existing reconstructions. Here, we demonstrate how theropod trackways can be used as indirect evidence of pre-avian aerial behavior, expanding the approaches available to study vertebrate flight origins. This involved exploring the behavioral implications of a two-toed Cretaceous-aged theropod trackway produced by a small, bird-like microraptorine moving at high speed. Applying first principle running biomechanics, we were able to conclude that the trackway is atypical, indirectly evidencing pre-avian aerial behavior. This trackway documents the evidence of wing-assisted aerodynamic force production during locomotion, supporting a broader distribution of this behavior than currently known. These findings support previously proposed aerial behavior in early bird-like theropods, showing how trackways will help to deepen our understanding of theropod flight origins.

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Is this really telling us about the origin of flight? Does a running takeoff from the ground support a ground-up origin of flight?

 It's suggestive, but the authors state they "cannot make any claim linking a specific aerial behavior to the trackway (e.g., launch, landing, accelerated downward glides, or wing-assisted stride extension)"
If it was landing the critter could have come down from the trees.
 

And are the tracks really diagnostic at the subfamily level?

 See:
 https://www.nature.com/articles/s41598-018-35289-4

I'm concerned about a couple of things. First, haven't some other maniraptorans than microraptorines been shown to have a habitually raised pedal digit II? Second, aren't the hind wing flight feathers of Microraptor (and perhaps others, including Archaeopteryx) a potential problem for a cursorial theropod?