Tyrannosaurus rex joins the large reptile tree

Minor bone change made June 16, 2015 on a note sent minutes ago (see below) and June 19, 2015 with the addition of taxa to the Theropoda (Fig. 2).

The most iconic dinosaur,
the hero of Jurassic World, and everyone’s favorite is Tyrannosaurus rex (Fig. 1).

Figure 1. The skull of Tyrannosaurus rex in several views, bones colorized to aid identification and extent. The dorsally expanded parietal shield anchored large neck muscles to hold the giant skull in place and handle the high stresses involved with every skull slam on its dinosaurian prey. It would be great if all paleontologists started illustrating skulls and skeletons with colors as it is so much easier to understand. Many do already.

Figure 1. The skull of Tyrannosaurus rex in several views, bones colorized to aid identification and extent. The dorsally expanded parietal shield anchored large neck muscles to hold the giant skull in place and handle the high stresses involved with every skull slam on its dinosaurian prey. It would be great if all paleontologists started illustrating skulls and skeletons with colors as it is so much easier to understand. Many do already.

As readers know, I have avoided
doing the large well-known dinosaurs in favor of the lesser-known basal dinosauroids like PVL 4597, Trialestes and Herrerasaurus. I wanted to know the evolutionary relationships dinosaurs had with other prehistoric reptiles while others concentrate their efforts on the more popular dinosaurs.

But now and then
you have to add some more popular forms, like T-rex, Gallus the chicken and, on another branch of the large reptile tree, humans (Homo sapiens). Whenever any taxon is added to the large reptile tree, its complete ancestry back to Devonian basal tetrapods can be traced. With that list of intervening taxa, you can see, more or less, the direct lineage of any included taxon (up to 556 at last count). You can see where traits were enlarged or added while others were reduced or eliminated.

Figure 2. How T-rex fits within the current taxon list, within the Theropoda. Many other tyrannosauroids are known, but not shown here.

Figure 2. How T-rex fits within the current taxon list, within the Theropoda. Many other tyrannosauroids are known, but not shown here.

Paleontologists know quite a bit
about the lineage of T-rex. Many of its closest relations are known. The majority of these are not included in the large reptile tree taxon list. So, with this in mind, the closest known sister on the present taxon list is Sinocalliopteryx and both nest on the branch leading to birds.

Did T-rex have feathers?
Earlier I suggested that the evolution of feathers in basal naked dinosaurs was associated with their adoption of a bipedal gait among basal archosaurs. Later larger dinos often developed scales, which quite possibly were derived from primitive feathers, just as chicken leg scales are derived from feathers. The fossil and extant evidence for feathers has its advent with Sinocalliopteryx in the taxon list of the large reptile tree and most taxa that follow also preserve feathers.

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4 thoughts on “Tyrannosaurus rex joins the large reptile tree

  1. Sooo you just traced Greg Paul’s field guide T. rex? Without attribution even? He might not be happy about that. Also you have completely misunderstood how he has illustrated the jugal-postorbital joint. Without first hand observations DGS can not even accurately reproduce the anatomical artwork of the skeletally best understood dinosaurs. That speaks volumes.

  2. Chris ~ what’s with the finger-pointing ‘gotcha!’ attitude? Good eye on the G. Paul tracing. That was indeed my source. I don’t attribute any tracings that I do. But I do attribute original art. A quick peak at a PHOTO of a T-rex showed me where I made my mistake, following G. Paul’s line. First hand observation was, evidently, not necessary. In any case, thanks for the tip. I want to fix any and all errors. Darren Naish would disagree with you that this was an example of DGS, because, as you say, this dinosaur’s bones are already well known. I readily acknowledge mistakes when better data comes in. And I thought I would catch someone calling a tracing of a drawing ‘DGS.’ I hope this easy repair ‘speaks volumes’ to you.

  3. Ok, but you traced “Original Art.” That’s not the same as making a tracing of a photo. Although I personally feel that when they are not your photos, that you should be crediting those source as well. They’re was no “gottcha attitude.” That was my dismay at an artist producing a blatant copy of another artists work and not bothering to attribute the original.

    As for first hand observations, just the jugal postorbital suture alone of a Tyrannosaur skull is larger than 80% of the subject matter here, not to mention that those anatomical details typically have comparatively minimal taphonomic distortion and are 3 dimensionally prepared. At that scale I nor anyone else would have a problem using a photograph to confirm an observation or new finding. But you trace features at mm scales, features that every single one of your colleges would use a microscope to trace and photograph, features that are sometimes smaller than the grain size of the matrix and therefore by definition couldn’t have been preserved. Then the only thing you do to confirm those observations is to throw them all into a computer program that is filled with other such dubious observations, and of course the computer sorts them by parsimony. But garbage in, garbage out as they say. Its all fine and good that you acknowledge your mistakes, which btw is a new behavior here just in the last 6mos or so, but you are so 100% positive that your current interpretations are the truth. And up until recently you pretended your older interpretations didn’t even exist, interpretations that you held at the time with just as much religious ferocity as being the truth. And no amount of real data can dissuade you from that truth. Unless you can see a reconstruction (which btw is a hypothesis, not data) you dismiss it out of hand. To make matters worse you fully admit that you do not understand much of the data presented to you and yet you still dismiss it when is provided, often by a person who thoroughly does. Finally while you are still looking at pictures to check your observations against, take a look at the lachrymal maxillary suture. Greg Paul illustrated it correctly, DGS did not. And weather or not its technically DGS matters little, the methodology is the same. You trace a shape and colour it in. The point being that it is demonstrably an unreliable methodology, without an appropriate means of verification.

  4. I’ll take another look, Chris. I hope you’re equally tough on every mistake you find in others. With regard to errors, some are more important than others. Some enter a cladogram, while others do not. That being said, I’ll throw the same challenge at you that I did to others. If my data is so bad so often, my results should be beyond redemption. All I ask is that you pick two taxa from the large reptile tree that should not belong together and let me know where the wrongly nested one should belong. Currently all sister taxa actually look like sister taxa, something many other cladograms cannot say. That means the method is working, even as little as it is used.

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