New clade of enigmatic early archosaurs? No.

Updated one day after publication. The taxa come from the Supp. Data, most not shown in the greatly simplified chronological cladogram.

Recently, Butler et al. (2014)
recovered a “new clade of enigmatic early archosaurs” comprised of Yonghesuchus, Gracilisuchus and Turfanosuchus.

Figure 1. Do these taxa nest in a single clade? No. Turfanosuchus, Gracilisuchus and Yonghesuchus. Each nests more closely with other taxa.

Figure 1. Do these taxa nest in a single clade? No. Turfanosuchus, Gracilisuchus and Yonghesuchus. Each nests more closely with other taxa. Yonghesuchus nests with the crocodylomorph Dromicosuchus. Gracilisuchus nests with Saltopus as a much more basal crocodylomorph. Turfanosuchus nests at the base of the Poposauridae.

Unfortunately they added the unrelated Mesosuchus (lepidosaur), Vancleavea (thalattosaur) and two pterosaurs (lepidosaurs).

And they did not add the true sisters of Gracilisuchus (Pseudhesperosuchus, Decuriasuchus, Lewisuchus, Saltopus, the SMNS 12591 specimen and Scleromochlus).

Red Flags
In the Butler et al. (2014) tree the following purported sister taxa are all “odd bedfellows” that do not look like one another.

  1. Prolacerta is derived from Mesosuchus (and presumably the rhynchosaurs)
  2. Euparkeria is derived from Tropidosuchus and Chanaresuchus.
  3. Tropidosuchus and Chanaresuchus are derived from Vancleavea.
  4. Vancleavea is derived from Erythrosuchus.
  5. Pterosaurs are derived from parasuchians!!!!!!
  6. Lagerpeton is derived from pterosaurs.
  7. Ornithosuchia is derived from Lewisuchus.
  8. Theropoda is derived from Ornithischia.
  9. Ornithosuchia is a sister to Pterosauria, also derived from Parasuchia.
  10. Revueltosaurus is a sister to the Aetosauria and derived from Ornithosuchia
  11. The new Gracilisuchus clade is derived from Revueltosaurus.
  12. Poposaurus and the poposaurs are derived from Qianosuchus, Xilosuchus and Arizonasaurus
  13. Prestosuchus and the Rauisuchidae is derived from Ticinosuchus.
  14. Hesperosuchus and the Crocodylomorpha are derived from Rauisuchidae.

Say it ain’t so!
As you can see, many of these relationships don’t make sense. Sister taxa share very few traits with one another (pterosauria and parasuchia, is the worst such example). Many relationships are upside down with basal taxa, like theropods, derived from derived taxa, like ornithischia. (M. Mortimer also had this problem a few years ago).

What is needed is a large reptile tree in which basal taxa are basal to derived taxa and all sisters look alike (share most traits). In the large reptile tree, sister taxa look quite a bit like one another. The authors should have cast a critical eye on these results, which are very similar to those of Nesbitt (2011), who also recovered many strange bedfellows.

If I had proposed that pterosaurs arose from parasuchians,
the ridicule would be endless and justified, as it is here. Taxon exclusion seems to be the culprit again, along with the tradition of using previously published matrices, even those riddled with Red Flags and strange bedfellows.

In the large reptile tree, Gracilisuchus nests with the SMNS 12591 specimen, Saltopus and Scleromochlus at the base of the Archosauria. Turfanosuchus nests at the base of the Poposauridae, between Decuriasuchus and the base of the Archosauria, not far from GracilisuchusYonghesuchus, nests between Dromicosuchus and Protosuchus.

And, because this is Science, you can repeat these experiments to see for yourself which taxa share more traits — that make sense.

Butler et al. 2014. New clade of enigmatic early archosaurs yields insights into early  pseudosuchian phylogeny and the biogeography of the archosaur radiation. BMC Evolutionary Biology  14:128. doi:10.1186/1471-2148-14-128
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.

8 thoughts on “New clade of enigmatic early archosaurs? No.

