Wednesday, July 14, 2010

* Comparing dinosaur cladograms to the fossil record

Here is a totally fascinating report on how the published dinosaur cladograms compare to the stratigraphic (time) record.
It is significant that there is very high congruence (being in synch) when a cladogram covers an actual dinosaur group (eg. Hadrosauridae, Sauropoda etc) but a total lack of congruence when it covers Paraves.

Wills et al (2008):
Evidence for the evolutionary history of most groups derives from two independent sources. The first is the distribution of phylogenetically informative characters or markers in extant and extinct taxa. The second is the stratigraphic or temporal sequence in which taxa occur as fossils. Neither source of data can be read uncritically, and both require interpretation. Phylogenies incorporate assumptions concerning rooting and models of evolution. The resulting trees are therefore inferences rather than data. Fossils require varying degrees of interpretation depending upon the nature of the material, and dates may be subject to large margins of error. For these reasons, it is often desirable to compare inferences by mapping cladograms onto stratigraphic range charts 
"Over all 19 data sets, congruence was extremely high (Table 1). The average GER (Wills, 1999) for static first occurrence dates was 0.767, with the best data set being the Hadrosauridae (Horner et al., 2004; 0.956) and the worst being the Paraves (Turner et al., 2007; 0.558)."
" The least congruent data sets were the Paraves (Turner et al., 2007; GERt = 0.571), Stegosauria (Galton and Upchurch, 2004b; GERt = 0.611), Prosauropoda (Galton and Upchurch, 2004a; GERt = 0.720), and Ceratopsia (Xu et al., 2002; GERt = 0.755)."

Paraves is objectively calculated as the worst in terms of congruence. In fact, the article says that it is "indistinguishable from random". And that is because it is based on the incorrect dino-to-bird idea.
It would be very interesting to see the level of congruence if someone were to create a cladogram based on the ideas I have been presenting.

Note: Here is the Turner et al cladogram (2007):


  1. This cladogram doesn't include epidexipteryx, scansoriopteryx, pedopenna, jingfengopteryx, and anchiornis, which are all advanced eumaniraptorans from the mid to late Jurassic (also koparion, palaeopteryx, praeornis, and "Lori"), which render the"temporal paradox" obsolete. Using ghost lineages to argue against the monophyly of a group is very lazy, using this argument, couldn't you also argue that latimeria isn't a coelocanth because there's an 80 million year ghost lineage? What about tardigrades? There's a ghost lineage stretching back from the late Cretaceous to the early Cambrian. Also, this cladogram is not based on an idea, but actual data

  2. I said:
    The Paraves cladogram is objectively calculated by Wills et al, as the worst in terms of congruence. In fact, the article says that (along with Galton and Upchurch 2004b) it is "indistinguishable from random".

    Did you understand this point?
    How do you understand it?