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.

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.


2 thoughts on “Three odd little theropods

  1. I often find myself on your blog and website, reading articles and benefiting from your skeletal restorations. I’m a wildlife ecologists, not a paleontologist, but I enjoy drawing extinct organisms and doing my best to reconstruct them as accurately as I can manage. That being said, I right away noticed that your content does not align well with mainstream thought (e.g. wikipedia). Today I noticed that you do not group Segisaurus with coelophysids, like everybody else, so I got curious and googled for outside opinions on your research. Darren Naish’s article on the Scientific American website popped up and I read through it. Perhaps oddly, it made me angry. His implication that paleontologists should not take your research seriously was particularly irksome to me. I’ve looked over your methods and they certainly seem unconventional and speculative, but they are definitely possible. I enjoy reading your articles because of your unique, unconventional perspective. It’s as if Naish has forgotten that every theory on reptile evolution is, at best, speculative. I believe that voices like yours are vital to scientific discussion and I STRONGLY disagree with Naish’s insinuation that paleontologists should boycott your websites. Right or wrong, your theories are a very valuable part of the scientific process. Science is not a sacred defense of truth, where priests must silence the dissonant. Science is merely a tool for exploring the world and your methods can be described as exactly that (unconventional tools for exploring extinct life forms), regardless of how disruptive they may be to mainstream science. If history has taught us anything, once “science” reaches a consensus, it is almost certainly incorrect. You might be the best thing that’s ever happened to paleontology, not because you’re correct, but because you have upset the equilibrium of scientific consensus. So, please, keep pushing into mainstream science and get your voice heard. Without people like you, paleontology is as good as dead.

    • Thank you, Caleb. Much appreciated. I have confessed to over 100,000 corrections, which means there were 100,000+ mistakes earlier. I have also told readers that every new taxon (nearly 2000 at present, including pterosaurs and therapsids not included in the LRT) was new to me. So mistakes will happen — but not because of taxon exclusion.

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