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

When did T-rex lose its feathers?

There will be two answers here:
1) phylogenetically; and 2) ontogenetically as Bell et al. 2017 discuss changing ideas regarding the integument of tyrannosauroids.

Tradtional taxon exclusion
has given the Bell et al. team a different ancestry of tyrannosaurs than in the large reptile tree (LRT, 1307 taxa). Even so, Early Cretaceous taxa are the last to preserve feathers or filaments in the large and giant members of this clade.

A few facts before we get started:

  1. Mid-sized Early Cretaceous Yutyrannus (from the allosaur clade, Fig. 1) has filaments
  2. Giant Late Cretaceous Tyrannosaurus (a tyrannosauroid, Fig. 1) has scales preserved in small patches and no filaments preserved (Fig. 2).
  3. Small-sized Zhenyuanlong (a stem tyrannosaur, Fig. 2) has flight and contour feathers, but no elongate coracoids for flapping
  4. Bell et al. include Yutyrannus in the ancestry of tyrannosaurs and ignore Zhenyuanlong.
  5. Plucked poultry reveals naked skin, except around the feet
  6. Large dinosaurs of all types also lose their feathers phylogenetically
Figure 1. Late Cretaceous Tyrannosaurus, which has scales, to scale with Early Cretaceous allosaurid, Yutyrannus, which has filaments.

Figure 1. Late Cretaceous Tyrannosaurus, which has scales, to scale with Early Cretaceous allosaurid, Yutyrannus, which has feather-like filaments. This is the largest theropod, so far, to have such filaments.

Bell et al. report
“Recent evidence for feathers in theropods has led to speculations that the largest
tyrannosaurids, including Tyrannosaurus rex, were extensively feathered. We describe fossil integument from Tyrannosaurus and other tyrannosaurids (Albertosaurus, Daspletosaurus, Gorgosaurus and Tarbosaurus), confirming that these large-bodied forms possessed scaly, reptilian-like skin. These new findings demonstrate that extensive feather
coverings observed in some early tyrannosauroids were lost by the Albian, basal to Tyrannosauridae. This loss is unrelated to palaeoclimate but possibly tied to the evolution of gigantism, although other mechanisms exist.”

And they conclude,
“Gigantism (i.e. increased body mass) affords greater heat retention: a thermodynamic by-product of the square-cube law and linked to reductions in hair in large modern terrestrial mammals.”

Figure 2. Tyrannosaurus (without feathers) to scale and directly compared to Zhenyuanlong (with feathers).

Figure 2. Tyrannosaurus (without feathers) to scale and directly compared to Zhenyuanlong (with feathers). Integument patches shown from Bell et al. 2017. Note the reduction of the forelimbs and hind limbs as tyrannosaurs grow in size phylogenetically. For those who don’t like the LRT phylogeny, this GIF animation shows just how similar tiny Zhenyuanlong and Tyrannosaurus really are.

A modern analogy: small furry hyrax ~ large naked elephant
Just as baby elephants can have a bit more vestigial hair than their parents do, baby giant theropods might have had more vestigial filaments. And considering the small patches of scales found for giant theropods so far, small patches of vestigial filaments might still have been present elsewhere, perhaps trailing the forelimbs, for instance. We just don’t know yet.

Figure 4. The small furry hyrax is in the lineage of the large naked elephant, analogous to small feathery theropods and large naked theropods. The fingers and incisors already show similarities.

Figure 4. The small furry hyrax is in the lineage of the large naked elephant, analogous to small feathery theropods and large naked theropods. The fingers and teeth already show similarities here.

The authors discuss hatchling tyrannosaurs
as they report, “Finally, the presence of epidermal scales in a large adult individual does not rule out the possibility that younger individuals possessed feathers—a developmental switchover that, to our knowledge, would be unprecedented at any rate.” No birds have more feathers as hatchlings than as adults.

What are tyrannosaur scales? And did birds lose their scales?
According to bird studies (Dhouailly 2009) theropod scales may be [phylogenetically] derived from feathers. (Remember chickens and other birds are naked underneath.) Scales and scutes can develop at any place and at any time from naked skin. Consider the ankylosaurs, as an extreme example. Naked and/or furry skin can develop from scales. Consider the scaly tail of the opossum ancestral to the tail of a hamster or lemur, as examples.

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.

