Taxa missing from the ancestry of Tyrannosaurus in Lü et al. 2014

Lü et al. 2014
introduced the tyrannosaur, Qianzhousaurus (not yet in the LRT) and their own cladogram of Tyrannosauroidea (Fig. 1). The large reptile tree (LRT, 1406 taxa, subset Fig. 4) and a quick look on Google confirm only the taxa closest to Tyrannosaurus  and Compsognathus (yellow) in common with the Lü et al. taxon list. Taxa in blue are more closely related to Allosaurus in the LRT. Gray taxa are largely incomplete.

Figure 1. Qianzhousaurus cladogram from Lü et al. Colors added based on the LRT.

Figure 1. Qianzhousaurus cladogram from Lü et al. 2014. Colors added based on the LRT. Too little known taxa are scraps.

Look for that dorsally expanded quadratojugal
like the one shown here (Fig. 2, 7) for feathery Zhenyuanlong. Only tyrannosaurs have that. (I just pulled another Larry Martin!) Better yet, you can add the missing taxa from figure 4 to your tyrannosaur/theropod cladogram and see where they nest. Let me know if you confirm or refute the LRT hypothesis of relationships.

Another trait tyrannosaurs share is an upturned premaxilla
(Fig. 7) after Compsognathus. 

Figure 0. Taxa ancestral to tyrannosaurs beginning with the CNJ7 specimen of Compsognathus.

Figure 2. Taxa ancestral to tyrannosaurs beginning with the CNJ7 specimen of Compsognathus. Tianyuraptor has been more recently repaired with an upturned premaxilla based on phylogenetic bracketing and a better fit with bones (Fig. 3).

Short note today. 
We looked at this problem earlier here and here when reviewing the tyrannosaur books that came out a few years ago.

Figure 2. Tianyuraptor skull in situ and reconstructed.

Figure 3. Tianyuraptor skull in situ and reconstructed.

Figure 1. Subset of the LRT focusing on basal theropods. Pink area are more or less goose-sized and smaller taxa.

Figure 4. Subset of the LRT focusing on basal theropods. Pink area are more or less goose-sized and smaller taxa.

Figure 1. Masiakasaurus drawings from Carrano, Loewen and Sertic 2011) with photos from same.

Figure 5. Masiakasaurus drawings from Carrano, Loewen and Sertic 2011) with photos from same. Given these few bones, the LRT nests this taxon as a  tyrannosaur ancestor. close to Tianyruaptor (Fig. 3).

Figure 1. Fukvenator parts to scale lifted from Azuma et al. 2016. Note, the larger skull, hind limb and foot match Zhenyuanlong in size and general morphology. Only the manus is relatively larger. I suspect the smaller skull scale bar.

Figure 6. Fukvenator parts to scale lifted from Azuma et al. 2016. Note, the larger skull, hind limb and foot match Zhenyuanlong in size and general morphology. Only the manus is relatively larger. I suspect the smaller skull scale bar.

The purported long snout of Qianzhousaurus
is little different from that of Alioramus (Fig. 7).

Figure 1. The following taxa nest in the clade of Tyrannosaurus at present: Gorgosaurus, Alioramus, Zhenyuanlong, Huaxiagnathus, Tinayuraptor and Ornitholestes.

Figure 7. The following taxa nest in the clade of Tyrannosaurus at present: Gorgosaurus, Alioramus, Zhenyuanlong, Huaxiagnathus, Tinayuraptor and Ornitholestes.

References
Lü J-C, Yi L-P, Brusatte SL, Yang L, Li H and Chen L 2014. A new clade of Asian Late Cretaceous long-snouted tyrannosaurids. Nature Communications 5:3788. DOI: 10.1038/ncomms4788

Masiakasaurus: a large compsognathid, not a ceratosaur/abelisaur

This new taxon examination began with
a recent paper by Delcourt 2018 on ceratosaur palaeobiology that included Masiakasaurus (famous for its strong procumbent dentition, Fig. 1). When I looked at the restored skull in Delcourt 2018, figure 2, alongside other abelisaur/ceratosaur skulls, I was struck by the thought, first voiced by Ernie on Sesame Street, “One of these things is not like the other.” Other funny examples are here.

Figure 1. Masiakasaurus drawings from Carrano, Loewen and Sertic 2011) with photos from same.

Figure 1. Masiakasaurus drawings from Carrano, Loewen and Sertic 2011) with photos from same.

Delcourt 2018 reported,
“Ceratosaur theropods ruled the Southern Hemisphere until the end of the Late Cretaceous. However, their origin was earlier, during the Early Jurassic, a fact which allowed the group to reach great morphological diversity.” Perhaps there is just a little too much diversity in Delcourt’s taxon list. See below.

