Partitioning – part 2 – post-cranial characters only
Bennett (2012) discussed the value of partitioning a family tree into discrete parts (skull, limbs, post-crania, etc.) to help understand the the tree as a whole. Earlier I deleted all the post-cranial traits and recovered the same tree topology as without deletions. Here I delete all the cranial traits from the large reptile tree. I also delete any taxa for which only the skull iss known (otherwise there would be no scores at all for such taxa) and I delete taxa without limbs (snakes, etc.) for the same reason.
The results (Fig. 1) do not closely mirror the original large reptile tree. Only some (mostly derived) clades are retained. The base of this tree is unresolved, including a large number of unrelated taxa including mixing some amniotes with non-amniotes. Certainly more characters further describing various aspects of the post-crania would have resolved more of this tree. This makes sense as there is always a lack of diversity at the base of any clade.
Here, strangely, the arboreal drepanosaurids become sisters to the unrelated Triassic ‘rib’ gliders and together they are sisters to the marine Enaliosauria, sans Claudiosaurus, which nests correctly with other basal diapsids.
Here, strangely, turtles (Odontochelys and Proganochelys) and pareiasaurs nest with the burrowing lizard taxon, Bipes.
Here, hearkening back to tradition, the rhynchosaurs and trilophosaurs nest with basal archosauriforms and prolacertiforms.
Figure 1. The large reptile tree partitioned into post-cranial traits only. Light orange areas = new Archosauromorpha. Lt. green = new Lepidosauromorpha. Blue = non-reptiles. Greyed areas are shifts from the large reptile tree placements.
Pterosaurs still nest with basal fenestrasaurs and tritosaur lizards. Poposaurs still nest with dinosaurs. Vancleavea still nests with thalattosaurs. Pararchosauriforms are still distinct from Euarchosauriforms.
These results conclude our look at partitioning with the present character set. Smaller subsets (limbs, vertebrae, etc.) would do nothing to improve resolution.
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.
References
Bennett SC 2012. The phylogenetic position of the Pterosauria within the Archosauromorpha re-examined. Historical Biology. iFirst article, 2012, 1–19.
2012-10-01 02:04:42
Source: http://pterosaurheresies.wordpress.com/2012/10/01/partitioning-part-2-post-cranial-characters-only/
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