Evolution of the Dinosaurs YouTube video by Manabu Sakamoto PhD

One of Dr. Sakamoto’s major interests is
“How did major groups of animals radiate?” So we have similar interests. This slide show lecture apparently on ZOOM (or a similar format) is 56 minutes in duration and was streamed live March 12, 2021.

Sakamoto received his PhD from the U of Bristol in England,
which does not bode well. That’s where too many recent myths about pterosaurs and dinosaurs had their genesis.

In his slide labeled ‘Birds are dinosaurs’
Sakamoto includes an illustration of Microraptor (Fig. 1), which has wings and feathers, but is not a bird in the large reptile tree (LRT, 1817+ taxa), but a bird mimic arising from Ornitholestes  (Fig. 1). Sakamoto had so many birds to choose from, but chose a non-bird.

Figure 1. Changyuraptor to scale with Ornitholestes, Scriurumimus and Microraptor.

Figure 1. Changyuraptor to scale with Ornitholestes, Scriurumimus and Microraptor.

In his slide labeled ‘What makes a dinosaur?’
Sakamoto includes four illustrations and photos of four traits he reports are common to dinosaurs. That’s called a “Pulling a Larry Martin” because it is fraught with convergence in various non-dinosaurs. He should have used the “Last Common Ancestor (LCA) hypothesis.

In his slide labeled ‘Dinosauromorphs’
Sakamoto includes lagerpetids and notes reduced toes 1 and 5. That’s not true of sauropods, which have a huge toe 1. Lagerpetids are not related to dinosaurs when more taxa are added. Lagerpetids are proterochampsids convergent with dinosaurs. He lists Marasuchus among the dinosauromorphs. In the LRT it nests as a basal theropod even though the acetabulum is 90% not-perforated, as in ankylosaurs (see “Pulling a Larry Martin” above).

So far, not so good,
and we’re only 16 minutes into the video. So glad I did not waste time and money getting an education at the University of Bristol, like Dr. Sakamoto did. The professional academic Bristol program in dinosaurs is evidently behind the times.

In his slide labeled ‘A modern definition of Dinosauria’
Sakamoto correctly reports, dinosaurs are “members of the least inclusive clade containing Triceratops horridus and Passer domesticus (house sparrow),” but incorrectly includes ‘Dinosauromorphs’ as outgroup taxa between Crocodylomorpha and Dinosauria. In the LRT there are no taxa between Crocodylomorpha and Dinosauria.

In his slide labeled ‘major dinosaur groups’
Sakamoto reaches into the past to divide dinosaurs into Saurischia and Ornithischia. By contrast the LRT, with more taxa, divides dinosaurs into Theropoda and Phytodinosauria (Fig. 2) with a set of herrerasaurids preceding this split. So far Sakamoto is extending the reputation of U of Bristol for perpetuating myths.

Figure 2. Subset of the LRT focusing on the Phytodinosauria with Buriolestes at its base.

Figure 2. Subset of the LRT focusing on the Phytodinosauria with Buriolestes at its base.

In his slide labeled ‘…but there is only one true tree!’
Sakamoto presents his best estimate from data: an unresolved branching of Sauropodomorpha, Theropoda and Ornithischia. Based on what Sakamoto has presented thus far, the problem in Sakamoto’s presentation appears to be due to taxon exclusion. The LRT fully resolves the origin of dinosaurs by including more taxa. So why go to Bristol when you can learn with complete resolution online here?

In his slide ‘Dating dinosaur origins’
Sakamoto attempts to time the origin of dinosaurs, but without resolution or precise timing. In the LRT the dino-croc split occurred prior to the Ladinian (Late Middle Triassic) when the most primitive LCA of Dinosauria, PVL 4597 roamed South America.

 

Figure 4. The PVL 4597 specimen nests at the base of the Archosauria, not with Gracilisuchus.

Figure 3. The PVL 4597 specimen nests at the base of the Archosauria, not with Gracilisuchus.

