Yutyrannus: NOT a tyrannosaur!

Modified December 27, 2015 and December 29, 2015 with the addition of a reconstruction of Yutyrannus and a theropod cladogram. 

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.

Figure 1. Yutyrannus reconstructed.

Figure 1. Yutyrannus reconstructed.

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.

Figure 2. 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.

 

I’ve added a new image (Fig. 2b) based on a DGS tracing of a photograph of the specimen ZCDM V5000 that is slightly different than the original drawing (Fig. 2a).

Figure 2b. DGS tracing of one of the specimens of Yutyrannus. Figure 1 has been modified to the new skull.

Figure 2b. DGS tracing of one of the specimens of Yutyrannus. Figure 1 has been modified to the new skull.

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.” 

Figure 1. Theropod cladogram. With the addition of Guanlong and the identification of prior errors, the nesting of the microraptors separates from the tyrannosaurs, but Guanlong nests with Sinocalliopteryx, Allosaurus and Yutyrannus, not tyrannosaurs.

Figure 3. Theropod cladogram. With the addition of Guanlong and the identification of prior errors, the nesting of the microraptors separates from the tyrannosaurs, but Guanlong nests with Sinocalliopteryx, Allosaurus and Yutyrannus, not tyrannosaurs.

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.

Figure 4. 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 ChinaNature 484 (7392): 92–95. doi:10.1038/nature10906. Get a PDF here.

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3 thoughts on “Yutyrannus: NOT a tyrannosaur!

  1. “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.”

    At this point, you should be asking yourself whether everyone else is wrong about every tetrapod group ever, or whether your methods are flawed. You can’t use your usual excuse here and say everyone else needs to use a wider taxon sample or species-level OTUs, because numerous other matrices have been made for theropods using many more characters and taxa than your 221 and 44. Cau et al. (2015) features two analyses that include 860 and 1549 characters and 152 and 120 theropod taxa, for instance. As someone who is a theropod expert, I can say basically all of your reconstructions are highly flawed and dissimilar to what the bones actually look like. Brief example- it’s immediately obvious no theropod has such a short scapula as you give Dave. You missed the impression of the distal half of the bone and have it upside down to boot. And there are literally tens of examples like that in each tracing you do. Thus what you are coding isn’t real- your cladogram is showing how imaginary animals nest in your tiny and flawed matrix.

  2. Thanks, Mickey. I’ll put the theropod taxa together in one image in the near future and have a look see. Changes, if they happen, will be published. Thanks for the input on the Sinornithosaurus. Unfortunately larger scapular elements won’t change any scores.

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