First Zhenyuanlong, then Tianyuraptor, Ornitholestes and finally Fukuivenator were recovered as taxa basal to tyrannosaurs — in contrast to traditional nestings by Brusatte and Hone. In the case of Tianyuraptor (Zheng et al. 2010), I followed the original tracing (which turned out to be neither as clear nor as accurate as needed) and created a reconstruction with a short neck, following the pattern of Zhenyuanlong (Fig. 2). The short neck of Zhenyuanlong gave my mind a prior ‘tradition’ or ‘bias’ permitted the acceptance of that short neck.
Fortunately, M. Mortimer cautioned that
17 dorsals in Tianyuraptor was too high a number for theropods. 13 or 14 should be the maximum number for theropods with 5 sacrals, according to Mortimer. A subsequent DGS tracing of the fossil itself (Fig. 1) revealed that 17 was indeed too high. Only 15 are currently considered to be dorsals. One dorsal had to be removed when a hole in the matrix between two dorsals was judged to not include a missing dorsal. More cervicals were recovered, more closely matching the number found in more primitive proximal taxa like Ornitholestes, Compsognathus and possibly Sinornithosaurus. Among theropods tested in the large reptile tree, only these taxa have more than 25 presacrals. Microraptor, also in this clade. lt has 25 pre-sacrals, which is still higher than most theropods and many more than in tyrannosaurs, which appear to lose several presacrals.
M. Mortimer also noted
that Tianyuraptor does not have an anterior process on the pubic boot. And this is so. That process doesn’t appear until just barely in Zhenyuanlong. And I’m happy to make that change.
neither of these changes in interpretation changes the nesting of Tianyuraptor or the large reptile tree topology, something M. Mortimer was evidently hoping to do. Note that a longer neck and more cervicals is found in the predecessor taxon, Ornitholestes (Fig. 2). So that character change just moved one node.
M. Mortimer also noted
that the scapulae of Zhenyuanlong are not dorsally expanded as in tyrannosaurs. I wondered why Mortmer wrote this, because I did not trace the scapulae with dorsal expansions. After taking another look at the photos, I see I have omitted the dorsal expansions hidden among the other bones. Here they are (Fig. 3), just like those in tyrannosaurs. Sorry, Mickey… and thanks!
Mortimer also noted, “Or for Zhenyuanlong, you reconstruct a tyrannosaur-like dorsally expanded quadratojugal, but it actually has a dromaeosaurid-like quadratojugal with a narrow dorsal process and long posterior process as seen and labeled in the paper’s figure 2.”
To which I replied, “The back of the skull is such a mess that Lü and Brusatte opted to avoid identifying any bones there. What Lü and Brusatte identify as a right anlgle quadratojugal I identified as two bones, the horizontal rim of the surangular and a vertical slender bone with an expanded base that appears to be the broken jugal ramus of the quadratojugal, which currently lacks a jugal ramus if all identifications are correct. I can see how that bone could be identified as a quadratojugal as it was by Lü and Brusatte. They identified the top of the quadratojugal as the quadrate, but that would be a very short quadrate. They did not identify the bone inside the surangular, which I identified as the quadrate. It fits the skull reconstruction and looks like a tyrannosaur quadrate. They key to resolving this argument may be higher resolution images and a disassembly of the Zhenyuanlong skull, either by hand or digitally, to identify all the bones properly. The rest of the skeleton (except the stiffened tail) more parsimoniously nests with tyrannosaurs, so, being human, I lean that way on skull bone IDs.”
On a more entertaining tyrannosaur note,
there is a wonderful 2013 YouTube video by animator Teddy Cookswell showing the misadventures of a hatchling T-rex that is very well done. Find it here or click on the image (Fig. 4).
There’s another YouTube video promoting a new biography of Léon Foucault, inventor of the gyroscope and Foucalt pendulum, and the man who proved the Earth rotates by demonstrating this with a pendulum. The author, Amir Aczel and his book, “Pendulum: Leon Foucalt and the Triumph of Science,” provide some interesting insights into the acceptance of new ideas by the mathematics and science communities — and that’s why I bring it up here.
Aczel reports on all the dismissals Leon Foucault received after showing the Earth turned by using a pendulum — and by providing the formula for determining the length of time a pendulum would take to complete a circuit depending on its latitude on the Earth (24 hours at the pole, never at the Equator, 32 hours at Paris). Foucault was not considered to be either a scientist or a mathematician by the science and math elite. So his reports and results were dismissed by others. Foucault was an engineer and built the first apparatus that allowed the pendulum to swing continually and without building up torque in the line, both of which enabled his experiment to succeed.
Zheng X-T; Xu X; You H-L; Zhao, Qi; Dong Z 2010. A short-armed dromaeosaurid from the Jehol Group of China with implications for early dromaeosaurid evolution. Proceedings of the Royal Society B 277 (1679): 211–217.