Baron 2020 questions dinosaur origins

Baron 2020 discusses
the origin of dinosaurs (Fig. 1) in the Late Triassic of South America.

From the abstract
“Whilst the interrelationships between the major dinosaur clades remains to be fully resolved, the current data does seem to comprehensively answer the question of where the dinosaurs first originated.”

Actually
the dinosaur clades have been fully resolved for several years in the large reptile tree (LRT, 1707+ taxa). South America is where the last common ancestor of the dinosaurs, and all the proximal outgroups to that taxon reside (Fig. 1). We know dinosaur ancestors back to Cambrian chordates. So it is time to move on from questioning dinosaur origins. We’ve known this for several years. Academia needs to catch up.

Baron cites
(Baron et al., 2017a) as “a large scale study of early dinosaurs and their closest kin posed the first serious challenge in modern times to the traditional model of early dinosaur evolution and interrelationships.” Baron then and now omit a citation for a larger scale study first posted here in 2011 when Daemonosaurus (Sues et al. 2011) was described. Baron et al. 2017 were repositioning Chilesaurus as an early orninithischian and claiming credit for a hypothesis of interrelationships first posted here online two years earlier in 2015.

Baron was made aware of these earlier citations
via email, but chose to ignore them yet again. The earlier citation should always get the credit, no matter the circumstances. The resurrected clade ‘Ornithoscelida’ (Baron et al. 2017) is not support when more taxa are added.

After reviewing other competing hypotheses, Baron confesses,
“This lack of current overlap between datasets and taxon sampling has had a detrimental overall effect on our understanding of early dinosaur evolution and has offered very little by way of a solution to the any of issues still outstanding. The author recognises his own failing in this respect and would further seek to draw attention the fact that the original ‘challenge’ to a Southern Hemisphere point of origination was speculative, rather than robustly supported by data.”

Notably, none of these studies
included basal bipedal crocodylomorphs, which nest as the proximal outgroup taxa to the Dinosauria + Herrerasauridae in the LRT. Rather, Baron’s consensus tree includes:

  1. Silesauridae within Orinithisichia. Silesaurus is a poposaur in the LRT.
  2. Lagerpetidae as the proximal outgroup to the Dinosauria. Lagerpeton is a larger Tropidosuchus sister in the LRT.
  3. Pterosauromorpha as the proximal outgroup to Lagerpetidae + Dinosauria. Pterosaurs are lepidosaurs in the LRT. Scleromochlus is a basal bipedal crocodylomorph in the LRT.
  4. Aphanosauria includes outgroup taxa to taxa listed here (Fig. 1). Members include Teleocrater and Yarasuchus, dead end taxa nesting between rauisuchians and poposaurs in the LRT.

So taxon exclusion
remains the problem here. And face it, sometimes it takes an outsider to see problems PhDs and textbook writers surround themselves with by wearing blinders. As I discussed in Facebook recently with a famous dinosaur artist, most people follow the money and do what is popular and accepted. It’s better to follow the science. Science will catch up to popular myths sooner or later.

Figure 1. The origin of dinosaurs in the LRT to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.  Note the phylogenetic miniaturization at the origin of Archosauria (Crocs + Dinos).

Figure 1. The origin of dinosaurs in the LRT to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Pseudhesperosuchus, Herrerasaurus, Tawa and Eoraptor.  Note the phylogenetic miniaturization at the origin of Archosauria (Crocs + Dinos). These are the taxa studies need to include while they exclude Silesaurus and pterosaurs.

Baron 2020 offers some suggestions
“First, to try and resolve the issue relating the topology within the dinosaur lineage, the datasets produced in each of the various analyses discussed above should be combined and an effort made to consistently score all species using a standardized set of definitions for anatomical characters and character states.”

“Second, and most importantly, it is only through the full incorporation of data from newly discovered species both within and without Dinosauria, that more confidence could be placed in our understanding of the geographic setting of the common ancestor of all dinosaurs.”

Yes. Adding taxa will solve this problem. Follow the example of the LRT.

