Theropod trackways as indirect evidence of pre-avian aerial behavior

Open access:
https://www.pnas.org/doi/10.1073/pnas.2413810121

Abstract

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.

On 10/27/24 1:37 AM, Pandora wrote:
> Theropod trackways as indirect evidence of pre-avian aerial behavior
>
> Open access:
> https://www.pnas.org/doi/10.1073/pnas.2413810121
>
> Abstract
>
> 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.

Is this really telling us about the origin of flight? Does a running
takeoff from the ground support a ground-up origin of flight? And are
the tracks really diagnostic at the subfamily level?

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
>>
>> Open access:
>> https://www.pnas.org/doi/10.1073/pnas.2413810121
>>
>> Abstract
>>
>> 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.
>
> 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

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
>>>
>>> Open access:
>>> https://www.pnas.org/doi/10.1073/pnas.2413810121
>>>
>>> Abstract
>>>
>>> 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.
>>
>> 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?