More data on the holotype of Pappochelys

Earlier we looked at Pappochelys (Figs. 1-4), touted as a stem turtle, but nesting in the large reptile tree at the base of the Placodontia and Sauropterygia.

I found online
a pretty good photo of the holotype of Pappochelys (SMNS 91360, Fig. 1). This taxon is also known from about 19 other less complete referred specimens, many including bones that fill in gaps left by the holotype. These specimens also document a variety of ontogenetic ages and sizes, as noted earlier.

Originally Pappochelys was considered a stem turtle
with no more than nine dorsal vertebrae and ribs (Fig. 2). Here, in the large reptile tree, it was recovered as a basal placodont close to Palatodonta, not related to turtles like Proganochelys and Odontochelys.33-37 steps are added when Pappochelys is forced to nest with turtles.

This is the holotype
of Pappochelys, SMNS 91360 (Fig. 1). Click to enlarge. It seems like there are more ribs here and the number of gastralia appears to suggest a longer torso than originally imagined (Fig. 2). The holotype may not represent the entire dorsal series, whether in vertebrae or ribs.

Figure 1. Schock and Sues counted a maximum of nine dorsal vertebrae, but is that the total number of dorsal vertebrate in Pappochelys. It is if you want it to be a turtle. It may not be if you reconstruct the holotype like this. Click to enlarge. Note the differences in gastralia tip shapes. Note the difference in sizes of the dorsal vertebrae. The longest dorsal ribs appear to be skewed toward the posterior torso. Certainly these images are not 100% correct. Instead they represent a best guess based on the data.

Figure 1. Schock and Sues counted a maximum of nine dorsal vertebrae, but is that the total number of dorsal vertebrate in Pappochelys. Nine is a good number if you want Pappochelys to be a turtle. It may not be turtle if you reconstruct the holotype like this or add Pappochelys to the large reptile tree. Click to enlarge.  Note the difference in sizes of the dorsal vertebrae. The longest dorsal ribs appear to be skewed toward the posterior torso, so I did the same with the scattered gastralia. The color tracings of the gastralia were originally traced from the photo and transferred to the original drawing, then transferred again into a regular order. Certainly these images are not 100% correct. Instead they represent a best guess based on the data. The gastralia are so scattered that one cannot determine that some tips point anteriorly, especially since Pappochelys is not related to turtles.

It is always better to use just one specimen in analysis. 
That is why I have revised the reconstruction based on the holotype. In this case we trust Schoch and Sues with regard to their list of referred specimens, as they trust their own judgement. There are no other vaguely similar taxa recognized as present in these strata and referred specimens preserve key elements not found in the holotype, like the skull.

What Schoch and Sues identified
as a femur on the holotype (Fig.1) is the shape and size of a posterior dorsal rib (#6, Fig. 3). A smaller, better femur is found on another specimen and it has an offset proximal head (Fig. 3) not illustrated by Shoch and Sues in situ, only in their reconstruction (Fig. 2).

In the Schoch and Sues reconstruction (Fig. 2)
the dorsal view reconstruction shows a much larger gastralia basket than the lateral view shows (Fig 2). That’s not scientific. The Schoch freehand drawings also indicate the pectoral girdle migrating beneath the anterior dorsal ribs in lateral view based on this incongruity. That’s what turtles do, but Pappochelys is not related to turtles. So that’s imaginary and hopeful.

The Shoch and Sues tracing (Fig. 1)
shows a straight rib (#3) with a T-shaped cross section, but the Schoch reconstruction does not show any large straight ribs. The dorsal ribs all bend posteriorly in the Shoch reconstruction except the small, short anterior rib.

None but
the first and second of the in situ caudal vertebrae appear to have any transverse processes, yet Schoch illustrated transverse processes on all the caudals and scored them as appearing beyond the fifth one caudally.

The coracoid
identified by Schoch and Sues in the holotype (Fig 3) is the same size and shape as the ischium, but it could still be a coracoid.

