The Search for Epipophyses Beyond the Dinosauria

This post has been modified from the original to correct inaccuracies.

Figure 1. Herrerasaurus epipophyses (epi, in pink) on a cervical in three views. Postzygopophyses (poz, bone articulations) in yellow.

Figure 1. Herrerasaurus epipophyses (epi, in pink) on a cervical in three views. Postzygopophyses (poz, bone articulations) in yellow.

Wiki reports, “The epipophyses are bony projections of the cervical vertebrae found in dinosaurs (Fig. 1 in pink) and some fossil basal birds. The presence of epipophyses is a synapomorphy (distinguishing feature) of the group Dinosauria. Epipophyses (Fig. 1) were present in the basalmost dinosaurs, but absent in closely related ancestors of this group like Marasuchus and Silesaurus (Fig. 2). The immediate ancestor of the Dinosauria, Gracilisuchus, did not have epipophyses.

Silesaurus cervicals. Note the lack of epipophyses.

Figure 2. Silesaurus cervicals. Note the lack of epipophyses.

Then I heard pterosaurs also had epipophyses. However, I found that only some derived pterosaurs have them (Figs 3, 4). Since dinosaurs and pterosaurs are on opposite sides of the large reptile tree, I wondered if epipophyses were more widespread than the Wiki author asserted. So I looked around.

Epipophyses are not present on these pterosaurs.

Figure 3. Epipophyses are not present on these pterosaurs.

Tiny epipophyses on the third cervical of Anhanguera.

Figure 4. Tiny epipophyses (in pink) on the third cervical of the ornithocheirid pterosaurs Anhanguera.

Epipophyses on Columbyua, the common loon and on Macrocnemus, but not Cosesaurus.

Figure 5. Epipophyses on Colymbus, the common loon and on Macrocnemus, but not Cosesaurus.

Evidently, they are more widespread

Here’s what I found (with some help from M. Mortimer, see below). Epipophyses are present in Colymbus, the loon (Fig. 4, itself a bird and therefore a dinosaur), and in Anhanguera (Fig. 4, a pterosaur), Tanystropheus (Fig. 6) and Macrocnemus (Fig. 5). These last three now nest with lizards. Epipophyses are not found in Cosesaurus (Fig. 5) or most pterosaurs (Fig. 3). Other large pterosaurs, like Pteranodon and Quetzalcoatlus, do not have epipophyses.

Epipophyses on Tanystropheus, a relative to Cosesaurus and pterosaurs.

Figure 6. Epipophyses on Tanystropheus, a relative to Cosesaurus and pterosaurs.

Epipophyses strengthen the neck, but are not always associated with a long neck (Fig. 3). Perhaps epipophyses are more widespread than this. For now, it’s enough to know what epipophyses are and that epipophyses are indeed present beyond the Dinosauria. According to Wiki, epipophyses disappear in some dinosaurs. All the more reason that this trait should be scored on a genus-by-genus basis.

World’s Largest Southern Hemisphere Pterosaur – Tropeognathus

Restoration of the world's largest southern hemisphere pterosaur, Tropeognathus

Figure 1. Restoration of the world’s largest southern hemisphere pterosaur, Tropeognathus. Wish they had oriented the hind limbs laterally. The elbow appears to be overextended. And the fingers are not oriented palmar side ventrally.

Just published and available free online (Kellner et al. 2013) bits and pieces (nothing complete or articulated), the world’s largest southern hemisphere pterosaur, Tropeognathus, a crested ornithocheirid from the Early Cretaceous. My, what a big crest you have!

Other than the model maker’s problems (see caption), the paper got it right. Good job.

References
Kellner et al. 2013. The largest flying reptile from Gondwana: a new specimen of Tropeognathus cf. T. mesembrinus Wellnhofer, 1987 (Pterodactyloidea, Anhangueridae) and other large pterosaurs from the Romualdo Formation, Lower Cretaceous, Brazil. Anais da Academia Brasileira de Ciências (2013) 85(1): 113-135. (Annals of the Brazilian Academy of Sciences) Printed version ISSN 0001-3765 / Online version ISSN 1678-2690.

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.

Addendum figure. This is a better rendition of the new hindquarters of the PVL specimen. Apologies for any earlier inaccuracies. Thanks to M. Mortimer for pointing out I had mistaken a right ischium for a left one and tarsal inaccuracies. If there are further problems, please let me know, or contact Romer.

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.

 Subset of the large reptile tree focusing on the Archosauria = crocs + dinos.

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 TriceratopsNeornithes [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 

How Experts Have Disfigured Pterosaurs – part 2

Anurognathus by Mark Witton following the reconstruction by Chris Bennett (2007) that is different in all respects from all other pterosaurs.

Figure 1. Anurognathus by Mark Witton following the reconstruction by Chris Bennett (2007) that is different in all respects from all other anurognathid pterosaurs (fig. 2). You don’t see pedal digit 5 because it extends, full length, to frame the uropatagium (or connect to the main wing membrane) in this interpretation. Note also the lack of distal wing phalanges, m4.4 and m4.5 (the ungual) when other anurognathids have these.

Yesterday we discussed some of the disfiguring ways in which pterosaurs have been reconstructed and restored by pterosaur experts Mark Witton and David Unwin, mostly by the way they moved the bones into odd configurations, especially to demonstrate pterosaur walking. Today we’ll talk about misinterpretations of pterosaur fossils and how those bad images have propagated themselves through the Internet.