“Another substantial omission of most studies of this kind are pterosaurs. Pterosauromorpha is a clade of flying Mesozoic reptiles that are very closely related to the dinosaurs, forming with them the clade Ornithodira.” 

No. That’s a myth. Adding taxa removes pterosaurs from dinosaurs and nests them with lepidosaurs. We’ve known this since 2007, but textbooks must be sold.

“As a final point, it is worth remembering that during the Late Triassic, every continent was united into a single landmass, Pangea.”

True! Even so, you have to include more basal bipedal crocs and a raft of other taxa to figure out who is in and who is out. That’s where the LRT can be more than helpful. The debate is over when you have minimized taxon exclusion, as in the LRT.

Bottom line:
Baron and other workers choose their taxa. The LRT recovers taxa for you. Take the bias, myth and tradition out of the equation.


References
Baron MG 2020. Difficulties with the origin of dinosaurs: a comment on the current debate. Palaeovertebrata 43 (1)-e3 . doi: 10.18563/pv.43.1.e3
Baron MG, Norman DB, Barrett PM 2017. A dinosaur missing-link? Chilesaurus and the early evolution of ornithischian dinosaurs. Biology Letters 13 (8): 20170220. https://doi.org/10.1098/rsbl.2017.0220
Langer et al. (8 co-authors) 2017. Untangling the dinosaur family tree. Nature 551: doi:10.1038/nature24011
Mortimer M, Gardner N, Marjanovic D and Dececchi A 2018. Ornithoscelida, phytodinosauria, saurischia: stesting the effects of miss cores in matrices on basal dinosaur phylogeny. SVP abstracts.
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 Bpublished online 

https://pterosaurheresies.wordpress.com/2017/08/16/you-heard-it-here-first-chilesaurus-is-a-basal-ornithischian-confirmed/

https://pterosaurheresies.wordpress.com/2017/11/08/you-heard-it-here-first-daemonosaurus-is-an-ornithischian/

https://pterosaurheresies.wordpress.com/2018/10/26/svp-2018-the-clade-ornithoscelida-tested/

https://pterosaurheresies.wordpress.com/2018/06/24/dr-baron-tip-toes-around-the-radiation-of-dinosaurs/

https://pterosaurheresies.wordpress.com/2017/11/03/dinosaur-family-tree-langer-et-al-responds-to-baron-et-al-2017-in-nature/

https://pterosaurheresies.wordpress.com/2017/03/23/new-radical-dinosaur-cladogram-baron-norman-and-barrett-2017/

Was the first dinosaur egg soft?

Norell et al. (8 co-authors) 2020
used phylogenetic bracketing to determine that the first dinosaur egg (still unknown) was soft. They made one mistake that invalidates their phylogenetic bracket (Fig. 1).

Figure 1. From Norell et al. 2020 misleading readers by placing pterosaurs, Lagerpeton and Silesaurus in the lineage of dinosaurs after crocodylomorphs.

Figure 1. From Norell et al. 2020 misleading readers by placing pterosaurs, Lagerpeton and Silesaurus in the lineage of dinosaurs after crocodylomorphs.

From the Norell et al. abstract:
“However, pterosaurs—the sister group to dinosauromorphs—laid soft eggs.”

Simply adding taxa reveals this is wrong.
In the large reptile tree (LRT, 1698+ taxa) pterosaurs nest within Lepidosauria. The pterosaur – dinosaur myth was invalidated by Peters 2000, 2007. So we have to toss out pterosaurs as an invalid nesting. What are we left with?

According to Norell et al.
Crocodylia create rigid calcite eggs. So do members of the Theropoda (including birds). So do members of the phytodinosaur clades, Ornithopoda and Macronaria. Exceptions occur among the highly derived Ceratopsia, which lay soft eggs. Two more exceptions include the primitive sauropodomorphs, Massospondylus and Mussaurus. More importantly, egg shellls remain unknown for basal poposaurs, basal crocodylomorphs, basal theropods and basal phytodinosaurs.

