• Tag Archives Yutyrannus
  • The return of the scaly T. rex to modern paleo-art

    Tyrannosaurus rex walking towards camera. Art by John Sibbick.

    [NOTE: Post has been updated to include a section on scale size]

    This has certainly been an interesting year. Two papers dropped in the past three months that have put the brakes on a recent trend in paleo-art. That trend? Why the feather-coated T. rex of course.

    First, in March, we saw the release of a paper detailing a new species of Daspletosaurus and its relationship to D. torosus.

    Carr, T.D., Varricchio, D.J., Sedlmayr, J.C., Roberts, E.M., Moore, J.R. 2017. New Tyrannosaur with Evidence for Anagenesis and Crocodile-Like Facial Sensory System. Scientific Reports. 7(44942):1–11.

    In this paper, Carr et al. argue for the designation of a new Daspletosaurus species, D. horneri. The authors argue, based on skull shape and chronostratigraphic position, that D. horneri was the direct ancestor to D. torosus. I thought that the authors put forth a compelling argument for this anagenic event and backed up their position well. Interestingly, this part of the paper should have been the most controversial. As anyone who has read anything from Horner and Scanella over the past eight years can attest, arguing for a direct ancestor-descendant relationship for dinosaurs is difficult to do and even harder to win over others in the field. So it is somewhat surprising to see a case for anagenesis in Daspletosaurus taken so well by the palontological community. All the more so given that it involves a tyrannosaur, the poster children for “cool guy” dinosaurs.

    Instead, the most controversial part of the paper wound up being their soft-tissue reconstruction of the face for D. horneri. The author responsible for the soft-tissue reconstruction was Jayc Sedlmayr of Louisiana State University. Sedlmayr did his doctorate on osteological correlates for vasculature in extant archosaurs (birds & crocs). He is the seminal alumnus of the WitmerLab and thus is well within his wheelhouse for this type of soft-tissue reconstruction. Sedlmayr borrowed heavily from the work of another WitmerLab alumnus, Tobin Hieronymus, whose PhD work involved osteological correlates for integument on the skulls of animals. Although the skin is often well away from the underlying bones on most of the body, there are exceptions when it comes to the skull. There, areas that are not heavily muscled, tend to show intimate connections between the skin and the underlying bone. Hieronymus used these connections to determine how different integumentary appendages (scales, hair, feathers) affect the underlying bone (Hieronymus & Witmer 2007; Hieronymus et al. 2009). The authors found that the surface texture along the skull of D. horneri was “hummocky”. That is, it was covered in lots of closely packed ridges. According to Hieronymus & Witmer (2007), this texture correlates to scales as the overlying integumentary appendage. Thus, according to the authors, D. horneri had a scaly face (this is grossly oversimplified as the authors were able to piece together a variety of different integument variants along the skull, but you get the idea).

    Scaly tyrannosaur cannonball one had been shot.

    Then two weeks ago, we saw the release of another paper on tyrannosaur integument. However, unlike the previous paper, this one was specifically dedicated to integumentary types in tyrannosaurids.

    Bell, P.R., Campione, N.E., Persons, W.S., Currie, P.J., Larson, P.L., Tanke, D.H., Bakker, R.T. 2017. Tyrannosauroid Integument Reveals Conflicting Patterns of Gigantism and Feather Evolution. Biology Letters. 13:20170092

    In this paper, the authors set out to survey all known instances of “skin” impressions for tyrannosaurids. Their list of taxa included Albertosaurus, Tarbosaurus, Daspletosaurus, and Gorgosaurus. Their results pretty definitively indicated that scales were the predominant integumentary appendage on tyrannosaurids. The authors then went on to speculate why that would be if earlier tyrannosauroids had filamentous integument. They performed an ancestral character state reconstruction based on Parsimony and Bayesian-based trees from Brussatte and Carr 2016. Their results found that filaments came out strongly as the ancestral character for tyrannosauroids, but by no later than Tyrannosauridae proper, a reversion to scales had taken effect. The authors attributed this to body size evolution. Namely, larger tyrannosauroids reverted to scales over protofeathers.

    Cannonball number 2 had just been shot.

    Continue reading  Post ID 1711

  • “Feathers” on the big, “feathers” on the small, but “feathers” for dinosaurs one and all?


    Yutyrannus artwork by Brian Choo. Sciurumimus artwork by Arkady Rose

    This year has seen the discovery of two big deal dinosaur specimens. At least they are a big deal in regards to dinosaur integument and, possibly, metabolism.

    First off from a few months ago we had the announcement the theropod Yutyrannus hauli, the “beautiful feathered tyrant.”

    Xu, X., Kebai, W., Ke, Z., Qingyu, M., Lida, X., Sullivan, C., Dongyu, H., Shuqing, C., Shuo, W. 2012. A Gigantic Feathered Dinosaur from the Lower Cretaceous of China. Nature. Vol.484:92-95

    This was not just a single fossil, but a collection of three fossils (one might be tempted to call it a family group, but that would only be speculation). As with all other dinosaur fossils that have been found to have filamentous integument, these guys come from Liaoning, China. They are suspected to have come from the Jehol Group in the Yixian formation. I say suspected because the complete three specimen set was a purchase from a fossil dealer, an all too common occurrence for Chinese fossils. As such the provenance information is unknown. A lot of Chinese fossil dealers don’t like to give away the location of their find due to the potential loss of other profitable specimens. This current trend in China is a good example of what happens when capitalism comes into play with fossil collecting (something that the U.S. has been mostly, but not entirely, able to avoid). So it is currently uncertain whether these fossils are from the Yixian. However given that all the others guys are too it is probably a good bet. Given the sketchy nature in which many Yixian fossils are collected, coupled with the possibly large consequences of the find, one should naturally be skeptical of the fossil. Had it been one individual on multiple slabs I would question its validity as a real thing. However since Y.huali is known from three individuals, and the filaments seem to follow a consistent pattern around the body (compare that to the helter-skelter nature of Tianyulong‘s preservation), forgery seems unlikely. These guys are probably the real deal. This has some potentially far reaching consequences to interpretations of Late Cretaceous coelurosaurs and the Jehol Biota itself (more on this in a bit).

    The second announcement came just a few weeks ago. This was the discovery of a potentially new, miniscule theropod from Bavaria Germany.

    Rauhut, O.W.M., Foth, C., Tischlinger, H., Norell, M.A. 2012. Exceptionally Preserved Juvenile Megalosauroid Theropod Dinosaur with Filamentous Integument from the Late Jurassic of Germany. PNAS Early Edition:1203238109v1-201203238.

    The specimen is exceptionally well preserved. So well preserved in fact that it actually looks like a plastic toy. While this degree of preservation warrants importance all its own, the main interest behind this new guy—dubbed: Sciurumimus albersdoerferi (Albersdörfer’s squirrel mimic)—is the apparent presence of filamentous integument on the body coupled with its apparent placement among much more basal theropods. This discovery has far reaching consequences for theropod integument interpretations. Note: As with Y.hauli, Sciurumimus albersdoerferi was also purchased from a private collector. I don’t suspect forgery here either as this was in Germany, where fossil dealing is neither a big problem nor a lucrative business. The exceptional detail on the specimen would also require a substantial amount of theropod knowledge to pull off. Anyone having that amount of knowledge is more likely to be a real paleontologist than a get rich quick forger.

    Continue reading  Post ID 1711