Masiakasaurus knopfleri (Sampson, Carrano and Forster 2001; Carrano, Loewen and Sertic 2011) was originally considered a ‘bizarre predatory dinosaur’ related to abelisaurids like Majungasarus. Here, in the large reptile tree (LRT, 1240 taxa) Masiakasaurus is related to Tianyuraptor, which also has procumbent teeth and a long torso. Essentially Masiakasaurus is a larger compsognathid leading to giant tyrannosaurs, not far from larger ornithomimosaurs (Fig. 4).

Figure 2. Tianyuraptor skull in situ and reconstructed.

Figure 2. Tianyuraptor skull in situ and reconstructed.

Other taxa with a descending anterior dentary with teeth
include Tianyuraptor (Fig. 2) and the large Compsognathus (CNJ79, Fig. 3) both of which share a long list of traits with Masiakasaurus. All of these taxa have really long cervical ribs.

Figure 1. The large (from Peyer 2006) and small Compsognathus specimens to scale. Several different traits nest these next to one another, but at the bases of two sister clades. Note the differences in the forelimb and skull reconstructions here. There may be an external mandibular fenestra. Hard to tell with the medial view and shifting bones.

Figure 3. The large (from Peyer 2006) and small Compsognathus specimens to scale. Several different traits nest these next to one another, but at the bases of two sister clades. Note the differences in the forelimb and skull reconstructions here. There may be an external mandibular fenestra. Hard to tell with the medial view and shifting bones.

Figure 4. Subset to the LRT focusing on Masiakasaurus and kin.

Figure 4. Subset to the LRT focusing on Masiakasaurus and kin.

Taxon exclusion plagues the Delcourt paper. Neither Tianyuraptor nor Compsognathus are mentioned in the text. Nor could I find the taxon Masiakasaurus mentioned with these two.

Inappropriate taxon inclusion. Like Tianyuraptor, Limusaurus also should not have been included as a ceratosaur. The LRT nests Limusaurus with oviraptorids.

When Masiakasaurus was first described
by Sampson et al. 2001, the authors reported, “[Masiakasaurus] is unique in being the only known theropod with a highly procumbent and distinctly heterodont lower dentition. Such a derived dental morphology is otherwise unknown among dinosaurs.” Actually, and this was easy to overlook, the large Compsognathus (Fig. 3) was known since Bidar et al., 1972, but it is more conservative in this feature. Tianyuraptor was reported several years later, in 2010 and the anterior dentary is broken and flipped in situ (Fig. 2). Fukuivenator is known from bits and pieces.

Addendum from Mickey Mortimer:
“Etrigansauria [from the Delcourt paper] is just a junior synonym of Neoceratosauria, which is basically ignored by Delcourt.  The phylogenetic taxonomy in this paper is horrible, ignoring Phylocode Article 11.7, ignoring earlier and better definitions than those of Wilson et al. (2003), redefining Ceratosauroidea as if it were Abelisauroidea, proposing definitions that only work in the topology being used, and citing incorrect definitions for Elaphrosaurinae, Noasaurinae and Furileusauria.  More details on my blog-“

http://theropoddatabase.blogspot.com/2018/06/etrigansauria-unnecessary-demon.html

References
Bidar AL, Demay L and Thomel G 1972b. Compsognathus corallestris,
une nouvelle espèce de dinosaurien théropode du Portlandien de Canjuers (Sud-Est de la France). Annales du Muséum d’Histoire Naturelle de Nice 1:9-40.
Carrano MT, Loewen MA and Sertic JJW 2011. 
New materials of Masiakasaurus knopfleriSampson, Carrano, and Forster, 2001, and implications for the morphology of the Noasauridae (Theropoda: Ceratosauria). Smithsonian Contributions to Paleobiology. 95: 53pp.
Delcourt R 2018. Ceratosaur palaeobiology: new insights on evolution and ecology of the southern rulers. Nature.com/scientificreports 8:9730 | DOI:10.1038/s41598-018-28154-x
Lü J and Brusatte SL 2015. A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution. Scientific Reports 5, 11775; doi: 10.1038/srep11775.
Sampson SD, Carrano MT and Forster CA 2001. A bizarre predatory dinosaur from the Late Cretaceous of Madagascar. Nature. 409 (6819):504–506. doi:10.1038/35054046.
|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.

wiki/Tianyuraptor
wiki/Masiakasaurus
wiki/Fukuivenator

 

Eotyrannus compared to Gorgosaurus

Updated Marc 28, 2018 with the realization that the purported nasal is actually the nasal + frontal + broken lacrimals. 

Hutt et al. 2001
brought us the bits and pieces of an Early Cretaceous (Barremian, 125 mya) theropod assigned to the Tyrannosauroidea, Eotyrannus from Southern England. All the other tyrannosaurs are Late Cretaceous from Eastern Asia and Western North America.

