John Conway – Paleoartist extraordinaire

John Conway is a paleoartist whose work deserves a wider audience. I encourage all readers to check out his website here.

Conway has the eye of a true artist. His work is simply beautiful. He also brings new insight into familiar and not so familiar specimens. His choice of colors, point-of-view and lighting are unique and more than satisfying. His work invites close inspection and admiration. His work evokes mood and involvement.

Here’s a selection from his homepage.

Figure 1. The art of John Conway. Click to go to enlarge and go to his website.

Sure I have the usual rant/quibbles
about his Rhamphorhynchus (he followed the invalidated Sordes cruropatagium model of Sharov/Bakhurina/Unwin), but those are easily overlooked when seduced by his talents for portraying it. In any case, Conway illustrated this falsified hypothesis more clearly than anyone else ever and, in doing so, answered the persistent question: “Was the cloaca above or below the ‘cruropatagium’?” [Conway indicates it was below, evidently, making sex a wee bit more difficult, but excrement did not stain the membrane].

Earlier I also made notes on his Pteranodon proportions.

Don’t miss his Anhanguera cutaway. It’s a classic. Be sure to run your mouse over the “Skeleton :: Musculature :: Pulmonary :: External“ caption to see all four images. A truly amazing illustration.

Best YouTube Dinosaur Video I’ve Seen

Figure 1. Acrocanthosaurus Paluxy River attack video. Click to view. 43 minutes.

This Acrocanthosaurus video on YouTube is extremely well done. Animation, explanation and new insights, all fascinating and credible. I can’t say enough. Must see video for dino fans.

Essential proof that giant theropods took on much larger prey 110 million years ago.

Originally produced for Mega Beasts on the Discovery Channel.

References
youtube/Acrocanthosaurus

TV worth watching: PBS special on prehistoric Australia

I endorse the new PBS/Nova series on prehistoric Australia called, “Australia: First 4 Billion Year.” It’s a fast-paced eye-opener.

The first in the four/part series can be seen here, Australia: Awakening. Host Dr. Richard Smith journeys back to the very beginning of the Australian story.

The second in the series can be seen here, Australia: Life Explodes, focusing on Ediacaran, Cambrian, Silurian and Devonian fossils.

Figure 1. Australia: Monsters, part 3 of the 4-paet series by PBS/Nova. Click to go the PBS/Nova site.

The third in the series can be seen here, Australia: Monsters, featuring dinosaurs and enaliosaurs.

The final part can be seen here after in airs May 1, Australia: Strange Creatures, featuring the monotremes and marsupials, of course.

The Origin of Dinosaurs, Mortimer vs. Peters and the ‘Zipper Check’ Test

Fellow blogger, Mickey Mortimer, at the Theropod Database Blog, has been pretty rough on yours truly lately. From name calling to finger-pointing to associating me with people who have been kicked off the DML*. I gather from Mortimer’s comments that I am sorely in need of a lesson in phylogenetic analysis.

All true. 
As everyone knows, I’m not classically trained. I don’t have immediate access to fossils, but rely on photos and line drawings for my data. On the plus side, I’ve created a larger gamut reptile family tree than anyone so anyone can trace the origin of any major reptile clade. I’m always interested in receiving data that will improve the sometimes crappy data I sometimes deal with. And I change things like images and data when new data or new insights come along. Science is not immutable. Everyone coming here to the Pterosaur Heresies website has permission to change their mind without fear of being vilified.

(That’s not always the case “out there” as we’ve also seen here).

For instance,
when Mortimer suggested that Silesaurus had gastralia, I found the new paper describing it and I was happy to make that change to the matrix. Behind the scenes, my own studies often include rescoring data, especially when new taxa are added. New insights are always coming along. Mortimer calls me “dishonest” for doing this. However, I think it’s important to remove wrong data and replace it with better data whenever possible.

Getting back to our story
Mortimer has been “correcting” the wording and the scorings of the large reptile tree/dinosaur subsection (2000+ “corrections” so far) and Mortimer’s results are as follows (Fig. 1) in graphic form with Sacisaurus at the base and theropods as derived taxa (derived from Sacisaurus and sauropodomorphs):

Figure 1. Basal dinosaur tree as recovered by Mortimer. Here Sacisaurus is the most basal dinosaur. A sister to Sacisaurus gives rise to ornithischians (Heterodontosaurus) and to saurischians, which give rise to theropods. Thus, in Mortimer’s view, theropods are derived from beaked planteaters like Sacisaurus, and non-beaked plant-eaters, like Massospondylus. Daemonosaurus, despite its similarity to Heterodontosaurus and Massospondylus nests as a sister to Tawa in Mortimer’s tree. This is pretty much just the opposite of the large reptile tree shown in figure 2.