Bennett’s 2007 Anurognathus (Figs. 1, 2), which is more accurately called the flat-head anurognathid (Fig. 2), is a prime example of misinterpretation that fails all tests for validity (see more here). More worrisome, Bennett’s interpretation has become widely adopted by artists, some having a PhD in paleontology, without testing (performing their own skull tracings) or criticism (the morphology is way different than in related taxa (Fig. 2), but then who knows that? No one else has attempted anurognathid skull tracings and reconstructions but yours truly and maybe Döderlein and Wellnhofer on a very limited basis.

It’s bad enough when one scientist on a bender (Fig. 2), promotes this, but when others, (Fig. 1) follow, then we’ve got widespread madness. As you can see (fig. 2) Bennett’s interpretation bears no resemblance to the other anurognathids, all of which have a large naris, large antoribital fenestra, eyes in the back half of the skull and a narrow skull between the upper temporal fenestrae. Bennett (2007) promoted the idea that anurognathids had but three wing phalanges. However, more derived anurognathids, like Jeholopterus, also have a manual 4.4 and 4.5 (the ungual). So, why are these data ignored?

Figure 2. Anurognathid skulls in phylogenetic order.

Figure 2. Anurognathid skulls in phylogenetic order.

Note that in every case (fig. 2), but the Bennett (2007) reconstruction (on gray field), the nares are large, the antorbital fenestra is larger, the orbit is in the back half of the skull (even if it extends slightly into the front half) and, although you can’t see it from these angles, the parietal is narrow between the upper temporal fenestrae, as in most other reptiles with upper temporal fenestrae and all squamates close to pterosaurs. Most of Bennett’s 2007 other mistakes are listed and rectified here.

Santanadactylus hand and fingers

Figure 3. Click to enlarge. Santanadactylus hand with metacarpals preserved at a 45 degree angle to the anterior face of metacarpal 4.

Bennett (2008) is also the author of the hypothesis on pterosaur origins who suggested the palms of pre-pterosaurs supinated, finger 5 disappeared, finger 4 hyper-hyper-extended until it became able to fold against the back of the metacarpus, metacarpals 1-3 migrated as a unit to the former palmar now anterior face of metacarpal 4, and the wing ungual was lost because it would have otherwise caught on nearby trees (Figs 3,4). All this in an effort to avoid having to acknowledge that Cosesaurus and Longisquama may have had something to do with the origin of pterosaurs. He also studied a ornithocheirid metacarpus (Fig. 3) in which mc1-3 were preserved at a 45 degree angle, which Bennett assumed meant they had detached themselves from mc4 (fig. 4). Actually they had been raised like a drawbridge by currents following the removal of the large extensor tendon. So Bennett completely misunderstand pterosaur basics like this and promotes such misinformation.

Pterosaur finger orientation in lateral view

Figure 4. Pterosaur finger orientation in lateral view, the two hypotheses. There’s no room for a giant extensor tendon in the Bennett model that many experts seem to prefer. When the experts  acting as manuscript referees hold such bad hypotheses, its no wonder competing hypotheses don’t get published.

Such disfigurement leads to odd configurations, like upside-down fingers illustrated by Bennett (1991) here (fig. 5).

Bad Pteranodon reconstruction from Bennett 1991, 2000 in which the fingers faced palmar side up and the elbow bent at an impossible angle with regard to the shoulder joint.

Figure 5. Bad Pteranodon reconstruction from Bennett 1991, 2000 in which the fingers faced palmar side up and the elbow bent at an impossible angle with regard to the shoulder joint. Unwin (2005) replaced the skull and flipped the hand.

Sometimes it just takes a more careful examination of the evidence.
Paleontologists have a lot to deal with (students, grant writing, trips to foreign lands, etc.). Like all of us, sometimes they overlook the little things, especially when the paradigm says those little things should not be there. Often their cartoonish tracings reflect the interest they show in their subjects. Refusing to study in detail the overlapping bones of a crushed specimen had led to bad reconstructions, with an example here.

Conventional wing shape in pterosaurs supported by Unwin, Elgin, Hone, Bennett, Wilkinson, Frey and others vs heretical wing shape supported by Peters and Conway.

Figure 6. Above: Conventional wing shape in pterosaurs supported by Unwin, Elgin, Hone, Bennett, Wilkinson, Frey and others vs heretical wing shape supported by Peters and Conway. All the evidence from smaller pterosaurs supports the lower wing and uropatagium shape. And doggone it! It just makes sense not to overextend the elbow, not to miss align the femoral head axis with the acetabulum, not to extend the fingers palmar side anteriorly and not to put the pteroid pointing forward in the sesamoid cup of the medial metacarpal. See what a beautiful and functional wing you get when you follow anatomical rules!

Finally there’s the old wing shape problem
Wilkenson (2007, fig. 6) and others support a deep chord wing membrane attached to the ankles. Here the hand is also palmar side anterior while flying. And the elbow is overextended. This is an embarrassing reconstruction when ALL the evidence demonstrates a narrow-at-the-elbow narrow chord wing shape NOT attached to the ankle. The fingers are palmar side ventral while flying. And the elbow does not overextend, but is angled close to a right angle, as in birds and bats. A narrow chord wing membrane prevents the sort of wing folding with wing drooping that has ruined hundreds of artist reconstructions, IMAX films and Jurassic Park III ptero reconstructions.

That’s why the Pterosaur Heresies and ReptileEvolution.com present evidence when we depart from conventional thinking — especially when conventional thinking departs from logical thinking, precise observation, reconstruction and phylogenetic analysis.

