Adding Homo sapiens to the large reptile tree

Not sure why I didn’t think to do this earlier.
I added Homo sapiens to the large reptile tree (still not updated) and ran a phylogenetic analysis to see where we nest. To no one’s surprise Homo (Fig. 1) nested with the cynodont Procynosuchus among the Therapsida (no other mammals are yet entered).

Figure 1. Homo sapiens alongside sister taxa Australopithecus and Ardipithecus (both in gray).

Figure 1. Homo sapiens alongside sister taxa Australopithecus and Ardipithecus (both in gray). Click to learn more.

Entering characters for Homo and Procynosuchus
was more than enlightening as so many traits were shared between the two. You should try it sometime!

Figure 2. Procynosuchus, a basal cynodont therapsid synapsid sister to humans in the large reptile tree (prior to the addition of advanced cynodonts including mammals).

Figure 2. Procynosuchus, a basal cynodont therapsid synapsid sister to humans in the large reptile tree (prior to the addition of advanced cynodonts including mammals). Click to learn more.

What happens when taxa are excluded? (How deep can we go?)
The contribution of cynodont traits to the story of human evolution was more powerful than I thought. I was surprised at one happened when I took one step further.

Deleting only Procynosuchus
results in Homo nesting results in Homo nesting between Dibamus and Tamaulipasaurus (Fig. 2) two burrowing skinkomorph squamates. My guess is the fusion/loss of so many skull bones, the brevity of the rostrum, the great depth of the coronoid process of the dentary and the complete lack of postcranial characters for the two burrowing taxa are attracting the taxon Homo with similar skull traits.

With the present character and taxon list, these skinkomorphs nest closer to humans than Biarmosuchus and more basal synapsids, like Dimetrodon. They’re just not human enough.

Biarmosuchus, the most basal therapsid.

Figure 3. Biarmosuchus, the most basal therapsid and not a cynodont. Despite nesting as a basal therapsid, its traits do not attract the taxon Homo more than others do. 

You think THAT’S ridiculous. Let’s take the next step…

Figure 2. Tamaulipasaurus nests with Homo sapiens when the basal cynodont, Procynosuchus, is excluded.

Figure 2. Tamaulipasaurus nests with Homo sapiens when the basal cynodont, Procynosuchus, is excluded. The fusion of skull bones, the short rostrum, and the large coronoid process of the dentary are traits shared with humans.

Deleting all the skinkomorph squamates
results in Homo nesting as a turtle/pareiasaur ancestor. Here the short face, anterior nares, tall pelvis and loss of manual and pedal phalanges appear to attract Homo to turtles like Proganochelys.

Proganochelys. Formerly the most primitive turtle.

Figure 2. Proganochelys. Formerly the most primitive turtle. Click to learn more. 

See what happens with taxon exclusion?
Strange bedfellows can result. So many current problems and enigmas in paleontology can be readily settled with a large enough family tree.

In the same light, I challenge paleontologists
to add thalattosaurs to Vancleavea studies… to add fenestrasaurs to pterosaur studies… to add mesosaurs to ichthyosaur studies… and to add millerettids to caseasaur studies. There’s no harm in doing so, and we all might learn something.

 

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