DGS Embryo Lizards at PLOS

I’m happy to show you
examples of professional paleontologists using digital equipment to render bones, segregate bones and reconstruct fossil taxa. This one is from Fernandez et al. 2015.

Figure 1. Fossil lizard eggs rendered after CT scanning. Colors represent various parts of the body. Their digital segmentation is the same as my digital segregation, only hi-tech . THIS is the way to render bones in roadkill fossils. Let's make this standard practice.

Figure 1. Fossil lizard eggs rendered after CT scanning. Colors represent various parts of the body. Their digital segmentation is the same as my digital segregation, only hi-tech . THIS is the way to render bones in roadkill fossils. Let’s make this standard practice.

The above eggs are totally scrambled.
Lucky for us Fernandez et al. put in the effort to segregate, identify and reconstruct every bone in the egg. They did an excellent job!

From the Discussion:
“The digital segmentation of the two least crushed eggs (SK1-1 and SK1-2) shows that both embryonic skeletons are mostly disarticulated, but assembled into clusters reflecting the original position.” (Fig. 1). These workers used a CT scanner to reassemble this scrambled egg.

Along the same lines
and lacking a CT scanner, I use Photoshop, but the idea is the same: to extract as much data as possible from difficult specimens.

And after the bones are digitized
they can be moved about and reconstructed (Fig. 2). I want to encourage all workers to adopt the practice of coloring each bone in situ. Much better than simply drawing a line to the center of each bone and leaving the shape of the bone to the reader’s imagination.

Figure 2. Reconstructed embryo lizard skull from digitized data.

Figure 2. Reconstructed embryo lizard skull from digitized data.

Which lizard is it?
Just eyeballing it here, but Liushusaurus (Fig. 3) and Bahndwivici are close matches and the former is a contemporary. Not a perfect match, but close enough for now.

Figure 3. The basal scleroglossan, Liushusaurus, is a close match to the lizard embryo.

Figure 3. The basal scleroglossan, Liushusaurus, is a close match to the lizard embryo. The post cranial bones are likewise quite similar. Note the rostrum does not elongate here, another example of isometric growth.

Both are basal scleroglossans.
Based on sister taxon first appearances, both had been around since the Late Permian.

Figure 5. Bahndwivici, a basal anguimorph, scleroglossan squamate similar to the embryo in the egg.

Figure 4. Bahndwivici, a basal anguimorph, scleroglossan squamate similar to the embryo in the egg.

Npw, about those eggs
The authors noted these eggs had gekko-like hard eggshells, but attributed them to anguimorph lizards (monitors, mosasaurs, etc.). In the large reptile tree Liushusaurus nests just basal to geckos AND anguimorphs. So, the diversity described in the paper’s headline is maybe… not so much. Bahndwivici nests basal to anguimorphs like monitors and mosasaurs.

And please note
the embryo is an isometric match to its adult counterpart. So isometry can and does occur in the growth of certain lepidosaurs, like pterosaurs.

And on that note
Wills someone please fix the Wikipedia entry for Aurorazhdarcho. It includes a wide variety of pterosaurs of all shapes and sizes, some with small rostra and some with elongate rostra, all attributed to one genus based on the false paradigm of allometry during isometry in pterosaurs.

References
Fernandez V, Buffetaut E, Suteethorn V,  Rage J-C, Tafforeau P and Kundrát M 2015. Evidence of Egg Diversity in Squamate Evolution from Cretaceous Anguimorph Embryos. PLoS ONE 10(7):e0128610. doi:10.1371/journal.pone.0128610

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2 thoughts on “DGS Embryo Lizards at PLOS

  1. Rendering a model from CT scan data is not the same as tracing pareidolia in photoshop no matter how much the end result looks the same. One method is reproducible, the other depends on the light in which the photo was taken, the resolution of the photo, and the whim of the practitioner. One method can mathematically tell what is and is not bone based on the scan density of the specimen. The other method, see previous sentence.

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