Figure 4. Subset of the LRT focusing on the theropod-bird transition, distinctly different than in Hartman et al. 2019. Here in a fully resolved cladogram, birds and anchiornithids are monophyletic. Taxon inclusion resolves cladistic issues raised by Hartman et al.

Figure 4. Subset of the LRT focusing on the theropod-bird transition, distinctly different than in Hartman et al. 2019. Here in a fully resolved cladogram, birds and anchiornithids are monophyletic. Taxon inclusion resolves cladistic issues raised by Hartman et al.

This topic was inspired by the following video on YouTube:

References
Bell PR, Campione NE, Persons WS, Currie PJ, Larson PL, Tanke DH, Bakker RT 2017. Tyrannosauroid integument reveals confllcting patterns of gigantism and feather evolution. Biology Letters 13: 20170092. http://dx.doi.org/10.1098/rsbl.2017.0092
Dhouailly D 2009. A new scenario for the evolutionary origin of hair, feather, and avian scales. Journal of Anatomy 214:587-606.

the-origin-of-feathers-and-hair-part-3-feathers/

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

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

 

 

 

 

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.

The Tyrannosaur Chronicles by David Hone

A new book
by Dr. David Hone called The Tyrannosaur Chronicles is now out. He reports here, “Although there is no more famous and recognisable dinosaur than Tyrannosaurus, the public perception of the animal is often greatly at odds with the science. The major image people have of them is the iconic jeep chasing scene in the film Jurassic Park. However, because they are among the best-studied of all dinosaurs, we can say that the tyrannosaurs almost certainly had feathers and may have fought and even ate each other.”

Figure 1. The Tyrannosaur Chronicles by Dr. David Hone is a new book chronicling tyrannosaurs.

Figure 1. The Tyrannosaur Chronicles by Dr. David Hone is a new book chronicling tyrannosaurs.

I have not read the book yet, but I’ll note a possible problem gleaned from quote pulled from a review.

Kirkus Reviews reports: While correctly surmising that tyrannosaurs and other dinosaurs were carnivores, scientists erroneously assumed that they were some kind of previously unknown “giant land reptile.” Subsequent fossil discoveries in polar regions ruled out this possibility since coldblooded reptiles could not survive such extreme cold weather.”

I hope this is a misquote or I’m misreading this. It’s not news that tyrannosaurs and dinosaurs have been and will always be giant land reptiles. They nest in the clade Reptilia, no matter how cold-adapted they might have been. Hone might be going back, back in time to the first English discoveries from 50 years earlier, like Iguanodon and Megalosaurus, the first dinosaurs, which were named terrible lizards, and originally titled, “British Fossil Reptiles.”

And I hate to judge a book by its cover, but…
That small crested dinosaurs in the lower left corner is Guanlong, an ancestor not of tyrannosaurs, but of allosaurs in the large reptile tree. No word yet if Hone included the verified ancestors of tyrannosaurs, Zhenyuanlong, Tianyuraptor and Fukuiraptor.  On that note, GotScience.org evidently quotes Hone when it reports, Early tyrannosaurs had crests used for sexual display and social rank.”

Book and academic publishing is fraught with such risk and danger. Once you print it, you can’t retract or revise it. Sympathetically, I know from experience the things I would have changed about my early papers now, but was less experienced then.

Thankfully
I hear that Hone discusses feathers and such.

Amazon Reviews are universally positive:

  1. Dinosaurs are endlessly fascinating, and the massive, blood-thirsty tyrannosaurs are most popular (and scary) of the lot! Here, renowned dinosaur expert David Hone reveals their story, and how we know what we know about these most amazing of ancient reptiles. — Professor Mike Benton, University of Bristol
  2. Tyrannosaurs are probably the world’s favourite dinosaurs. But what do we really know about this group? David Hone reviews the biology, history, evolution, and behaviour of the tyrant kings – an excellent read, containing the very latest in our understanding of Tyrannosaurus rex and its closest relatives. — Dr Tom Holtz, University of Maryland
  3. Without doubt, the best book on tyrannosaurs I’ve ever read. This is an awesome dinosaur book. — Professor Xu Xing, Chinese Academy of Sciences

Do not be confused with this website:
http://traumador.blogspot.com which earlier featured ‘Traumador the tyrannosaur in the Tyrannosaurus Chronicles’ which can be silly and serious all on the same blog, explained here as:

The Tyrannosaur Chronicles is a blog written by Traumador the Tyrannosaur about his many exploits.Traumador is a tyrannosaurid who hatched from an egg that magically survived the K/Pg Extinction Event and was discovered in Alberta by Craig, an aspiring paleontologist (and the mastermind behind the blog in real life). He eventually gets a job at the Royal Tyrell Museum and things get interesting from there.