When we use phylogenetic bracketing to make a statement like this
we need to be sure that we have the proper phylogeny. Norell et al. relied on tradition and myth rather than testing. They were wrong. In their claodgram, Norell et al. are hopeful that pterosaurs arose between crocodylomorphs and Lagerpeton (a bipedal proterochampsid also not related to dinosaurs). The Norell et al. cladogram was invalidated by Peters 2000 using four prior phylogenetic analyses. Those citations do not appear in Norell et al. (fufilling Bennett’s curse). In the LRT Silesaurus is a poposaur and thus a dinosaur-mimic, less related to dinosaurs than crocodylomorphs.

When we find eggs for Herrerasaurus and Eoraptor
then we can send a manuscript to Nature. Norell et al. were premature at best, misleading and myth perpetuating at worst. That the referees considered this manuscript okay to publish shows the dinosaur – pterosaur myth is still widespread and deeply entrenched, as discussed earlier here.


References
Norell et al. 2020. The first dinosaur egg was soft. Nature https://doi.org/10.1038/s41586-020-2412-8
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 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.

https://www.cnn.com/2020/06/17/world/soft-dinosaur-eggs-scn/index.html
https://www.cnet.com/news/soft-shelled-dinosaur-eggs-crack-the-mystery-of-missing-fossils/

Is the rise of meat-eating dinosaurs complicated?

No.
A Smithsonianmag.com writer is trying to make the ordinary extraordinary by claiming, “The Rise of Meat-Eating Dinosaurs Is More Complicated Than We Thought. “

Figure 1. Herrerasaurus from Black 2020. This is a basal dinosaurs. This is not an omnivore.

Figure 1. Herrerasaurus from Black 2020. This is a basal dinosaurs. This is not an omnivore.

Writer Riley Black (formerly Brian Switek)
writing in smithsonianmag.com declares: “The earliest dinosaurs arose about 235 million years ago during the Middle Triassic. They didn’t look much like modern favorites Triceratops or Spinosaurus. Instead, these lanky creatures didn’t get much bigger than a German shepherd. The current spate of evidence suggests they were omnivorous.”

Black also provides this image (Fig. 1) of middle Triassic Herrerasaurus, the basalmost dinosaur in the large reptile tree (LRT, 1688+ taxa) and this is no omnivore. This taxon is 3 meters or 16 feet long, not the size of a German shepherd.

Black continues:
“Up until now, paleontologists thought theropods remained generally small and on the ecological sidelines from about 235 through 201 million years ago. It was only after a mass extinction at the end of the Triassic, at the 201 million-year mark, that carnivorous dinosaurs started to get big. But that view is starting to change thanks to a new reading of the bone trail by scientists who think large meat-eaters may have appeared much earlier. Virginia Tech paleontologist Christopher Griffin says a key player in this story is Herrerasaurus.”

Confused?  So am I. This brings us back to where the LRT starts, regarding dinosaurs. Everyone in paleo knows Herrerasaurus is a Middle Triassic carnivorous dinosaur. The little German shepherd-sized dinos are either made up or never existed. In either case, Black doesn’t list or illustrate them.

Black continues:
“The known carnivorous dinosaurs during the later part of the Triassic appeared to be smaller and less imposing than the crocodile relatives they lived alongside (such as Postosuchus from the southwestern United States). Thanks to a better understanding of dinosaur growth, however, paleontologists have found that some of those little theropods were hiding a secret.”

Postosuchus is not a crocodile relative in the LRT. Herrerasaurus is closer to crocodiles in the LRT because only crocodylomorphs and dinosaurs make up the clade Archosauria.

Black continues:
“The few remains we’ve found of larger Triassic theropods come exclusively from immature animals that are still growing rapidly,” Griffin says. These young carnivores would have grown to lengths exceeding 18 feet in adulthood. That’s a little less than half a full-grown T. rex, but enough to make you want to avoid meeting such a carnivore face-to-face.”

A few Late Triassic theropod lengths: Tawa is 2m long. Coelophysis is 3m long. Both are represented by adult skeletons. Again, where are these imaginary few remains?

