Three odd little theropods

The large reptile tree nests Marasuchus, Procompsognathus and Segisaurus (Fig. 1) together in a clade within the Theropoda. These three differ in many ways, yet their similarities trump those differences.

Figure 1. Procompsognathus, Marasuchus and Segisaurus nest together in the Theropoda despite their many differences.

Figure 1. Procompsognathus, Marasuchus and Segisaurus nest together in the Theropoda despite their many differences. Click to enlarge.

Procompsognathus and Segisaurus have been nested together previously (Carrano et al. 2005), despite their obvious differences. Marasuchus typically nests outside the Dinosauria (Nesbitt 2011), but only in tests that do not include Procompsognathus and Segisaurus. We looked at the Marasuchus problem earlier here. And we looked at some Nesbitt (2011) problems here.

Deleting Procompsognathus and Segisaurus does not change the nesting of Marasuchus. Deleting Tawa and Coelophysis likewise does nothing to shift the nesting of Marasuchus.

These three are not in the lineage of birds.

References
Carrano MT, Hutchinson JR and Sampson SD 2005. New information on Segisaurus halli, a small theropod dinosaur from the Early Jurassic of Arizona: Journal of Vertebrate Paleontology, v. 25, n. 4, p. 835-849.
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.

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