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.

 

 

 

 

 

 

 

 

 

 

Haya 2021: still suffering from taxon exclusion

Barta and Norell 2021
give us a detailed look at every bone in the basal ornithischian, Haya griva (Fig. 1). We looked at Haya earlier here and nested it close to Pisanosaurus in the large reptile tree (LRT, 1810+ taxa).

Figure 1. Haya in lateral view.

Figure 1. Haya in lateral view.

For reasons unknown
Barta and Norell did not include Chilesaurus and Daemonosaurus (Fig. 2) in their text or phylogenetic analysis.

Figure 1. Skulls of Daemonosaurus, Haya and Jeholosaurus to scale.

Figure 1. Skulls of Daemonosaurus, Haya and Jeholosaurus to scale.

The hypothesis of interrelationships 
that nested Chilesaurus and Daemonosaurus as phytodinosaurs basal to Ornithischia (Fig. 2) has been online since 2011.

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.

No matter how much detail you put into your study of a taxon
it is all for naught if you decide to exclude pertinent taxa. You will not understand the phylogeny of that taxon, how it relates to others. Haya is a basalmost ornithischian in the LRT, an hypothesis of interrelationships not confirmed by Barta and Norell due to taxon exclusion. They had a chance to deliver big news and muffed it.

The Barta and Norell cladogram suffered from massive loss of resolution
at many nodes. Never a good sign. If you can tell two taxa apart generically, as fossils, you should be able to lump and separate them in a cladogram.

Perhaps too many incomplete taxa were tested.
Don’t include incomplete taxa until you have your tree topology all worked out first.


References
Barta DE and Norell MA 2021. The osteology of Haya griva (Dinosauria: Ornithischia) from the Late Cretaceous of Mongolia. Bulletin of the American Museum of Natural History 445: 1-111.

 

‘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

Testing for bipedalism in archosaurs (and pterosaurs)

Grinham, VanBuren and Norman 2019
looked at the origin of bipedalism in the archosaur and pre-archosaur ancestors of birds.

They report, “We test whether facultative bipedality is a transitionary state of locomotor mode evolution in the most recent early archosaur phylogenies using maximum-likelihood ancestral state reconstructions for the first time. Across a total of seven independent transitions from quadrupedality to a state of obligate bipedality, we find that facultative bipedality exists as an intermediary mode only once, despite being acquired a total of 14 times. We also report more independent acquisitions of obligate bipedality in archosaurs than previously hypothesized, suggesting that locomotor mode is more evolutionarily fluid than expected and more readily experimented with in these reptiles.”

The authors used the cladograms of Ezcurra 2016 and Nesbitt 2011,
both of which are riddled with inappropriate taxon inclusion and exclusion problems as reported earlier here and here. Therefore comparisons regarding the number of times obligate bipedality in archosaurs occurred is useless lacking a consensus phylogenetic contaxt. In the large reptile tree (LRT, 1542 taxa) bipedality occurs only once in archosaurs. It just precedes the origin of the archosaurs (crocs + dinos only). Ezcurra, Nesbitt and Grinham et al. include a long list of inappropriate taxa in their inclusion set according to the LRT that skews results (e.g. the lepidosauromorphs: Jesairisosaurus, Macrocnemus, Mesosuchus, Gephyrosaurus, Planocephalosaurus, Eudimorphodon, Dimorphodon).

Grinham, VanBuren and Norman 2019
follow Nesbitt 2011 who listed the pterosaurs Eudimorphodon and Dimorphodon as archosauriforms. Grinham et al. 2017 considered both to be quadrupeds without explanation. The only pterosaur paper cited by Grinham et al. is Padian 2008. Peters 2007 recovered pterosaurs with lepidosaurs like Huehuecuetzpalli, later validated, expanded and published online in LRT. Peters 2000, 2011 reported on bipedal pterosaur tracks and restricted most cited pterosaur ichnites to flat-footed beach-combing pterosaur clades. Use keyword “bipedal pterosaur tracks” in the SEARCH box to see prior samples of digitigrade and bipedal tracks reported by this blogpost along with their citations.