Black finally raises the curtain on her main attraction:
“Late last year, Ludwig-Maximilian University of Munich paleontologist Oliver Rauhut and colleague Diego Pol named an exceptional skeleton of a Middle Jurassic carnivore they called Asfaltovenator. This was a large animal, more than 25 feet long, that approached the average size of the later Allosaurus and bears more a passing resemblance to the later dinosaur.”

This is no big deal. Between the Late Triassic and the Late Jurassic we expect to find theropod dinosaurs bigger than their ancestors and smaller than their descendants with transitional morphologies.

Black concludes with a quote: 
“There is much more to be learned about theropod evolution during this time,” Rauhut says, with finds like Asfaltovenator hinting at what remains to be uncovered.”

Again, no big deal. There is always ‘much more to be learned’ about all taxa ‘during this time.’ Some people complain because I was a journalism major. Sometimes that degree comes in handy.


References
Black R 2020. The Rise of Meat-Eating Dinosaurs Is More Complicated Than We Thought. online here.

Shrinking dinosaurs and the evolution of endothermy in birds

A new paper by Rezende et al. 2020
correlate small size with endothermy at the genesis of birds from larger theropod precursors.

A problems arises
due to taxon exclusion at the origin of dinosaurs (Fig. 1) when small size, bipedalism and the genesis of proto-feathers already correlates with endothermy… tens of millions of years before the advent of birds. Rezende et al. apparently decided not to include the genesis of dinosaurs in their study… but should have done so.

Figure 1. The origin of dinosaurs in the LRT to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.  Note the phylogenetic miniaturization at the origin of Archosauria (Crocs + Dinos).

Figure 1. The origin of dinosaurs in the LRT to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.  Note the phylogenetic miniaturization at the origin of Archosauria (Crocs + Dinos).

From the abstract:
“The evolution of endothermy represents a major transition in vertebrate history, yet how and why endothermy evolved in birds and mammals remains controversial.”

Controversial? No. Everyone knows the warm-blooded, high-energy tetrapods all had their genesis after phylogenetic miniaturization. We covered that earlier with mammals, dinosaurs and pterosaurs.

“Here, we combine a heat transfer model with theropod body size data to reconstruct the evolution of metabolic rates along the bird stem lineage. Results suggest that a reduction in size constitutes the path of least resistance for endothermy to evolve, maximizing thermal niche expansion while obviating the costs of elevated energy requirements.”

This has been known for decades.

“In this scenario, metabolism would have increased with the miniaturization observed in the Early-Middle Jurassic (~180 to 170 million years ago), resulting in a gradient of metabolic levels in the theropod phylogeny.”

The authors are unaware that phylogenetic miniaturization preceded the origin of dinosaurs in the tiny Middle Triassic taxon PVL 4597 (Figs. 1, 4).

“Whereas basal theropods would exhibit lower metabolic rates, more recent nonavian lineages were likely decent thermoregulators with elevated metabolism. These analyses provide a tentative temporal sequence of the key evolutionary transitions that resulted in the emergence of small, endothermic, feathered flying dinosaurs.”

Seems logical, but as mentioned above, these authors are a few nodes too late. Small endothermic dinosaurs were present in the Late Triassic following PVL 4597.

The Rezende et al. cladogram
(Fig. 2) includes many large to giant theropod dinosaurs and it does not match the large reptile tree (LRT, 1631+ taxa, Fig. 3), which includes more smaller theropods.

Figure 2. Cladogram from Rezende et al. with colors added to show three size classes, under a meter, about a meter, and more than a meter in length.

Figure 2. Cladogram from Rezende et al. with colors added to show three size classes, under a meter, about a meter, and more than a meter in length. Note the transition from large (purple) to medium (green) to little (small). Compare to figure 3 from the LRT.

Figure 4 in Rezende et al.
shows the evolution of ectothermy (240-220mya) to inertial homeothermy (giant taxa, 370kg, 215-190mya) to feathers (190-160mya) to endothermy (180-160mya) to flight (170-160mya).

Taxon inclusion sets can be biased
to present the story you want to tell. In the Rezende et al. cladogram (Fig. 2) a large number of Middle and Late Jurassic giants are included. In the LRT (Fig. 3) small taxa are present throughout the lineage of theropods. Scipionyx (at the base of Jurassic large theropods) is also a small taxon, but workers consider it a juvenile of a medium-sized taxon.