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
Bennett SC 2007. 
A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.
Bennett SC 2008.
Morphological evolution of the wing of pterosaurs: myology and function. Zitteliana B28: 127-141.
Döderlain L 1923
Anurognathus ammoni, ein neuer Flugsaurier. Sitzungsberichte der Königlich Bayerischen Akademie der Wissenschaten, zu München, Mathematischen-physikalischen Klasse: 117-164.
Elgin RA, Hone DWE and Frey E 2011. 
The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica doi: 10.4202/app.2009.0145 online pdf
Ji S-A and Ji Q 1998. A New Fossil Pterosaur (Rhamphorhynchoidea) from Liaoning. Jiangsu Geology 4: 199-206.
Peters D 2001. 
A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15:277–301.
Wilkinson MT 2007. Sailing the skies: the improbable aeronautical success of the pterosaurs. The Journal of Experimental Biology 210, 1663-1671. pdf

wiki/Anurognathus

How Experts Have Disfigured Pterosaurs – part 1

The reason and soul of PterosaurHeresies is to reveal the flagrant and untenable errors that continue to float around pterosaurs (in particular) and prehistoric reptiles (in general). We’re not just sniping here. Evidence is always provided when a case is made. And we do provide credit where workers have done their homework.

Here we’ll document some of the worst efforts wrought by experts in the ptero trade.

Case in point:
This YouTube video of an ornithocheirid pterosaur walking (Fig. 1) almost could not be worse. Unfortunately it was based on “expert testimony” from notable experts (see below). It might also owe some due to the Walking With Dinosaurs series from the BBC, which featured a similar giant ornithocheirid.

 Pterosaur walk cycle posted on YouTube. Click to view. While following conventional thinking, this model demonstrates exactly why the hypotheses it is based on are so wrong.

Figure 1. Pterosaur walk cycle posted on YouTube. Click to view. While following conventional thinking, this model demonstrates exactly why the hypotheses it is based on are so wrong.

Problems galore
1. Wing membrane attached to the ankles – not found anywhere in the fossil record. Awkward as hell as you’ll see it in action when you click on the video.
2. Fingers pointing forward – ichnites say laterally to posteriorly.
3. Pteroid pointing forward – all fossils indicate medially, but many papers indicate anteriorly
4. Wing folding – needs to butt up against the metacarpus and ulna as fossils show
5. Convex neck – all fossils show a concave dorsal neck
6. Hind limbs – way too robust. Should be mere sticks with tiny feet, smaller than shown.
7. Skull way too small

Positives
1. Widely splayed femora.
2. Upright torso
3. Elbows back
4. Robust thighs

Don’t Blame the Artist (too much)
He or she was only following the conventional thinking of today’s pterosaur experts, the ones who are ruining pterosaurs right before our eyes by producing visions of walking pterosaurs that do not follow the evidence. In many cases, there is a flagrant disregard and internal inconsistency.

Case in point
In Dr. David Unwin’s book The Pterosaurs From Deep Time (p201), he promotes this image (Fig. 2)  as “Restoration of Anhanguera (Fig. 3) in the posture that pterodactyloids are now thought to have adopted while walking.”

According to Unwin 2006, this is the posture that pterodactyloids are now thought to have adopted while walking. The position of the elbows contradicts his text, which states, "[the humerus] lay nearly parallel to the body."

Figure 2. According to Unwin 2006, this is the posture that “pterodactyloids are now thought to have adopted while walking.” It is based on Bennett (1991, figure 4). However, the position of the elbows here contradicts his text, which states, “[the humerus] lay nearly parallel to the body.” If you put your elbows out, which way to your fingers turn? In, not out. It takes maximum pronation to make them turn out again.

Problems with this figure
1. Lacks metacarpals 1-3. Lacks distinct phalanges on manual digits 2 and 3.
2. Pteroid articulates with tip of preaxial carpal
3. Elbows anterior to shoulders (try it yourself to see how awkward this is)
4. Feet way too big
5. Knees not aligned with prepubes, which are missing
6. Femora not bowed (so that axially aligned head fits into acetabulum socket)
7. Pelvis incorrect (looks like a Germanodactylus pelvis)
8. Humerus too small
9. Sternal complex too flat (looks like a Pteranodon sternal complex)
10. Too few ribs

Here’s what Anhanguera should look like:

Anhanguera

Figure 3. Anhanguera. Note the tiny feet, the bowed femora, the elbows back (the way Unwin described them but did not draw them), etc. etc. In this pose it’s not clear that manual digit 1 would ever touch the substrate, but then only individual pedal ichnites are known for ornithocheirids, no trackways.

Derived from Bennett 1991
Unwin’s 2005 figure was based on Dr. Chris Bennett’s 1991, 2000 reconstruction (Fig. 4) of Pteranodon, which had all of Unwin’s faults and a few of its own. The finger’s on Bennett’s Pteranodon faced palmar side up because Bennett mistakenly reconstructed the metacarpals palmar side forward while flying. We discussed problems with that hypothesis earlier. See a couple of good Pteranodon post-crania here. See some more or less complete Pteranodon here and here.

Bad Pteranodon reconstruction from Bennett 1991, 2000 in which the fingers faced palmar side up and the elbow bent at an impossible angle with regard to the shoulder joint.

Figure 4. Bad Pteranodon reconstruction from Bennett 1991, 2000 in which the fingers faced palmar side up and the elbow bent at an impossible angle with regard to the shoulder joint. Unwin (2005) replaced the skull and flipped the hand. Due to the saddle-like shape of the shoulder joint, rotation should have been impossible, but Bennett ignores this.

Dr. Unwin’s Robodactylus
Unwin (2006) reports that Don Henderson and he “had our first baby.” It was a computer generated walking Anhanguera, they called Robodactylus that was differently configured than his illustration (Fig. 2), but still ignored many morphological traits.

Robodactylus. This is supposed to represent Anhanguera. After tilting the backbone up, "Suddenly it all fell into place," according to Unwin.