From the abstract
“Numerous character states are shared with tyrannosaurids but the new taxon appears to be excluded from the group that comprises aublysodontine and tyrannosaurine tyrannosaurids. We conclude that the taxon is a basal tyrannosauroid and as such it is one of the earliest and (with the exception of some teeth and an isolated ilium from Portugal) the first from Europe.”

The authors provided a reconstruction that was unlike
that of any other theropod in the large reptile tree. The tall naris and rectangular profile (Fig. 1, lower right) are unknown elsewhere among tested taxa.

Figure 1. The bits and pieces of Eotyrannus restored as a skull. It appears the original nasal is actually the nasal + frontal and some lateral bones.

Figure 1. The bits and pieces of Eotyrannus restored as a skull. It appears the original nasal is actually the nasal + frontal and some lateral bones. Original restoration at lower right. Gorgosaurus at upper right.

Here (Fig. 1), the bits and pieces
come together as a very gorgosaur-ish theropod, but it arrives pretty darn early in the fossil record. There’s a nice fused set of nasals—a very tyrannosaur-ish trait. Even so, there’s not very much to work with. In the last round of changes to the theropod subset I dropped Eotyrannus from the (LRT). Just too few characters to work with.

References
Hutt S, Naish D, Martill DM, Barker MJ and Newbery P 2001. A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 22:227-242.
Naish D 2011. Theropod Dinosaurs, chapter 29 in Batten DJ (ed) English Wealden Fossils. The Palaeontological Association (London), pp. 526-559.

wikiEotyrannus

The origin of giant ‘birds’: Tyrannosaurus, a giant Zhenyuanlong

Today we conclude our foray into giant birds with a non-bird.
I could not resist this one. Today’s taxa are not birds, but very convergent. Hope you like it as we revisit the very bird-like Zhenyuanlong, with its long wing feathers, and its giant descendant, Tyrannosaurus rex (Fig. 1). We looked at this heretical pair revealed by phylogenetic analysis for the first time in the large reptile tree earlier here.

Figure 1. Zhenyuanlong compared to scale with the foot of T-rex and a another overall view of T-rex to a similar overall length.

Figure 1. Zhenyuanlong compared to scale with the foot of T-rex and a another overall view of T-rex to a similar overall length.

Tyrannosaurus rex (Osborn 1905) Late Cretaceous, 65 mya, 12.3 m in length, was derived from a sister to Sinocalliopteryx and was a sister to bird-like dinosaurs in the large reptile tree. Several varieties are known. Some are more robust. Others are gracile and smaller.

Zhenyuanlong suni (Lü and Brusatte 2015, JPM-0008) Early Cretaceous, 122 mya, over 1m in length, was derived from a sister to Tianyuraptorand is an ancestral sister to Tyrannosaurus. The fossil preserves wing feathers and so was considered the largest of the Chinese winged dromaeosaurs. Click here to see the list of traits shared with tyrannosaurs not with dromaeosaurs and to learn more. Note the short torso and tall, narrow orbit. This fossil shows that tyrannosaurs once had flight feathers.

We also looked at
the tiny arms of T-rex earlier here. They were tiny wings.

Figure 0. Taxa ancestral to tyrannosaurs beginning with the CNJ7 specimen of Compsognathus.

Figure 0. Taxa ancestral to tyrannosaurs beginning with the CNJ7 specimen of Compsognathus.

References
Lü J and Brusatte SL 2015. A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution. Scientific Reports 5, 11775; doi: 10.1038/srep11775.
Osborn HF 1905. Tyrannosaurus and other Cretaceous carnivorous dinosaurs. Bulletin of the AMNH (New York City: American Museum of Natural History) 21 (14): 259–265.

wiki/Tyrannosaurus
wiki/Zhenyuanlong

SVP abstracts 2017: Megaraptora

Samathi and Chathasit 2017 bring us
new insights into the clade Megaraptora (Fukuiraptor, Zhenyuanlong and kin). These are generally mid-sized heavily feathered, winged, but nonviolent theropods.
From the Samathi and Chathasit abstract:
“Megaraptora is a clade of medium to large-sized theropod dinosaurs with large-clawed, strong pneumatization, and long and gracile legs. The basal member was found from the Barremian of Japan, whereas the more derived clade, the Megaraptoridae, is known from the Cenomanian to Santonian rocks of South America and Australia. Despite many discoveries and studies, the phylogenetic status of this group as derived Allosauroidea, basal Tyrannosauroidea or basal Coelurosauria is still debated. This study shows that the position of Megaraptora in theropod phylogeny is still unclear.” 
Nowhere in the abstract
do Samathi and Chathasit refer megaraptors to the Dromaeosauridae, which was the contention of Lü and Brusatte 2015. The large reptile tree (LRT) nests Zhenyuanlong, Tianyuraptor, Huaviagnathus and Fukuiraptor as basal tyrannosaurs derived from a sister to Ornitholestes.
References
Lü J and Brusatte SL 2015. A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution. Scientific Reports 5, 11775; doi: 10.1038/srep11775.
Samathi A and Chanthasit P 2017.
Two new basal megaraptora (Dinosauria: Theropoda) from the early Cretaceous of Thailand with comment on the phylogenetic position of Siamotyrannus and Datanglong. SVP abstracts 2017.