The pubis
identified by Shoch and Sues in the holotype (Fig 3) has no articular surfaces that fit the ilium. That ‘bone’ is here identified as the pubis AND ischium with appropriate articular surfaces that fit the ilium.

The ilium
of the 91895 specimen does not match the ilium of the holotype, which is narrower in all respects.

Figure 2. Pappochelys according to R. Schoch. Note the mismatch in the gastralia (ghosted area in lateral view, red bones otherwise).

Figure 2. Pappochelys according to R. Schoch. Note the mismatch in the gastralia (ghosted area in lateral view, red bones otherwise). Schoch and Sues presented Pappochelys as a turtle ancestor, but created distortions like those above to do so. Compare to bone tracings in figure 1.

Schoch and Sues provided a freehand drawing
of Pappochelys (Fig. 2), uniting parts from several specimens and filling in gaps where necessary. Freehand drawings are always biased (see above). There’s no way to get around it. It’s better Science to trace the original elements precisely (Fig.1), no matter if the bones are crushed or broken. Using DGS permits one to segregate some bones from others and lift, rotate and shift them, as is, to create a reconstruction.

Figure 3. Comparing elements from different Pappochelys specimens to scale. The ilia do not match. Nor do the femora. The 91360 specimen is identified here as a dorsal rib. What Schoch and Sues identified as a pubis would not fit on the ilium of the same specimen. I think they show two bones, the pubis and the ischium as illustrated here.

Figure 3. Comparing elements from different Pappochelys specimens to scale. The ilia do not match, even accounting for breaks. Nor do the femora. The 91360 specimen is identified here as a dorsal rib. What Schoch and Sues identified as a pubis would not fit on the ilium of the same specimen. I think they show two bones, the pubis and the ischium as illustrated here with appropriate articular surfaces.

More precision
was needed in the Schoch and Sues study. More taxon inclusion was also needed in their small focused analysis.

Figure 4. Pappochelys overall revised. Note that various specimen numbers may indicate different size individuals. All pectoral elements are individual specimens.

Figure 4. Pappochelys overall revised. Note that various specimen numbers may indicate different size individuals. All pectoral elements are individual specimens. Pappochelys may have had fewer dorsal vertebrae than its placodont sisters. Or not. A more complete dorsal series will tell us.

While the above rendition is more precise than before,
even more precision is necessary to complete the task of positively identifying each bone. We don’t know how many dorsal vertebrae were present. A sister taxon, Majiashanosaurus appears to have 18. See the skull in more detail here.

Based on the 92068 rib,
(Fig. 4) some Pappochelys specimens (or a species similar to it) grew to be twice as large as the holotype.

References
Schoch RR and Sues H-D 2015. A Middle Triassic stem-turtle and the evolution of the turtle body plan. Nature (advance online publication) doi:10.1038/nature14472 online

Aurornis (pre-bird) skull, traced using DGS

Aurornis xui (Godefroit et al. 2013, Late Jurassic, 50cm in length, 160 or 125mya) is one of the few outgroup taxa known for Archaeopteryx and the birds. (Balaur is another in the large reptile tree).

Auronis is a small, gracile dromaeosaur
without a large elevated pedal digit 2. The skull is complete, but slightly disarticulated (Fig. 1). A little DGS colorizes the bones. These can then be reassembled to form a skull in lateral view.

Fig. 1 Aurornis skull in situ, various elements segregated from the in situ fossil and reassembled into a complete and articulated skull. Only the easy bones are colorized here, leaving others uncolored. No doubt there are some errors here. I had only a medium resolution image and my knowledge of dinosaur skulls is still at the freshman stage. The hole in the surangular is an artifact. The little lavender ovals are displaced sclerotic bones.

