RA Frigot 2016
produced an abstract that appears to have no basis in reality. After reading the notes below, please send any examples of any pterosaur with a retroverted pubis, as noted in her abstract headline. I find no such examples in my fairly large collection of reconstructions.
From the Frigot 2016 abstract
“It has been demonstrated that the pelvis in archosaurs (1) repeatedly shows convergence towards acquisition of an anteriorly projecting ilium and a retroverted pubis. Pterosaurs have independently evolved these features, with the anterior iliac process universal across the taxon and the retroverted pubis occurring in several taxa (2). The latter cannot be appreciated as readily in pterosaurs as in other archosaurs due to the fused nature of the ischium and pubis (3). Geometric and linear morphometrics were used to quantify the shape and angle of the anterior margin of the pubis or puboischiadic plate. The angle and the PCA score were applied as end taxa to a reduced phylogenetic tree and nodes were reconstructed using least-squares parsimony. Retroversion is defined here as the anterior margin of the pubis subtending an angle of greater than 90° to the long axis of the spinal column (4).“
“By examining the pubis, it can be seen that it becomes retroverted not once at the base of the Pterodactyloidea, as is consistent with existing hypotheses on gait, but in several different lineages independently. Due to the constraints of flight, it is unlikely that this retroversion accommodated a more massive gut, as is the consensus in Ornithischia and Therizinosauroidea. Retroversion has been associated with increased femoral retraction in Maniraptora, and a similar function of the retroverted pubis in pterosaurs is hypothesized here (5).”
“As the pubis becomes retroverted, the surface area caudad to the femur increases and surface area craniad to the acetabulum is reduced. Accordingly, moment arms of femoral protractors originating from the puboischiadic plate are reduced, and in some cases come to function as additional adductors. By contrast, the adductors are brought immediately ventral to the acetabulum, giving them greater mechanical advantage. This shape change is likely enabled by the expansion of the hip protractors onto the anteriorly expanded ilium. In terms of gait, a strongly retroverted pubis is unlikely to correspond to a vertical clinging style of arboreality, as the caudally rotated retractors are at an extreme mechanical disadvantage. This suggests either a terrestrial mode of locomotion, or a horizontal substrate arboreality (6). In addition, strong femoral retractors and adductors played a crucial role in developing and maintaining tension in the wing membrane (7), and in maintaining its planform and preventing collapse of the wing.”
What am I not getting here?
This abstract doesn’t make sense. How did it pass peer review?
Figure 1. The pelvis and prepubis of several tritosaurs, fenestrasaurs and pterosaurs
Frigot RA 2016. Retroversion of the pubis in pterosauria and its significance in reconstructing gait. Abstract from the 2016 meeting of the Society of Vertebrate Paleontology.