Why T-rex had tiny forelimbs

quaShort answer:
T-rex (Figs. 1, 2) forelimbs were former wings, not former grasping, predatory tools. Kiwi wings (Fig. 3), which have claw tips, are good analogs. Tyrannosaurus forelimbs were relatively smaller and likewise useless. Taxon exclusion is once again the reason why this has not been able to be documented before. 

What others say:
Science Daily“The tiny arms on the otherwise mighty Tyrannosaurus rex are one of the biggest and most enduring mysteries in paleontology.”

Thoughco.com“T. Rex males mainly used their arms and hands to grab onto females during mating (females still possessed these limbs, of course, presumably using them for the other purposes listed below).  T. Rex used its arms to lever itself off the ground if it happened to be knocked off its feet during battle,  T. Rex used its arms to clutch tightly onto squirming prey before it delivered a killer bite with its jaws. they were exactly as big as they needed to be. This fearsome dinosaur would quickly have gone extinct if it didn’t have any arms at all.”

Popularmechanics.com“The simple truth is that scientists aren’t sure exactly why T. rex’s arms are so short, but there’s a number of possible explanations. Perhaps the most likely is that the dino’s arms just weren’t very useful.”

FieldMuseum.org – “One of the big mysteries about T. rex is its tiny forelimbs,” says Pete Makovicky, Associate Curator of Dinosaurs. “We don’t know how it used them. But there could be clues in the fossils. When a bone is used a lot, the wear and tear cause tiny fractures that heal over time. With the right tools, we can see microscopic changes in the bones caused by that healing process. You also see things like a wider bone marrow cavity. When we remove SUE’s arm, we’re going to take it to the Argonne National Laboratory to try to look for these characteristics that will tell us how much it was used.”

Chicago Tribune
story here. Great images of a rising T-rex cyber model here from Kent Stevens, U of Oregon. Another set of images here from TyrannosaurTuesday.blogspot.com.

The answer, as usual here, comes from phylogenetic analysis.
Distinct from prior tyrannosaur studies, the large reptile tree (LRT, 1040 taxa) recovers the feathered, winged theropod, Zhenyuanlong (Fig. 1). as the proximal ancestor to the tyrannosaur clade. Theropods with large feathered wings don’t use them to grasp prey or mates.

Figure 0. Taxa ancestral to tyrannosaurs beginning with the CNJ7 specimen of Compsognathus.

Figure 0. Taxa ancestral to tyrannosaurs beginning with the CNJ7 specimen of Compsognathus.

No other studies
found large feather wings on tyrannosaur ancestors. And as long as they don’t, they’ll keep thinking T-rex forelimbs were primitive grasping organs.

Figure 2. Taxa in the Compsognathus/Tyrannosaurus clade, a subset of the large reptile tree to scale. Also included are Microraptor, Sinornithosaurus, Dilong and Zhenyuanlong.

Figure 2. Taxa in the Compsognathus/Tyrannosaurus clade, a subset of the large reptile tree to scale. Also included are Microraptor, Sinornithosaurus, Dilong and Zhenyuanlong.

The kiwi forelimb is a good T-rex forelimb analog
The kiwi (Fig. 2) has vestigial forelimbs that are essentially useless. Even so, they were relatively much large than T-rex forelimbs. Kiwis have no trouble getting up, mating or anything else tyrannosaurs are supposed to do with their forelimbs.

Figure 2. Kiwi skeleton GIF animation (2 frames) showing the vestigial and useless forelimb tipped with a claw, an analog to the vestigial forelimb of T-rex.

Figure 3. Kiwi skeleton GIF animation (2 frames) showing the vestigial and useless forelimb tipped with a claw, an analog to the vestigial forelimb of T-rex.

A recent lecture
by Tyrannosaur Chronicles author Dr. David Hone, available here on YouTube, noted two traits common to all tyrannosaurs: fused nasals and D-shaped (in cross-section) premaxillary teeth. Zhenyuanlong does not have these traits. Thus the Hone traits have not been validated by the LRT. Instead those traits appear to have a wider distribution by convergence, like the arctometatarsals we looked at earlier.