Fig. 1 Aurornis skull in situ, various elements segregated from the in situ fossil and reassembled into a complete and articulated skull. Only the easy bones are colorized here, leaving others uncolored. No doubt there are some errors here. I had only a medium resolution image and my knowledge of dinosaur skulls is still at the freshman stage. The hole in the surangular is an artifact. The little lavender ovals are displaced sclerotic bones.

Like many other small theropods,
Aurornis was feathered, agile and fast, a descendant of basal dromaeosaurids, like Halplocheirus. In palatal view, the internal nares are located on the anterior palatines and the anterior palate is narrow but solid. The premaxilla is still relatively short and toothed. The pterygoids are narrow and have lost their primitive triangular shape. As a result of taphonomy, tracings for the anterior dentary teeth are distinct from one another. The wider, more typical, pointed teeth are the correct morphology.

Figure 2. Aurornis in several views alongside Archaeoperyx to scale.

Figure 2. Aurornis in several views alongside Archaeoperyx to scale.

On a side note:
Pappochelys (‘grandfather turtle’) has been getting a lot of press, none critical. Take a fresh look at all the PR here.

On another side note:
Chilesaurus, which the large reptile tree nested as the long sought and current most basal member of the Ornithischia, and we looked at earlier here, was given a good look over at the TheropodDatabase blog here.  Evidently others also think the original Chilesaurus report has issues.

References
Godefroit P, Cau A, Hu D-Y, Escuillié, Wu, W-H and Dyke G 201. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Nature 498 (7454): 359–362.

wiki/Aurornis

 

Eohyosaurus – a new basal rhynchosaur

Eohyosaurus wolvaardti, SAM-PK-K-10159 (Butler 2015, Fig. 1) is a new basal rhynchosaur from the early Middle Triassic (Anisian) of the Karroo supergroup, known from a single skull. It is similar to Mesosuchus.

Figure 1. Eohyosaurus reconstructed. This taxon nests between, Trilophosaurus + Azendohsaurus and the Rhychosauridae.

Figure 1. Eohyosaurus reconstructed from several views of a single specimen. This taxon nests between, Trilophosaurus + Azendohsaurus and the Rhychosauridae (Figs. 2, 3).

Butler et al. did a thorough and excellent job
of describing their specimen. They nested it accurately.

Unfortunately,
Butler et al. added two non-rhynchosaurian outgroups (Prolacerta broomi and Protorosaurus speneri) to their cladistic analysis and omitted many others (Figs. 2, 3).

Figure 2. Rhynchosaur tree from Butler et al. Color area added for rhynchosauridae.

Figure 2. Rhynchosaur tree from Butler et al. Color area added for rhynchosauridae.

In the large reptile tree (Fig. 3 subset) the protorosaurs are not related to the rhynchosaurs. And rhynchosaurs are derived from sphenodontians. That was the original assessment, but the lack of fusion in the ankles of rhynchosaurs caused Cruickshank (1972) and Benton (1983) to consider rhynchosaurs close to protorosaurs and archosaurs, like Prolacerta and Proterosuchus. Carroll (1988) considered this valid in his landmark textbook and Dilkes (1998) agreed. Details here, here and here.

They’re all wrong,
if you include the following taxa (Fig. 3) and all the 556 intervening taxa.

Figure 3. Here is where Eohyosaurus fits on the large reptile tree.

Figure 3. Here is where Eohyosaurus fits on the large reptile tree.

Butler et al. considered
Noteosuchus the earliest known rhynchosaur (Early Triassic). Actually it’s a transitional clade member bridging Clevosaurus, a sphenodontian, to Eohyosaurus and Mesosuchus, basal rhynchosaurs.

All you young and old scientists (paleontologists)
keep adding taxa and see what your tree recovers.