Mortimer’s results conflict with those of the large reptile tree, which looks like this (Fig. 2) in graphic form where carnivorous Herrerasaurus is primitive and beaked Sacisaurus is derived from Eoraptor:

Figure 2. Dinosaur relations as recovered from the large reptile tree. Here short-faced plant-eaters, like Massospondylus and Heterodontosaurus, are derived from meat-eaters, like Herrerasaurus via Daemonosaurus. Eoraptor has been difficult to classify, perhaps because it is a key taxon at the base of the phytodinosauria, along with Pampadromaeus.

Figure z. Cautionary tale. Why the last minute zipper check is so important!

The Zipper Check
Before us men go out to face the day we touch our fly (pants zipper) to make sure it’s up, not down. That’s the Zipper Check. It’s that one last simple test to make sure there are not going to be any embarrassing moments in the near future. Lining up basal dinosaur skulls (Fig. 2) represents my zipper check**. This little graphic told me my results were going to be okay. The line-up makes sense. Derived traits are found in derived taxa.

Unfortunately, somehow, and despite best intentions, long hours and many years of experience, Mortimer’s tree (Fig. 1) came out the exact opposite of mine (Fig. 2). I suggested a zipper check before Mortimer published. But, well… now it’s out there.

Data Matrix vs Graphic Presentation
I’m using a series of skulls in today’s blog to quickly get across a point that you could also gather over many hours lingering over either Mortimer’s or my data matrix or both. Ease of use is paramount here.

You be the judge.
It’s difficult for me to agree with the results of Mortimer’s tree, but I may be in the minority. Whatever mistakes that are present in the large reptile tree (and there must be some, but fewer than this morning since I dug into it a bit today), evidently the mistakes were not large enough to create an illogical solution, but, instead, appear to echo actual evolutionary events.

Even if my data is voodoo, I stand by my results (until better data comes in!)

The Reason for the Different Trees
I think the rescorings of Mortimer’s tree gave added weight to traits that would link poposaurids to rauisuchids (an outgroup). That’s why Sacisaurus nested as basal. On the other hand, I used the same characters as are found throughout the rest of the large reptile tree. That’s why poposaurids nested as phytodinosaurs in my tree. Others think poposaurids are convergent with dinosaurs. I think they are dinosaurs and the description of dinosaur traits needs to expand (or contract) to include them. The definition (Passer + Triceratops) still works.

And, as always, if you have better data, please forward it. Changes will be made where necessary. Can you find the change I made this morning to the archosaur portion of the tree? Hint: Adding wrist characters was key.

I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

>>>>

*Come to think of it, I, too, was kicked off the DML too! I had the gall to suggest that we test Digital Graphic Segregation techniques versus actually looking at 2D fossils with the naked eye or microscope. According to published results with Jeholopterus, Vancleavea and Shenzhoupterus, to name a few, DGS definitely has its place in the pantheon of tools that can be used by paleontologists. And DGS is used, especially with fish fossils and anywhere else where the scene can be visually confusing. I don’t encourage the use of one tool over another, but the use of all tools to test one method against another.

** The Zipper Check test would also be useful for taxa like Lagerpeton, Vancleavea, pterosaurs, caseasaurs, Bennett’s anurognathid, parasuchians, Rotodactylus, and any other strange bedfellows that don’t look AT ALL like their purported sisters. Sometimes there are ‘by default’ nestings due to a too small gamut list of included taxa that needs expansion to other possible candidate taxa.

Nesting Eoraptor in the Large Reptile Tree

Eoraptor lunensis (Fig. 1) is an early (Carnian, Triassic, 1 meter long, PVSJ 512) bipedal dinosaur introduced by Sereno et al. (1993). Only the skull has been published, and before being fully prepped. The whole skeleton (Fig. 4), sans the tail tip, is known. I understand a monograph should be out this year. Digimorph published the skull in several views. The post-cranial data I’m working with is from Greg Paul (Fig. 4), published online here.

Figure 1. Eoraptor skull modified from Sereno et al. 1993.

I should have added Eoraptor earlier considering the importance of this taxon.

Figure 2. Eoraptor skull, traced from Digimorph image. Here the premaxillary teeth appear to be longer.

The Wiki/Eoraptor entry reports, “Eoraptor was one of the world’s earliest dinosaurs. It was a two-legged saurischian, close to the ancestry of theropods and sauropodomorphs” and lacked specialized predatory dinosaur traits. Sereno (195) considered Eoraptor the earliest recorded theropod closest to “the hypothetical dinosaurian condition that any other dinosaurian subgroup.“

Figure 3. Dinosaur family tree. Here’s where Eoraptor nests in the large reptile tree.

Indeed it is.
The large reptile tree (Fig. 3) nested Eoraptor with Panphagia and Pampadromaeus, a clade basal to the Phytodinosauria, derived from basal Theropoda like Herrerasaurus. According to Sereno et al. (1993), Eoraptor has distinct premaxillary and anterior maxillary leaf-shaped teeth. Currie (1997) also found Eoraptor closer to the hypothetical ancestor of both saurischian and ornithischian dinosaurs. More recently, Sues et al. (2011), in their study of Daemonosaurus, considered Eoraptor a basal theropod.