Figure 6. Tyrannosaurus forelimb compared to Gorgosaurus. Note the larger coracoid in T-rex.

Figure 6. Tyrannosaurus forelimb compared to Gorgosaurus. Note the larger coracoid in T-rex. It might have been resting on it.

Remember
we never want to put all our trust in just one or two traits (see above). Otherwise we’d be pulling a Larry Martin, famous for arguing phylogeny based on one or two traits alone. Instead we’re always looking for a suite of traits based on a character list of at least 150. The LRT has 228 multi-state characters and it continues to lump and separate all of its 1040 included taxa successfully, while documenting gradual accumulations of derived states.

In the present ancestry of tyrannosaurs other traits emerge.
Among the 228 traits, the LRT found several dozen shared by T-rex and Zhenyuanlong, including the elevated orbit, the hourglass-shaped quadratojugal, the pubic boot and a very short dorsal vertebral series. Noteworthy, all of these traits, other than the hourglass-shaped quadratojugal are also found elsewhere in the LRT by convergence. Don’t forget, we’re looking for the most parsimony in a suite of traits. Otherwise Pinnipedia and Cetacea would still be valid clades.

Essentially,
T-rex is just a giant, flightless Zhenyuanlong. No longer small enough to fly, the feathered flapping organs of T-rex became smaller due to lack of use. Blame it on the genes that those useless forelimbs keep appearing. We’ve also seen vestigial traits in pterosaurs (manual digit 5, ungual 4, pedal digit 5 in derived taxa), snake precursors (legs) and in baleen whales (tooth buds in embryos).

Postscript
Within 24 hours of this post T. Kaye alerted me to Giffin 1995 who wrote: “the data suggest that the brachial plexus, and therefore the cervical/dorsal vertebral transition, of the theropod dinosaurs studied was located considerably posterior to its presently accepted location, and that the forelimbs of the giant carnosaurs Tyrannosaurus rex and Carnotaurus sastrei were of biologically insignificant use.”

References

Giffin EB 1995. Postcranial paleoneurology of the Diapsida. Journal of Zoology 235(3):389-410.
Hwang SN, Norell MA, ji Q and Gao K-Q 2004.
 A large compsognathid from the Early Cretaceous Yixian Formation of China. Journal of Systematic Palaeontology 2(1):13-30.
Lü J and Brusatte SL 2015. A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution. Scientific Reports 5, 11775; doi: 10.1038/srep11775.
Osborn HF 1905. Tyrannosaurus and other Cretaceous carnivorous dinosaurs. Bulletin of the AMNH (New York City: American Museum of Natural History) 21 (14): 259–265.

 

wiki/Tyrannosaurus
wiki/Zhenyuanlong

 

 

 

 

Arctometatarsals should have been a great clade trait…

But it’s not.
Arctometatarsals describe a type of theropod metatarsals in which metatarsal 3 is pinched off proximally by flanking metatarsals 2 and 4. In addition, distally metatarsal 3 is typically just slightly anterior to its flanking metatarsals, which slightly back it up. You would think such a trait would only develop once and identify or diagnose a clade – but that is not the case, as earlier workers (like Snively et al. 2004) discovered and described.

Figure 1. Arctometatarsals on T-rex vs. normal metatarsals on Allosaurus.

Figure 1. Arctometatarsals on T-rex vs. normal metatarsals on Allosaurus.

Similarly
the large reptile tree (LRT, subset Fig. 1) does not find an arctometatarsal clade. The LRT finds at least six convergent instances where the third metatarsal is pinched between the flanking second and fourth metatarsals. None of these instances are related to each other. Rather, all are separated from one another by normal metatarsals.

Figure 1. Theropod dinosaurs and the arctometatarsal taxa (in blue).

Figure 1. Theropod dinosaurs and the arctometatarsal taxa (in blue).

Snively et al report, 
“A Bayesian phylogenetic analysis indicates that an arctometatarsus evolved in the common ancestor of the Tyrannosauridae + (Ornithomimosauria + Troodontidae) clade, but other optimizations are plausible.” That hypothesis was not supported by the LRT. Moreover, only one tested troodontid has an arctometatarsal trait. Troodon also has this trait, but it is not yet a tested taxon.

Snively et al report, 
“The most likely selective benefit of the structure was increased agility; if so, homoplasy indicates multiple exaptive and adaptive pathways towards predation and escape roles.”
Perhaps so! But these taxa have little in common distinct from other theropods, other than the pinched third metatarsal.

As we’ve seen before,
and this fact just hammers it home: convergence in RAMPANT throughout the LRT. That’s why we leave it to the software to recover the tree. No one wants to pull a Larry Martin here by creating or disputing relationships based on a single trait.