Figure 4. Robodactylus. This is one frame in a walking sequence that is supposed to represent Anhanguera. After tilting the backbone up, “Suddenly it all fell into place,” according to Unwin. Note the incorrect parasagittal hind limbs and the improved “elbows back” posture. A careful look reveals the wing fingers are anterior to the forelimbs, which is a result of oversimplification while making the model.

I remember seeing the Henderson/Unwin presentation and shaking my head at how Frankenstein-ish it appeared. The worst aspect of this model is the position of the hind limbs in the parasagittal place. The best aspects include the elbows back and elevated torso. However, the elbows should have been almost straight below the shoulders (fig. 3).

But wait, it gets worse
After tackling Anhanguera, Henderson and Unwin digitized Rhamphorhynchus to create Roborhamphus (Fig. 5). Remember that Unwin (2006) thinks that all basal pterosaurs had a membrane that extended between the hind limbs (including pedal digit 5) and tail based on his misidentification of features in Sordes.  He reported, “Effectively, in these early pterosaurs, all four limbs [and the tail] were linked to one another.” 

Linking the hind limbs to a tibia’s length of tail with uropatagia is how Henderson and Unwin decided the tail was unable to rise at its base. This is their infamous “raincoat test” that shows how awkward and bound up early pterosaurs were in their view. All this disfigurement is all due to Unwin’s misinterpretation of Sordes and the importance he gave it, trumping all other evidence (Fig. 6b).

Roborhamphus. This is how Henderson and Unwin animated Rhamphorhynchus during a walking cycle. Hmm. If this is right, then maybe pterosaurs did indeed share a recent common ancestor with parasuchians.

Figure 5. Roborhamphus. This is how Henderson and Unwin animated Rhamphorhynchus during a walking cycle. Hmm. If this is right, then maybe pterosaurs did indeed share a recent common ancestor with parasuchians. (jess kiddn) Good luck getting Roborhamphus off the ground! They reported they could not raise the torso without “the tail bashing into the ground.”  This pose, to their surprise, worked.  Here the feet appear to be way too small, perhaps cheated to enable a recovery stroke without too much toe drag. Not sure if the wings are foreshortened in this view, but they should be much longer (see fig. 6).

The darkwing specimen of Rhamphorhynchus muensteri demonstrating more accurate proportions.

Figure 6. The darkwing specimen of Rhamphorhynchus muensteri demonstrating more accurate proportions, a little chubbier than Roborhamphus with longer wings and a bendable tail base. The uropatagia do not bind the hind limbs and the wing does not attach to the hind limbs.

Here’s the real darkwing Rhamphorhynchus (Fig. 6, 6b) based on DGS with its torso and tail raised. It’s those little bendable proximal caudals that enable the tail to rise, pulled by sacral muscles that Henderson and Unwin did not consider. In the Henderson/Unwin model (Fig. 5) Unwin (2006) reported, “Remember that the body, neck and head lay in almost a straight line in these animals (as also for example in lizards and crocodiles), and this fitted neatly with the horizontal walking posture of Roborhamphus.” Like birds, that’s not true of any pterosaur, except, perhaps, while flying.

Wing membranes and uropatagia in a basal pterosaur, the darkwing Rhamphorhynchus.

Figure 6b. Wing membranes and uropatagia in a basal pterosaur, the darkwing Rhamphorhynchus. The uropatagia did not connect to the tail, only the pelvis, so the tail could rise as in figure 6. The wing membrane does not attach to the ankle. Those patches that appear to do so are body fluids fossilized by bacterial activity. They have no wing structure to them.

Azhdarchid Problems
Dr. Mark Witton will soon have his pterosaur book out. Previews can be seen here. This is the Witton and Naish (2008) vision of a walking Zhejiangopterus pterosaur (Fig. 7) published in Naish’s blog.

A walking Zhejiangopterus by Mark Witton. Here all four limbs are planted at the same time. The foot-to-foot distance is much larger than the hand-to-hand distance. This configuration also plants the manus anterior to the pes, which is the opposite of what we see in fossil ichnites.

Figure 7. Click to follow link. A walking Zhejiangopterus (Witton and Naish 2008). Here all four limbs are planted at the same time. The foot-to-foot distance is much larger than the hand-to-hand distance. This configuration also plants the manus anterior to the pes, which is the opposite of what we see in fossil ichnites. By elevating the backbone all problems are solved. The outstretched and cantilevered neck is also a potential problem, like the Kent, Stevens sauropod neck in the ONP (osteologically neutral pose) rather than the more biologically followed (OEP) osteologically elevated pose (see fig. 4), promoted, ironically, by Taylor, Wedel and Naish (himself, 2009). The depth of the pelvis is far too shallow here. See figure 5 for an alternative stance. Try walking with your arms at length in front of you while you walk and see how quickly the lactic acid builds up. Then imagine putting the weight of a large skull at the end of six-foot-long arms and you’ll get an idea how quickly tiring this Witton and Naish pose would become for this poor azhdarchid.

Not sure why Witton and Naish (2008, Fig. 7) tried to promote their hypothesis of a walking pterosaur by planting all four feet on the ground in a pattern that does not fit known ichnites or tetrapod walking cycles. Two of those limbs need to be elevated (recovery phase). In order to match tracks that place the manus print just aft of the pedal imprint the backbone needs to be elevated (see animation, fig. 10). The knees need more bend on initial contact. The neck also needs to be elevated, following hypotheses in Naish’s own work (Taylor, Wedel and Naish 2009).