In his slide ‘Early dinosaurs spread across the globe,
but started out just in the Southern hemisphere’ Sakamoto graphically considers Ladinian Lagerpeton and Asilisaurus ‘Basal Dinosauromorpha’, but verbally calls them early dinosaurs. Neither are dinosaurs in the LRT. Asilisaurus is a poposaur, the proximal outgroup for the Archosauria. Like many of his contermporaries, Sakamoto completely ignores the basal bipedal crocodylomorphs that the LRT nests as the proximal outgroup to the Dinosauria.

At this point we’re 30 minutes in
and very little Sakamoto has reported so far is verified by the LRT.

So we’re going to stop here.
The ratio of myth to fact is way too high. The ratio of missing taxa to included taxa is also way to high. Sakamoto now teaches at the U of Lincoln. If you are thinking of spending tuition money there, you have this preview to help you in your decision.

 

 

 

 

 

 

 

 

 

 

‘Pennaraptora’ — avoid this junior synonym

A new volume published by the AMNH
(eds. Pittman and Xu 2020), is all about the the putative clade, ‘Pennaraptora’ (Fig. 1). According to the preface, “Pennaraptora comprises birds themselves as well as the pennaceous feathered dromaeosaurids, troodontids, scansoriopterygids, and oviraptorosaurians.”

Here
in the large reptile tree (LRT, 1727+ taxa; subset Fig. 2) scansoriopterygids are birds, not oviraptorosaurian sisters. Oviraptorosaurians are terminal taxa in a larger clade that includes therizinosaurs and the CNJ79 specimen of Compsognathus and that clade is the sister clade of the Compsognathus holotype, struthiomimids and tyrannosaurids (Fig. 2). The last common ancestor of all these clades in the LRT is Aorun zhaoi (Choiniere et al. 2013; IVPP V15709, Late Jurassic 161mya).

So this multipart study on ‘Pennaraptorans’ is off to several bad starts. Neither ‘Aorun‘, nor ‘Tyrannoraptora’ (see below) are mentioned in the text. Several taxa have been omitted from this clade, including the last common ancestor.

Only two generic taxa and “their last common ancestor (LCA)”
should be enough to define a clade. Look what bad things can happen when you use four suprageneric taxa (Fig. 1). Don’t let in generic taxa that do not belong and omit generic taxa that do belong. Even so, and surprisingly, all taxa employed here are clade members. Unfortunately the clades and a few taxa are a little mixed up due to taxon exclusion.

Figure 1. Cladogram of the Pennaraptora from Pittman and Xu eds. 2020. Color overlays added to show clades in the LRT (Fig. 2).

Figure 1. Cladogram of the Pennaraptora from Pittman and Xu eds. 2020. Color overlays added to show clades in the LRT (Fig. 2).

Foth et al. defined Pennaraptora in 2014.
“Pennaraptora is a clade defined as the most recent common ancestor of Oviraptor philoceratops, Deinonychus antirrhopus, and Passer domesticus (the house sparrow), and all descendants thereof,”  Again, this definition only needs the first two taxa. Passer nests within “all descendants thereof”. Even so, this is a definition we can work with (Fig. 2).

Figure 2. Subset of the LRT focusing on Pennaraptora 2014 = Tyrannoraptora 1999. Here Khaan and Velociraptor substitute for Oviraptor and Deinonychus.

Figure 2. Subset of the LRT focusing on Pennaraptora 2014 = Tyrannoraptora 1999. Here Khaan and Velociraptor substitute for Oviraptor and Deinonychus.

In the LRT ‘Pennaraptora’
is almost a junior synonym of Compsognathidae (Cope 1871; Fig. 2) because two specimens of Compsognathus are basalmost taxa. However, Aorun is the last common ancestor taxon. It was originally considered the oldest known coelurosaurian theropod and a juvenile.

Figure 3. Aorun compared to several other theropods to scale.

Figure 3. Aorun compared to several other theropods to scale.

Figure 4. Aorun skull in situ and slightly restored. This is the basalmost tyrannoraptor.

Figure 4. Aorun skull in situ and slightly restored. This is the basalmost tyrannoraptor in the LRT.

According to Wikipedia, Aorun is now considered a member of
the Tyrannoraptora (Sereno 1999) defined as, “Tyrannosaurus, Passer their last common ancestor [Aorun] and all of its descendants.” So Pennaraptora (2014) is a junior synonym of Tyrannoraptora (1999). The two define the same clade in the LRT and share a last common ancestor.