From past experience,
such as when Hone attempted to compare the two hypotheses of pterosaur origins by dropping one, or when Hone attempted to show that Dmorphodon had a mandibular fenestra, or when Hone supported the deep chord bat wing model for pterosaur wings, or when Hone flipped the wingtips of Bellubrunnus, we might be wary about what Dr. Hone puts out there. But I don’t think you can go very wrong with tyrannosaurs, the most studied dinosaur. And the reviews speak high praise.

Soft tissue in Cretaceous dino bone. Still controversial.

The T-rex collagen (Schweitzer et al. 2016) controversy is back, this time on PlosOne.

From the abstract
“Recovery of still-soft tissue structures, including blood vessels and osteocytes, from dinosaur bone after demineralization was reported in 2005 and in subsequent publications. Despite multiple lines of evidence supporting an endogenous source, it was proposed that these structures arose from contamination from biofilm-forming organisms. To test the hypothesis that soft tissue structures result from microbial invasion of the fossil bone, we used two different biofilm-forming microorganisms to inoculate modern bone fragments from which organic components had been removed. We show fundamental morphological, chemical and textural differences between the resultant biofilm structures and those derived from dinosaur bone. The data do not support the hypothesis that biofilm-forming microorganisms are the source of these structures.”

From the comments
Tom Kaye writes:We are delighted to see that seven years after publication, our biofilm hypothesis still has enough merit to generate a manuscript to test it experimentally. Our comments below.

1. The two week growth period was arbitrary.
2. No details of the nutrient supply over time.
3. Biofilms mineralize as is well known by plaque on teeth. Ultra-pure water means no minerals to modify the biofilm.
4. Iron is the basis for Dr. Schweitzer?s claims of extraordinary preservation. No iron is available in this experiment, but the resulting biofilms are compared to dinosaur ?vessels? with iron. 
5. The experiment DID produce tubular branching structures fully consistent with the claims of Kaye et al 2008.

The design of the experiment with limited inputs insured only limited outcomes which were then compared to a natural process that included factors outside the range of the experiment. Mineralized or iron reinforced biofilms could never be expected in the results of this experiment by design. 

We look forward to further experiments that mimic the natural process of biofilm formation.” 

Schweitzer’s Reply to the Kaye Comments:
“Kaye’s original comments, and our responses below each .

1. The two week growth period was arbitrary.
Mr Kay misunderstand the point of the current paper. Our intent in undertaking the current project was to test the hypothesis that biofilm would 1. invade fossil bone under naturally occurring conditions that might reasonably exist in dinosaur bone; and 2. take on the shape and character of vessels (uniform wall diameter, coherency and retention of branching patterns, and retention of an open lumen). We also tested the hypothesis that specific antibodies can differentiate source and composition of materials retained in fossils. We did accomplish these goals with a growth period of 2 weeks (also see below). There is much in the literature about optimal phases of microbial growth, and there is precedent for this growth period in the literature, cited below. Additionally, much is already known about the conditions of growing biofilm; that was not the point of this manuscript. Conditions used in labs to generate optimal biofilm growth (ie, continual flow of water, additional nutrients, agitation, etc as employed by Kaye et al 2008) would not occur in dinosaur bone exposed in the Montana badlands. That was what we tried to imitate.
Note also that Tom does not address our chemical/molecular data at any point in these comments, only our approach for growing biofilm. We were able to show biofilm growth in bone under highly regulated conditions, which was our goal, thus how we might have done it differently is irrelevant to our central hypothesis (see below). Furthermore, duration of growth period, once the biofilm invaded bone, was not pertinent to our central questions. It could grow forever and not produce the vertebrate proteins recognized by our antibodies. Chemically, the biofilm hypothesis is not supported. Neither is it supported morphologically.

2. No details of the nutrient supply over time.  
See below, and our inoculation details in the methods provided in the paper.

