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Bat wing ‘pose’ in pterosaurs? – SVP abstracts 2016

Tuesday, November 15, 2016 11:27
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Manafzadeh and Padian 2016
attempt to provide insights into pterosaur abilities by comparing certain skeletal elements with those of a chicken, then a bat.

From the Manafzadeh and Padian 2016 abstract (abridged)
“Hip mobility is determined in part by the osteological morphology of the acetabulum and femoral head. However, the joint capsule and its ligaments constrain motion to a smaller range than what seems possible from dry bones alone. Paleontologists have tried to reconstruct the locomotion of extinct ornithodirans (1) (bird-line archosaurs) without accounting for ligamentous constraints in the hips of their extant avian relatives. We dissected the hip joint capsules of 30 free-range farmed specimens of the domestic chicken (Gallus galls) (2). For each specimen, maximum hip ranges of motion in the sagittal, frontal, and transverse planes were first determined from manipulation of carcasses. These values were then compared to ranges of motion obtained from manipulating the femora and pelvic bones alone. In the light of archosaur soft tissue homologies, these data suggest that many inferences drawn from dry bones alone have overestimated ranges of hip motion and have proposed stances and gaits for ornithodirans that would have been made implausible or impossible by soft tissues. Specifically, our findings suggest that ligamentous constraints would have prevented batlike incorporation of the pterosaur hindlimb into a uropatagium. (3) These data suggest that the “4-wing gliding” model of basal maniraptoran flight (e.g., Microraptor) would have been difficult or impossible if it required bringing the hindlimbs into a strictly horizontal plane.” (4)

Notes

  1. Everyone should know by now, pterosaurs are not stem birds. This has been known for 16 years (Peters 2000). They are stem squamates in the LRT. This has been known for 5 years, since the origin of ReptileEvolution.com and for 11 years if you read abstracts from Flugsaurier meetings (Peters 2007).
  2. Thus, using a chicken (Gallus) is inappropriate. Among living taxa, the use of the squamate Chlamydosaurus would have been phylogenetically much closer to pteros. Even then, a stretch.
  3. The bat-wing pterosaur argument has never been supported by evidence. And the uropatagium myth has also never found any evidence. It is founded on one misinterpreted specimen. Funny that the uropatagium is not found in chickens and makes its one and only appearance in the abstract here at the conclusion. Did pterosaurs have a bat-like wing [deep chord]? Or did they adopt a bat-like pose [upside down]? The abstract headline needs to clarify which is correct.
  4. The inability of theropods to abduct the femur into the parasagittal plane was shown in a Nova PBS special. Details and links here.
  5. If you want to see the range of poses in pterosaurs, click here to start. The angle of the femoral head to the shaft varies widely within the Pterosauria, from dino-like in Dimorphodon, to more splayed in higher taxa like Pteranodon (Fig. 1), Anhanguera and Quetzalcoatlus.
  6. Working with reinflated pterosaur bone replicas (Fig. 1) shows the femoral head, though able to rotate on its axis and wobble about its axis, need not move much in order to supply all necessary movement to the hind limb in flight or walking. The same holds true working with uncrushed bones. Reconstructions are SO important and so typically ignored.
Standing Pteranodon

Figure 1. Standing Pteranodon Remember, the wing membranes fold up to near invisibility in all known fossils that preserve a folded wing as the membrane is stretched between wingtip and elbow with a small fuselage fillet to mid thigh from the elbow.

References
Manafzadeh AR and Padian K 2016. Could pterosaurs adopt a batlike wing pose? Implications of a functional analysis of the avian hip ligaments for the evolution of ornithodiran stance and gait. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.
Peters D 2000. A redescription of four prolacertiform genera and implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293-336.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.

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