Figure 3. Subset of the LRT focusing on theropods and basal birds. Colors added for large (greater than a meter), medium (about a meter), and small (less than a meter) in length. Compare to figure 2 from Rezende et al. Note the depth of small taxa, some of which give rise to large taxa.

Figure 3. Subset of the LRT focusing on theropods and basal birds. Colors added for large (greater than a meter), medium (about a meter), and small (less than a meter) in length. Compare to figure 2 from Rezende et al. Note the depth of small taxa, some of which give rise to large taxa. Scipionyx at the base of the giant Jurassic theropods, is also a tiny taxon, but is considered a juvenile.

From the Rezende et al. discussion section:
“Two exceptional phenomena are observed during the evolution of birds: a sustained (but not necessarily gradual) miniaturization lasting millions of years and the emergence of endothermy. We argue that these phenomena are mechanistically linked.”

Figure 4. The genesis of the Archosauria embodied in PVL 4597 to scale with a modern archosaur, Cyanocitta, the blue jay.

Figure 4. The genesis of the Archosauria embodied in PVL 4597 to scale with a modern archosaur, Cyanocitta, the blue jay.

Unfortunately,
taxon exclusion invalidates this entire paper. The origin of the clade Archosauria (crocs + dinosaurs) had its genesis in a tiny taxon, PVL 4597 (Figs. 1, 4). That’s where endothermy first evolved. That’s where extradermal membranes (proto-feathers on naked skin) first appeared (more or less retained in both theropods and phytodinosaurs) and later turned into scales on larger dinos.

Birds likely have a higher endothermy
than non-avian theropods, and giant dinosaurs might have had a lower endothermy than smaller dinosaurs, but small theropods with a high endothermy and a bipedal configuration were present throughout the Triassic and Jurassic.

Many times tiny dinosaurs gave rise to
medium, large and giant clades in the LRT. The origin of birds was not the first time dinosaurs became small and endothermic. It was the second time.

If the Rezende et al.  paper sounds familiar, it is.
…and we looked at it earlier here. 


References
Rezende EL, Bacigalupe LD, Nespolo RF and Bozinovic F 2020. Shrinking dinosaurs and the evolution of endothermy in birds. Science Advances 2020:6 eaaw4486 1 January 2020
Lee MSY, Cau A, Naish D and Dyke GJ 2014. Sustained miniaturization and anatomicial innovation in the dinosaurian ancestors of birds. Science 345(6196):562–566.

 

Updated ‘Origin of Dinosaurs and Birds’ YouTube video

When I first posted a video on YouTube
featuring the origin of dinosaurs and birds several years ago, the large reptile tree (LRT, 1611+ taxa) had 500 some taxa and the video featured genera going all the way back to Devonian tetrapods. That far back was unnecessary and became outdated last year with the addition of more tetrapods to the LRT. I will do the same with the other videos as time allows.

And one more thing…
as the late Steve Jobs used to say. The above pterosaur video was updated, as well, to be more concise and informative.

Best regards
and thank you for your readership.

Meet Gnathovorax: the most primitive herrerasaur/dinosaur

Pacheco et al. 2019
introduce Gnathovorax cabreirai (Figs. 1), a new herrerasaurid (Fig. 2) based on “an exquisite specimen” (Fig. 3)

Figure 1. Gnathovorax compared to Herrerasaurus, PVL 4597 and Decuriasuchus.

Figure 1. Gnathovorax compared to Herrerasaurus, PVL 4597 and Decuriasuchus. Phylogenetic miniaturization occurred at the genesis of bipedalism in PVL 4597.

Unfortunately,
taxon exclusion prevented Pacheco et al. from understanding and appreciating the micro-evolution now documented at the base of the Dinosauria (Fig. 1) based on the large reptile tree (LRT, 1594 taxa). The authors omitted basal bipedal crocs, like Pseudhesperosuchus (Fig. 4), the basalmost archosaur PVL 4597 (Fig. 1) and the basal poposaur, Decuriasuchus (Fig. 1).