Eoraptor is a key taxon in the family tree of basal Dinosauria. While close to theropods, the snout is shorter and rounder, the teeth are “leaf-shaped,” and the orbit is larger. These traits continue to evolve in Phytodinosauria.

Figure 4. Eoraptor skull from Sereno et al. (1993). Eoraptor body image is copyrighted artwork from Greg Paul with permission. Based on an Eoraptor skeleton created for a Don Lessem traveling dinosaur show from several years ago.

Interesting PostScript
When working with Sacisaurus, I thought it strange that the postorbital had an odd convex bump just posterior to the eye. Now I see that it is evidently derived from Eoraptor, which likewise shared that postorbital bump.

Figure 4. Dinosaur relations as recovered from the large reptile tree. Here short-faced plant-eaters, like Massospondylus and Heterodontosaurus, are derived from meat-eaters, like Herrerasaurus via Daemonosaurus and Pampadromaeus.

A Key Taxon
The figure above represents the phylogenetic nesting of Eoraptor as a sister to Pampadromaeus, which is descended from a sister to Herrerasaurus and basal to the Phytodinosauria: Ornithischia,  Saurompodomorpha and Poposauridae. Seems to make sense on the face of it. And this is why Eoraptor has been hard to classify into traditional categories.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Currie PJ 1997. Theropoda. In Encyclopedia of Dinosaurs (P.J. Currie, and K. Padian, Eds.) pp 731-736. Academic Press, San Diego, California.
Sereno PC, Forster CA, Rogers RR and Moneta AM 1993. Primitive dinosaur skeleton form Argentina and the early evolution of the Dinosauria. Nature 361, 64-66.
Sereno PC 1995. Theropoda: early evolution and major patterns of diversification. Journal of Vertebrate Paleontology 15(3, suppl.):52A-53A
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, published online.

Wiki/Eoraptor

Donald Duck Dinosaur Skeleton

Just had to share this one (old news (2008) for most, new for me).

Donald Duck skeleton. Note the long sacral series and very birdy hips. Pedal digit 1 has never been seen in cartoons, but is appears here. Contrast those with the very human (but lacking one digit) forelimbs and hands. All tongue in cheek, of course.

Follow these links to see the skeletons of other cartoon characters, Tom & Jerry, Roadrunner, Wile E. Coyote and Bugs Bunny.

Link 1 - Link 2 - Link 3

Here are the nephews, Huey, Dewey and Louie (not sure which is which). This caught my eye and brought a big smile.

Huey, Dewey and Louie skeletons

South Korean artist, Hyungkoo Lee, created this ‘Animatus’ series with the “intention to analyze anatomical structures and physical forms of animation characters, within the hypothesis to visualize their possible anatomical foundation.” Skeletons are a hybrid mix of animal bones and synthetic materials.

They are also a hybrid mix of avian (dinosaur feet) and human (mammal hands), but note the wishbone, long coracoids and sternum!

Disney (1929) had his own take on animated skeletons here.

Earlier Roadrunner was transformed into Pterorunner here. 

Poposaur palates

The palates of poposaurs are poorly known Some have not been described or reconstructed (Fig.1). Others have been wrongly reconstructed or partially reconstructed (Fig. 4). Here (Fig. 1) are two poposaurs, Effigia and Shuvosaurus next to Daemonosaurus (Sues et al. 2011, also largely guessed at from broken pieces) and Thecodontosaurus, which provides more certitude. Most unfortunately, the palate of Lotosaurus has not been described or illustrated despite the presence of several specimens and museum casts. The little question is: On Daemonosaurus, which way do the ectopterygoids go? Long side against the pterygoid, as in rauisuchids? Or short side, as in Effigia and other dinosaurs?

Figure 1. Poposaur palates (Effigia and Shuvosaurus) along with Daemonoaurus and Thecodontosaurus (= Pantydraco, from Yates 2003)

On rauisuchians, as in ornithosuchians (Fig. 2), the ectopterygoid has a larger contact area with the lateral pterygoid and it produces a small “stem” to contact the jugal (as in Saurosuchus) or the maxilla (as in Riojasuchus). If you flip the ectopterygoid of Daemonosaurus, you get the rauisuchian type of ectopterygoid. Left as is (Fig. 1), however, you get the dinosaurian type,  and that is the preferred reconstruction here based on phylogenetic bracketing.