References
Snively E, Russell AP and Powell GL 2004. Evolutionary morphology of the coelurosaurian arctometatarsus: descriptive, morphometric and phylogenetic approaches. Zoological Journal of the Linnean Society 142:525–553.

Huaxiagnathus: yet another basal tyrannosauroid!

Updated May 23, 2016 with a deeper maxilla posterior to the antorbital fenestra. This was needed, as pointed out by M. Mortimer, to house the tooth roots. I missed the splinter that made the difference and someday may try to trace the palatal elements, which I have avoided at present. 

Huaxiagnathus orientalis
(Hwang et al. 2004, Fig. 1) was originally considered a large compsognathid. The Hwang et al tree (now 12 years old) nested Huaxiagnathus with Compsognathus and Sinosauropteryx in the clade Compsognathidae, derived from a sister to Ornitholestes, and basal to therizinosaurs, alvarezsaurs, oviraptors, birds, and deinonychosaurs.

Figure 1. Huaxiagnathus in situ with reconstructed skull, pes, manus and pelvis. Note the relatively large pedal digit 3, the large hyoid, and the twisty lacrimal. Hwang et al. did not provide a reconstruction.

Figure 1. Huaxiagnathus in situ with reconstructed skull, pes, manus and pelvis. Note the relatively large pedal digit 3, the large hyoid, and the twisty lacrimal. Hwang et al. did not provide a reconstruction.

Here
in the large reptile tree Huaxiagnathus nests at the base of the tyrannosauroids, between Tianyuraptor + Fukuivenator and Zhenyuanlong. Yet, another heresy…

Hwang et al. reported the absence of a sternum. 
That’s odd because all current sisters have a sternum. The fossil was collected by farmers, but no preparator was mentioned. Perhaps there was a village preparator. After many tests  conducted by AMNH personnel, the fossil was determined to be genuine, singular and not a chimaera. Given the presence of both humeri where they are, the sternum should be between them. It is not, so one wonders if the sternum was removed by the preparators to expose the underlying humerus. A DGS tracing appears to show the remains of a posterior sternum (Fig. 2, magenta, contra Hwang et al.).

Figure 2. Pectoral region of Huaxiagnathus with various elements colored for clarity. The magenta bone appears to be posterior rim of a sternum, overlooked or considered an elbow by Hwang et al.

Figure 2. Pectoral region of Huaxiagnathus with various elements colored for clarity. The magenta bone appears to be posterior rim of a sternum, overlooked or considered an elbow by Hwang et al. A second overlay colorizes bits and pieces of the possible sternum extending toward the coracoids.

The Hwang et al. diagnosis reports: 
“Differs from other known compsognathids in having

  1. a very long posterior process of the premaxilla that overlaps the antorbital fossa,
  2. a manus as long as the lengths of the humerus and radius combined,
  3. large manual unguals I and II that are subequal in length and 167% the length of manual ungual III,
  4. a first metacarpal that has a smaller proximal transverse width ( i.e. “narrower”) than the second metacarpal and
  5. a reduced olecranon process on the ulna.”

Comments:

  1. The premaxilla doesn’t overlap the maxillary fossa, but tyrannosaurs have a similar long posterior process
  2. true! and no related taxa share this trait, even those with more bird-like morphologies
  3. okay… but that’s a pretty exact percentage for ungual three! (similar to Zhenyuanlong, though)
  4. if so, then just barely a smaller transverse width
  5. as in several basal tyrannosauroid sisters
  6. Not mentioned above, but those pedal proportions seem unique, with a dominant pedal digit 3. The hyoid is enormous. So few and so large are the maxillary teeth that they seem to be unusual, especially compared to the tiny teeth of Compsognathus. There seem to be many ossified stiffening element scattered throughout the vertebral column. Higher resolution should solve this problem.

Like tyrannosauroids
Huaxinagnathus had a short neck and large skull longer than the cervicals and just about as long as half the presacral length. The convex maxilla orients the premaxilla into an ‘up’ orientation. The quadratojugal, here broken into several parts, has a mushroom dorsal process that meets a squamosal ‘lid’. The lacrimal has the familiar tyrannosaur-ish in and out twist. The the maxillary teeth are BIG and few.

Figure 3. Huaxiagnathus skull with elements colorized and reconstructed in figure 4. Orignal tracing is in black outline. Many of the bones are broken.

Figure 3. Huaxiagnathus skull with elements colorized and reconstructed in figure 4. Orignal tracing is in black outline. Many of the bones are broken.

A reconstruction puts the elements
back into their in vivo positions (Fig. 4). Many of the bones are broken and had to be repaired. The scleral elements are scattered.

