December 8, 2014
3:23 pm: Starting on Larson (2013).
“In part due to the
absence of additional specimens, the validity of Nanotyrannus came under question by various researchers,
culminating in 1999 when Carr assigned the specimen to Tyrannosaurus rex. Carr presented a compelling argument…”
[Clarification: What I
did was show that all of the differences between the Cleveland skull and adult T.
rex are identical to the differences that are seen between juvenile and
adult Albertosaurus libratus, and that it shares similarities with adult
T. rex that are best explained by the small skull belonging to the same
species, namely T. rex - the only tyrannosaurid in strata of the Late Maastrichtian of the American West.]
“Carr’s 1999 paper kindled a debate that has grown hotter by
the year.”
[The scientific literature, as penned by actual scientists, does not show a debate beyond the dissenting view in Currie (2003). Carr et Williamson (2004) did not engage that article since it was submitted for publication - and possibly in press - by the time the 2003 article was published.]
3:40 pm: Stop.
References cited
Carr, T.D
., and Williamson, T. E. 2004. Diversity of Late Maastrichtian Tyrannosauridae
(Dinosauria: Theropoda) from western North America. Zoological Journal of the
Linnean Society 142: 419-523.
Currie,
P. J. 2003. Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous
of Alberta, Canada. Acta Palaeontologica Polonica 48(2): 191-226.
Larson, P. 2013. The case for Nanotyrannus; pp. 14-53 in J. Michael Parrish, Ralph E.
Molnar, Philip J. Currie, and Eva B. Koppelhus (Eds.) Tyrannosaurid
Paleobiology. Indiana University Press, Bloomington.
"The scientific literature, as penned by actual scientists, does not show a debate beyond the dissenting view in Currie (2003)"
ReplyDeleteDon't forget Witmer and Ridgely (2010). While they refrained from taking either side in the end, their discussion certainly leans pretty heavily toward the pro-Nanotyrannus side-
"... an interesting suite of apparently derived attributes observed in CMNH 7541 that might suggest that it represents a taxon separate from T. rex"
"Gorgosaurus and Tyrannosaurus are more similar to each other in their patterns of basicranial pneumatic foramina than either is to the highly asymmetrical apertures of CMNH 7541, and there is no evidence to suggest that either of the two named taxa went through an ontogenetic stage resembling CMNH 7541."
"Although the possibility cannot be ruled out, it seems hard to believe that the animal pertaining to CMNH 7541 would have ontogenetically transformed all of these attributes (both primitive and derived) and grown up to be a typical member of Tyrannosaurus rex."
"CMNH 7541 does not pertain to a hatchling ... and thus it is hard to envision such major morphological changes."
Indeed, their reason for not definitively maintaining Nanotyrannus isn't that they think the differences could end up being ontogenetic, but rather that the holotype has characters that are so weird amongst tyrannosaurids that they think it could be an aberrant individual of juvenile Tyrannosaurus-
"That said, we recognize that some aspects of CMNH 7541 are unusual enough that its being simply aberrant may always remain possible, which is why we have never stated definitively that it is not a juvenile T. rex."
Witmer and Ridgely, 2010. The Cleveland tyrannosaur skull (Nanotyrannus or Tyrannosaurus): New findings based on CT scanning, with special reference to the braincase. Kirtlandia. 57, 61-81.
Hi Mickey, I hadn't included that later work since it was not published at the time that Larson (presumably) submitted his revised manuscript for publication. Despite the 2013 date of the Tyrannosaurid Paleobiology volume, it took a long time for it see the light of day. That is why the most recently cited work in Larson's article does not go past 2008. I was limiting my comment to that specific historical context in order to be most faithful to his meaning.
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