Figure 2. Click to enlarge. Euparkeriid, ornithosuchian, rauisuchian, aetosaurian, and basal archosaur palates. Here are Euparkeria and Osmolskina, both euparkeriids. Ornithosuchus and Riojasuchus are ornithosuchids. Saurosuchus and Postosuchus are both rauisuchians. Stagonolepis is an aetosaur. Pseudhesperosuchus is close to the basal archosaur pattern with a much smaller ectopterygoid and smaller ectopterygoid/pterygoid contact. The original configuration is shown on the right side. A possible alternative is shown on the left. Not sure how it was preserved. I’d like to know if you have this data. If the left is correct in figure 2 (Pseudohesperosuchus), and Shuvosaurus is also correct in figure 1, these suggest that Daemonosaurus is correctly drawn in figure 1.

Figure 4. Silesaurus palate with missing elements restored on the right. Illustration (without color) from Dzik 2003 who illustrated missing elements on the left.

Silesaurus Palate The missing ectopterygoid and palatine were not illustrated for Silesaurus. Given the palates of related taxa (Fig.1), I have added the missing elements on the right here (Fig. 4) to match them. Thus these restorations are guesses that appear to make sense in context. When better data come along, we’ll make improvements.

This has been a first attempt at reconstructing the palates of several poposaurs at once based on similar morphologies in close kin. The palates should remain somewhat similar. If anyone has good data on the palates of other rauisuchians and basal dinosaurs, please forward them on.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

Figure 3 is absent from this post now. Apologies. I had it in my files for several years and thought it had been published by now. It had not. 

 

References Bonaparte JF 1969. Dos nuevas “Faunas” de reptiles Triasicos de Argentina: I. Gondwana Symp., IVGS: 283-306.
Borsuk-Bialynicka M and Evans SE 2009. Cranial and mandibular osteology of the Early Triassic archosauriform Osmolskina czatkowicensis from Poland. Palaeontologia Polonica 65, 235–281.
Brusatte SL, Benton MJ, Desojo JB and Langer MC 2010. The higher-level phylogeny of Archosauria (Tetrapoda: Diapsida), Journal of Systematic Palaeontology, 8:1, 3-47.
Chatterjee S 1985. Postosuchus, a new Thecodontian reptile from the Triassic of Texas and the origin of Tyrannosaurs. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 309 (1139): 395–460. doi:10.1098/rstb.1985.0092.
Chatterjee S 1991. An unusual toothless archosaur from the Triassic of Texas: the world’s oldest ostrich dinosaur? Abstract, Journal of Vertebrate Paleontology, 8(3): 11A.
Chatterjee S 1993. Shuvosaurus, a new theropod: an unusual theropod dinosaur from the Triassic of Texas. National Geographic Research and Exploration 9 (3): 274–285.
Dzik J 2003. A beaked herbivorous archosaur with dinosaur affinities from the early Late Triassic of Poland. Journal of Vertebrate Paleontology 23: 556-574.
Ewer RF 1965. The Anatomy of the Thecodont Reptile Euparkeria capensis Broom Philosophical Transactions of the Royal Society London B 248 379-435. doi: 10.1098/rstb.1965.0003
Rauhut OWM 1997. On the cranial anatomy of Shuvosaurus inexpectatus (Dinosauria: Theropoda). In: Sachs, S., Rauhut, O. W. M. & Weigert, A. (eds) 1. Treffen der deutschsprachigen Palaeoherpetologen, Düsseldorf, 21.-23.02.1997; Extended Abstracts. Terra Nostra 7/97, pp. 17-21.
Long R and Murry P 1995. Late Triassic (Carnian-Norian) Tetrapods from the Southwestern United States. New Mexico Museum of Natural History and Science Bulletin 4, Pp. 153-163.
Sill WD 1974. The anatomy of Saurosuchus galilei and the relationships of the rauisuchid thecodonts. Bulletin of the Museum of Comparative Zoology 146: 317-362.
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, published online
Walker AD 1961. Triassic reptiles from the Elgin area: Stagonolepis, Dasygnathus and their allies. Philosophical Transactions of the Royal Society B 244:103-204.
Walker AD 1964. Triassic reptiles from the Elgin area: Ornithosuchus and the origin of carnosaurs. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 248(744): 53-134.
Yates AM 2003. A new species of the primitive dinosaur Thecodontosaurus (Saurischia: Sauropodomorpha) and its implications for the systematics of early dinosaurs. Journal of Systematic Palaeontology 1(1):1-42. wiki/Daemonosaurus wiki/Shuvosaurus

The “Truth” About Dinosaurs [Creationism Tour Comes to Town]

There is creation-based touring dinosaur show that came to my town this weekend. It’s called ‘The Truth About Dinosaurs‘ and you can see the gist of it here on YouTube, presented by Dr. G. Thomas Sharp (Fig. 3).

Figure 1. Billboard for The Truth About Dinosaurs at Harvester Church in St. Charles, MO, USA.