3. Biofilms mineralize as is well known by plaque on teeth. Ultra-pure water means no minerals to modify the biofilm.  
There are adequate minerals present in the bone “framework” in which we conducted our experiments, and microbes are perfectly capable of mobilizing these as a mineral source. Yes, biofilms do mineralize, and in that capacity no doubt play a role in preserving some “soft” materials in the rock record through consolidation. Biofilm can overgrow flat materials, like skin or feathers, in a thin layer which, when mineralized, will preserve aspects of the underlying structure (but obviously not the chemistry of the original material unless it is also preserved)… But NO data, including that presented by Kaye et al. 2008, support the hypothesis that mineralized biofilm will result in solid-walled three-dimensional structures with a lumen. Additionally, we have shown here that when minerals are REMOVED, any shape that was initially present is immediately lost. Thus, mineralized biofilm is not supported as a source for our solid walled, easily manipulated, lumen-possessing structures consistent with vertebrate vessels.

4. Iron is the basis for Dr. Schweitzer?s claims of extraordinary preservation. No iron is available in this experiment, but the resulting biofilms are compared to dinosaur ?vessels? with iron. 
Iron is quite obviously not the only means of preservation, just one we have tested and demonstrated experimentally. We proposed that iron-generated reactive oxygen species were responsible for chemical crosslinking that acted as a fixative to stabilize the vessels before decay. The biofilms used in our experiment were chemically fixed, thus an adequate model with which to compare “iron-fixed” dinosaur vessels.

5. The experiment DID produce tubular branching structures fully consistent with the claims of Kaye et al 2008.
Absolutely *NOT*. A ‘tubular structure’ by definition contains a lumen. We never observed a lumen in these biofilm structures (as we stated in the text); thus they were NOT tubular structures. The vessels, consistent with all vertebrate blood vessels, always demonstrate a lumen, in all analyses, from SEM to TEM sections and in sectioning for LM/fluorescence. Furthermore, as we state in the paper, once the bone was removed through demineralization the biofilms were disrupted with the slightest agitation and did not hold any shape even when fixed—that is why sections of these materials differ so completely from dinosaur vessels also figured. The vessels were physically removed from the chelating buffers used to demineralize the bone, washed multiple times, collected into embedding bullets, and sectioned, and still retained both structure and lumen. This was impossible to accomplish with the biofilm, even when fixed.

6. The design of the experiment with limited inputs insured only limited outcomes which were then compared to a natural process that included factors outside the range of the experiment. Mineralized or iron reinforced biofilms could never be expected in the results of this experiment by design. 
This is simply not true. In Kaye’s original paper, he grew biofilms on a flat surface under conditions of controlled recirculated water flow and nutrients added, which are not “natural” conditions occurring inside a fossil bone, buried in or exposed on the surface of sediments; thus his original paper also included factors “outside the range” of natural processes. As stated above, minerals can be (and often are) mobilized from bone itself and most certainly would have been required deep in dinosaur cortical bone in the arid, isolated badlands of Montana, where access to minerals and nutrients were limited primarily to the dinosaur bone itself and access to water was limited and sporadic. The process of microbial mobilization of bone mineral and organic matrix leaves characteristic alterations in bone microstructure, which were not observed in our specimens. For the experiments in the current paper, our goal was to attempt to mimic what might occur in nature, under natural conditions, in dinosaur cortical bone. To preserve any fossil material requires that the materials are stabilized before they can decay. Thus, the initial stages of the decay/stabilization process is capable of being approximated in the lab in relatively short time spans. Our previous experiments showed that without some kind of fixative, blood vessels isolated from bone degrade almost to completion in less than a week. Because stabilization must occur, or at least begin, within this range, a two week growth period overlapped this value. Kaye’s own contention (2008) is that structures he observed in isolated pieces of ‘float’ bone fragments, mostly from turtle plastron/carapace, resulted from modern biofilm invasions. Thus, our experiment tested these conditions rigorously.