Padian 2008 reported
“Peters (2000) also reached the conclusion that pterosaurs were not ornithodirans, and found instead that they were nested within what is traditionally considered the Prolacertiformes. It remains to be seen whether other workers can duplicate this result, but a recent analysis by Hone and Benton (2007) failed to find support for Peters’ analyses. For the present, because five different analyses have found that pterosaurs are ornithodirans, and the systematic community seems to have largely accepted this, the present paper will proceed with this provisional conclusion, without discounting other possible solutions.”

We looked at the bogus results
of Hone and Benton 2007 earlier here. They dropped taxa proposed as pterosaur ancestors by Peters 2000 because their inclusion would have tilted their supertree toward the topology recovered by Peters 2000, who tested four previously published cladograms by adding novel taxa to them. One year earlier than Peters 2000, co-author Benton 1999 had proposed Scleromochlus as a pterosaur sister/ancestor, which Peters 2000 invalidated. Evidently professor Benton did not appreciate that and succeeded, at least in Padian’s eyes, to dismiss Peters 2000 as an unacceptable and suppressible minority view.

Note that none
of Padian’s “five different analyses” used novel taxa proposed by Peters 2000. Padian’s report, “The systematic community seems to have largely accepted this,” demonstrates that Padian and his community were adverse to testing the novel taxa of Peters 2000 on their own terms, preferring the cozy comfort of tradition and orthodoxy — and they did this after Peters 2000 invalidated earlier efforts simply by adding a few taxa. Very easy to do. Even today it remains impossible to explain the origin of pterosaurs as archosaurs in a phylogenetic context because they are not archosaurs. In the world of academics, taxon exclusion remains a useful tool. We should all fight against this practice.

Later Padian 2008 reports, 
“Alternatively, if we consider that pterosaurs evolved from quadrupedal basal archosauromorphs such as Prolacertiformes (Peters, 2000), a rather different model of limb evolution must be proposed. In prolacertiforms the humerus is longer than the forearm and the femur is longer than the tibia; the glenoacetabular length is also long, as in most terrestrial quadrupeds. To attain the proportions seen in basal pterosaurs, the relative lengths of humerus and forearm and of femur and tibia would have to have been reversed, and the vertebral column would have had to shorten considerably (or the limb segments increase). These changes are independent of the extensive reorganization of the joints for erect posture and parasagittal gait, for which there is no evidence so far in prolacertiforms.”

Figure 1. Click to enlarge. The origin of the pterosaur wing and the migration of the pteroid and preaxial carpal. A. Sphenodon. B. Huehuecuetzpalli. C. Cosesaurus. D. Sharovipteryx. E. Longisquama. F-H. The Milan specimen MPUM 6009, a basal pterosaur.

Note: Padian 2008 chose to ignore the limb proportions
of Longisquama (Figs. 1, 2) another taxon proposed by Peters 2000 with a humerus shorter than the forearm, as in pterosaurs. He also ignored Sharovipteryx, another taxon proposed by Peters 2000, with a femur shorter than the tibia. In the world of academics, taxon exclusion remains a useful tool. We should all fight against this.

Padian 2008 also chose to ignore the evidence for bipedalism
in Cosesaurus (Fig. 2) matching facutatively bipedal Rotodactylus tracks (Peters 2000) and Sharovipteryx (Fig. 2), an obligate biped based on proportions. Both have the short torso relative to the limb length sought for and purposefully overlooked by Padian 2008 (see above quotation). In the world of academics, taxon exclusion remains a useful tool. We should all fight against this.

Figure 3. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx.

Figure 2. The origin of pterosaurs now includes Kyrgyzsaurus, nesting between Cosesaurus and Sharovipteryx.

Students of paleontology:
I’m sorry, this is just the way it is.

Getting back to bipedalism in archosaurs,
the LRT, subset Fig. 4) documents the patterns and possibilities of bipedal locomotion in taxa preceding dinosaurs. The topology here employs more taxa, pushes pterosaurs over to lepidosaurs (Peters 2007) and nests only Crocodylomorpha + Dinosauria within the Archosauria. Poposauria is the proximal outgroup. This is where bipedalism in archosaurs first appeared. Other bipedal taxa achieved this ability by convergence. Secondary quadrupedalism occurred several times in archosaurs, and by convergence in certain derived pterosaurs (e.g. ctenochasmatids and azhdarchids), as evidenced by their backward pointing manual digit 3 in ichnites.

