Sometimes we miss the big picture.
Here then, for your approval and disapproval are comparisons between closest kin found by the Nesbitt (2011) tree versus those found by the large reptile tree. We started at the base with Mesosuchus. Yesterday we looked at Vancleavea. Today we look at Euparkeria, surrounded by Tropidosuchus + Chanaresuchus on primitive side and the phytosauria led by Parasuchus on the derived side (Fig. 1).
- Here (Fig. 2) are the selected Nesbitt (2011) sisters for visual comparison. They don’t look like sisters to me with their disparate shapes and proportions.
- Euparkeria does not fit here.
While Tropidosuchus and Parasuchus do share a suite of characters (dorsal naris, long narrow rostrum among them), several intervening taxa, like Chanaresuchus and Proterochampsa are missing here. Even with this distance, Euparkeria shares very little with these two and belongs with erythrosuchids and primitive rauisuchians. Here they are (Fig. 3), as promised yesterday.
Euparkeria fits better here.
Matching the Nesbitt (2011) tree, Euparkeria nested with the Garjainia (and Erythrosuchus) and Ornithosuchus in the large reptile tree (Fig. 3). Being surrounded by two pararchosauriforms (Fig. 2) is quite odd. They share very few traits not more closely shared by other taxa. This should have raised red flags and should have been cause for concern regarding the scoring of Nesbitt’s (2011) characters, no matter how many he used. In real evolution, sister taxa should look alike (Fig. 3) with slight variation. In real evolution, one should be able to trace a gradual accumulation of character traits, as we do with fossil hominids. The rules don’t change with reptiles. You need to take the shortest path, the one with the fewest changes, to nest sister taxa. One look at these results brings immediate understanding that there’s something wrong in the Nesbitt (2011) matrix that produces such strange bedfellows.
Choristodera and the Chanaresuchidae
While Tropidosuchus is on our minds… previously overlooked, the choristoderes were descendants of Youngina and a basal taxon produced parasuchians and chanaresuchians, according to the results recovered from the large reptile tree. Comparing the the choristodere, Cteniogenys, with the chanaresuchid, Gualosuchus, is instructive. The former lacks an antorbital fenestra, but it developed independently in the common ancestor of parasuchia and chanaresuchidae, the BPI 2871 specimen of Youngina, a taxon not far from Gualosuchus.
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.
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.