References
Benton MJ 1983. The Triassic reptile Hyperodapedon from Elgin, functional morphology and relationships. Philosophical Transactions of the Royal Society of London, Series B, 302, 605-717.
Benton MJ 1990. The Species of Rhynchosaurus, A Rhynchosaur (Reptilia, Diapsida) from the Middle Triassic of England. Philosophical transactions of the Royal Society, London B 328:213-306. online paper
Benton MJ 1985. Classification and phylogeny of diapsid reptiles. Zoological Journal of the Linnean Society 84: 97-164.
Butler R, Ezcurra M, Montefeltro F, Samathi A, Sobral G 2015. A new species of basal rhynchosaur (Diapsida: Archosauromorpha) from the early Middle Triassic of South Africa, and the early evolution of Rhynchosauria. Zoological Journal of the Linnean Society 10.1111/zoj.12246.
Carroll RL 1988. Vertebrate Paleontology and Evolution. WH Freeman and Company.
Cruickshank ARI 1972. The proterosuchian thecodonts. In Studies in Vertebrate Evolution (ed. Jenkins KA and Kemp TS) 89-119. Edinburgh: Oliver and Boyd.
Dilkes DW 1995. The rhynchosaur Howesia browni from the Lower Triassic of South Africa. Paleontology 38(3):665-685.

The PMOL Changchengopterus manus – DGS

A while back we looked at the new Changchengopterus (the one that did not nest with the holotype). Here is a closer look at the hand.

Figure 1. PMOL Changchengopterus manus in situ and reconstructed. Click to animate to show flexor and extensor tendons. Note the presence of digit 5. The unguals invivo  point ventrally,  When crushed, like this, they often show their anterior (medial) faces. Shapes of the unguals are shown in gray. The pteroid articulates with the radiale.

Figure 1. PMOL Changchengopterus manus in situ and reconstructed. Click to animate to show flexor and extensor tendons. Note the presence of digit 5. The unguals invivo  point ventrally,  When crushed, like this, they often show their anterior (medial) faces. Shapes of the unguals are shown in gray. The pteroid articulates with the radiale.

Earlier we solved the problem
of flexor tendon insertion and flexion, here, here and here.

Figure 2. Traditionally digit 5 has been overlooked. Hopefully this GIF animation will help you see it.

Figure 2. Traditionally digit 5 has been overlooked. Hopefully this GIF animation will help you see it. Look for an ungual, two other phalanges, a metacarpal and an carpal, as in Longisquama and Cosesaurus, but in this case all overlain by soft tissue (probably tendons) and riddled with cracks.

Earlier we looked at
the manual digit 5 problem in pterosaurs here, here and here. The reduction of manual digit 5 is documented here. Cosesaurus and Longisquama, two pterosaur outgroups, retain a distinct manual digit 5 of the same morphology.

References
Zhou C-F and Schoch RR 2011. New material of the non-pterodactyloid pterosaur Changchengopterus pani Lü, 2009 from the Late Jurassic Tiaojishan Formation of western Liaoning.  N. Jb. Geol. Paläont. Abh. 260/3, 265–275 published online March 2011.

 

Pappochelys: NOT a turtle ancestor, not even close.

Updated July 1, 2015 with a tracing of the holotype of Pappochelys (Fig. 6). See July 1, 2015 for an update on Pappochelys

The following notes demonstrate 
the great capacity of unrelated reptiles to converge on character traits, in this case, expanded ribs and other traits. In such cases, only a large, species/specimen-based phylogenetic analysis, like the large reptile tree, can resolve such problems with great confidence, parsimony and logic. Otherwise, as in the case of Pappochelys (pah-poe-kee-luss), results can be frustrating (see below).

Fiigure 1. The turtle mimic Eunotosaurus from the Middle Permian was actually closer to Acleistorhinus.

Fiigure 1. The turtle mimic Eunotosaurus from the Middle Permian was actually closer to Acleistorhinus.

Yesterday, a new paper in Nature
by Schoch and Sues (2015) purported to document the transitional taxon between the derived millerttid, Eunotosaurus (Fig. 1), and the basal turtle, Odontochelys (Fig. 2). They employed two cladograms  (Figs.1, 2) based on Lyson et al. 2010. Both recovered topologies that are not supported by the large reptile tree. Both employ several suprageneric taxa, always a bad sign.