No Bitching Without A Solution
Here (fig. 8) and here (running Quetzalcoatlus) all the problems are solved. The neck is held high. The wings are completely folded. The manus could easily impress behind the pes (as in Fig. 10). The fingers extend laterally to posteriorly. The foot and hand both have recovery phases. The center of gravity is just anterior to each footfall, as in humans. The hands are like ski poles, not contributing to thrust. And this pterosaur (figs. 8, 10) is ready to take off from a standing start. You can see the animated model (fig. 10) matches the tracks in morphology, size and gait.

There are several specimens of Zhejiangopterus.

Figure 8. Click to enlarge. There are several specimens of Zhejiangopterus. Here I am showing the standing pose with that giant skull better balanced over the body and, with bent knees and and upright torso, these feet are able to implant just in front of each hand while walking. And this pterosaur is ready to spread its wings and fly after launching itself with those huge thigh muscles.

Pterodactylus problems

Pterodactylus walking. Note the foot will never plant itself in front of the hand here. And why are both hands on the ground at the same time as the back foot? Hmm.

Figure 9. Pterodactylus walking. Note the foot will never plant itself in front of the hand here. And why are both hands on the ground at the same time as the back foot? Hmm. At least one foot is off the ground here. That’s a positive. Note the wing membrane behind the elbow: nice!! But also look at how far that fuselage fillet has to stretch here. Untenable. See Figure 10 for a more upright solution.

The same problems attend this poor chap (Fig. 9) with the horizontal backbone. At no time in the step cycle of this pterosaur are those forelimbs going to provide thrust, but rather braking. Pterosaurs were secondarily quadrupedal and many could go both ways. Not sure why workers insist on giving pterosaurs a horizontal backbone. Matching the skeleton to tracks (Fig. 4) is easy to do and gives much more tenable results.

Pterodactylus walk matched to tracks according to Peters

Figure 10. Click to animate. Plantigrade and quadrupedal Pterodactylus walk matched to tracks

Ichnites don’t tell how long the implantation of the manus was. Here that time appears shorter than the implantation of the foot. The manus steadied the pterosaur while applying no thrust.

Earlier we covered bipedality and quadrupedality in pterosaurs here. We covered bipedal take-off in pterosaurs here and here. Tomorrow we’ll take on more monstrous reconstructions.

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
Taylor, M. P., Wedel, M. J. & Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54, 213-220.
Witton M and Naish D 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3 (5): e2271. doi:10.1371/journal.pone.0002271

Blood pressure in an elevated Tanystropheus

Yesterday we looked at the possibility of underwater leaping in Tanystropheus for snatching prey and, with a little momentum, for reaching the surface for a breath.

Just like a giraffe or an upright sauropod
Tanystropheus had to have had a specialized circulatory system and a large heart in order to raise its neck. And also like a giraffe, Tanystropheus probably another sort of system to keep blood from pooling in its legs and tail whenever the neck was raised. This post was inspired by a recent one on sauropods here at PHENOMENA, a science salon hosted by National Geographic Magazine.

Tanystropheus underwater among tall crinoids and small squids.

Figure 1. Tanystropheus in a vertical strike elevating the neck and raising its blood pressure in order to keep circulation around its brain and another system to keep blood from pooling in its hind limb and tail.

That vertical pipe of a neck would have elevated the head nearly eight feet (250 cm) above the heart in the largest Tanystropheus specimens. That’s longer than the neck height of a giraffe, but far shorter than that of a large sauropod. In giraffes the heart rate is high, up to 170 bpm. We can imagine Tanystropheus might have also had an elevated heart rate, especially for a large lizard. What does this mean? Well, phylogenetically Tanystropheus was surrounded by bipeds, some of them, the fenestrasaurs, were speedy. Some of them, the drepanosaurs, were slow.

The blood pressure of a giraffe is the highest of all animals, reaching about 300 over 200 mm Hg to pump blood up a neck seven feet long to reach its brain. The blood pressure of Tanystropheus might have been a little higher.

Perhaps related – or not
If Tanystropheus fed underwater, the trachea might have been valved in order to keep an air bubble in the lungs and restricting its rise up the windpipe whenever submerged under at least eight feet of water pressure. Likewise the blood vessels might have been similarly valved to keep blood in the “upper stories.”

Few animals are comparable to a Tanystropheus and fewer of them are alive today. All hypotheses about soft tissue can only be considered guesses.

Whatever the case… not bad for a lizard.

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
Bassani F 1886. Sui Fossili e sull’ età degli schisti bituminosi triasici di Besano in Lombardia. Atti della Società Italiana di Scienze Naturali 19:15–72.
Li C 2007. A juvenile Tanystropheus sp.(Protoro sauria: Tanystropheidae) from the Middle Triassic of Guizhou, China. Vertebrata PalAsiatica 45(1): 37-42.
Meyer H von 1847–55. Die saurier des Muschelkalkes mit rücksicht auf die saurier aus Buntem Sanstein und Keuper; pp. 1-167 in Zur fauna der Vorwelt, zweite Abteilung. Frankfurt.
Nosotti S 2007. Tanystropheus longobardicus (Reptilia, Protorosauria: Reinterpretations of the anatomy based on new specimens from the Middle Triassic of Besano (Lombardy, Northern Italy). Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano, Vol. XXXV – Fascicolo III, pp. 1-88
Peyer B 1931. Tanystropheus longobardicus Bass sp. Die Triasfauna der Tessiner Kalkalpen. Abhandlungen Schweizerische Paläontologie Gesellschaft 50:5-110.
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus(Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-16.

wiki/Tanystropheus

Giraffe circulation pdf

Underwater Leaping in Tanystropheus

Added September 21, 2020:
Think about a bubble net, as in humpback whales, coming form the long, dead=air storage vessel that is that elongate trachea. That long neck rotating like an inverted cone to surround confused fish just above the jaws.

