Estimating dino/croc divergence times: Turner et al. 2017

This might have been yet another case
of scientists TRUSTING authority (= the work of others) rather than TESTING competing phylogenetic analyses. In this case, however, two of the three authors in Turner, Pritchard and Matze 2017 relied on their own flawed (= serious taxon exclusion problems) phylogenetic analyses and for good measure they threw in a third flawed (= more taxon exclusion problems) analysis (Nesbitt 2011) that we examined and reexamined in an 11-part series.

In any case, since none of the trees
in the new Turner et al. study  stand up to scrutiny (= do not agree with one another, do not produce gradual accumulations of traits in derived taxa and depend on long ghost lineaages), everything Turner et al. (2017) did afterwards has no credibility and no utility. So sadly, the entire paper is a waste of their time. Metaphorically, they built their house on sand.

On the other hand,
when you start with a study that provides a gradual accumulation of derived traits in all derived taxa, and minimizes the effect of taxon exclusion, like the large reptile tree (LRT (949 taxa) then you’ve metaphorically built your house on solid ground. And it’s much simpler to pinpoint the dino/croc divergence time because you are provided with a last common ancestor for these sister clades: Gracilisuchus (Figs. 1, 2). Crocs and dinos are sister taxa. None of the studies used by Turner et al. (Pritchard et al. 2015, Nesbit 2011, Turner 2015) recovered that tested relationship.

Figure 1. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Herrerasaurus, Tawa and Eoraptor.

Figure 1. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Herrerasaurus, Tawa and Eoraptor.

So when did dinos and crocs diverge?
Let’s look a the three most recent taxa both clades share in common in reverse chronological and phylogenetic order:

  1. Gracilisuchus = 230 mya.
  2. Turfanosuchus = 235 mya.
  3. Decuriasuchus = 240 mya.

So that narrows the divergence time pretty well…

And how did Turner et al. do?
They report,“The average ghost lineage for the group as sampled is 31 million years.” Their conclusion states no firm date or date range. Rather, their whole paper appears to be a long story on how they tested this that and the other without getting around to their headline topic. And without nailing down a last common ancestor or a croc/dino divergence time.

Figure 2. Basal crocs. Decuriasuchus and Gracilisuchus are found in both croc and dino lineages.

Figure 2. Basal crocs. Decuriasuchus and Gracilisuchus are found in both croc and dino lineages.

All the other taxa
and all the other testing performed by Turner et al. were for nought.

For more information
on any of the taxa employed by Turner et al, just look them up at ReptileEvolution.com.

References
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History;352:1–292.
Pritchard AC, Turner AH, Nesbitt SJ, Irmis RB and Smith ND 2015. Late Triassic tanystropheids (Reptilia, Archosauromorpha) from Northern New Mexico (Petrified Forest Member, Chinle Formation) and the biogeography, functional morphology, and evolution of Tanystropheidae. Journal of Vertebrate Paleontology. ;e911186.
Turner AH 2015. A Review of Shamosuchus and Paralligator (Crocodyliformes, Neosuchia) from the Cretaceous of Asia. PLoS ONE. 2015;10(2):e0118116. doi: 10.1371/journal.pone.0118116. pmid:25714338
Turner AH, Pritchard AC and Matzke NJ 2017. Empirical and Bayesian approaches to fossil-only divergence times: A study across three reptile clades. PLoS ONE 12(2): e0169885. doi:10.1371/journal.pone.0169885

 

Advertisements

5 thoughts on “Estimating dino/croc divergence times: Turner et al. 2017

    • …You know, you really should have. Instead you wrote the next post.

      First rule of holes: if you’re in one, stop digging.

  1. David, you know if I fixed those problems, you’d find others. And if I fixed all the problems you’d remind me that I have not seen the specimens first hand. And then you’d say I have too few traits for so many taxa. It goes on and on. I’ve heard it all. Granted, more focused studies on smaller clades could use all of the above. But the present large gamut study, despite its flaws, is still lumping and separating taxa very well and producing gradual accumulations of derived traits. Even among congeneric taxa! And you hate that!

    I’m not in a hole. I’m on a hill. But always willing to repair mistakes.

    • David, you know if I fixed those problems, you’d find others.

      That’s an evil accusation.

      It’s also a very handy excuse for you: why bother to learn how phylogenetic analysis works, when everyone else in the field is evil anyway?

      And if I fixed all the problems you’d remind me that I have not seen the specimens first hand.

      We talked about this just a few days ago. I haven’t seen all the specimens myself, have never pretended otherwise, and neither have Ruta & Coates for instance. Still, there are cases where you’ve misinterpreted the published literature, including all published pictures.

      I’ve heard it all.

      Yeah, you’ve just never taken the time to listen.

      is still lumping and separating taxa very well and producing gradual accumulations of derived traits.

      I’ll bite: the whole “Paratetrapoda” trainwreck. Jason and I gave you a long list of character states that show your tree means: 1) “Paratetrapoda” has an extremely long branch, the exact opposite of “gradual accumulations of derived traits”; 2) all the apomorphies of that branch are parallelled in Tetrapoda, a fact at odds with “lumping and separating taxa very well”.

      We really think you should add these characters to your matrix.

      I’m not in a hole. I’m on a hill.

      You’re too shortsighted to see where you are, and you refuse to visit an ophthalmologist and get glasses – even though that’s all free to you, because Jason and I are trying to be your NHS.

      I invest more time in some of my comments here than you invest in many of your blog posts. I’m trying to help you. And you accuse me of being a cartoon villain who wants to keep telling people they’re wrong forever.

      You even implicitly accuse me of thinking your taxon sample is too large, the one thing I’ve never done – it’s too large for your present character sample, and obviously the way to fix this is to enlarge and correct your character sample, not to reduce your taxon sample.

      I’ve been reading up on scales, so I’ll add several scale characters to my matrix tomorrow, if not today. It’ll be the first time most of them are included in any phylogenetic analysis.

  2. This reply has a different tone than the others. Thank you for that. Except for the ‘evil’ comment. To your points, I’ll reiterate. Like you (trying to build affinity here) I’m looking at taxa and characters, and adding them to a matrix, and reporting results… mistakes, vagaries and all included. All mistakes are corrected. So far that number is well into the tens of thousands.

    Funny thing, the matrix keeps lumping and separating taxa and clades. And for some reason the mammals all lump together. So do the snakes. So do the pterosaurs, but not with the dinosaurs. And I found Tulerpeton nesting as the last common ancestor of all reptiles, now split into those closer to lepidosaurs and those closer to archosaurs. That’s novel. If valid this would be worthy of a dissertation. Unfortunately, I have to wait for others to validate it, and that’s happening slowly, in parts, not the whole.

    This tree is a hypothesis of relationships. It is a proposed blueprint. We can still make changes! But with every additional taxon interacting mathematically with every other taxon, the structure is getting stronger and stronger. That’s just due to each taxon and each score getting less and less important when compared to the mass of the whole tree, like space debris accumulating to become a planet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s