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. Yesterday we started at the base (Fig. 1) and the ill-advised inclusion of Mesosuchus. Today we reexamine the mistaken inclusion of Vancleavea (we did this several months ago, but differently).
Nesbitt (2011) included the new Triassic reptile, Vancleavea, in his list of Archosauriform taxa. It nested between Erythrosuchus and Tropidosuchus + Chanaresuchus (Figs. 1, 2). Since evolution works in minute steps, you may rightly ask, what’s wrong with this picture?
The much larger and more inclusive large reptile tree, recovered Vancleavea with the thalattosaurs, Helveticosaurus and Askeptosaurus (Fig. 3). Nesbitt’s 2011 study did not include these sisters.
Tropidosuchus and Chanaresuchus
The large reptile tree also recovered Tropidosuchus with Chanaresuchus (matching Nesbitt 2011) and Lagerpeton (Fig. 4), which nests closer to dinos in the Nesbitt (2011) tree. That’s pretty far from Erythrosuchus. So the three putative sisters found by Nesbitt (2011) are all strange bedfellows.
I’ll show pix of erythrosuchids and kin in a blog or two.
Fewer anatomical differences signal a closer relationship. Conversely, that means sister taxa share are a larger suite of traits. Our trees should recover sisters with a large suite of traits. By not including thalattosaurs, Vancleavea was inappropriately nested with archosauriforms by Nesbitt (2011).
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.