The odd thing is there were dinosaurs all over the platform (stage) leading to what would be the altar (but there is no altar in modern churches). Now the platform is where the band (singers, guitars, drums, etc.) plays. The specimens were all from North America (Albertosaurus, Edmontosaurus, Triceratops and Pteranodon). The last of which I recognized was made by my own hand. It was the Triebold specimen. Later it was explained to me that ALL the specimens were purchased from Triebold Paleontology.

Figure 2. Dinosaurs in church from the ‘The Truth About Dinosaurs’ traveling show. Red lights add to the drama. That’s Albertasaurus and Triceratops on stage.

Figure 3. Dr. G. Thomas Sharp (photo from a few years ago), the speaker for The Truth About Dinosaurs.

I have to agree with Dr. Sharp’s opening remarks. He said that all of us (as individuals) approach data with a personal bias, whether religious or secular (in other words, supernatural or natural). And therein lies the great divide. It cannot be breached. So long as Creationist not only prefer, but insist upon supernatural processes governing prehistory, then no amount of natural logic or processes will persuade them. Any arguments against all the animals coming to Noah’s ark (like the pesky problem of oceans separating Australia and the Western Hemisphere from the Middle East) are quickly dismissed by supernatural explanations. “God brought them to the ark.” Not sure where all the water came from to cover Mt. Everest, then disappear, all within a year? “God did that, too.”

What is particularly distressing is their reliance on the terms “could be,” “might be,” and “we should keep an open mind toward” with regard to various animals like the Yeti and various sea monsters in cryptozoology. They also have glommed on to Mary Schweitzer’s claims of soft tissue preservation in T-rex and similar PlosOne claims in a mosasaur.

Figure 1. Dinosaur man footprint. Note the layers in the dinoprint which means it was carved out rather than compressed, ignoring the lack of pad impressions and the bad anatomical knowledge of the sculptor. Embracing falsehoods like this have no place in a religious institution and make Christianity look bad.

I asked about footprints relating to Mokele-mbembe and I was shown a purported human footprint overprinted with a theropod track. Both were obviously carved by a poor anatomist as the print cut through several layers, rather than compressing several layers of sediment. The morphology of both carvings were also impossible to believe. Look at the depth of that big toe!!

What do Creationist believe?
Creationists insist on a literal translation of Genesis 1 in which the first man and woman were created a day or two after animals 4600 years ago. They also tend to ignore Genesis 2 in which man was created before the animals and later woman was formed from a rib). I wondered if that means dinosaurs were gone within the first 2000 years. No, pictures of dragons in medieval images bring them up to the Middle Ages before their extinction, according to Dr. Sharp’s entourage.

Figure 4. Sculpture supposedly of Stegosaurus, according to Dr. Sharp. A closer look reveals long ears and bad stegosaur proportions. This more likely represents a baby Sumatran rhinoceros and the “plates” are decorations or leaves. An unfortunate coincidence.

The church was packed (I went on Saturday at 5 pm, with two more services due for Sunday morning). The kids swarmed the stage. Even grownups had the pictures taken against the specimens. It was a real crowd-pleaser.

I think everyone bought into Dr. Sharp’s arguments and rhetoric. Certainly this represents this particular church’s dogma. No question and answer period followed (this was, after all, replacing the sermon), but a Sunday evening adult class was held with the promise of a q & a. Unfortunately, Dr. Sharp waxed on about Mt. St. Helens and how catastrophes can do as much damage in a day as otherwise over a thousand years. Nothing about dinosaurs, unfortunately.

My take
Having written a book on the evolution of humans from bacteria on up (From the Beginning), I’ve been interested in what Creationists have to say on the subject. I’ve been told that stars further from us than 5000 light years were created with their starlight already in progress, on its way to Earth. Creationist appear to cling to any rumor that supports their cause and reject everything from the geological column to transitional taxa that does not support their cause. They make up the rest. They do believe in micro-evolution (the sort that creates different breeds of dogs, for instance), but to them, there’s no time (only 4600 years) to go beyond that. So there’s no macro-evolution in their beliefs.

Getting back to my original theme, so long as Creationists embrace supernatural agents in their “Science” there can be no changing of their minds through logic. There can be no meeting of the minds. Heck, if regular paleontologists are constantly at loggerheads, there is nary a hope for arguing with or persuading a Creationist.

I would hope that modern paleontologists would never stoop to the level of creationist tactics, but, alas, they do so again and again in order to protect their trusted paradigm (without testing it). Still no archosaurs come close to pterosaurs, yet still pterosaurs are included in archosaur studies. Still no pterosaurs have been found with a wing membrane attached to the ankle.

It’s sad when well-meaning Christians promote and cling to obvious fakes and call it “The Truth.” It’s also inappropriate for religion to get into the realm of science and vice-versa.

