Digital modeling of pterosaurs (Henderson 2010)

Yesterday, and the day before, we reviewed Hone and Henderson (2013) who conducted computational experiments with four misbegotten digital pterosaur models (Fig. 1). They reported that pterosaurs were unlikely floaters that would have struggled to keep their noses above the surface and so risked drowning, despite their air-filled skeletons.

Jurassic Park 3 logo, including a nice Pteranodon in ventral view with narrow chord wings.

After seeing Jurassic Park I, II and III, many readers may think that digital modeling with computers has already reached some sort of acme, able to accurately model these reptiles with ultra-precision. Unfortunately, when it comes to academic publication, that’s not always the case. And yet such works as Hone, Sullivan and Bennett (2009), Henderson (2010) and Hone and Henderson (2013) continue to be published.

Bring up the quality please
I have no beef with digital models, but the quality has to be there. The last time I saw Hone present a digital model it was for a sabertooth paw built with digital cylinders designed to discredit PILs (Hone, Sullivan and Bennett 2009, Fig. 1). These cylinders did not echo the real bone configurations. Taking up this challenge (Peters 2010) used a real sabertooth paw (Fig. 1) and found PILs, as anyone can.

Figure 1. Above: A digital Smilodon pes created by Hone, Sullivan and Bennett. This is a poor substitute for a tracing of the real Smilodon manus and pes, with naturally flexed and extended phalanges and complete PILs added. Lesson: try to avoid digital models until the accuracy rises to the occasion.

Figure 1. Above: A digital Smilodon pes created by Hone, Sullivan and Bennett.
This is a poor substitute for a tracing of the real Smilodon manus and pes, with naturally flexed and extended phalanges and complete PILs added. Lesson: try to avoid digital models until the accuracy rises to the occasion. Due to these flexions and extensions, cat paws are more of a 3D problem in PILs, rather than the more typical planar configuration.

In similar fashion,
Henderson’s (2010) digital model of Quetzalcoatlus (Fig. 3) has been wisely criticized as also being inaccurate*. It’s as if he did not pay any attention to the bones and soft tissues preserved and the implications those have for muscle masses, especially those of the hind limb. In other words, Henderson seems to have skipped a very important step: start with the bones and create an accurate reconstruction on paper before going digital. The same holds true for his Rhamphorhynchus (Fig. 2).

Figure 2. Henderson (2010) modeled Rhamphorhynchus with a deep chord wing, tiny thighs and shallow pelvic area and an inflexible neck, all inaccurate based on reconstructing the bones.

Figure 2. Henderson (2010, above left) modeled Rhamphorhynchus with a deep chord wing, tiny thighs and shallow pelvic area and an inflexible neck, all inaccurate based on reconstructing the bones (lower and at right). Perhaps of more importance to the floating argument, the phalanges are too slender in the Henderson model, so yes, they would make less efficient pontoons in that model.

 

Figure 2. Quetzalcoatlus recreated as a digital model by Henderson 2010 compared to a bone reconstruction. No wonder the results were odd. The math was wrong.

Figure 3. Quetzalcoatlus recreated as a digital model by Henderson 2010 compared to a bone reconstruction. No wonder the results were odd. The geometry and the math had no chance of being correct with such a wrong reconstruction.

I have no trouble with those who make 3D reconstuctions digitally. I think that’s the wave of the future. I do have a problem with those who claim they are accurate when they are not. And likewise I have a problem with referees and colleagues who give a green light to these little monsters, permitting these pterosaur experts to disfigure pterosaurs.

* from Wikipedia/Quetzalcoatlus: “Henderson’s work was further criticized by Habib, who pointed out that although Henderson used excellent mass estimations, they were based on outdated pterosaur models,”

References
Henderson, DM.  2010. Pterosaur body mass estimates from three-dimensional mathematical slicing, Journal of Vertebrate Paleontology, 30(3):768-785.
Hone DWE, Sullivan C, Bennett SC 2009. Interpreting the autopodia of tetrapods: interphalangeal lines hinge on too many assumptions.Historical Biology (Impact Factor: 1.19). 03/2009; 21:67-77. DOI:10.1080/08912960903154503
Hone DWE, Henderson DM 2013. The posture of floating pterosaurs: Ecological implications for inhabiting marine and freshwater habitats, Palaeogeography, Palaeoclimatology, Palaeoecology (2013 accepted manuscript), doi: 10.1016/j.palaeo.2013.11.022
Peters, D. 2010. In defence of parallel interphalangeal lines. Historical Biology iFirst article, 2010, 1–6 DOI: 10.1080/08912961003663500

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