Figure 2. Cladogram from Pacheco et al. 2019. Colors added over the nodes to show where taxa nest in the LRT.

Figure 2. Cladogram from Pacheco et al. 2019. Colors added over the nodes to show where taxa nest in the LRT where Ornithischia and Sauropodomorpha are derived from basal Phytodinosauria.

Lacking pertinent taxa
also prevents Pacheco et al. (Fig. 2) from recovering the clade Phytodinosauria, which splits from basal Theropoda in the LRT.

Figure 3. Gnathovorax in situ from Pacheco et al. 2019. Green bones belong to other taxa.

Figure 3. Gnathovorax in situ from Pacheco et al. 2019. Green bones belong to other taxa.

Between Euparkeria (Fig. 4) and Dinosauria
are several transitional taxa not listed by Pacheco et al. The phylogenetic miniaturization at the base of the Archosauria is a common phenomenon at the origin of major vertebrate clades.

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Figure 4 The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus,  Pseudhesperosuchus, Herrerasaurus, Tawa and Eoraptor.The LRT is here for researchers to use
as a taxon checklist to make sure they are including all pertinent taxa in their smaller, more focused studies. Just because you’re a traditional paleontologist does not mean you have to omit non-traditional taxa.


References
Pacheco C, Müller RT, Langer M, Pretto FA, Kerber L and Dias da Silva S 2019. Gnathovorax cabreirai: a new early dinosaur and the origin and initial radiation of predatory dinosaurs. PeerJ 7:e7963 http://doi.org/10.7717/peerj.7963

Is CRILAR‐Pv 552 Lewisuchus? … and what is Lewisuchus?

Ezcurra et al. 2019
bring us a partial skeleton in 3D (CRILAR‐Pv 552, lower Carnian, Late Triassic; Fig. 1) of material that agrees with both Lewisuchus admixtus (Fig. 1; Romer 1972; Bittencourt et al. 2014) and Pseudolagosuchus major, both previously known from non-overlapping partial skeletons.

Figure 1. Combining anterior traits from Lewisuchus and limb traits from Pseudolagosuchus, CRILAR-Pv 552 appears to ally the two taxa. Here are two restorations. Ezcurra et al. prefer the quadrupedal pose. The LRT indicates Lewisuchus was bipedal based on limb size disparity.

Figure 1. Combining anterior traits from Lewisuchus and limb traits from Pseudolagosuchus, CRILAR-Pv 552 appears to ally the two taxa. Here are two restorations. Ezcurra et al. prefer the quadrupedal pose. The LRT indicates Lewisuchus was bipedal based on limb size disparity. The ventral pubis reconstruction is based on LRT sister taxa. Their restoration bears little to no similarity to Silesaurus or its poposaur sisters.

From the abstract
“Here, we describe a new dinosauriform partial skeleton (CRILAR‐Pv 552) recently collected in the Chañares Formation that preserves previously unknown anatomical regions for the dinosaur precursors of this unit (e.g., premaxilla, inner ear, anterior zeugopodium) and allows comparisons with other dinosauriform specimens. CRILAR‐Pv 552 is referred to Lewisuchus admixtus because it possesses a proportionally large skull, a laterally projected, shelf‐like ridge on the jugal, and recurved, finely serrated middle‐posterior maxillary and dentary teeth ankylosed to the bone, and the absence of a coracoid foramen. The new specimen preserves a dorsally bowed dentary with a lateroventral shelf that is identical to a dentary associated with the holotype of Lewisuchus admixtus. Additionally, the morphology of the new specimen is completely congruent with that of specimens of Pseudolagosuchus major, bolstering the hypothesis that the latter species is a subjective junior synonym of Lewisuchus admixtus. A preliminary phylogenetic analysis with updated scorings for Lewisuchus admixtus found this species at the base of Silesauridae.”