Coelurosauria (von Huene 1914 is defined as theropods closer to birds than to carnosaurs. In the LRT Tyrannoraptora is also a junior synonym for Coelurosauria.


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.
Choiniere JN, Clark JM, Forster CM, Norella MA, Eberth DA, Erickson GM, Chu H and Xu X 2013. A juvenile specimen of a new coelurosaur (Dinosauria: Theropoda) from the Middle–Late Jurassic Shishugou Formation of Xinjiang, People’s Republic of China. Journal of Systematic Palaeontology. online. doi:10.1080/14772019.2013.781067
Cope ED 1871. On the homologies of some of the cranial bones of the Reptilia, and on the systematic arrangement of the class. Proceedings of the American Association for the Advancement of Science 19:194-247
Foth C, Tischlinger H and Rauhut OWM 2014. New specimen of Archaeopteryx provides insights into the evolution of pennaceous feathers. Nature. 511 (7507): 79–82.
Huene F v 1914. Über de Zweistämmigkeit der Dinosaurier, mit Beiträgen zer Kenntnis einiger Schädel. Sep.-Abd. Neuen Jahrb. für Mineralogie Beil.-Bd.37:577–589. Pls. vii-xii.
Ostrom JH 1978. The osteology of Compsognathus longipes. Zitteliana 4: 73–118.
Peyer K 2006. A reconsideration of Compsognathus from the upper Tithonian of Canjuers, southeastern France, Journal of Vertebrate Paleontology, 26:4, 879-896.
Pittman M and Xu X eds. 2020.
Pennaraptoran theropod dinosaurs. Past progress and new Frontiers. Bulletin of the American Museum of Natural History 440; 353pp. 58 figures, 46 tables.
Wagner JA 1859. Über einige im lithographischen Schiefer neu aufgefundene Schildkröten und Saurier. Gelehrte Anzeigen der Bayerischen Akademie der Wissenschaften 49: 553.

wiki/Compsognathus
wiki/Tyrannoraptora
wiki/Aorun
wiki/Pennaraptora

Saturnalia skull parts!

Bronzati, Müller and Langer 2019 bring us
additional skull data for the basal sauropodomorph, Saturnalia tupiniquim (Fig. 1).

FIgure 1. GIF movie of Saturnalia skull as originally restored and using phylogenetic bracketing to restore a longer rostrum and teeth only anterior to the orbit.

FIgure 1. GIF movie of Saturnalia skull as originally restored and using phylogenetic bracketing to restore a longer rostrum and teeth only anterior to the orbit.

Saturnalia tupiniquim (Langer et al. 1999) Carnian, Late Triassic period, ~225 mya, 1.5 m in length, was one of the oldest true dinosaurs yet found. It was basal to the clade Prosauropoda, 

Figure 1. Grallator illustration from Li et al. 2019 with two basal phytodinosaur possible sisters to the track maker, Pampadromaeus and Saturnalia.

Figure 2. Grallator illustration from Li et al. 2019 with two basal phytodinosaur possible sisters to the track maker, Pampadromaeus and Saturnalia.

The skull was recently described (Bronzati, Müller and Langer 2019). It had a large orbit, like Pantydraco. More cervicals were present and each one was elongated, creating a much longer neck. The scapula was narrow in the middle. The forelimbs were more robust with a large deltopectoral crest on the humerus. The hind limbs were more robust. The calcaneum did not have such a large tuber.

Figure 2. Subset of the LRT focusing on the Phytodinosauria.

Figure 3. Subset of the LRT focusing on the Phytodinosauria.

Adding scores to Saturnalia
provided an opportunity to review scores for other phytodinosaurs in the large reptile tree (LRT, 1568 taxa). These changes resulted in small modifications to the tree topography and higher Bootstrap scores (Fig. 2). Basal phytodinosaurs still give rise to the clades Sauropodomorpha and Ornithischia.