In the large reptile tree, now with 556 taxa, Eunotosaurus and Odontochelys are not closely related. On that note, Schoch and Sues report in their own  testing, a TNT analysis (Fig. 3) produced a tree topology distinct from their own Bayesian analysis (Fig. 4), especially with regard to their key taxon, Eunotosaurus (Fig.1), which nested far from turtles in the Bayesian analysis.

Figure 1. Odontochelys with a newly reconstructed skull.

Figure 2. Odontochelys, a basal soft-shelled turtle with teeth.

Odontochelys (Fig. 2) is indeed a basal turtle.
It nests with Trionyx, the extant soft-shelled turtle in the large reptile tree, so it is not as primitive as others suggest. It shared a common Early to Middle Permian ancestor with Elginia and Sclerosaurus, two more primitive horned turtle sisters (Fig. 7). Elginia nests with the giant horned turtle, Meiolania as reported earlier. Sclerosaurus had a broad flat torso with discrete osteoderms prior to carapace formation. This is how the carapace had its genesis according to the large reptile tree (Fig. 7).

Figure 1. from Schoch  and Sues 2015 with colors added here to denote clades recovered by the large reptile tree. This is their TNT analysis result.

Figure 3. from Schoch and Sues 2015 with colors added here to denote clades recovered by the large reptile tree. This is their TNT analysis result.

The Schoch and Sues abstract
described the 220 million-year-old, Late Triassic, Odontochelys as having a ‘partly formed shell’, but the large reptile tree nested it with the living soft shell turtle, Trionyx, so the structure was derived, not primitive. So turtles are more ancient than the Late Triassic.

Schoch and Sues listed the 260-million-year-old Eunotosaurus as a hypothetical stem turtle, but it actually nests with Acleistorhinus and Delorhynchus, convergent with turtles in several respects.

Schoch and Sues considered the new reptile, Pappochelys rosinae (“grandfather-turtle”, 20 cm in length, 240 mya, Ladinian, Middle Triassic; SMNS 91360, SMNS 90013 and other referred specimens, including a very small individual), intermediate between Eunotosaurus and Odontochelys (but only in their TNT analysis, Fig. 3).

Figure 2. Second cladogram recovered by Schoch and Sues 2015 recovered by Bayesian analysis.

Figure 4. Second cladogram recovered by Schoch and Sues 2015 recovered by Bayesian analysis. The use of suprageneic taxa is always dangerous due to cherry picking and taxon exclusion. Note where Eunotosaurus (in pink) nests here.

From the Schoch and Sues abstract: “The three taxa [Eunotosaurus, Pappochelys and Odontochelys} share anteroposteriorly broad trunk ribs that are T-shaped in cross-section and bear sculpturing, elongate dorsal vertebrae, and modified limb girdles. Pappochelys closely resembles Odontochelys in various features of the limb girdles. Unlike Odontochelys, it has a cuirass of robust paired gastralia in place of a plastron. Pappochelys provides new evidence that the plastron partly formed through serial fusion of gastralia. Its skull has small upper and ventrally open lower temporal fenestrae, supporting the hypothesis of diapsid affinities of turtles.”

Their analysis, based on Lyson et al. 2010,
included 198 character traits (originally 191) and generated a single MPT.

They had to add 7 traits to achieve their results
When the original data set (191 characters) was analysed using TNT, with scores for Pappochelys included, the analysis yielded three MPTs that differed in the positions of Archosauriformes, Prolacerta, and rhynchosaurs, as well as of kuehneosaurids, lepidosaurs, and the turtle-sauropterygian clade. That’s several big changes! I applaud them for their honesty. They report, in that analysis, Pappochelys was found to nest below Eunotosaurus, but still within a clade with turtles.