For those who believe in the gospels, Christ himself was all about “evidence” as he turned water into wine, healed the blind, multiplied bits of bread and fish and calmed the storms, all before large audiences. I appreciate what has been discovered about the Shroud here and here. Unfortunately, none of these “miracles” can be repeated (although the Shroud examiners have taken things further than anyone expected). That’s why these miracles are considered in the realm of religion (faith based on one source), not Science (lack of faith, in other words: testing from a variety of sources).

Another look at Daemonosaurus

This post has been updated with images of the palate which affected the reconstruction of the skull in dorsal view. The rescoring issues brought up by M. Mortimer in TheropodDatabase made me reconsider the morphology of Daemonosaurus (Figs. 1-6). I wondered if I had gotten some details wrong.

Turns out I did.

Figure 1. For comparison sake, this is Daemonosaurus as traced by Sues et al. 2011. Here I flipped and warped the upper image to match the substrate outline in order to remove whatever positional lens distortion was present. Red lines were added by me. They are of little consequence here. Layering the two gives an “X-ray” image of the fossil in which the right side premaxilla and dentary had shifted anteriorly relative to its counterpart. That reveals little details one could never guess at, like the little ellipse in front of the left dentary is the medial tip of the right dentary.

Let’s fix that.
This time I traced both sides of the in situ skull in colors (Figs 2-5) from photographs in Sues et al. 2011. Then I re-reconstructed the skull (Fig. 6) using DGS methods. It is surprising how much like Heterodontosaurus and Massospondylus (Fig. 7) this short-snouted dinosaur really was …  and even more so with the corrections. Here are the images and interpretations. As always, you be the judge.

(Hopefully all prior posts have been updated, so old images can be seen on Google previews)

Unfortunately the original drawings by Sues et al. 2011 (fig. 1) did not label the bones. Some are obvious. Others are not. Likewise, I did not label bones, but their colors carry over to the reconstruction (Fig. 7), so their identities should be relatively easy to follow and understand.

Figure 2. Daemonosaurus left skull elements colorized. The squamosal (dark green) is broken up because another bone overlies much of it.

Here (Fig. 2) are the left skull elements. That dark green element is the palpebral, not duplicated (apparently lost) on the right side. See figure 7 if you’re not familiar with the palpebral. The light blue element is the prefrontal which is duplicated on the right. So the palpebral is not the prefrontal. The antorbital fenestra includes a disarticulated strip (magenta) that seems to fit as the interior portion of the lacrimal (light magenta) portion of the antorbital fossa. If it’s something else, then you’ll have to tell me what it is.

Figure 3. Daemonosaurus, mandible left. The dentary shifted relative to the posterior elements.

The left mandible is shown here (Fig. 3) largely beneath the skull. That’s a large articular in brown.

Figure 4. Daemonosaurus skull right (flipped)

The right side elements are here (fig. 4) flipped for ready comparison and “X-ray” layering. Certain elements are better preserved on this side. Others are not. That’s not a gracile quadratojual (in light green, my earlier error), but a possible pterygoid stem (quadrate process). In any case, it’s too small to be a dinosaur quadratojugal and especially to small if we consider how Daemonosaurus nests with ornithischians.

Figure 5. Daemonosaurus mandible right (flipped) and better articulated.

The right mandible is a little easier to see here (fig. 5) as it is more completely articulated. Both sides have a raised coronoid process. We don’t find that on too many theropods.

Figure x. Added the day after this post. Likely palatal elements in Daemonosaurus on the right side (here flipped).

Curious about the palatal elements I traced these likely to possible elements. Blue = pterygoid. Brown (dark orange) = palatine. Deep red = ectopterygoid.

Figure y. Added the day after this post. Likely palatal elements in Daemonosaurus on the left side.

The palate elements are all broken up in the Daemonosaurus skull, so based on fitting puzzle pieces together (some missing) based on Lesothosaurus and Massospondylus this is the current best guess as to the morphology of the palate. Basal dinosaur palates are otherwise very poorly known.

Figure 6. Daemonosaurus skull reconstruction in dorsal, lateral and palatal views. Note several palate bones are put together here from broken parts based on the palates of Lesothosaurus and Maassospondylus. Palate colors have changed with the latest revision.

The reconstruction of the traced elements reveals a deeper quadrate/quadratojugal than earlier reconstructed, as in Heterodontosaurus. I included both premaxillae since the teeth are differently shaped. Compare these elements to similarly colored elements on the four tracings above. Everything fits and these traits point toward a basal ornithischian, with or without that mysteries anterior dentary enigma.

Figure 7. Daemonosaurus compared to sister taxa and basal theropods. Note the depth of the premaxilla and mandible, not duplicated in Tawa. The robust postorbital is shared with the planteaters. The quadrated/quadratojugal extends below the jugal in the plant eaters, not Tawa.

