Monday, July 1, 2013
Literature review I: Larson, 2013
This entry is a challenge for me to pen, because I have two manuscripts in progress that have direct bearing on the ontogeny of Tyrannosaurus rex. I really do not want to deal with Larson's article in brevity, but my hands are tied because I will not put unpublished data here.
The bottom line is that Larson’s article “The case for Nanotyrannus” is a litany of straw man arguments and false analogies, misinterpretations of osteology, misunderstandings of variation and ontogeny, all rooted in a limited data set and a verificationist approach. None of it convinces me that the hypothesis I published in 1999 is incorrect: the weight of evidence shows that the Cleveland skull is referable to Tyrannosaurus rex, based on a comparison with the growth series of a well-known tyrannosaurid (namely, Albertosaurus libratus).
The Cleveland skull shows the juvenile features that are seen in all tyrannosaurid taxa, not just A. libratus, but also A. sarcophagus, Daspletosaurus torosus, and T. bataar (Carr, 1999; Currie, 2003). It also shows features that are shared with adult T. rex (yes, and adults lower in the tyrannosaurine phylogenetic hierarchy); ergo, the simplest hypothesis is that the skull is (1) a juvenile tyrannosaurid that is (2) referable to T. rex. From what I’ve read, Larson (2013) has set this line of reasoning aside in favor of something complicated.
On a lighter note, if that Late Cretaceous oviraptorid embryo (Larson, 2013: 44) – evidently in an egg – had the loving attention of so much ink, then we would have learned a lot more from that specimen about the rules of theropod ontogeny and evolution, instead of this taxonomic wallow!
Carr, T. D. 1999. Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Theropoda). Journal of Vertebrate Paleontology 19:497-520.
Currie, P.J. 2003. Cranial anatomy of tyrannosaurid dinosaurs from the late Cretaceous
Alberta, Canada. Acta Palaeontologica Polonica 48: 191–226.
Larson, P. L. 2013. The case for Nanotyrannus in J. M. Parrish, R. A. Molnar, P. J. Currie., and E. B. Koppelhus (eds.) Tyrannosaurid Paleobiology, University of Indiana Press, Bloomington and Indianapolis, pp. 15-53.
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