Digging into another cladogram, pt. 3

Continuing this experiment…
yesterday and the day before I opened up and pruned a cladogram from Nesbitt et al. 2017, wondering how the tree topology could be so different from the LRT. The two competing analyses share very few traits in common. Nesbitt et al. used nearly twice as many characters. Many are tiny traits found in ankles, braincases and vertebral articulation patterns. In this review based on published data I cannot deal with such minutia, so those scores have to stand. Otherwise taxon inclusion, exclusion and scoring problems were found yesterday.

Today
I looked at scores for two more sets of taxa that nest together in the large reptile tree (LRT, 1560 taxa), but not in Nesbitt et al. 2017. The first set includes Scleromochlus and Gracilisuchus (Fig. 1), two basal crocodylomorphs in the LRT. In counterpoint, in the Nesbitt et al. tree these two nest far from other crocs and far from each other. 

Figure 1. The ancestry of Scleromochlus going back to Lewisuchus, Saltoposuchus, Terrestrisuchus, SMNS 12591 and Gracilisuchus.

Figure 1. The ancestry of Scleromochlus going back to Lewisuchus, Saltoposuchus, Terrestrisuchus, SMNS 12591 and Gracilisuchus.

After re-scoring,
Scleromochlus nests with Gracilisuchus in the reduced and rescored Nesbitt et al. cladogram (Fig. 2). A variety of other small bipedal crocs (Fig. 2) nest with them in the LRT.

The second set of taxa
include Turfanosuchus, Qianosuchus and Yarasuchus (Fig. 3). In the original Nesbitt et al. tree these three nest far from each other. They nest together after re-scoring. 

Figure 2. Revised cladogram from Nesbitt et al. 2017. This experiment continues.

Figure 2. Revised cladogram from Nesbitt et al. 2017. This experiment continues.

Overall the similarity
to other clade members is striking in both restored clades.

Figure 3. Yarasuchus, Qianosuchus and Turfanosuchus nest together in Nesbitt et al. 2017 after rescoring.

Figure 3. Yarasuchus, Qianosuchus and Turfanosuchus nest together in Nesbitt et al. 2017 after rescoring.

We’re not quite at the mid-point of this experiment,
so there is no expectation that other clades will remain inviolate in the rescored version of Nesbitt et al. 2017 (Fig. 2) as more taxa enter the testing phase. I am not surprised that so many wrong scores were originally entered because we talked about the many ‘odd bedfellows’ generated by Nesbitt 2011, examined in a nine-part series ending here.


References
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.
Nesbitt S et al. 2017. The anatomy of Teleocrater Rhadinus, an early avemetatarsalian from the lower portion of the Lifua Member of the Manda Beds (Middle Triassic). Journal of Vertebrate Paleontology 142-177. https://doi.org/10.1080/02724634.2017.1396539

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