Reptile Tree Experiments

Traditional paleontologists insist on nesting pterosaurs with archosaurs, despite no evidence to support such a relationship. Well, two can play at that game.

I took the large reptile tree and separated the two halves in PAUP (deleting first one branch, then the other). Then I took one taxon at a time from one branch and force nested it within the other branch. Here I’ll report the results. We’ll start with the pterosaur, MPUM 6009, which earlier nested with turtles (also force misnested) and sauropterygians, not where traditional paleontologists presumed.

ALL of the nestings will seem odd. That’s because they don’t belong there!

Placing a new lepidosauromorph within the new Archosauromorpha clade
The basal pterosaur MPUM 6009 nested with Pachypleurosaurus, a basal sauropterygian, far from the basal archosaurs pterosaurs have been traditionally force nested with.

I also reduced the taxon list to just the Archosauriformes plus the pterosaur MPUM 6009. In this case the pterosaur nested between Ticinosuchus and the armored Aetosaurus. Very bad matches there.

Macrocnemus, a putative prolacertiform, nested between the basal enaliosaurs Hovasaurus, Stereosternum and Pachypleurosaurus, several nodes away from Prolacerta.

Hyperodapedon, a rhynchosaur and rhynchocephalian, nested between Youngoides, Doswellia and basal Proterochampsidae.

Casea, a large millerettid, nested not with synapsids, but in an unresolved clade that included all taxa between Cephalerpeton and Broffia.

Placing a new archosauromorph within the new Lepidosauromorpha clade
Scleromochlus, a tiny basal crocodylomorph, nested with Hyperodapedon, a large rhynchosaur.

Herrerasaurus, a basal dinosaur, nested between the rhynchocephalians Trilophosaurus +  Mesosuchus + Hyperodapedon.

Dimetrodon, a fin-backed basal synapsid, nested with Tetraceratops, a basal diadectomorph.

Pachypleurosaurus, a basal sauropterygian so attractive to pterosaurs when force nested, instead nests between Saurosternon + Palaeagama and Coelurosauravus, a gliding reptile.

Prolacerta, a basal protorosaurian, nested with Azendohsaurus, a derived rhynchocephalian. This proved prophetic when Azendohsaurus moved to the protorosaurs in November 2014.

Lotosaurus, a fin-backed basal dinosaur, nested with Hyperodapedon.

What Does This Study Tell Us?
First of all, this study demonstrates that any taxon will nest in any other clade by default. It will not resemble its putative sisters, but it will find a place nevertheless. That’s why it’s so important to take a step back after recovering tree results and looking for mismatches among putative sisters. Again, pterosaurs don’t belong with archosaurs. Strangely they nest with basal sauropterygians when the taxon list deletes nearly all of the new Lepidosauromorpha, as demonstrated by testing. With those deletions and exclusions they nest most parsimoniously with tritosaur fenestrasaur lizards, a clade that demonstrates a gradual accumulation of pterosaurian traits.

A priori assumptions, based on tradition rather than phylogenetic testing run the same accidental risk with their taxon lists that we just played out on purpose. No phylogenetic testing should be considered valid unless some sort of overarching study has set the parameters for taxon inclusion and exclusion. All sister taxa should look like each other. A gradual accumulation of derived traits should be present for all taxa.

Earlier views that placed rhynchosaurs and trilophosaurs with basal archosauriforms and protorosaurs did so only in the absence of more parsimonious sister taxa. Earlier views that placed caseids with synapsids suffer from the same problem. The list of mistakes in traditional nesting is long. This blog will continue to point out bad nestings due to taxon exclusion as they occur, supported by the large (and growing larger) reptile tree.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

3 thoughts on “Reptile Tree Experiments

  1. This would be a good idea, except your data are too flawed for it to matter. Ironically, Tetraceratops is probably close to Dimetrodon, as therapsids evolved from sphenodontid-like synapsids. Ditto for Prolacerta and Azendohsaurus, as both are basal archosauromorphs.

  2. Where’s your tree? Where’s my flawed data? So far you’re just repeating untested tradition and sniping from the sidelines. Please be specific and scientific. I would be happy to make changes if you can provide superior data/trees. This the only tree that actually tested the alternatives. Statistically, the more taxa and characters, the less individual errors actually count, if any are present.

  3. It’s true no one else has a tree with the taxonomic resolution and scope yours does. I’ve never faulted you for that, and indeed think others should follow your example there. The flawed data is two part- inaccurate codings based on misinterpretations, plus poorly formed characters. The former is too tedious to go through for taxa outside my area of expertise (and we’d just end up arguing over whose interpretation was right), but the latter is easy to quickly show. Email your reptile matrix and I’ll have a go at presenting specific, scientific problems.

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