In figure 7 Daemonosaurus is compared to various sister taxa and to theropods purported to be more closely related by M. Mortimer. It’s really no contest. Daemonosaurus does not resemble Tawa more so than it resembles the plant-eaters. I’m not going to list all the traits that Daemonosaurus shares with other phytodinosaurs here when every aspect is a slam-dunk.  But I encourage you to examine every bone, one-by-one and decide for yourself which bone in other taxa shown in figure 7 they most closely resemble.

Figure 8. Daemonosaurus reconstructed by Sues et al. (2011) as theropod-like as possible. Even ignoring as many phytodinosaur traits as possible, this is still not a bad transitional taxon toward the phytodinosauria, given its enlarged postnarial premaxilla, reduced antorbital fenestra, short snout, robust postorbital/postfrontal, sloping squamosal and straight retroarticular process.

Daemonosaurus is a key taxon in the study of the dinosaur evolution, not a theropod oddity. Daemonosaurus gives us our best key as to how basal carnivorous dinosaurs (theropods or pre-theropods close to basal crocs) evolved into sauropodomorphs, ornithischians and even poposaurs.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
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, published online 

wiki/Daemonosaurus

Meet the mother (or father or sister) of all dinosaurs!

PVL 4597 is the closest thing we now have to a dinosaur ancestor
Earlier we looked at PVL 4597 (Lecuana and Desojo 2012), a taxon attributed to Gracilisuchus (Romer 1972). Inspired to take another look at it, I did so and recoded several characters (Fig. 1). The large reptile tree (Fig. 2) now nests PVL 4597 at the base of Trialestes + the Dinosauria. Trialestes may be slightly closer to dinosaurs, but it is known from less published material and much of it broken up.

No doubt PVL 4597 is a sister to Gracilisuchus near the base of the Archosauria
It’s also a bigger sister with a perforated acetabulum, the beginnings of a truncated anterior ilium, a ventrally and slightly posteriorly directed pubis, with metatarsals 3 and 4 of nearly equal length and pedal digit 5 with one phalanx without a ginglymal joint (for the reception of the next phalanx). These are traits PVL 4597 shares with certain basal dinosaurs in the large reptile tree. Prior to the nesting of PVL 4597, Gracilisuchus was our closest known dinosaur ancestor, but it also nested more firmly with basal crocs, as it continues to do (Fig. 2).

PVL 4597 is not a dinosaur,
but among the 330+ taxa in the tree, it is extremely close to them. This is how dinosaurs (and by extension birds) began.

Figure 1. Until further notice, here is the most basal dinosaur now known and a descendant to a sister of Gracilisuchus. Purple is the partially perforated (no embayment of the ilium) acetabulum. Green areas are reconstructed from broken edges.

Perforated or Not?
According to Lecuana and Desojo (2012), “On the basis of the preserved region of the acetabulum, it can be inferred that it was not perforated…” Unfortunately, given the pieces to work with, they just don’t fit more closely together unless the scale bars are wrong. According to Lecuana and Desojo (2012), “The absence of a discrete ischiatic surface contrasts with the ancestral condition of Archosauromorpha” and “an articular surface for the pubis cannot be seen anteriorly.” Here (fig. 1) the hypothetical connection is short, small and weak, with very little articular surface between the pubis and ischium. And, of course, this reconstruction produces the semi-perforate acetabulum. The lack of an articular surface on the ischium refers to a pubic articulation. Otherwise it is clear that the proximal portion of the ischium is semi-circular for the anchoring of the rotating femur.

Figure 2. Subset of the large reptile tree focusing on the Archosauria = crocs + dinos. Click to see the rest of the tree.

Ankle Joints 
Like Gracilisuchus, PVL 4597 retains a “crocodile-normal” ankle joint. This is close to, but not quite, the mesotarsal simple-hinge joint we see in Herrerasaurus, in which the astragalus has an ascending process and is twice the width of the calcaneum, which does not have a tuber. However, the importance of this trait is mitigated by the nesting of poposaurs deep within the Dinosauria, at the base of the Phytodinosauria. Poposaurs have a similar sort of “croc-normal”  ankle subequal astragalus and a calcaneum with a tuber, but this sort of ankle may have developed independently and by convergence, as in crocodylomorphs, as we discussed earlier.

This ankle is not a conventional dinosaurian ankle. No, the mesotarsal ankle with the small calcaneum without a tuber evolved later. Then, apparently, the old-style ankle returned in certain poposaurs.

Like Gracilisuchus the femoral head is inturned but not rectangular or sharply inturned. The fourth trochanter was weakly developed. Both of these taxa were just getting into bipedal locomotion. A large, sharp fourth trochanter is common in dinosaurs.

Like Gracilisuchus, PVL 4597 had relatively short legs with a tibia shorter than the femur and the tibia less than twice the ilium length. The latter is a trait shared with dinosaurs other than theropods.