References
Bronzati M, Müller RT, Langer MC 2019. Skull remains of the dinosaur Saturnalia tupiniquim (Late Triassic, Brazil): With comments on the early evolution of sauropodomorph feeding behaviour. PLoS ONE 14(9): e0221387. https://doi.org/ 10.1371/journal.pone.0221387
Langer MC, Abdala F, Richter M, and Benton M. 1999. A sauropodomorph dinosaur from the Upper Triassic (Carnian) of southern Brazil. Comptes Rendus de l’Académie des Sciences, 329: 511-517.
Langer MC 2003. The pelvic and hind limb anatomy of the stem-sauropodomorph Saturnalia tupiniquim (Late Triassic, Brazil). PaleoBios, 23(2): 1-30.

wiki/Saturnalia

Convolosaurus enters the LRT basal to pachycephalosaurs

Originally it was considered a basal ornithopod.

FIgure 1. Convolosaurus from Andrzejewski, Winkler and Jacobs 2019, re built from a flock of juvenile specimens.

FIgure 1. Convolosaurus from Andrzejewski, Winkler and Jacobs 2019, re built from a flock of juvenile specimens.

Andrzejewski, Winkler and Jacobs 2019 report,
“The new ornithopod, Convolosaurus marri gen. et sp. nov., is recovered outside of Iguanodontia, but forms a clade with Iguanodontia exclusive of Hypsilophodon foxii. The presence and morphology of four premaxillary teeth along with a combination of both basal and derived characters distinguish this taxon from all other ornithopods.” 

Figure 2. Subset of the LRT focusing on the clade Phytodinosauria. Convolosaurus nests closer to the dome head dinosaurs, not the ornithopods.

Figure 2. Subset of the LRT focusing on the clade Phytodinosauria. Convolosaurus nests closer to the dome head dinosaurs, not the ornithopods.

By contrast
the large reptile tree (LRT, 1419 taxa) nests Convolosaurus basal to the Agilisaurus + Stegoceras at the base of the Pachycephalosauria (dome-head dinos). All these taxa were included in the original paper, but they did not nest together. Andrzejewski, Winkler and Jacobs 2019 did not nest their cladogram on Chilesaurus and Daemonosaurus, two taxa missing from their cladogram. This may have played a part in the different tree topologies.

Then again…
the LRT presently does not include Hypsilophodon or Thescalosaurus, taxa that nest with Convolosaurus in Andrzejewski, Winkler and Jacobs 2019. Soon they will be added. Then we’ll revisit this. 

Figure 3. Convolosaurus cladogram from Andrzejewski, Winkler and Jacobs 2019. Note the complete lack of consensus between the tree topology and figure 2.

Figure 3. Convolosaurus cladogram from Andrzejewski, Winkler and Jacobs 2019. Note the complete lack of consensus between this tree topology and the LRT in figure 2. In the LRT Haya and Pisanosaurus nest together near the base of the Ornithischia, but not here. 

Convolosaurus marri (Andrzejewski, Winkler and Jacobs 2019; SMU 72834; 2.5m in length) informally nicknamed the “Proctor Lake hypsilophodont”, this specimen is known from a flock of subadults.


References
Andrzejewski KA, Winkler DA and Jacobs LL 2019. A new basal ornithopod (Dinosauria: Ornithischia) from the Early Cretaceous of Texas. PLoS ONE. 14 (3): e0207935. doi:10.1371/journal.pone.0207935.

Dr J Gauthier lecture video on birds + dinos

If you watch this…
Stay for the brilliant question and answer period at the end.

And…
returning to an earlier subject…
Geologist Randall Carlson reports on Joe Rogan Experience #606 (1:35:44) —  “See, here’s the thing. Modern science does tend to get over specialized. And so what happens is, they guy looking at extinctions might not be looking at glacial melting. The guy looking at glacial melting… the geologist is not looking at what’s going on in the sky. They’re not looking at traditions, you know, traditions from thousands of years ago. What it does is, because of the powerful of this specialization, this specialization is extremely powerful, but the thing of it is… it’s easy to miss the big picture. What that does is, it opens the door for generalists, guys who are just, people who are just, men or women, anybody who is curious about this stuff, look into it and try to see the big picture.”

In other words…
taxon exclusion problems can be solved by a wide gamut analysis of the entire range of tetrapods now known.