Figure 4. Huaxiagnathus skull and hyoid reconstructed. See figure 4b for other clade member skulls.

Figure 4. Huaxiagnathus skull and hyoid reconstructed. See figure 4b for other clade member skulls.

Basal theropod subset of the large reptile tree
shows the nesting of Huaxiagnathus in the basal tyrannosauroids (Fig. 5). Both Compsognathus specimens have a most recent common ancestor, with no intervening taxa. Huaxiagnathus, originally considered a compsognathid is one if the whole clade is considered the Compsognathidae. Otherwise, Only Struthiomimus and the Compsognathus holotype form a clade and are sisters. The CNJ79 specimen of Compsognathus is not the adult form of the holotype (contra Peyer 2006), but deserves a new generic name.

Figure 1. Basal theropod subset of the large reptile tree showing troodontids basal to birds and separate from dromaeosaurs.

Figure 5. Basal theropod subset of the large reptile tree showing the two Compsognathus specimens. Hauxiagnathus is a basal tyrannosauroid derived from a sister to Compsognathus.

So…
with every new taxon repairs do get made to the large reptile tree, but the tree topology does not change very often. The theropod subset just keeps growing without shifting around. You would think that if there were enough scoring mistakes the tree topology would change. The key thought here is that some repairs actually cement relationships. The repairs typically, but not always, remove misinterpreted ‘autapomorpies.’ For instance, the ilium of Zhenyuanlong was earlier misinterpreted as having a longer anterior process, which would be an autapomorphy for the clade. A reexamination revealed the relatively longer posterior process (Fig. 6). So, it’s true what they say about me, I don’t get it right the first time all the time.

Figure 6. Zhenyuanlong has a new ilium with a shorter anterior process.

Figure 6. Zhenyuanlong has a new ilium with a shorter anterior process that was earlier misinterpreted.

Huaxiagnathus further cements
the relationships of Zhenyuanlong, Tianyuraptor and Fukuivenator to the tyrannosaurs (contra Hone 2016) and Brusatte (2015). For its size, it looks like one (Fig. 7) with robust lower limbs, large teeth on a curved maxilla, a large head relative to the neck and torso. And don’t forget to picture this skeleton with lots of feathers as in Zhenyuanlong (Fig. 6).

Figure 7. Huaxiagnathus reconstructed in lateral view.

Figure 7. Huaxiagnathus reconstructed in lateral view, sans feathers.

References
Brusatte S 2015. Rise of the Tyrannosaurs. Scientific American 312:34-41. doi:10.1038/scientificamerican0515-34
Hwang SN. Norell MA, ji Q and Gao K-Q 2004. A large compsognathid from the Early Cretaceous Yixian Formation of China. Journal of Systematic Palaeontology 2(1):13-30.

wiki/Huaxiagnathus

Update on Tianyuraptor – and a few worthy YouTube videos

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.

Figure 1. Tianyuraptor with DGS tracing locating more cervicals than before and reconstructed as a string of vertebral centra. The pelvis is also shown traced and reconstructed.

Figure 1. Tianyuraptor with DGS tracing locating more cervicals than before and reconstructed as a string of vertebral centra. The pelvis is also shown traced and reconstructed.

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.

Unfortunately
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.

Figure 5. Ornitholestes, Tianyuraptor and Zhenyuanlong are close relatives of Tyrannosaurus rex in the large reptile tree. Here Tianyuraptor has a much longer neck and a slightly shorter torso.

Figure 5. Ornitholestes, Tianyuraptor and Zhenyuanlong are close relatives of Tyrannosaurus rex in the large reptile tree. Here Tianyuraptor has a much longer neck and a slightly shorter torso.

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!

Figure 3. Zhenyuanlong scapulae. Note the dorsal expansions, as in tyrannosaurs, peeking out from behind the other bones.

Figure 3. Zhenyuanlong scapulae. Note the dorsal expansions (in blue), as in tyrannosaurs, peeking out from behind the other bones. It’s a bit of a mess in both cases.

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.” 

Figure z. The skull of Zhenyuanlong with DGS tracings identifying the quadrate, quadratojugal and squamosal different from the original identifications.

Figure z. The skull of Zhenyuanlong with DGS tracings identifying the quadrate, quadratojugal and squamosal different from the original identifications.

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).

Figure 2. Click to animate video by Teddy Cookswell of T rex hatchling.

Figure 4. Click to animate video by Teddy Cookswell of T rex hatchling. Please ignore the anterior pteroids and flapping wing membranes of the pterosaur, minor problems with an otherwise wonderful depiction.

And finally
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.