By contrast
the large reptile tree (LRT, 1565 taxa) Lewisuchus nests within the Crocodylomorpha near the base where most taxa are small and bipedal, contra the authors’ restoration (Fig. 1). Everything in the new specimen seems to agree with the Lewisuchus restoration previously proposed other than a reduction in the ilium, closer to Crocodylomorpha than to the basalmost archosaur, the last common ancestor of dinos and crocs, PVL 4597. By contrast, another basal croc, Pseudhesperosuchus (Fig. 2), has a small ilium similar to that of CRILAR-Pv 552, and by homology Lewisuchus and Pseudolagosuchus.

Figue 1. A new reconstruction of the basal bipedal croc, Pseudhesperosuchus based on fossil tracings. Some original drawings pepper this image. Note the interclavicle, missing in dinosaurs and the very small ilium, only wide enough for two sacrals. The posterior dorsals are deeper than the anterior ones.

Figue 1. A new reconstruction of the basal bipedal croc, Pseudhesperosuchus based on fossil tracings. Some original drawings pepper this image. Note the interclavicle, missing in dinosaurs and the very small ilium, only wide enough for two sacrals. The posterior dorsals are deeper than the anterior ones.

Supplementary material
indicates, “Scorings of Lewisuchus admixtus changed from the data matrix of Baron et al. (2017), as modified by Langer et al. (2017) and Nesbitt et al. (in press).” 17 pre-dinosaur taxa are included among the 85 taxa. The rest are dinosaurs. Missing from the Ezcurra et al. taxon list (and all that it evolved from) are the following Lewisuchus sisters in the LRT: PVL 4597, Pseudhesperosuchus and Junggarsuchus. So taxon exclusion is a problem with Ezcurra et al.

Minor note:
As before, no trees were saved in the provided .nex file. Remember, fellow workers: Save those MPTs in a .nex file by using the ‘store tree‘ pull down menu item.


References
Bittencourt JS, Arcucci AB, Maricano CA and Langer MC 2014. Osteology of the Middle Triassic archosaur Lewisuchus admixtus Romer (Chañares Formation, Argentina) its inclusivity, and relationships amongst early dinosauromorphs. Journal of Systematic Palaeontology. Published online: 31 Mar 201. DOI:10.1080/14772019.2013.878758
Ezcurra MD, Nesbitt SJ, Fiorelli LE and Desojo JB 2019. New specimen sheds light on the anatomy and taxonomy of the early Late Triassic dinosauriforms from the Chañares Formation, NW Argentina. The Anatomical Record. doi:10.1002/ar.24243
Nesbitt SJ. et al. 2010. Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira. Nature 464(7285):95-8 .
Romer AS 1972. The Chañares (Argentina) Triassic reptile fauna; XIV, Lewisuchusadmixtus, gen. et sp. nov., a further thecodont from the Chañares beds. Breviora 390:1-13

wiki/Lewisuchus

paleonerdish.wordpress.com/2019/08/29/a-new-dinosauriform-specimen-from-the-chanares-formation-of-north-western-argentina

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

New origin of dinosaurs video by Dr. Sterling Nesbitt

There’s a new YouTube video
featuring Dr. Sterling Nesbitt describe his version of dinosaur origins.

Unfortunately
Dr. Nesbitt ‘pulls a Larry Martin‘ by concentrating on key dinosaurian traits and not concentrating on the last common ancestor (Fig. 2) in a wide gamut phylogenetic analysis, like the large reptile tree (LRT, 1515 taxa, subset Fig. 3). Nesbitt is great at finding bones in the field, and describing new taxa, but Nesbitt 2011 and Nesbitt 2017 omitted key proximal outgroups to the Dinosauria (Figs. 2, 3) and so he keeps missing ‘the big picture.’

Continuing an invalid tradition
Dr. Nesbitt nests the tropidosuchid proterochampsid, Lagerpeton, as a close dinosaur outgroup. He also nests pterosaurs close to the base of the Dinosauria, which has been a big mistake for nearly 20 years. Dr. Nesbitt omits bipedal crocodylomorphs (Figs. 2, 3) from his dinosaur cladograms, another traditional academic mistake.