Joe Rogan says (1:37:46),
“People love to be able to dismiss anything that’s not mainstream, right?” To which Randall Carlson replies, “Because there’s this cult of authority.” Randall Carlson continues (1:38:40) “They’ve got this idea in their mind that there’s this authority that’s got it all explained, which makes it easy, because if somebody’s got this all explained, then we don’t need to concern ourselves with it or think about it. Right? So, what I see is, ‘Okay… forget about who says what. Look at the facts. Let the facts dictate to us what the meaning of all this is. And let’s look at all points of view.” 

The idea that a meteor impact ended the last Ice Age,
and killed the northern megafauna first proposed by Randall Carlson and others gained new hard evidence with the recent discovery of a Paris-sized crater on the north rim of Greenland. Details and videos here: https://earthsky.org/earth/meteorite-crater-under-greenland-ice

Mirischia: a transitional theropod pelvis

Of the tens of thousands of mistakes I have made
while creating ReptileEvolution.com, the LRT and this blog over the last 7 years, this time I read ‘right’ and I applied ‘left’ to the ilium of Mirischia. Here corrections were made within 24 hours of its original posting. Thanks to MM for reporting the error. Apologies for the error.

Naish, Martill and Frey 2004
bring us an Early Cretaceous Santana Formation theropod pelvis and femur they named Mirischia asymmetrica (Fig. 1; SMNK 2349). They align the specimen with the French compsognathid (CNJ79), which is correct.

A key taxon
The traits visible in the Mirischia pelvis and femur (Fig. 1) are just enough to nest it between the Compsognathus clade (which includes tyrannosaurs, ornithomimosaurs and microraptors) and the Ornitholestes clade (which includes dromaeosaurs, troodontids and birds). And it is transitional in size, too.

Figure 1. The pelvis of Mirischia with color overlays and ilium correctly oriented. Below Mirischia pelvis compared to the CN79 specimen of Compsognathus and Ornitholestes.

Figure 1. The pelvis of Mirischia with color overlays and ilium correctly oriented. Below Mirischia pelvis compared to the CN79 specimen of Compsognathus and Ornitholestes. The yellow ‘bone’ between the pubes of Mirischia is ossified gut contents.

References
Choiniere JN, Clark JM, Forster CA and Xu X 2010. A basal coelurosaur (Dinosauria: Theropoda) from the Late Jurassic (Oxfordian) of the Shishugou Formation in Wucaiwan, People’s Republic of China. Journal of Vertebrate Paleontology. 30 (6): 1773–1796.
Naish D, Martill DM and Frey E 2004. Ecology, systematics and biogeographical relationships of dinosaurs, including a new theropod from the Santana Formation (?Albian, Early Cretaceous) of Brazil. Historical Biology 16(2–4):57–70.

 

The Theropoda: just a few (albeit heretical) changes to traditional trees

Adding taxa
is a method I have supported in order to discover taxonomic relationships among reptiles. The large reptile tree (theropod subset in Fig. 1) has now passed 650 taxa. The theropod subset has been considered at odds with traditional trees. But when you really look at it, maybe, not so much.

Figure 1. Theropod subset of the large reptile tree. Unresolved clades are resolved in heuristic analyses. Here traditional clades are named. A few taxa nest somewhere other than their traditional nestings here. Click to slightly enlarge.

Figure 1. Theropod subset of the large reptile tree. Unresolved clades are resolved in heuristic analyses. Those are due to incomplete skeletons. Here traditional clades are named. A few taxa nest somewhere other than their traditional nestings here. Click to slightly enlarge.

I added four more theropods
to the large reptile tree and applied traditional names to various clades (Fig. 1). Those additions and all scoring corrections did not change the overall tree topology.

Tradition is upheld overall here
as the major clades: 1. Neotheropoda; 2. Avetheropoda/Averostra; 3; Tetanurae; 4. Maniraptora; 5. Paraves; 6. Deinonychosauria/Eumaniraptora; 7. Troodontidae; and 8. Birds/Aves appear in their traditional order and with most of their traditional taxa.