Figure 3. Subset of the LRT focusing on the archosauromorph synapsid-grade taxa and diapsid-grade taxa with color added to bipedal taxa.

Figure 3. Subset of the LRT focusing on the archosauromorph synapsid-grade taxa and diapsid-grade taxa with color added to bipedal taxa.

As documented here and elsewhere
It does not matter if certain hypotheses are peer-reviewed and published or not.
Academic authors can choose to omit pertinent taxa and papers knowing that ‘friendly’ academic referees and editors will likewise choose to overlook such omissions. Apparently all academics seek and work to maintain the orthodox line, no matter how invalid it may be.

That’s why this blogpost and ReptileEvolution.com came into being.
We’re talking about hard science. Ignoring and omitting hard evidence cannot be tolerated or coddled. I ask only that academic workers rise to the professionalism they seek to inspire in their own students. History will put this all into perspective. Professional legacies may end up in shame unless they take action soon. Just test the taxa. 


References
Benton MJ 1999. Scleromochlus taylori and the origin of the pterosaurs. Philosophical Transactions of the Royal Society London, Series B 354 1423-1446. Online pdf
Ezcurra MD 2016 The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ 4, e1778. (doi:10.7717/peerj.1778)
Grinham LR, VanBuren CS and Norman DB 2019. Testing for a facultative locomotor mode in the acquisition of archosaur bipedality. R. Soc. open sci. 6: 190569. http://dx.doi.org/10.1098/rsos.190569
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Nesbitt SJ 2011. The early evolution ofArchosaurs: relationships and the origin of major clades. Bull. Am. Museum Nat. Hist. 352, 1–292. (doi:10.1206/352.1)
Padian K 2008. Were pterosaur ancestors bipedal or quadrupedal? Morphometric,
functional, and phylogenetic considerations. Zitteliana R. B Abhandlungen der Bayer.
Staatssammlung fur Palaontologie und Geol. 28B, 21–28.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Peters, D 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605

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.

Restoring and re-nesting Murusraptor

Traditional megaraptorans,
like Megaraptor namunhuaiquii (Novas 1998, Fig. 1) and Murusraptor barrosaensis (Coria and Currie 2016; Rolando, Novas and Agnolin 2019; MCF-PVPH-411; Fig. 1), are currently only known from bits and pieces. Perhaps for these reasons Wikipedia reports, “the clade Megaraptora (Benson, Carrano and Brusatte 2010 ) has controversial relations to other theropods.”

According to Wikipedia
“Murusraptor is a megaraptoran, one of a group of large predatory dinosaurs whose exact classification remains disputed. Once believed to be dromaeosaurids, they have since been classified as either allosauroid carnosaurs or as tyrannosauroid coelurosaurs. While the discovery of Murusraptor does not clarify as of yet the placement of this group of theropods, the specimen does add further clarity to some aspects of megaraptoran anatomy and potentially, eventual classification of the Megaraptora within the theropod evolutionary tree.”

Definition
Megaraptora (Benson et al 2010) “The most inclusive clade comprising Megaraptor namunhuaiquii, but not Chilantaisaurus tashuikouensis.” 

Wikipedia reports,
“Megaraptorans were most diverse in the early Late Cretaceous of South America, particularly Patagonia. However, they had a widespread distribution. Fukuiraptor, the most basal (“primitive”) known member of the group, lived in Japan. Megaraptoran material is also common in Australia, and the largest known predatory dinosaur from the continent, Australovenator, was a megaraptoran.” 

Taxa traditionally included within Megaraptora:

  1. Megaraptor (known from a long maxilla and forelimb, Figs. 1, 2)
  2. Fukuiraptor (known from jaw fragments, coracoids, humeri, femur, acetabulum, two vertebrae
  3. Australovenator (known from a dentary, a few dorsal ribs, distal forelimbs and nearly complete hind limbs)
  4. Murusraptor (known from several skull elements and other bones Figs. 1, 2)

Of these, only two, Megaraptor and Murusraptor, are tested in the LRT.