In the large reptile tree
deletions and addition don’t produce that sort of anarchy and large changes in tree topology.

Schoch and Sues report,
“Robustness of nodes was assessed by bootstrap, resulting in collapse of many nodes, including Diapsida and the placement of Eunotosaurus at the base of the turtle clade.”

If they only had the large reptile tree to work with, this would not have happened.

Schoch and Sues also note, |
“Although the trunk region is disarticulated in all available specimens, the maximum number of  trunk vertebrae did not exceed nine.”
Since each specimen was incomplete, I wonder how they came up with that number? … except that Eunotosaurus and turtles have a short dorsal series with long vertebral centra. …or no partial specimen had more than nine scattered vertebrae preserved (typically far fewer). Based on the varying sizes and shapes of the dorsal ribs, it would appear that more ribs would be necessary to fill in the shape gaps, and along with more ribs you need more vertebrae (Fig. 6). In the large reptile tree recovered sister taxa among basal enaliosaurs (Figs. 5-7) have far more than nine dorsal vertebrae.

Schoch and Sues further note,
“In ventral view, the anterior gastralia extend anterolaterally, whereas the reverse obtains on the posterior gastralia. None of the available fossils preserves undisturbed pairs of gastralia.” (Fig. 6). Not sure how Schoch and Sues came to this conclusion, based on the evidence they presented, except that appears to be the pattern in Odontochelys (Fig. 2). I know of no other examples where this also happens. Note in the related placodonts, Paraplacodus (Fig. 6) and Placocodus, the lateral gastralia tips point dorsally and crushing could have produced such a pattern as interpreted by Schoch and Sues. I hope they weren’t trying to force fit an interpretation to disarticulated remains.

Figure 1. Pappochelys skull compared to sister taxa including Palatodonta and the original reconstruction of Schoch and Sues.

Figure 5. Pappochelys skull  reconstructed from colorized bone images compared to sister taxa including Palatodonta and the original reconstruction of Schoch and Sues. Pappochelys certainly looks like Palatodonta and Paraplacodus, but not Odontochelys. Note the very narrow frontals, totally unlike turtles, totally like Palatodonta.

In the Bayesian analysis
Schoch and Sues reported, “An unexpected result was the (albeit weakly supported) traditional placement of Eunotosaurus among Parareptilia and completely separate from Pappochelys, Odontochelys and Testudines, all of which were recovered as the sister-group of Sauropterygia among Diapsida. Pappochelys was firmly recovered as the sister-taxon to Odontochelys + (Proganochelys + Testudines).”

Figure 6. Pappochelys compared to placodont sister taxa and compared to the Schock and Sues reconstruction, which appears to have several scale bar errors and underestimated the number of dorsal vertebrae. Click to enlarge. So few ribs and vertebrae are known for Pappochelys that their order, size and number could vary from that shown here. Note the ribs of Paraplacodus are also expanded. The number of dorsal vertebrae is unknown and probably more than nine based on sister taxa.

Figure 6. Pappochelys compared to placodont sister taxa and compared to the Schock and Sues reconstruction, which appears to have several scale bar errors and underestimated the number of dorsal vertebrae. Click to enlarge. So few ribs and vertebrae are known for Pappochelys that their order, size and number could vary from that shown here. Note the ribs of Paraplacodus are also expanded. The number of dorsal vertebrae is unknown and probably more than nine based on sister taxa. The pectoral girdle of Pappochelys is from several specimens.

In figure 6
note the relatively large pelvis, short torso and long legs in the Schoch and Sues version of Pappochelys. Those proportions approach those of speedy terrestrial reptiles, not what one would expect of turtle ancestors. I think their estimates were off. Certainly their scale bars were off, unless the measurements were taken from several different ontogenetic age specimens. The Schoch and Sues reconstruction also overlooks the great variety in rib shapes and sizes in Pappochelys. While creating the reconstruction I also had trouble reconciling the scale bars with their reconstruction in which certain elements are twice or half what they should be. Compare skull sizes to pelvis sizes in their reconstruction vs. mine.