Heresy is introduced here

  1. A clade between Tawa and Coelophysis includes Marasuchus, Segisaurus and Procompsognathus, taxa too often omitted from traditional theropod trees.
  2. Several former compsognathids, including Juravenator, Sinosauropteryx, now nest as derived maniraptors close to Limusaurus + Khaan and another former compsognathid, Sinocalliopteryx, now nests with spinosaurs.
  3. Several former tyrannosauroids, including Proceratorsaurus, Dilong, Guanlong and Xiongguanlong now nest with spinosaurs.
  4. A former ornithomimid, Deinocheirus, now nests with spinosaurs.
  5. Several former dromaeosaurs, including Microraptor, Sinornithosaurus, Zhenyuanlong and Tianyuraptor now nest with tyrannosauroids.
  6. A former bird/dromaeosaur, Rahonavis now nests with basal therizinosaurs.
  7. A former ceratosaur, Limusaurus, now nests with oviraptors.
  8. Eotyrannus and Tanycolagreus nest together as basal Paraves.

The following taxa do not belong in theropod studies
because they are basal phytodinosaurs.

  1. Eodromaeus
  2. Eoraptor
  3. Daemonosaurus
  4. Chilesaurus

The problem for traditional theropod workers is
the above heretical sisters really do look like sisters, both overall and in detail. With 651 nesting opportunities, this is where they found maximum parsimony (the fewest changes to their morphology).

These nestings look like heresies, but they follow prior work

  1. Ornithomimosaurs and maniraptors were both derived from Compsognathidae (Compsognathus) according to Lee et al. 2014.
  2. A series of small troodontids give rise to birds according to Godefroit et al. 2013.
  3. Dilophosaurus nests with Coelophysis according to Sues et al., 2011.
  4. Others I missed? It’s better for everyone when I’m not the first to notice taxonomic similarities.

Added taxa
have, so far, only supported earlier clades from earlier large reptile tree topologies. There have been score changes, but that’s standard operating procedure when adding taxa. It goes to show that a pretty good tree CAN have scoring mistakes. The best tree, of course, has no mistakes.

It is so good to have photo references
to look over when trying to decide what an unidentified or misidentified crumb of bone might represent. I can’t imagine having to buy a ticket to go revisit a fossil every time I needed to see it again. The logistics would prove nightmarish. (You have to realize that NO ONE does this). Remember, no one is an expert on a fossil the moment they first see it. Spending time with data makes you an expert on it. How much of an expert do you need your experts to be?

References
Lee YN, Barsbold R, Currie PJ, Kobayashi Y, Lee HJ, Godefroit P, Escuillié F and Chinzorig T 2014. Resolving the long-standing enigmas of a giant ornithomimosaur Deinocheirus mirificus. Nature 515 (7526): 257–260.
Godefroit P, Cau A, Hu D-Y, Escuillié, Wu, W-H and Dyke G 2013. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Nature 498 (7454): 359–362.
Sues H-D, Nesbitt SJ, Berman DS and Henrici AC 2011. A late-surviving basal theropod dinosaur from the latest Triassic of North America. Proceedings of the Royal Society B 278 (1723): 3459–3464

Proceratosaurus: another theropod leaves the tyrannosauroids for the spinosauroids

This blogpost
continues a series of prior blogposts featuring the tested removal of taxa traditionally considered to be in the ancestry of Tyrannosaurus. Find those posts here, here, here and here. There were also a few blogposts that added non-traditional taxa to the lineage of tyrannosaurs. Find those here, here and here.

Figure 1. Only the lower 7/8 of the skull of Proceratosaurus is known. Here the skull in siitu, A tracing modified from Tracy Ford. And another tracing by Rauhut et al. 2010 with anterior and occipital views.

Figure 1. Only the lower 7/8 of the skull of Proceratosaurus is known. Here the skull in siitu, A tracing modified from Tracy Ford. And another tracing by Rauhut et al. 2010 with anterior and occipital views. Note the entire skull is concave ventrally, but the maxilla and jugal are both straight.

Proceratosaurus bradleyi
(Middle Jurassic, Bathonian, England, NHM R 4860, Fig. 1) was originally considered another Megalosaurus (Woodward 1910), then identified as a unique taxon, a likely ancestor of a another much larger and more robust horned theropod, Ceratosaurus (von Huene 1926). Those reports were made back in the day when there were very few theropods to compare with one another.

