Yutyrannus: NOT a tyrannosaur!
Okay, this is getting ridiculous.
I stayed away from dinosaurs, and theropod dinosaurs because I thought many others had covered them so thoroughly. Evidently, not so. Lots of theropods are getting nested at new nodes lately.
Yutyrannus is famous
for being a giant feathered theropod, several times larger than the next largest contender. Yutyrannus huali (Xu et al. 2012 ZCDM V5000 Zhucheng Dinosaur Museum, Shandong, Lower Cretaceous Yixian Formation) was originally considered a tyrannosauroid theropod.
Famous for feathers
Xu et al. report, “Most significantly, Y. huali bears long filamentous feathers, thus providing direct evidence for the pres- ence of extensively feathered gigantic dinosaurs and offering new insights into early feather evolution.”
Figure 1. Yutyrannus nests not with tyrannosaurs but with allosaurs. And it is feathered. Click to enlarge. Femoral length = 85 cm in the adult. That’s a pnenmatic midline crest created by the nasals. The postfrontal and postorbital are distinctly colored here but fused in the specimen.
Phylogenetic analysis
Xu et al. report, “Phylogenetic analyses using two different theropod matrices place this taxon among basal tyrannosauroids, but relatively close to the Tyrannosauridae.”
Unfortunately
the large reptile tree (now 620 taxa) nests Yutyrannus unambiguously with another giant theropod, Allosaurus. Not sure why we have such a difference here, unless untested basal tyrannosaurs converge strongly with Allosaurus. Or was there an initial bias? Or does Yutyrannus nest with tyrannosaurs when only theropod traits are employed? The large reptile tree uses such generalized traits that it covers every tested taxon from basal tetrapods to humans, turtles, snakes and birds.
Figure 2. Skull of Allosaurus for comparison to Yutyrannus.
I can’t believe this the first time
the tyrannosaur relationship of Yutyrannus was not recovered in a phylogenetic analysis. Let me know of any prior studies that recovered a similar nesting so I can give proper credit.
And Merry Christmas everyone…
References
Xu X, Wang K, Zhang K, Ma Q, Xing L, Sullivan C, Hu D, Cheng S, Wang S et al. 2012. A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature 484 (7392): 92–95. doi:10.1038/nature10906. Get a PDF here.
Source: https://pterosaurheresies.wordpress.com/2015/12/25/yutyrannus-not-a-tyrannosaur/