Throughout the Schoch and Sues paper
the authors make note of similarities between PappochelysEunotosaurus and Odontochelys.

  1. The large ribs bear sculpting on the dorsal surface, suggestive an intradermal origin.
  2. The dorsal ribs are T-shaped in cross-section
  3. The scapula is tall and slender
  4. The pelves closely resemble each other
  5. The pubis has a lateral process
  6. The S-shaped femur has an internal trochanter and an offset head.

But ALSO note that in both Schoch and Sues studies
eusaurosphargids and placodonts nest as sisters to the turtles. Schoch and Sues celebrate the fact that Pappochelys had a diapsid skull even though no turtles have  temporal fenestra. Turtles have only nested with diapsids in phylogenetic analyses based on molecular data. Their interpretation of Pappochelys. therefore, comes as something of a wonderful surprise in that it appears to tie morphological and molecular study findings together. To their credit, Schoch and Sues report that those molecular studies typically nest turtles with or close to archosaurs. We all agree that on the face of it such a nesting is out of the question. No morphological study has ever replicated that result.

The authors suggest that Eunotosaurus had upper temporal openings concealed by large supratemporals. The reader is probably already aware that no sister taxa of Eunotosaurus have upper temporal fenestrae and that if a bone covers an opening, it is no longer considered an opening.

Figure x. Two subsets of the large reptile tree focusing on Pappochelys and its enaliosaur relatives (left) and turtle relatives (right). Shifting Pappochelys to turtles adds 37 steps.

Figure 7. Two subsets of the large reptile tree focusing on Pappochelys and its enaliosaur relatives (left) and turtle relatives (right). Shifting Pappochelys to turtles adds 37 steps. Click to enlarge.

Testing Pappochelys
in the large reptile tree recovered a nesting close to the basal placodont, Palatodonta (skull only) and the much larger Marjiashanosaurus (post-crania only). Paraplacodus is not far removed and it has ribs with a T-shaped cross-section. Sinosaurosphargis is shaped like a turtle with a carapace and plastron of flat gastralia and it nests close by. Largocephalosaurus nests nearby and it has a tall slender scapula and a pubis with a lateral process. So reptiles near that node were experimenting with several turtle traits by convergence with actual turtles.

Of great interest in Pappochelys
is the lack of elongate dorsal transverse processes, common to eusaurosphargid and placodont sister taxa. However Anarosaurus and Pachypleurosaurus are also sisters and they, like Pappochelys and turtles, also lack elongate dorsal transverse processes.

Fingers and toes
Like EunotosaurusPappochelys has relatively slender fingers and toes, unlike those of turtle and their true ancestors, like Sclerosaurus. But that’s okay, because Eunotosaurus and Pappochelys are not related to turtles.

Convergence!
As noted above, nearly every turtle-like trait found in Pappochelys can be found in pachypleurosaurs, eusaurosphargids and placodonts. There is no doubt that Pappochelys evolved several turtle-like traits. Unfortunately, parsimony reveals that it was not a turtle, but developed those traits by convergence. I understand the excitement that Schoch and Sues must have felt about their discovery and its apparent importance. No wonder Nature wanted to publish it. But just like Limusaurus and Yi qi, more prosaic mundane explanations and interpretations are recovered when more taxa are included in analysis.

Revisiting the new Pappochelys
If Pappochelys had the same number of dorsal vertebrae as its sister taxa, then a new, long-bodied reconstruction emerges (Fig.6). Here we have an elongate, aquatic reptile without specialized teeth. It has relatively short, weak legs and a wider than deep torso with pachystotic bones. With such traits, Pappochelys could have been a bottom-dweller in a shallow lake environment. Large eyes might have given it good night vision.