In more recent times,
Proceratosaurus was phylogenetically nested (according to Wikipedia, Angela Milner and the BBC, Rauhut et al. (2010), Loewen et al. (2013) and Brusatte et al. (2015)) as the earliest member of the tyrannosaur lineage (Figs. 2-4).

Figure 3. Theropods from Rauhut et al. 2010. Here Proceratosaurus, Dilong and Guanlong nest with tyrannosaurs.

Figure 2. Theropods from Rauhut et al. 2010. Here Proceratosaurus, Dilong and Guanlong nest with tyrannosaurs, but key taxa are missing.

The question is why do their trees and the large reptile tree differ?
The answer could be (once again) due to taxon exclusion and tradition. The shift in nestings could be due to the lack of more attractive sister taxa in traditional tyrannosaur studies. The large reptile tree includes those more attractive sister taxa. But that is not the complete answer in every case.

Figure 4. Tyrannosaurs from Brusatte et al. 2013. Some taxa nest elsewhere in the large reptile tree. Others are missing from this tree.

Figure 3. Tyrannosaurs from Brusatte et al. 2013. Some taxa nest elsewhere in the large reptile tree. Others are missing from this tree. Click to enlarge.

Could it be scoring?
I have not checked the scores and matrices in other studies. I do know that the sisters in the large reptile tree do share long lists of character traits, but D-shaped premaxillary teeth (often touted as a key trait restricted to tyrannosaurs) are not among the traits listed there. Did Spinosaurus and Suchomimus also have D-shaped premaxillary teeth? I don’t know. If not, could that trait be in their relatively short-snouted ancestors by convergence? At this point the answer is, apparently so.

Rauhut (2010 reported, “As close relationships of Proceratosaurus with several of the clades included in this analysis (coelophysoids, spinosauroids, and maniraptorans) have never been proposed previously, these clades were collapsed [individually] into [a] single operational taxonomic unit[s] (OTU[s]).” 

That’s a problem
as the large reptile tree found Proceratosaurus to nest closest to basalmost spinosauroids (former tyrannosauroids). Now do you see why it is SO important NOT to employ suprageneric taxa — ever! It is possible that Rauhut et al. (and those that followed) created their own problems by creating suprageneric taxa where they should not have done so. In Science you have to be open to any and all answers, without bias or a priori assumptions wherever practicable and possible. That’s why it is so convenient to start with the large gamut of possibilities provided by the large reptile tree (now 647 taxa and growing).

Figure 5. Theropods from Loewen et al. with pertinent taxa highlighted.

Figure 4. Theropods from Loewen et al. with pertinent taxa highlighted.

Proceratosaurus was added
to the large reptile tree (subset in Fig. 5) and it did not nest with tyrannosaurs, but with smaller Early Cretaceous taxa that traditionally nest with tyrannosaurs, but now nest with spinosaurs. Everyone agrees that Proceratosaurus nests with Guanlong and Dilong. Everyone else agrees that these three nested with tyrannosaurs (Figs. 2-4). So, I am the only unorthodox heretic at present.

Figure 2. The Dinosauria subset of the large reptile tree as of February 5, 2016. Here Proceratosaurus nests with several former long-snouted tyrannosaurs now closer to spinosaurs and allosaurs.

Figure 5. The Dinosauria subset of the large reptile tree as of February 5, 2016. Here Proceratosaurus nests with several former long-snouted tyrannosaurs now closer to spinosaurs and allosaurs.

The large reptile tree
provides ancestral taxa that share more traits (see below) with Late Cretaceous tyrannosaurs than the traditional putative Jurassic and Early Cretaceous candidates provided by the authors listed in the references. I promote these recovered candidates so they will be tested by others, as I have tested their candidate taxa.

Without a doubt,
the Late Cretaceous tyrannosaurs are all monophyletic. The question is, which taxa phylogenetically preceded them in the Early Cretaceous and Jurassic? Note that none of the taxon lists in any of the studies totally match one another. On the other hand, all of the studies are in general agreement. However, the recovered topologies don’t exactly match one another. And so the game is afoot.

Getting back to Proceratosaurus
Take a look at its sister on the allosaur branch in the large reptile tree: it’s Ceratosaurus. So maybe von Huene (1926) was on to something… or he was lucky.