Other megaraptoran traits according to Wikipedia

  1. “Their forelimbs were large and strongly built,
  2. The ulna bone had a unique shape (except Fukuiraptor).
  3. The first two fingers were elongated, with massive curved claws ,
  4. The third finger was small. 
  5. Megaraptoran skull material is very incomplete, but a juvenile Megaraptor described in 2014 preserved a portion of the snout, which was long and slender. 
  6. Leg bones referred to megaraptorans were also quite slender and similar to those of coelurosaurs adapted for running. 
  7. Although megaraptorans were thick-bodied theropods, their bones were heavily pneumatized, or filled with air pockets. The vertebrae, ribs, and the ilium bone of the hip were pneumatized to an extent which was very rare among theropods, only seen elsewhere in taxa such as Neovenator
  8. Other characteristic features include opisthocoelous neck vertebrae
  9. and compsognathid-like teeth.” 

Several of the above traits
are shared with other taxa. The LRT employes a suite of 231 shared, unique and often convergent traits to lump, split and ultimately nest all taxa. Surprisingly, even the poorly preserved, disarticulated and incomplete Megaraptor and Murusraptor found secure nodes.

Araciaga, Rolando, Novas and Agnolin 2019
bring us ‘new evidence about the phylogenetic relationships of Megaraptora.’ They report, “The current study lends further support to the hypothesis that megaraptorans are basal members of Coelurosauria (supported by 20 synapomophies), with strongest affilation with Tyrannosauroidea (supported by > 20 synapomorphies).”

From their abstract:
“Murusraptor is particularly similar to juvenile specimens of tyrannosaurids; both share: 1) lacrimal with a long anterior prosess; 2) corneal process and; 3) lateral pneumatic fenestra; 4) square and dorsoventrally low frontals; 5) parietals with well-developed sagittal and nuchal crests, among other features. The current study lends further support to the hypothesis that megaraptorans are basal members of Coelurosauria (supported by 20 synapomophies), with strongest affilation with Tyrannosauroidea (supported by > 20 synapomorphies).”

“Murusraptor is unique in having several diagnostic features that include anterodorsal process of lacrimal longer than height of preorbital process, and a thick, shelf-like thickening on the lateral surface of surangular ventral to the groove between the anterior surangular foramen and the insert for the uppermost intramandibular process of the dentary.

“Other characteristic features of Murusraptor barrosaensis n.gen. et n. sp. include a large mandibular fenestra, distal ends of caudal neural spines laterally thickened into lateral knob-like processes, short ischia distally flattened and slightly expanded  dorsoventrally. Murusraptor belongs to a Patagonian radiation of megaraptorids together with Aerosteon, Megaraptor and Orkoraptor.”

A little backstory with links for more details:
Aerostean is a giant (9m) Late Cretaceous theropod with no skull material known. Orkorpator is a large (6m) Latest Cretaceous theropod includes only a post-orbital and quadratojugal for skull material and bits and pieces otherwise.

Figure 1. Murusraptor compared with related taxa to scale.

Figure 1. Murusraptor compared with related taxa to scale. Ghosted rostrum of Guanlong added to missing rostrum of Mururaptor.

Phylogenetic analysis
In the large reptile tree (LRT, 1415 taxa; Fig. 4) Megaraptor (Fig. 1) nests with the basal theropod, Sinocalliopteryx. Murusraptor (Fig. 1) nests between long-snouted Dilong and the long-snouted Guanlong / Spinosaurus clade.

One problem comes from
the hypothesis of relationships published by Coria and Currie 2016 that nests long-snouted Xiongguanlong, Dilong, Proceratosaurus and Guanlong with robust-snouted Tyrannosaurus, rather than with long-snouted spinosaurs. Even so, Coria and Currie 
nest Murusraptor with Megaraptor. The closest theropod also tested in the LRT is the finback allosaurAcrocanthosaurus. So, the Coria and Currie cladogram is different in most respects from the LRT. Coria and Currie also nest the giant horned theropod, Ceratosaurus, as a basalmost/outgroup taxon. In the LRT (Fig. 4) Ceratosaurus has no descendants.

Figure 2. Megaraptor, Murusraptor and Sinocalliopteryx. See figure 1 for revised restoration of Murusraptor. Not to scale.

Figure 2. Megaraptor, Murusraptor and Sinocalliopteryx. See figure 1 for revised restoration of Murusraptor. Not to scale. The Rolando et al. restoration draws more on Megaraptor and Dilong.