Earlier we looked at an underwater bipedal configuration for Tanystropheus. Such a pose would have solved all sorts of neck and balance problems. Here (Fig. 1) is a proposal for using the epipubic bones as caudofemoralis anchors to increase vertical thrust in that environment. Thrust would be used to snare prey or reach the surface for air.

Basically the illustration (Fig. 1) says it all.
Epipubic bones on the large Tanystropheus could have anchored more powerful caudofemoralis muscles to provide more thrust during vertical strikes and trips to the surface. Of course, momentum would have taken Tanystropheus further than shown here.

What were these bones?
Odd chevrons? That’s the best guess so far. Otherwise in close kin there were no large chevrons  and the caudal transverse processes did not extend more than ten caudals back. So, when large thrusters were needed, they grew in this giant in new ways, whichever way helped the most.

Tanystropheus in a vertical strike powered by the enlarged caudofemoralis anchored by the so-called epipubic bones.

Figure 1. Tanystropheus in a vertical strike powered by the enlarged caudofemoralis (in red) anchored by the so-called epipubic bones, which may instead by enlarged and modified chevrons or neomorphs. This push could have been followed by a vertical leap/drift, whether to head to the surface or snatch unwary prey.

Just another crazy thought…

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
Bassani F 1886. Sui Fossili e sull’ età degli schisti bituminosi triasici di Besano in Lombardia. Atti della Società Italiana di Scienze Naturali 19:15–72.
Li C 2007. A juvenile Tanystropheus sp.(Protoro sauria: Tanystropheidae) from the Middle Triassic of Guizhou, China. Vertebrata PalAsiatica 45(1): 37-42.
Meyer H von 1847–55. Die saurier des Muschelkalkes mit rücksicht auf die saurier aus Buntem Sanstein und Keuper; pp. 1-167 in Zur fauna der Vorwelt, zweite Abteilung. Frankfurt.
Nosotti S 2007. Tanystropheus longobardicus (Reptilia, Protorosauria: Reinterpretations of the anatomy based on new specimens from the Middle Triassic of Besano (Lombardy, Northern Italy). Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano, Vol. XXXV – Fascicolo III, pp. 1-88
Peyer B 1931. Tanystropheus longobardicus Bass sp. Die Triasfauna der Tessiner Kalkalpen. Abhandlungen Schweizerische Paläontologie Gesellschaft 50:5-110.
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus(Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-16.

wiki/Tanystropheus

Better resolution reveals more in ?L. rossii (Renestosaurus)

Updated with a new reconstruction July 2, 2014.

Earlier I worked with a low resolution black and white image of MFSN 19235 published in Renesto (1992), who questioned the affinity of Langobardisaurus? rossii (Bizzarini and Muscio 1995). Since this specimen definitely does not belong to Langobardisaurus, I suggested the generic name, Renestosaurus. Now, with better imagery, courtesy of Dr. Renesto, more precise details can be gleaned.

Figure 1. Click to enlarge. Better resolution image of Renestosaurus (above). Color tracings of elements (below). Recontructed pes, manus, pelvis and pectoral girdle (on white).

Figure 1. Click to enlarge. Better resolution image of Renestosaurus (above). Color tracings of elements (below). Recontructed pes, manus, pelvis and pectoral girdle (on white).

To all appearances the pelvis is missing. Actually one side had drifted to the posterior dorsals. The other drifted caudally. Both are small. The right foot is disarticulated and reconstructed here. It is smaller than the manus. The left tarsals are between the right femur and right crus. Some left toe bones are nearby on top of the proximal right crus. What Renesto considered a pelvis is the left femur. The left forelimb is largely disarticulated beneath the dorsal ribs. The complete pectoral girdle is visible.

 

Figure 2. Langobardisaurus(?) rossii (MFSN 19235) reconstructed. Here it nests between basal sphenodontids and basal tritosaurs + squamates.

Figure 2. Langobardisaurus(?) rossii (MFSN 19235) reconstructed. Here it nests between basal sphenodontids and basal tritosaurs + squamates.

A digger?
The robust proximal humerus and large manus hint at a digging niche. Too bad the skull is unknown.

Phylogenetic nesting
Despite the changes in a few scores, Renestosaurus continues to nest as it had before, with Homoeosaurus and Dalinghosaurus in a clade of pre-squamates derived from a sister to Gephyrosaurus. This clade was unknown prior to it recovery in the large reptile tree.

DGS
This is yet another example of DGS (Digital Graphic Segregation) helping to uncover details in a crushed fossil specimen. Higher resolution always helps, but if low resolution is all that is available, well, then that’s what we work with. In any case, more details were uncovered here using a photograph than were revealed from first-hand observation. I’m not bragging. I’m just suggesting other paleontologists should use this tool too.

And the use of the large reptile tree helped eliminate all other possible nesting opportunities from this list of several hundred taxa.

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
Bizzarini F and Muscio G 1995. Un nuovo rettile (Reptilia, Prolacertiformes) del Norico di Preone (Udine, Italia Nordorientale). Nota Prelimininare. Gortania – Atti Mus. Friulli. Sti. Nat., 16 (1994): 67-76, Udine.
Bizzarini F, Muscio G and Rossi IA 1995. Un nuovo rettile fossile Langobardisaurus? rossiin. sp. Prolacertiformes (Reptilia) della val Preone (UD), Prealpi Carniche Italine. 1-35 Grafiche Tipo, Catelgomberto.
Renesto S and Dalla Vecchia F 2007. A revision of Langobardisaurus rossii Bizzarini and Muscio, 1995, from the Late Triassic of Friuli (Italy)*

The SMNS flathead anurognathid skull: bone by bone

Two recent blog posts by J. Headden, illustrations by M. Witton and various other odd reconstructions of the skull of the SMNS anurognathid (Bennett 2007), the flathead pterosaur, prompted today’s post. I realize I have not provided sufficient clear imagery and so, here it is (in rollover images or see below).

