Re: [dinosaur] Archosaur bipedality (free pdf)

["David Marjanovic" <david.marjanovic@gmx.at>]

>From the paper:

"Figured reconstructions in publications were considered to be indicative of 
the authorsâ determination of locomotor mode and of equal merit to textual 
determination. In instances where only diagrams were presented as the basis for 
determining the locomotor style, the reconstructed posture of the animal was 
considered to be indicative of the determination. In instances where both 
quadrupedal and bipedal diagrams were presented, taxa were determined to be 
facultative bipeds. We consider this to be justifiable because diagrams only 
come to exist in the literature as the consequence of a cascade of decisions: 
firstly, authors have made an intellectual assessment of an animal's posture 
based on their understanding of the osteological material that is available; 
secondly, that figure has been produced by the authors themselves or on the 
authors' behalf (and approved by them); thirdly, the peer-review process has 
deemed that figure appropriate for publication in a scientific journal. 
Therefore, the reconstruction must be considered representative of a reasonable 
scientific understanding of the animal at the time of publication. Taxa with no 
published locomotor mode were pruned from the dataset because the methods used 
in this study cannot accommodate unknown character states."

The optimism is unbelievable.

1) Reconstructions have to be in _some_ pose. When authors think the locomotor 
mode of their taxon _cannot_ be determined (or, say, would require serious work 
in biomechanics that may be beyond the scope of a descriptive or phylogenetic 
paper), they simply resort to the locomotor mode of a presumed close relative; 
to spell out the obvious, this should not be taken as evidence that any science 
has been done on the locomotor mode of the taxon in question.

2) Scientists, including whole teams of reviewers, have been known to disagree. 
Determinations of the locomotor modes of different taxa by different people are 
not necessarily comparable at all.

3) You'll be surprised to learn how little most reviewers care about figures. 
It's not as bad as with supplementary information, but still.

Now, the first and the third point only concern less than half of the paper, 
including the first two figures:

"To assess the sensitivity of our analytical approach, we replicated the 
following analyses using a dataset that excluded 15 taxa for which there was 
only diagrammatic data available."

This approach is used for the third and the fourth figure.

But in the first and the third figure alike, *Asilisaurus* is shown as 
quadrupedal, while *Silesaurus* is shown as facultatively bipedal, making 
*Silesaurus* represent a separate origin of facultative bipedality from 
original quadrupedality. Based on what? Sterling Nesbitt's gut feeling, but 
just for *Asilisaurus*, and Jerzy Dzik's gut feeling, but just for *Silesaurus*?

*Saturnalia* and *Efraasia* are shown as facultative bipeds in the second and 
the fourth figure. This should be considered disproved by the recent work on 
*Plateosaurus* which showed it wasn't able to walk quadrupedally; 
*Plateosaurus* is scored as an obligate biped, but the implications of the work 
that showed this were not understood.