Jones et al. 2021: Reptile backbone divisions and mobility

From the Jones et al. 2021 In brief:
“Jones et al. disprove the long-held idea that mammal backbone evolution involved a transition from reptile-like lateral bending to sagittal bending.”

Unfortunately, the study was conducted without a proper phylogenetic context. Outgroups included three salamanders (taxa unrelated to reptiles in the large reptile tree (LRT, 1811+ taxa).

Diadectes (Fig. 1) was cherry-picked as a ‘stem amniote‘ and ‘the ancestral condition for amniotes‘, but in the LRT Diadectes is a deeply nested lepidosauromorph amniote (= reptile) derived from Milleretta and not far from limnoscelids, pareiasaurs, procolophonids and turtles. This is a traditional mistake still taught at the university level due to taxon exclusion. At least two of the co-authors are from Harvard. So, kids, don’t go there. Harvard is not up-to-date!

In their results section
Jones et al. report, “there is less phylogenetic signal than expected under a Brownian motion model of evolution and that vertebral shape varies substantially within clades.”

That’s because they did not employ enough pertinent taxa. More taxa = more understanding of reptile phylogeny, just like a larger mirror collects more light and increases resolution in telescopes.

Figure 2. Diadectes (Diasparactus) zenos to scale with other Diadectes specimens.

Figure 1. Diadectes (Diasparactus) zenos to scale with other Diadectes specimens.

The whole concept of a transition from lateral undulation
to dorso-ventral undulation in the synapsid ancestors of mammals has been known for several decades. It was even included in Peters 1991, and not as an original hypothesis.

From the Jones et al. abstract:
“We show that the synapsid adaptive landscape is different from both extant reptiles and mammals, casting doubt on the reptilian model for early synapsid axial function, or indeed for the ancestral condition of amniotes more broadly. Further, the synapsid-mammal transition is characterized by not only increasing sagittal bending in the posterior column but also high stiffness and increasing axial twisting in the anterior column. Therefore, we refute the simplistic lateral-to-sagittal hypothesis and instead suggest the  synapsid-mammal locomotor transition involved a more complex suite of functional changes linked to increasing regionalization of the backbone.”

This was well-known decades ago.

Given this hypothesis, where do Jones et al. draw the transition zone?
Jones et al. indicate that dinocephalian synapsids walked like lizards by matching tracks (Fig. 1) and citing Smith 1993. They should have looked at dinocephalians more closely to see if Smith 1993 was correct. Turns out Smith 1993 was either incorrect or inaccurate.

Figure 2. Gaits illustrated by Jones et al. 2021. Compare the 'dinocephalian' to figure 3. It does not match.

Figure 2. Gaits illustrated by Jones et al. 2021. Compare the ‘dinocephalian’ to figure 3. It does not match.

This purported dinocephalian trackway
(Fig. 2, Smith 1993, Jones et al. 2021) does not match the hypothetical trackmaker (Fig. 2). The Smith 1993 trackway is so narrow the thumb prints overlapping the midline, something sprawling dinocephalians were unable to replicate (Fig. 3). That should have been checked, not just used ‘as is’ by Jones et al. 2021.

In similar fashion, too often workers use prior cladograms without checking for veracity. Science should be all about testing, checking, verifying. Too often it is about borrowing, trusting, accepting.

Figure 3. Dinocephalian in ventral view showing a widely splayed trackmaker.

Figure 3. Dinocephalian in ventral view showing a widely splayed trackmaker. Compare to figure 2 and 4.

Perhaps a better trackmaker
can be found for the Smith 1993 track in a larger relative to Hipposaurus (Fig. 4), a basal therapsid with the required 1) narrow pectoral girdle, 2) long slender limbs and 3) extremities that match the narrow-gauge tracks in size and configuration.

Figure 3. Image from Smith 1993, reprinted in Jones et al. 2021 falsified using their own data, then compared to a lithe large Hipposaurus with narrow toros and long limbs enabling a parasaggital gait matching the manus and pes.