The questions arose from the audience, would today’s scientists also look askance at such non-conformists? Aczel replied, “Yes.” As an example he cited the case of Swiss astronomer Michel Mayor who discovered the first extra solar planet in 1995 after many astronomers said 51 Pegasi would not have a planet because they tested it already. Mayor ignored conventional wisdom and found the planet. I don’t think that example actually illustrated the question, because Mayor was not dismissed after his discovery, rather he won awards (astronomy is different than paleontology, as we noted earlier). But Mayor’s urge and ability to test conventional wisdom was present in Aczel’s example.
Aczel summarized, “It is human nature to not want to accept new beliefs. People who believe a certain way, tend to hold on to their beliefs.  I believe that astronomers and mathematicians don’t always like to change their views or accept somebody else’s good results when they think it’s their territory.” 

References
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.

C-Span video of Amir Aczel

Rise of the Tyrannosaurs by Stephen Brusatte

Revised May 15, 2016 with a longer neck for Tianyuanlong, more like that of its outgroup sister, Ornitholestes. Grateful to M. Mortimer for suggesting I take another look at it, but the objections raised were not valid for this taxon. 

Scientific American has published several articles devoted to dinosaurs. “Rise of the Tyrannosaurs – New fossils put T.rex in its place” (Brusatte 2015) is one of the latest (Fig 1).

Figure 1. Rise of the Tyrannosaurs by Stephen Brusatte, Scientific American

Figure 1. Rise of the Tyrannosaurs by Stephen Brusatte, Scientific American. Cover art by James Gurney of Dinotopia fame.

From the online access page:

  • Paleontologists have known about T. rex and other giant tyrannosaurs for decades. But they were unable to piece together when the tyrannosaurs originated and what they evolved from because they lacked the fossils to do so.
  • Recent fossil finds have gone a long way toward filling those gaps in scientists’ understanding of this iconic group.
  • Together these discoveries reveal that tyrannosaurs have surprisingly deep—and humble—evolutionary roots.
  • Furthermore, the group encompasses a far greater diversity of forms than experts had anticipated—including some with truly bizarre anatomical features (Fig. 2).
Figure 2. Tyrannosaur ancestors according to Brusatte, artwork by Todd Marshall. Those on the left are actually closer to allosaurs and spinosaurs. Drag to desktop to enlarge.

Figure 2. Tyrannosaur ancestors according to Brusatte, artwork by Todd Marshall. Those on the left are actually closer to allosaurs and spinosaurs. Click to enlarge.

Despite the fantastic artwork,
the taxa in ‘the rise’ are actually basal to allosaurs and spinosaurs, not tyrannosaurs (Fig. 1), according to the large reptile tree (Fig. 4). Some of the ancestors recovered in the large reptile tree, like Zhenyuanlong, had extensive wing feathers (Fig. 3), which actually makes the ancestry of T-rex more interesting. And it makes the little hands of T-rex, vestigial wings.

Figure 3. Tyrannosaur ancestors to scale according to the large reptile tree. Drag to desktop to enlarge.

Figure 3. Tyrannosaur ancestors to scale according to the large reptile tree. Click to enlarge.

Here’s the subset of the large reptile tree
focusing on basal theropods (Fig. 4). Note how Proceratosaurus, Guanlong and Dilong could be considered basal to tyrannosaurs, but really they are closer to allosaurs in this cladogram. I think the mistake may lie, once again, in taxon exclusion, but also to misinterpretation.

Figure 4. Subset of the large retile tree focusing on theropods. Note the green taxa. While technically basal to tyrannosaurs, this clade is actually closer to allosaurs and spinosaurs. And the Brusatte text does not consider Zhenyuanlong, Tianyuraptor, Fukuiraptor and Ornitholestes.

Figure 4. Subset of the large retile tree focusing on theropods. Note the green taxa. While somewhat basal to tyrannosaurs, this clade is actually closer to allosaurs and spinosaurs. And the Brusatte text does not consider Zhenyuanlong, Tianyuraptor, Fukuiraptor and Ornitholestes.

We first learned about T-rex ancestors
(according to the large reptile tree) here, here, here and here. Here are Zhenyuanlong and kin again (Fig. 5), the more parsimonious ancestors of T-rex.

Figure 2. Ornitholestes, Tianyuraptor and Zhenyuanlong are close relatives of Fukivenator at the base of the tyrannosaur clade.

Figure 5. Ornitholestes, Tianyuraptor and Zhenyuanlong are close relatives of Tyrannosaurus rex in the large reptile tree. See how those little arms are actually vestigial wings?  The short back, long legs, large head are all tyrannosaur traits.

References
Brusatte S 2015. Rise of the Tyrannosaurs. Scientific American 312:34-41. doi:10.1038/scientificamerican0515-34

See a video on the production of the cover art and a peek inside the James Gurney studio here.

Learn more about artist Todd Marshall here.