Furthermore, conventional wisdom states that fossil bone does not retain original organics. Precisely because of this conventional and widely held belief, we designed our experiment to account for this presumed lack of organics, and this step of removing organics from bone was vital to our initial hypothesis. Although we have shown using multiple methods in multiple fossils that organics most likely persist in bone, we tested, again, this starting and widely held assumption. On the other hand, it is well known that microbes will grow almost anywhere there is organic material available to them, so to work with untreated bone still retaining organics would provide no new information. Thus, our experimental design required removing the organics from bone, to better approximate what is believed by many to best represent the composition of fossil material. This step was important to testing our hypothesis, which we state clearly in the paper. When Kaye argues that “No details were provided as to nutrient level or other parameters of the biofilm”, our response is that these details were not pertinent to our central hypothesis. We simply show that when additional nutrients are supplied, biofilm *will* grow in “naked” bone. There is precedent for this, cited in Neu et al 2003, where it is stated “a study is described in which a river inoculum was used as a sole source of nutrients (and inoculated only once, similar to our study) and the after 4 weeks the biofilm plateaued and no longer grew”. Based on these findings, then, we chose to halt the experiment half way, when we could observe biofilm growth but before sloughing of cells occurred, thus optimizing molecular response if it were present, as well as optimizing the chance of recovering coherent intact biofilm.” 

7. We look forward to further experiments that mimic the natural process of biofilm formation. 
We are satisfied that we have ruled out biofilm as a source of our vessels with abundant and varied data and will not pursue this. We will continue to base our future research on the well-supported hypothesis that these structures are endogenous. Multiple lines of evidence support this hypothesis, including recovery of sequences of multiple vertebrate proteins commonly associated with blood vessels and other bone organic components, but which are not generated by or associated with biofilm-producing organisms, the presence of which cannot therefore be explained by a biofilm origin. The data we present here, rigorously testing this alternative hypothesis, further eliminate the possibility that these arise from biofilm. Biofilms do not contain vertebrate proteins. Biofilms do not cross react with antibodies to vertebrate proteins. Dinosaur blood vessels do not respond to antibodies against bacterial proteins. Biofilms are morphologically distinct from blood vessels, are not cylindrical, and do not contain a lumen. There is no evidence to support a biofilm origin for the vessel structures recovered from these and other dinosaur materials.”

Once again,
I can’t weigh in on this argument. Both sides are steadfast. Only one can be correct. I know how both of them feel. A lot of work on both sides has come to loggerheads. Full disclosure: I have seen and tugged on the rubbery biofilms in the Tom Kaye lab.

References
Kaye TG, Gaugler G, Sawlowicz Z. Stepanova A. 2008. Dinosaurian soft tissues interpreted as bacterial biofilms. PLoS One. 2008;3(7):e2808. doi: 10.1371/journal.pone.0002808. pmid:18665236
Schweitzer MH, Moyer AE and Zheng W-X 2016. Testing the Hypothesis of Biofilm as a Source for Soft Tissue and Cell-Like Structures Preserved in Dinosaur Bone. DOI: 10.1371/journal.pone.0150238

M. Schweitzer on 60 minutes here

Kaye pictures here:
http://scienceblogs.com/grrlscientist/2008/07/30/a-closer-look-at-dinosaur-soft/

Fukuivenator: not a mystery, the basalmost tyrannosaur!

Updated February 28, 2016 with new restorations of Fukuivenator and Tianyuraptor and shifting Fukuivenator one node more primitive. 

Fukuivenator paradoxus 
(Azuma et al. 2016, FPDM-V8461, Fig. 1), was originally described as, “a bizarre theropod.” With a specific name like “F. paradoxus,” it’s easy to see there was mystery surrounding this theropod.

Unfortunately, this may just be a case
of taxon exclusion and a sour matrix. No reconstructions were published and several scale bars do not appear to be valid. I had no trouble nesting this theropod. Rather than bizarre, it shares a long list of traits with its new sisters (Figs. 2, 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 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.

From the abstract:
“While Fukuivenator possesses a large number of morphological features unknown in any other theropod, it has a combination of primitive and derived features seen in different theropod subgroups, notably dromaeosaurid dinosaurs.” 

From the Diagnosis
A relatively small theropod with the following unique features (comments follow):