Figure 4. Image from Smith 1993, reprinted in Jones et al. 2021 falsified using their own data, then compared to a lithe, large Hipposaurus with narrow toros and long limbs enabling a parasaggital gait matching the manus and pes.

Jones et al. 2021 discuss cervical, dorsal and lumbar regionalization,
without reporting that regionalization begins with Gephyrostegus (Fig. 5), a basalmost amniote (= reptile) in the LRT. This amphibian-like reptile was not mentioned by Jones et al. 2021. Smaller Diplovertebron (Fig. 5), a basal archosauromorph reptile, inherited and emphasized this regionalization.

Figure 1. Diplovertebron, Gephyrostegus bohemicus and Gephyrostegus watsoni. None of these are congeneric.

Figure 5. Diplovertebron, Gephyrostegus bohemicus and Gephyrostegus watsoni. None of these are congeneric.

 

 

Regionalization of the vertebral column
diminishes in some lepidosauriformes (Fig. 6) reaching a minimum in snakes. Regionalizaton increases in some owenettids, macrocnemids (including fenestrasaurs and pterosaurs) and iguanids.

Figure 6. Saurosternon, the first taxon in the lepidosauromorph lineage with sternae. Note the lack of differences between cervical, dorsal and there are no lumbar vertebrae.

Among archosauromorphs
regionalization did not diminish as much, as shown by Ophiacodon (Fig. 7) a basal synapsid in the lineage of therapsids.

Figure 1. Varanosaurus, Ophiacodon, Cutleria and Ictidorhinus. These are taxa at the base of the Therapsida. Ophiacodon did not cross into the Therapsida, but developed a larger size with a primitive morphology. This new reconstruction of Ophiacodon is based on the Field Museum (Chicago) specimen. Click to enlarge.

Figure 7. Varanosaurus, Ophiacodon, Cutleria and Ictidorhinus. These are taxa at the base of the Therapsida. Ophiacodon did not cross into the Therapsida, but developed a larger size with a primitive morphology. This new reconstruction of Ophiacodon is based on the Field Museum (Chicago) specimen. Click to enlarge.

By contrast, 
a basal archosauromorph diapsid, Archaeovenator (Fig. 8) reduces regionalization to a minimum. Lepidosauromorph turtles minimize lateral undulations when they evolve a carapace. So regionalization comes and goes.

Figure 2. Archaeovenator, a sister to Orovenator, is a protodiapsid.

Figure 8. Archaeovenator, a sister to Orovenator, is a protodiapsid.

 

 

One good reason for a lack of ribs in the lumbar region
was to make room for larger amniote eggs in the Earliest Carboniferous that even today greatly distends the abdomen of gravid lizards (Fig. 9).

Figure 4. Extant lizards, A. gravid, B. in the process of laying eggs, C. with egg clutch.

Figure 9. Extant lizards, A. gravid, B. in the process of laying eggs, C. with egg clutch.

Giving credit where credit is due
Jones et al. measured and graphed vertebral dimension across a wide swath of taxa, many closely related to one another. Expanding the taxon list to a wider gamut might have helped them see beyond the synapsids, a clade already well-studied for this factor.


References
Jones KE, Dickson BV, Angielczyk and Pierce SE 2021. Adaptive landscapes challenge the ‘‘lateral-to-sagittal’’ paradigm for mammalian vertebral evolution. Current Biology https://doi.org/10.1016/j.cub.2021.02.009
Peters D 1991. From the Beginning – The story of human evolution. Wm Morrow.
Smith RM 1993. Sedimentology and ichnology of floodplain paleosurfaces in the Beaufort Group (Late Permian), Karoo sequence, South Africa. Palaios 8, 339–357.

Miscellaneous year end stuff…

Just a few odd and ends as we near the the end of the year.

Here’s something from our guru:
Dr. Bob Bakker’s studies on Placerias locomotion (Fig. 1) at the Houston Museum of Natural History blog site.