Nesbitt’s taxon exclusion issues
are repaired in the LRT (subset Fig. 3) where the last common ancestor of every included taxon back to Silurian fish is documented and validated by minimizing taxon exclusion.

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Figure 2. The origin of dinosaurs to scale in the LRT. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Figure 1. Revision to the LRT with a focus on the Archosauria. Here taxa with a long carpus all nest within the Crocodylomorpha, following traditional thinking. Dinosaur outgroups are reduced. PVL 4597 is still the basalmost archosaur.

Figure 1. Revision to the LRT with a focus on the Archosauria. Here taxa with a long carpus all nest within the Crocodylomorpha, following traditional thinking. Dinosaur outgroups are reduced. PVL 4597 is still the basalmost archosaur.


References
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bull. Am. Mus. Nat. Hist. 352, 1–292.
Nesbitt et al. 2017. The earliest bird-line archosaurs and the assembly of the dinosaur body plan. Nature (online here).

https://pterosaurheresies.wordpress.com/2017/04/13/teleocrater-a-sister-to-yarasuchus-not-the-earliest-bird-line-archosaur/

https://pterosaurheresies.wordpress.com/2018/02/22/redefining-what-makes-a-dinosaur/

SVP 2018: Rare sternum(?) found in Tawa

Bradley et al. 2018
provide a very rare appearance of theropod sternal plates in several Late Triassic Tawa specimens (Fig. 1), the oldest yet discovered for dinosaurs. They report, “The morphology of all specimens is surprisingly similar to the sterna in avialans in that they bear a sternocoracoidal process, a space along the lateral margin likely homologous to the coracoid facet, costal processes with nutrient foramina in the spaces between them, and a reinforcing ridge possibly homologous to the Pila coracoidea in extant birds.” So this sounds like a single element, not paired plates.

Figure 1. The theropod Tawa compared to the closely related phytodinosaur, Eodromaeus.

Figure 1. The theropod Tawa compared to the closely related phytodinosaur, Eodromaeus.

No basal dino sister taxa in the large reptile tree preserve sternal plates.
In dinosaurs sternal plates appear in derived sauropods, in the basal ornithischian, Haya and most derived ornithischians and among theropods in most taxa derived from Compsognathus. So the appearance of sternal plate(s) in Tawa is odd.

An outgroup taxon,
Pseudhesperosuchus (Fig. 2) nesting at the base of the crocodylomorpha, preserves a narrow interclavicle articulating to the elongate coracoids. Given the phylogenetic bracketing and description, I wonder what they found in Tawa is instead the last interclavicle found in dinosaurs?

Figue 1. A new reconstruction of the basal bipedal croc, Pseudhesperosuchus based on fossil tracings. Some original drawings pepper this image. Note the interclavicle, missing in dinosaurs and the very small ilium, only wide enough for two sacrals. The posterior dorsals are deeper than the anterior ones.

Figue 2. A new reconstruction of the basal bipedal croc, Pseudhesperosuchus based on fossil tracings. Some original drawings pepper this image. Note the interclavicle, missing in dinosaurs and the very small ilium, only wide enough for two sacrals. The posterior dorsals are deeper than the anterior ones.

Bradley et al. report,
“From this new evidence, it is apparent that the distribution of sternal character states across avemetatarsalians shows unexpected variation rather than a stepwise accrual of traits leading to Aves.” No, “unexpected variation” is not the way evolution works. The evidence may have been misinterpreted, or relevant sister taxa may have not been included.

Avemetatarsalia
This traditional, but invalidated clade, Avemetatarsalia, includes pterosaurs, which have a sternal complex (sternum + clavicles + interclavicle). Earlier co-author Nesbitt 2011 scored the sternal complex as a single sternum. That might be a factor in their study. Most paleontologists omit Pseudhesperosuchus and kin from dino origin analyses. This team may have also done so. So I suspect some mixups are happening here. We’ll see. Alert the authors to this possibility, if you know them.

References
Bradley et al. (6 co-authors) 2018. Sternal elements of the early dinosaur Tawa hallae fill a critical gap in the evolution of the sternum in Avemetatatarsalia (Reptilia: Archosauria). SVP abstracts.