Friday, May 26, 2017

The Dinosaur to Bird Hypothesis Lacks Statistical Support

Cladograms which are based on bootstrap/jackknife, show that there is a large polytomy at the base of the coelurosaur clade. This is because the hypothesized nodes (Maniraptoriformes, Maniraptora, Pennaraptora) are not supported and therefore have been collapsed. The result is a much more correct picture of the taxa involved.

Xu et al
http://www.ivpp.cas.cn/qt/papers/201403/P020140314389417822583.pdf
See Figure S9


AND

Brusatte et al
https://www.cell.com/current-biology/fulltext/S0960-9822(14)01047-1
https://html2-f.scribdassets.com/iwsdsufi85tkruv/images/6-de642fd6b9.jpg



This means (to take one example) that we cannot tell what the relationship is between oviraptorids and Paraves from the cladistic analysis. The two possibilities are that oviraptorids were transitional between dinosaurs and Paraves OR that oviraptorids were secondarily flightless members of Paraves. It is important to note that the cladistic analyses cannot tell us which one is more credible.
Consequently we have to look for other indicators as to which is more credible.

We can immediately see that the alternative that oviraptorids were secondarily flightless members of Paraves means that we do not need to postulate ghost lineages. Also we do not need to postulate the pre-adaptations that are required by the idea that oviraptorids were transitional between dinosaurs and basal Paraves.

The same may apply to ornithomimosaurs and alvarezsaurids.

Also see:
https://www.academia.edu/32481358/The_Dinosaur_to_Bird_Hypothesis_Lacks_Statistical_Support
and
https://pterosaurnet.blogspot.com/2017/03/support-indices-do-not-support-dino-to.html