Like Gracilisuchus the proximal metatarsals of PVL 4597 were of subequal width, although mt1 was the narrowest. In basal dinosaurs mt1 and mt5 are narrower than the middle three metatarsals. Prosauropods and sauropods reverse this pattern and re-widen metatarsals 1 and 5.

Like Gracilisuchus there is a series of paramedian osteoderms in PVL 4597. 

More to come
There is more to PVL 4597 yet to be published, according to Lecuana and Desojo (2012). Earlier we noted the similarities in the skull of Gracilisuchus and Herrerasaurus. PVL 4597 further cements this relationship recovered by the large reptile tree.

Stance
Earlier workers (Romer 1972) wondered if Gracilisuchus was a biped or not. Close taxa, including dinosaurs like Herrerasaurus and Scleromochlus were both bipedal. Ancestors were not bipedal (although the derived rauisuchians, Smok and Postosuchus, gave it a shot by convergence).

Expanded costal plates
The expanded costal plates of Gracilisuchus are autapomorphic (no ancestors and few descendants (but see Hesperosuchus) have them). They strengthen the rib cage and play a role in respiration. Their appearances elsewhere in the tetrapod tree include Ichthyostega, an early tetrapod, Thrinaxodon, a cynodont, along with many birds, (like Ichthyornis) and velociraptors with their uncinate processes. Crocs have unossified uncinate processes.

Conventional Thinking
Most paleontologists (e.g. Nesbitt 2011, Irmis et al. 2007) hold that the odd biped Lagerpeton and pterosaurs were part of the heritage of dinosaurs. The large reptile tree does not support that hypothesis. Lagerpeton nests with the pararchosauriformes and pterosaurs nest with tritosaur fenestrasaur lizards.

Defining the Dinosauria
Dinosaurs are defined as the clade consisting of Triceratops, Neornithes [modern birds], their most recent common ancestor (MRCA), and all of its descendants (Benton 2004). Since PVL 4597 and Trialestes nest below the split between the ancestors of birds and Triceratops, so they are the last “common” ancestors now known. They are not dinosaurs, but nest just outside the Dinosauria proper.

Synapomorphies of Dinosaurs
From Wiki/Dinosaur, based on Nesbitt 2011, dinosaurs share the following traits. These are all either unknown or not found in PVL 4597 or Gracilisuchus. Boldface traits are preserved in the published version of PVL 4597. Once again only one and maybe two traits can be found in PVL 4597 and Gracilisuchus, so they nest outside the Dinosauria proper.

• exocciptials do not meet along the midline
• fossa (dip in the bone) frames the upper temporal fenestra – Gracilisuchus has this, but minimally.
• epipophyses present in anterior cervical vertebrae 3-5
• apex of deltopectoral crest 1/3 down the humerus
• radius length less than 80% of humerus
• fourth trochanter on the femur is a sharp asymmetrical flange – not on PVL 4597
• the articular facet for the fibula on the astragalus and calcaneum is less than a third the width - not on PVL 4597
• proximal articular surfaces of the ischium with the ilium and the pubis separated by a large concave surface - present on PVL 4597
• cnemial crest on the tibia arcs anterolaterally - not on PVL 4597
• proximodistally-oriented ridge on the posterior face of the distal tibia  - not on PVL 4597

It should be remembered that Nesbitt (2011) did not consider poposaurs and their kin to be dinosaurs, so that affects this list. We discussed this problem earlier.

And check out that pubis!
The pubis of PVL 4597 was vertically oriented, maybe a little skewed toward the back. This is exactly what we are looking for in an ancestor to Herrerasaurus and Panphagia and Ornithischia. And yes, I think the pubis evolved both ways from this primitive configuration: sometimes forward, sometimes backward. PVL 4597 represents the starting point.

In Summary
This situation is like that of the rhipidistian fish on the family tree of vertebrates. Sure they acted like fish and looked like fish, but they had a few traits that tell us they are the ones from which tetrapods arose. Same with PVL 4597. Archosaurs of this type ultimately begat dinosaurs. And yes, that means we’re still looking for that basal dinosaur that fulfills all of the traits on the Nesbitt (2011) checklist and still nests close to PVL 4597.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References

Benton MJ 2004. Origin and relationships of Dinosauria. In Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 7–19.
Irmis RB, Nesbitt SJ, Padian K, Smith ND, Turner AH, Woody D and Downs A 2007. A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs. Science 317 (5836): 358–361. doi:10.1126/science.1143325. PMID 17641198.
Lecuona A and Desojo  J B 2011. Hind limb osteology of Gracilisuchus stipanicicorum (Archosauria: Pseudosuchia). Earth and Environmental Science Transactions of the Royal Society of Edinburgh 102 (2):105-128.
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.
Romer AS 1972. The Chañares (Argentina) Triassic reptile fauna. An early ornithosuchid pseudosuchian, Gracilisuchus stipanicicorum, gen. et sp. nov. Breviora 389:1-24.
wiki/Gracilisuchus