  1. I’m incredibly confused by this post. Of your list of 14 “unusual bedfellows”, none are actually shown in Butler et al’s phylogeny. Literally none

    Really all this post seems to be demonstrating is that you don’t seem to understand how a cladogram works, as shown beautifully by your comments on parasuchianns and pterosaurs

    “Pterosaurs are derived from parasuchians!!!!!!”

    Oh for god’s sake, are you kidding me? How can you think the phylogeny is showing pterosaurs this? They aren’t even shown to be sisters! Rather they are shown to be sort of second cousins, separated by more than 35 million years of separate evolution (so not really that unusual that they would end up looking incredibly different).

    Parasuchians were found by Butler et al to be their own monophyletic group, with their own derived characters and their own line of evolution. They are descended from an ancestor which also went on to produce the archosaurs (dinos, pteros and crocs), but this does NOT mean that archosaurs are derived from parasuchians. They are a separate lineage which has evolved independently from pterosaurs and co.

    Just because the taxon labels end up close together on the phylogeny it doesn’t mean one is derived from the other! And just because a clade is drawn further down on the tree it does not mean it is not derived. The same goes for your comments on rhynchosaurs. Prolacerta is not shown by Butler to be derived from Rhynchosaurs, Rhynchosaurs are their own lineage with 50 million years of independent evolution. They have their own derived characters, they are just different to the derived characters of the other archosauriformeds (including prolacerta). The same goes for Erythrosuchids, Gracilisuchids… basically every single one of the 14 “red flags” is a product of your not being able to read a phylogeny.

  2. You need to see their Supp. Data. What is shown in their chronology tree is greatly simplified. And yes, as in Nesbitt et al. 2011, proximal pterosaur outgroup taxa include parasuchians. So they both share a common ancestor. Still, that’s a red flag. I understand how cladograms work. I’m raising hell because published work is showing crap for results.

    • I did see the supplementary data. That was what I was basing my comments off.

      If you do understand how cladograms work, why are your criticisms based on sisters being derived from one another? The fact that Parasuchians are an outgroup to pterosaurs does not mean pterosaurs are derived from parasuchians. Nor does the fact that pterosaurs share a common ancestor with parasuchians does not mean pterosaurs are derived from parasuchians. When you say “derived from” it implies that pterosaurs evolved from a parasuchian-like ancestor. No scientist has ever suggested this, nor is this what the Butler tree suggested.

      Pterosaurs and parasuchians are separated by 35 million years of independent evolution (at least); of course they will look a bit different. So no, not going to accept that as a red flag

  3. This is the shame of paleontology, turning the blind eye to better solutions while maintaining positions that strain credulity. Turn things around and imagine that I am the one promoting a parasuchus-pterosaur sister clade. Doesn’t that sound ridiculous?

    • Yes, a parasuchus-pterosaur sister clade does sound ridiculous. Its a good thing that the Butler phylogeny does not suggest a parasuchus-pterosaur sister clade. Having parasuchians and pterosaurs belonging to a monophyletic group that includes , aquatic, semi-aquatic, terrestrial, cursorial, arboreal, flying, carnivores, herbivores, piscivores, omnivores, ovivores, small, large, super-large, bipeds, facultative bipeds and quadrupeds seems to me perfectly reasonable. That is what the Butler phylogeny suggested.

    • So basically your argument boils down to “Ignore more than 90% of the archosaur taxa Butler included in their tree and the relationships found look silly”.

      You will forgive me if I don’t find that the most compelling argument (even allowing for your warped definition of “derived”)

  4. In the Butler tree, which taxa are ancestral or sisters to pterosaurs? Why is Vancleavea even in there? What traits does Euparkeria share with Tropidosuchus? Etc. etc. These are the questions I ask, and you should be asking.. When you look at the large reptile tree all these questions are answered and all relationships make sense. We’re all looking to model evolutionary patterns. In the human tree some Australopithecus are ancestral to Homo, but various other branches of Australopithecus are not ancestral to Homo. Right? Same here with all primitive taxa. There is a more tenable tree than the traditional tree hypothesized by Butler.

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