Figure 1. Flexibility study of Placerias by Dr. Bob Bakker at the HMNS blog site.

Figure 1. Flexibility study of Placerias by Dr. Bob Bakker at the HMNS blog site. Click to view site.

These were produced to “add life” to a skeletal mount and a fantastic illustration by Julius T. Csotonyi of Placerias chased from its watering hole by Smilosuchus.

On YouTube
Apple chief evangelist Guy Kawasaki talks about what he learned working for Steve Jobs.

Figure 2. Guy Kawasaki TED talk.

Figure 2. Guy Kawasaki gives a TED talk, what he learned working for Steve Jobs. Here he lists: “Don’t let the bozos grind you down.” Click to view.

Kawasaki’s TOP 12

  1. “Experts” are clueless. Listen to your heart. When you encounter naysay, go against the naysay. (Remember inspirational talks like this usually take on this David vs. Goliath attitude. My advice: pick and choose by testing. Much of what experts say is right on the mark. But look for red flags and strange bedfellows. And don’t let the bozos grind you down.)
  2. Customers cannot tell you what they want. (innovation leapfrogs the desires and paradigms of the masses, in this case reliance on textbooks, rather than testing)
  3. The action is on the next curve. That’s why reptile evolution.com tested (on this date 12/29/14) 476 taxa vs. 228 characters, far more than any prior study. Yes, the experiment.com taxon goal has been reached (although the funding goal will not be reached at the present rate, 27 days to go, 99% unfunded).
  4. Biggest challenges beget the best work. In our case, more taxa (=the biggest challenge) reduce morphological distance between taxa, provide more nesting opportunities for enigmas and previous ‘by default’ nestings. The large reptile tree has been a big challenge, and I’ve learned  a lot along the way over the last four years. Other than my kids, the large reptile tree represents my best work and my purpose in life.
  5. Design counts. (Shiny, thin aluminum is more appealing than clunky black plastic, according to Kawasaki). Hopefully the accuracy (whenever possible) and design of the website and skeletal graphics have attracted a certain amount of interest.
  6. Use big graphics and big fonts. (a suggestion for PowerPoint presentations.)
  7. Changing your mind is a sign of intelligence. Getting it wrong and making it right is okay! That’s good Science. I do this (get it wrong and make it right) all the time.
  8. Value is not equal to price. (more for marketing).
  9. A players hire A+ players. (for employee acquisition).
  10. Real CEOs demo. They put their neck on the block and their ass on the line.
  11. Real entrepreneurs ship. They ship, then they test. Kawasaki says, “Don’t worry, be crappy.” Put out the innovation, the revolution, then fix the minor problems. I wish this wasn’t true in my case, but sometimes it is. Finding a problem is disheartening. Fixing a problem is a relief.
  12. Marketing = unique value. Be in the upper right hand corner of the chart: uniqueness and value, not just valuable, not just unique.
  13. Bonus: some things need to be believed to be seen. Foster the belief in what you dream in order to make it a reality. The opposite is also true, some things cannot be seen unless you open your mind to the possibility. In Science testing lots of taxa that everyone ‘knows’ are not related ultimately provides a family tree in which every taxon is related.

I recently had a paper rejected.
Among the objections were “the results are unconventional” and “I don’t believe you can get complete resolution for 360 taxa with only 228 characters.” Well, now the total is 476 taxa with only 228 characters and the matrix shows no signs of slowing down.  In theory, theory and practice should produce identical results. In practice they often do not. “Unconventional” is not a bad thing. You can’t shed new light on a subject without changing conventional thinking. A discovery, by definition, breaks convention. And, of course, ‘belief’ is the prevue of religion and politics. Even though the referee tested the work and confirmed the results, he didn’t let Science trump Belief. And he played his ‘Belief’ card, so now we all know which side of the brain trumped the other.

In the new year
the Pterosaur Heresies and ReptileEvolution.com will continue to promote new discoveries and, when necessary, shed new light on old discoveries. Thank you for your interest and support.

There’s more to come.