  1. unusually large external naris (slightly smaller than antorbital fenestra in dorsoventral height) – also in Ornitholestes and Tianyuraptor (O&T)
  2. large premaxillary fenestra subequal in size to maxillary fenestra – also in Zhenyuanlong (Z)
  3. large oval lacrimal pneumatic recess posterodorsal to the maxillary fenestra on antorbital fossa medial wall – also in the tyrannosaur clade
  4. lacrimal with a distinct groove on lateral surface of anterior process and a ridge on lateral surface of descending process – detail too small to see
  5. postorbital frontal process with T-shaped-cross section and laterally-flanged squamosal process – also in the tyrannosaur clade
  6. an elongate tubercle on posterior surface of basal tuber of the basicranial region – detail too small to see
  7. highly heterodont dentition featuring robust unserrated teeth including small spatulate anterior teeth, large and posteriorly curved middle teeth, and small and nearly symmetrical posterior teeth  – also in the tyrannosaur clade
  8. cervical vertebrae with a complex lamina system surrounding the neural canal resulting in deep and wide grooves for interspinous ligaments and additional deep sockets  – also in the tyrannosaur clade
  9. anterior cervical vertebrae with interprezygapophyseal, postzygadiapophyseal, prezygadiapohyseal, and interpostzygapophyseal laminae connecting to each other to form an extensive platform  – also in the tyrannosaur clade
  10. anterior and middle cervical vertebrae with transversely bifid neural spines  – also in the tyrannosaur clade
  11. dorsal, sacral, and anterior caudal vertebrae with strongly laterally curved hyposphene and centropostzygapophyseal laminae that, together with the postzygapophyseal facet, form a socket-like structure for receiving the prezygapophysis – unfamiliar with this
  12. dorsoventrally bifurcated sacral ribs – also in Zhenyuanlong (Z)
  13. caudal zygapophyseal facets expanded to be substantially wider than the zygapophyseal processes;– unfamiliar with this and
  14. middle caudal vertebrae with transversely and distally bifid prezygapophyses.– unfamiliar with this
Figure 2. Ornitholestes, Tianyuraptor and Zhenyuanlong are close relatives of Fukuivenator at the base of the tyrannosaur clade. Gray zone on Ornitholestes skull marks off the boundary of the external naris.

Figure 2. Ornitholestes, Tianyuraptor and Zhenyuanlong are close relatives of Fukuivenator at the base of the tyrannosaur clade. Gray zone on Ornitholestes skull marks off the boundary of the external naris.

Nowhere in the text
do the authors list Zhenyuanlong, but Tianyuraptor is listed.The large reptile tree (subset fig. 3) nests Fukuivenator at the base of the tyrannosaurs between Tianyuraptor and Ornitholestes. One tree published by Azuma et al. also nests Fukuivenator with Ornitholestes, but it has many other problems and lacks resolution at several nodes. So here we have a tentative agreement with the published work.

Like Ornitholestes and Tianyuraptor
Fukuivenator has an enormous round naris (“all the better to smell you with, my dear~”)

Like Zhenyuanlong and T-rex
Fukuivenator has a taller than wide orbit and deeply rooted teeth. Premaxillary teeth are incisor (‘D’) -shaped.

Like Ornitholestes
The skull is shorter than the cervical series and shorter than half the presacral length.

Figure 2. Fukuiraptor nests with basal tyrannosaurs in the theropod subset of the large reptile tree.

Figure 2. Fukuivenator nests with basal tyrannosaurs in the theropod subset of the large reptile tree.

The authors note several dromaeosaurid traits
but Fukuivenator does not have a large killer claw. Fukuivenator actually provides more evidence that basal tyrannosaurs were dromaeosaur mimics, with large wing feathers and stiff tails, just like Microraptor, the bird mimic. Instead of being sharp-eyed predators, as we presume the deinonychosaurs, troodontids and birds were/are, some basal tyrannosaur clade members may have used their nose. So this is where T-rex became “a stellar smeller” back in the Late Jurassic/Early Cretaceous.

Not sure why professional paleontologists
are not seeing these relationships, but I think I smell a sour matrix over there that, like an old sock, has been used to many times without running it through the washer every so often.

As in pterosaurs and turtles and Vancleavea and caseids and mesosaurs…
if you can’t find a good sister taxon among the traditional sister taxa, then maybe you need to look elsewhere. In this case, Fukuivenator does not nest with dromaeosaurs, but very nicely with basalmost tyrannosaurs without paradox or bizarre qualities. I note this, as usual, without seeing the fossil firsthand, for which I am often vilified. This study shows that contributions can be done in paleontology without seeing the fossils firsthand.

References
Azuma Y, Xu X, Shibata1 M, Kawabe S, Miyata K and Imai T 2016. A bizarre theropod from the Early Cretaceous of Japan highlighting mosaic evolution among coelurosaurians. Nature Scientific Reports | 6:20478 | DOI: 10.1038/srep20478