Decoupling body shape and mass distribution in birds and their dinosaurian ancestors

Macaulay et all 2023 reported:
“It is accepted that non-avian theropod dinosaurs, with their long muscular tails and small forelimbs, had a centre-of-mass close to the hip, while extant birds, with their reduced tails and enlarged wings have their mass centred more cranially. Transition between these states is considered crucial to two key innovations in the avian locomotor system: crouched bipedalism and powered flight.”

“Centred close to the hips” fails to show this axis is directed toward the ground and must pass in the middle of the pedal phalanges below the zig-zagging = crouched hind limbs and metatarsi that all together provide bounce and propulsion.

“Centred more cranially” indicates these authors are not familiar with aerodynamics which dictate the center of mass in a flying anything must be near the center of the wing, essentially at the armpit in tetrapods.

No comparisons were made
to similarly volant and bipedal pterosaurs and their similarly non-volant and bipedal ancestors among Cosesaurus, Sharovipteryx and Longisquama (Fig 1).

Figure 1. Bergamodactylus compared to Cosesaurus. Hypothetical hatchling also shown. ” data-image-caption=”

Figure 1. Bergamodactylus compared to Cosesaurus. Hypothetical hatchling also shown.

” data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/05/mpum6009-basal-pterosaur588.jpg?w=584″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/05/mpum6009-basal-pterosaur588.jpg?w=584″ alt=”Figure 1. Bergamodactylus compared to Cosesaurus. Hypothetical hatchling also shown.” class=”wp-image-31019″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/05/mpum6009-basal-pterosaur588.jpg?w=584 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/05/mpum6009-basal-pterosaur588.jpg?w=128 128w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/05/mpum6009-basal-pterosaur588.jpg?w=256 256w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2018/05/mpum6009-basal-pterosaur588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />

No comparisons were made
to extant bipedal lepidosaurs, nor to extinct bipedal crocodylomorphs, poposaurs, rauisuchians, etc.

Genomic studies
of extant birds were considered factual data.

This is demonstrably wrong, as shown by the the large reptile tree, which tests traits.

Only one Solnhofen bird, identified as ‘Archaeopteryx’
was employed in this study.

This ignores the variety (Fig 2) already present in this fossil Lagerstatten.

Figure 3. Several Solnhofen birds, including Archaeopteryx, compared to Ostromia to scale. ” data-image-caption=”

Figure 3. Several Solnhofen birds, including Archaeopteryx, compared to Ostromia to scale.

” data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/12/archaeopteryx_specimens3.jpg?w=222″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/12/archaeopteryx_specimens3.jpg?w=222″ alt=”Figure 3. Several Solnhofen birds, including Archaeopteryx, compared to Ostromia to scale.” class=”wp-image-29374″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/12/archaeopteryx_specimens3.jpg?w=222 222w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/12/archaeopteryx_specimens3.jpg?w=444 444w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2017/12/archaeopteryx_specimens3.jpg?w=65 65w” sizes=”(max-width: 222px) 100vw, 222px” />

The authors failed to mention
the loss of chevrons in birds and Triassic pterosaurs that indicate the caudofemoralis muscles were becoming vestiges, then disappearing, only to be replaced by pre-femoral anchors and muscles along with more vertebrae incorporated into the sacral series.

The authors concluded,
“We recover modularity in the evolution of limb proportions and centre-of-mass that suggests fully crouched bipedalism evolved after powered flight.”

This falls in line with other issues in current paleontology that avoids, omits and ignores obvious comnparisons, facts and hypotheses, while embracing obvious myths.

None of the 8 co-authors, editors and referees were able to identify the above shortcomings. That’s why the independent researchers = amateurs must call them out.

Thanks to reader, Sean,
for bringing this study to my attention.

References
Macaulay S et al (7 co-authors) 2023. Decoupling body shape and mass distribution in birds and their dinosaurian ancestors. Nature Communications 14(1) DOI: 
10.1038/s41467-023-37317-y