Basic traits that Proceratosaurus, Guanlong and Dilong
share with Sinocalliopteryx, Deinocheirus and the spinosaurs.

  1. Long, low rostrum
  2. Sometimes smaller premaxillary teeth vs. maxillary teeth
  3. Tall orbit
  4. Premaxillary postero-lateral processes that may be present due only to the down tip of the naris.
  5. Ventral border of elongate naris formed by premaxilla + nasal
  6. Long, strongly recurved maxillary teeth
  7. Majority coverage of the quadrate by the squamosal and quadratojugal.
  8. Often, but not always, a nasal median crest.
  9. Often, but not always, a descending posterior skull relative to the maxilla

Given that
Sinocalliopteryx and Dilong had primitive feathers, all (except perhaps the giants) probably shared that rarely preserved trait. Given that the above nine traits are all skull traits, it is likely that this clade was trending toward a specific feeding niche, in this case, an aquatic one.

Someday this will all come together. 

References
Brusatte SL and Carr TD 2016. The phylogeny and evolutionary history of tyrannosauroid dinosaurs. Nature, Scientifice Reports 6 (8 pages), 20252; doi: 10.1038/srep20252.
Loewen MA, Irmis RB, Sertich JJW, Currie PJ, Sampson SD 2013. Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans. PLoS ONE 8(11): e79420. doi:10.1371/journal.pone.0079420
Rauhut OWM, Milner AC and Moore-Fay S 2010. Cranial osteology and phylogenetic position of the theropod dinosaur Proceratosaurus bradleyi(Woodward, 1910) from the Middle Jurassic of England. Zoological Journal of the Linnean Society, published online before print November 2009. doi:10.1111/j.1096-3642.2009.00591
von Huene F 1932. Die fossile Reptil-Ordnung Saurischia, ihre Entwicklung und Geschichte. Monographien zur Geologie und Palaeontologie (Serie 1), 4: 1–361.
Woodward AS 1910. On a Skull of Megalosaurus from the Great Oolite of Minchinhampton (Gloucestershire). Quarterly Journal of the Geological Society 66: 111–115.

Eotyrannus: what is it?

Updated March 28, 2018 with a new reconstruction of the skull after the realization that the purported nasal is actually the nasal + frontals + lacrimals.

Eotyrannus lengi
(Hutt et al. 2001, Naish 2011, Fig. 1) is a mid-sized Early Cretaceous, Barremian, theropod originally and later allied with tyrannosauroids like Tyrannosaurus.

From the Hutt et al. 2001 abstract:
“The teeth in the premaxilla are D-shaped in cross-section and the nasals are fused.”
These are traits shared with Tyrannosaurus. “The hands are elongate and slender and the hindlimbs are gracile.” These are not traits shared with Tyrannosaurus. “…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.”

Figure 1. Eotyrannus lengi from images in Hutt et al. 2001 and Naish 2011. The scale bars are all over the place. This taxon seems not to nest with Tyrannosaurus, but with Tanycolagreus.

Figure 1. Eotyrannus lengi from images in Hutt et al. 2001 and Naish 2011. The scale bars are all over the place. This taxon seems not to nest with Tyrannosaurus, but with Tanycolagreus. The high angle of the naris is unique going back to Herrerasaurus.

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

Unfortunately
the large reptile tree nests Eotyrannus with Tanycolagreus (Fig. 2) at the base of the clade that ultimately gave rise to birds. These two taxa may represent a clade of tyrannosauroid mimics at the base of the pre-bird clade. They may share a naris with a higher ascending angle other theropods.

Figure 2. Tanycolagreus nests as a sister to Eotyrannus in the large reptile tree. This appears to be a clade of tyrannosaur mimics at the base of the pre-bird clade.

Figure 2. Tanycolagreus nests as a sister to Eotyrannus in the large reptile tree. This appears to be a clade of tyrannosaur mimics at the base of the pre-bird clade.

Unfortunately
Eotyrannus is not known from more parts. What we do have, though, appears to be most similar to the contemporary Tanycolagreus among tested taxa. It’s a scrappy fossil. Not good for keeping up high resolution in the cladogram (Fig. 3).

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.
Senter, P 2007. A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda)”, Journal of Systematic Palaeontology, 5(4): 429-463