You’re looking at what appears to be a complete skull crushed ventrally with all parts intact and articulated. That is not the case. If so, you’d end up with a monster bearing little resemblance to other anurognathids and other pterosaurs in general (aka Bennett’s reconstruction, fig. 6 left). There was some shifting during taphonomy as will be made clear in the following photos. Reconstructing the parts produces a very nice anurognathid sharing most traits with other anurognathids (fig. 6 right), but the skull has a flatter morphology.


Figure 1. Skull of the flathead pterosaur. Some of the bones are orange. Others are tan. Still others, perhaps just the shapes they left, are white, as in the apparent fenestra in the top of the skull, which is nevertheless, divided medially. 

I realize the bones I found in this specimen are difficult to see. So today I present some of them as well as I possibly can (see figs. below). You can (and I encourage you to) use a rollover on the reptile evolution page on the flathead anurognathid here.

Bennett (2007) described this specimen and created reconstructions (fig. 6) in which his giant scleral ring was in the anterior half of the skull, the antorbital fenestra was relegated to a tiny zone bounded by bones he claimed he never found and the skull roof was as wide as any turtle’s with widely separated upper temporal fenestrae. Such a reconstruction is at odds with all other pterosaur skulls. Recall that Bennett also invoked the idea that the very wide frontal bones of the SMNS specimen were decayed centrally, providing windows to whatever bones were beneath them. Not so. His frontal bones are composed laterally on the left by a dorsal lacrimal piece (fig. 5) and medially by the narrow nasals (fig. 3). That’s a large corner of an ectopalatine seen through the bones.

SMNS-anurognathus maxillae

Figure 2. SMNS-anurognathus maxillae and teeth. The slender ascending process is broken in both cases. Note Bennett’s proposed “sclerotic ring” continues far beyond the confines of the skull. 

SMNS anurognathid sclerotic rings. They are small in the back half of the skull. Those are the narrow nasals between them.

Figure 3. SMNS anurognathid sclerotic rings. They are small in the back half of the skull. Those are the narrow nasals between them. All of these traits match those of other anurognathids. 

The SMNS anurognathid ascending process only of the premaxillae and frontals.

Figure 4. The SMNS anurognathid ascending process only of the premaxillae and frontals. Compare the frontals to the sclerotic rings (fig. 3), which nest within them.

SMNS anurognathus occiput and lacrimals. Note the extreme width of the occiput. This alone tells you the general shape of the skull, flatter than in other pterosaurs.

Figure 5. SMNS anurognathus occiput and lacrimals. Note the extreme width of the occiput. This alone tells you the general shape of the skull, flatter than in other pterosaurs. The fragile left lacrimal is broken into three parts. The right one has the sinuous shape that provides room for the dorsally bulging eyeballs (see fig. 6).

If you still can’t see the imagery I indicate above, please visit these rollover images. That way you won’t have to shift back and forth to compare images. You can also see the palate and other bones on the same web page.

Using DGS (digital graphic segregation, I was able to find symmetrical pairs for every bone in the skull, despite the layering of cranial bones atop displaced facial and palatal bones. All the bones, even those of the palate, resemble those in other anurognathid palates. Moreover, in the case of the SMNS anurognathid the palatal elements criss-cross and reinforce each other, providing maximum strength with minimum weight. The same cannot be said of the Bennett reconstruction.

anuroSMNSskull588

Figure 6. The SMNS anurognathus. On the left as Bennett (2007) reconstructed it identifying the left maxilla has a giant sclerotic ring (ignoring the teeth). Bennett’s palate does not resemble those of other anurognathids. On the right is the more accurate reconstruction based on DGS. Click for more information.

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.

Reference
Bennett SC 2007. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.

New material of the choristodere Lazarussuchus – Matsumoto et al. 2013

What a wonderful new fossil!
A complete and articulated Lazarussuchus (Hecht 1992) has just been described by Matsumoto, et al. (2013). The new specimen (Fig. 1, below) comes from the Paleocene of France.

Figure 1. Lazarussuchus, the old specimen (above) and the new specimen (below) from Matsumoto et al. 2013.

Figure 1. Click to enlarge. Lazarussuchus, the older Hecht 1992 specimen (above) and the newer specimen (below) from Matsumoto et al. 2013, to the same scale. The differences are subtle, including a longer neck and more robust limbs. These two were definitely congeneric but not conspecific.

Distinct from an earlier specimen
the new specimen has a taller skull, a distinct pelvis and more robust limbs. At the same scale the skulls were nearly identical in length, but in the new specimen the neck was more robust and nearly twice as long.

Unfortunately, by way of taxon exclusion,
the writers (Matsumoto, et al. 2013) got their phylogeny backwards. They reported, “Despite its age, most phylogenetic analyses place Lazarussuchus at or close to the base of the choristoderan tree, implying a very long unrecorded history.”  In contrast, the large reptile tree (also see fig. 2) nested Lazarussuchus as a derived choristodere. After all it had lost its lateral temporal fenestra, a primitive trait present in other choristoderes. Moreover, the Matsumoto (2013) tree nested choristoderes with sauropterygians and their tree improperly rooted with  Youngina.

One problem:
Matsumoto et al. included two basal sauropterygians and two lepidosaurs in their tree. These are not closely related to choristoderes in the large reptile tree. So, sadly, this group of scientists had no scientific basis or guidance for choosing their inclusion set as a subset from a much larger tested set. Instead they chose what they felt like choosing.