In counterpoint to Coria and Currie 2016,
Novas et al. 2016 reported, “megaraptorids retained several of the manual features present in basal tetanurans, such as Allosaurus. In this regard, Megaraptor and Australovenator are devoid of several manual features that the basal tyrannosauroid Guanlong shares with more derived coelurosaurs (e.g., Deinonychus).” 

In the LRT,
(Fig. 4) Guanlong is closer to Allosaurus than to Tyrannosaurus.

Figure 4. Megaraptor also preserves a complete and distinct manus, here compared to Sinocalliopteryx, which also has a digit 4, and Suchomimus has a robust ungual 1.

Figure 3. Megaraptor also preserves a complete and distinct manus, here compared to Sinocalliopteryx, which also has a digit 4, and Suchomimus has a robust ungual 1. According to the LRT, Suchomimus is not related to Megaraptor, but is shown here to demonstrate the convergence.

According to the writers of Wikipedia,
the large compsognathid, Sinocallioteryx (Figs. 1-3) is not related to megaraptorids, despite the many similarities in the skull. Curiously, other long-snouted theropods with massive curved claws on their forelimbs, like Suchomimus (Fig. 3), are also not traditionally considered related to megaraptorids. I wish they were. Everyone wishes they were. However, I have to report results, no matter how controversial, as I have for the last eight years. That way, if I made mistakes, someone will tell me. If someone has forgotten certain taxa, perhaps next time they will add them.

Figure 4. Subset of the LRT focusing on basal theropods. Megaraptor and Murusraptor are highlighted.

Figure 4. Subset of the LRT focusing on basal theropods. Megaraptor and Murusraptor are highlighted.

In conclusion
Murusraptor barrosaensis
  (Coria and Currie 2016; Rolando, Novas and Agnolin 2019; Late Cretaceous) was originally considered a sister to Megaraptor and close to tyrannosaurs. Here (Fig. 4) Murusraptor nests between Dilong and Guanlong closer to spinosaurs. Megaraptor nests with Sinocalliopteryx, a basal theropod, not close to Murusraptor. Wherever other traditional megaraptorans (see list above) nest has not yet been tested in the LRT. We looked at the relationship of long-snouted theropods with spinosaurs, rather than tyrannosaurs earlier here.


References
Rolando AMA, Novas FE and Agnolin FL 2019. A reanalysis of Murusraptor barrosaensis Coria & Currie (2016) affords new evidence about the phylogenetical relationships of Megaraptora. Cretaceous Research. https://doi.org/10.1016/j.cretres.2019.02.021
Benson RBJ, Carrano MT and Brusatte SL 2010. A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic.
Naturwissenschaften 97(1): 71–78.
Coria RA and Currie PJ 2016. A New Megaraptoran Dinosaur (Dinosauria, Theropoda, Megaraptoridae) from the Late Cretaceous of Patagonia. PLoS ONE 11(7): e0157973. doi:10.1371/journal.pone.0157973
Novas FE 1998. Megaraptor namunhuaiquii, gen. et sp. nov., a large-clawed, Late Cretaceous theropod from Patagonia. Journal of Vertebrate Paleontology. 18: 4–9. doi:10.1080/02724634.1998.10011030
Novas FE, Rolando AMA and Agnolín FL 2016. Phylogenetic relationships of the Cretaceous Gondwanan theropods Megaraptor and Australovenator: the evidence afforded by their manual anatomy. Memoirs of Museum Victoria. 74: 49–61.
Porfiri JD, Novas FE, Calvo JO.; Agnolín FL.; Ezcurra MD and Cerda IA. 2014. Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation. Cretaceous Research. 51: 35–55.

wiki/Megaraptor
wiki/Murusraptor
wiki/Megaraptora

Pelecanimimus joins the LRT

Yes, it is the basalmost ornithomimosaur,
(of three tested), but from whence did the theropod dinosaur, Pelecanimimus (Figs. 1-3), arise?

Figure 1. Rough tracing and reconstruction of Pelecanimimus based on low rez photos from 1994 paper.

Figure 1. Rough tracing and reconstruction of Pelecanimimus based on low rez photos from 1994 paper.

 

In the original paper
Pérez-Moreno et al. 1994 tested only Allosaurus, Albertosaurus, Deinonychus and Troodontidae in order of decreasing distance as outgroup taxa to Pelecanimimus + Ornithomimosauria using 22 characters. In the early days of PAUP this is all that most workers did back then… sort of testing the phylogenetic waters.

In a competing study
the large reptile tree (LRT) tests 1370+ taxa and recovers the holotype of Compsognathus as the proximal outgroup. In the same study members of the Troodontidae nest closer to birds (birds nest within the clade that includes some traditional troondontids, but not others).

Unique indeed…
The long down-curved jaws of Pelecanimimus are not found in either ancestral compsognathids nor descendant ornithomimosaurs. The wrist appears to be made of tiny bones, capable of minimal movement. ‘On the other hand’ the fingers are provided with large cylindrical joints for substantial flexion and extension.

Figure 2. DGS tracings from 1994 paper focusing on skull and manus of Pelecanimimus.

Figure 2. DGS tracings from 1994 paper focusing on skull and manus of Pelecanimimus.

A gular sac and cranial soft tissue are present
on the specimen. Not sure if we’re seeing radiating patterns of soft tissue aft of the ulna, or are those preparator chisel marks? Nothing glows in the UV image (Fig. 1), so let’s go with the latter.

Figure 4. Pelecanimimus to scale with Struthiomimus and Compsognathus.

Figure 3. Pelecanimimus to scale with Struthiomimus and Compsognathus.

References
Pérez-Moreno BP et al. (5 co-authors) 1994. A unique multi-toothed ornithomimosaur dinosaur from the Lower Cretaceous of Spain. Nature 370(4):363–367.

wiki/Pelecanimimus

SVP 2018: A super-matrix for an invalid ‘Thyreophora’

Raven, Maidment and Barrett 2018 report,
“The individual lineages, Ankylosauria and Stegosauria, have been studied thoroughly, but there has never before been a comprehensive whole-group cladistic analysis of Thyreophora.”

According to Wikipedia:
“Thyreophorans are characterized by the presence of body armor lined up in longitudinal rows along the body. Threophora (Nopsca 1915) has been defined (Sereno 1998) as the group consisting of all species more closely related to Ankylosaurus than to Triceratops. Thyreophoroidea was first named by Nopcsa in 1928 and defined by Sereno in 1986, as “ScelidosaurusAnkylosaurus, their most recent common ancestor and all of its descendants”. Eurypoda was first named by Sereno in 1986 and defined by him in 1998, as “Stegosaurus, Ankylosaurus, their most recent common ancestor and all of their descendants”.

Raven, Maidment and Barrett 2018 report,
“Here, the first species-level phylogenetic super matrix of the whole-group Thyreophora is presented, incorporating all previous known cladistic analyses of ankylosaurs, stegosaurs and basal thyreophorans and including all valid species within Thyreophora, for a total of 89 taxa and 338 characters.

Unfortunately
in the large reptile tree (LRT, 1308 taxa, Fig. 1) the last common ancestor of Ankylosauria and Stegosauria also includes among its descendants: heterodontosaurids, lesothosaurs, duckbills and horned dinosaurs.

So ‘Goodbye, Eurypoda and Thyreophora’
(unless these clades someday become more inclusive by consensus). The super-matrix of Raven, Maidment and Barrett 2018 probably does not include the LRT or the taxonomic tree it finds within the clade Ornithischia. So use their study to learn about the stegosaurs and the ankylosaurs, but not the last common ancestor of stegosaurs and ankylosaurs. That would be a sister to late-surviving Late Cretaceous Haya and/or Late Triassic Pisanosaurus.

Figure 4. Subset of the LRT focusing on the Phytodinosauria. Three sauropods are added here.

Figure 1. Subset of the LRT focusing on the Phytodinosauria. Scelidosaurus through Minmi are basal ankylosaurs. Lesothosaurus through Stegosaurus are basal stegosaurs.

References
Raven TJ, Maidment SC and Barrett PM 2018. The first phylogenetic super-matrix of the armored dinosaurs (Ornithischia, Thyreophora). SVP abstracts.

wiki/Thyreophora

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.