Another problem:
Matsumoto et al. did not include the real closest known taxa to choristoderes.

Figure 2. Matsumoto et al. (2013, left) with the addition of Ichthyostega and Cephalerpeton for rooting. Same tree with added taxa separates the sauropterygians from the choristoderes.

Figure 2. Matsumoto et al. (2013, left) nested sauropterygians with choristoderes. Here with the addition of Ichthyostega and Cephalerpeton for rooting, much the same tree topology is present. Same tree with added taxa from the large reptile tree properly separates the sauropterygians from the choristoderes.

Testing Matsumoto (2013) with the Large Reptile Tree
Starting with the 235+ taxa in the large reptile tree and deleting all but those taxa used by Matusmoto et al. (2013) and, like them, setting Youngina as the outgroup, I recovered much the same tree, except Gephyrosaurus nested at the base of Petrolacosaurus + Araeoscelis and Prolacerta nested closer to the Choristodera. Within the Choristodera Champsosaurus nested as a basal taxon.

Non-controversial outgroup taxa
Instead of guessing which taxon should be the outgroup, why not go all out?  Ichthyostega, a basal tetrapod, and Cephalerpeton, a basal reptile serve as non-controversial outgroups for all reptiles. Adding them to the matrix (Fig. 2, left) moves Youngina closer to Prolacerta and little else.

Adding several more pertinent taxa
Let’s add more taxa from and based on the large reptile tree (Fig. 2, right) as another test. That recovers a tree topology much more like the large reptile tree in which a longer list of various younginoids, Doswellia and Diandongosuchus nest close to the Choristodera. The sauropterygians now correctly nest further away with other Enaliosauria. The new Lepidosauromorpha, including Mesosuchus, nest together (in blue) and so do the new Archosauromorpha (in yellow), but they did not split from each other following Cephalerpeton, as in the large reptile tree. The reason: Too few pertinent taxa at the critical point were missing to make that division appear where it should.

The Nasal Question
Conventional thinking and Matsumoto et al. (2013) identify the two medial bones anterior to the frontals as prefrontals (Fig. 3, lavender). This is a common and traditional mistake when dealing with choristoderes. Following this pattern Matsumoto et al. identify the nasals (pink) as those tiny supranarial bones. This is false paradigm that probably goes back to Champsosaurus, in which the premaxilla is literally split into two separate bones, the ascending process and the tooth-bearing portion, due to the migration of the once dorsal nares back to the tip of the snout from its plesiomorphic position on top of the snout. All choristodere workers have since assumed the ascending process was the nasal since the real nasal and prefrontals are fused in Champsosaurus. So, given the examples of the closest known taxa (Figs. 3,4), in Matsumoto et al. (2013) the ascending process of the premaxilla was falsely labeled a nasal and the nasals were falsely labeled prefrontals.

 

Figure 3. The misidentification of the rostral bones in Lazarussuchus according to Matsumoto (2013, above) and relabeled below. Sister taxa demonstrate the continuing presence of large nasals that meet medially and the extent of the premaxilla ascending process. This false paradigm has to stop. Also see figure 4 for Youngina BPI 2871, which has a longer snout.

Figure 3. The misidentification of the rostral bones in Lazarussuchus according to Matsumoto (2013, above) and relabeled below. Sister taxa demonstrate the continuing presence of large nasals that meet medially and the extent of the premaxilla ascending process. This false paradigm has to stop. Also see figure 4 for Youngina BPI 2871, which has a longer snout.

Saved by the sister taxa
Related taxa (Figs. 3, 4), like Younginia, Younoides, Cteniogenys and Diandongosuchus demonstrate the conservative arrangement of the rostral bones. The prefrontals of Lazarussuchus did not meet medially, but were located at their conventional places, separated by large nasals. Not sure why (other than the Champsosaurus issue mentioned above) experts are missing this. Lack of more parsimonious related taxa indicated Matsumoto et al. (2013) have no idea where choristoderes nest in the reptile family tree. Here, when given 235+ other opportunities, choristoderes nest with younginiforms and within the pararchosauriforms: Doswellia, parasuchia and proterochampsia in the large reptile tree.

Fenestrae Coming and Going
Lazarussuchus is a diapsid lacking the lateral temporal fenestra present in sister taxa like Diandongosuchus and Younginoides (Fig. 3) and another choristodere, Cteniogenys (Fig. 4). Diandongosuchus is among the first taxa in its lineage to develop an antorbital fenestra, convergent with several other taxa with antorbital fenestra.

Youngina BPI 2871 and its descendants, according to the large reptile tree, the choristodere Cteniogenys and the chanaresuchid, Gualosuchus.

Figure 4. Youngina BPI 2871 and its descendants, according to the large reptile tree, the choristodere Cteniogenys and the chanaresuchid, Gualosuchus.

It’s discouraging when paleontologists do no apply due diligence to their work and leave it to  amateurs to correct their mistakes. Such mistakes can be eliminated and tested with widespread use of the large reptile tree, which has been available world wide for nearly two years now.

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.

Reference
Evans SE and Hecht MK 1993. A history of an extinct reptilian clade, the Choristodera: longevity, Lazarus-Taxa, and the fossil record. Evolutionary Biology 27:323–338.
Hecht MK 1992. A new choristodere (Reptilia, Diapsida) from the Oligocene of France: an example of the Lazarus effect. Geobios 25:115–131. doi:10.1016/S0016-6995(09)90041-9.
Matsumoto R, Buffetaut E, Escuillie F, Hervet S and Evans S 2013. New material of the choristodere Lazarussuchus (Diapsida, Choristodera) from the Paleocene of France.

wiki/Lazarussuchus