Now that we have two of these short-snouted, big-eyed placodonts, perhaps we can discard the false idea that Palatodonta was a juvenile. Rather, as in many other novel reptile clades, phylogenetic miniaturization accompanied the development of new body parts and character traits.

For the large reptile tree origin of turtles, click here and here.

The Pappochelys strata
were laid down in a shallow oligohaline or freshwater lake. It is the most common taxon in the Vellberg lake deposit and is represented by several growth stages. The authors consider Pappocehelys “critical evidence for the diapsid relationships of turtles and it provides a new stage for the evolution of the turtle body plan.”

Unfortunately,
Pappochelys is a basal placodont, unrelated to turtles.

However, Pappochelys is important to the large reptile tree because it ties a skull-only taxon (Palatodonta) to a skull-less taxon (Majiashanosaurus). So the tree is once again fully resolved, an unforeseen side-effect.

Added a day later: lots of news online about Pappochelys, some with audio

NPR
CBC.Canada
Smithsonian Magazine
Science Magazine – reports, “So having broad, dense bones and gastralia would have acted like a diver’s weight belt, helping Pappochelys fight buoyancy and forage on the lake’s bottom. But these bones would also have had a beneficial side effect: They would have offered some degree of protection from predators, such as large amphibians or fish living in the lake, by deflecting or blunting their bites.”

References
Lyson TR, Bever GS, Bhullar B-AS, Joyce WG and Gauthier JA. 2010. Transitional fossils and the origin of turtles. Biology Letters 2010 6, 830-833 first published online 9 June 2010. doi: 10.1098/rsbl.2010.0371
Schoch RR and Sues H-D 2015.
A Middle Triassic stem-turtle and the evolution of the turtle body plan. Nature (advance online publication) > doi:10.1038/nature14472 online

wiki/Pappochelys

The Origin of Dinosaurs as told by The Smithsonian, Wiki, etc.

Many of the biggest dino museums in the world
have produced their version of the origin of dinosaurs. Here’s what they have to say online:

Smithsonian – National Museum of Natural History
“The earliest dinosaurs were probably carnivorous, bipedal animals less than two meters long and weighing about 10 kilograms. From these small beginnings evolved thousands of different dinosaurs species.”

Wikipedia
“Dinosaurs evolved within a single lineage of archosaurs 232-234 Ma (million years ago) in the Ladinian age, the latter part of the middle Triassic. Dinosauria  is diagnosed by many features including loss of the postfrontal on the skull and an elongate deltopectoral crest on the humerus.

“The process leading up to the Dinosauromorpha and the first true dinosaurs can be followed through fossils of the early Archosaurs such as the Proterosuchidae, Erythrosuchidae and Euparkeria which have fossils dating back to 250 Ma, through mid-Triassic archosaurs such as Ticinosuchus 232-236 Ma. Crocodiles are also descendants of mid-Triassic archosaurs.

“Dinosaurs can be defined as the last common ancestor of birds (Saurischia) and Triceratops (Ornithischia) and all the descendants of that ancestor. With that definition, the pterosaurs* and several species of archosaurs narrowly miss out on being classified as dinosaurs. Archosaur genera that also narrowly miss out on being classified as dinosaurs include Schleromochlus 220-225 Ma, Lagerpeton* 230-232 Ma and Marasuchus* 230-232 Ma.

“The first known dinosaurs were bipedal predators that were 1-2 metres (3.3-6.5 ft) long. Spondylosoma may or may not be a dinosaur; the fossils (all postcranial) are tentatively dated at 235-242 Ma.

“The earliest confirmed dinosaur fossils include saurischian (‘lizard-hipped’) dinosaurs Nyasasaurus 243 Ma, Saturnalia 225-232 Ma, Herrerasaurus 220-230 Ma, Staurikosaurus possibly 225-230 Ma, Eoraptor 220-230 Ma and Alwalkeria 220-230 Ma. Saturnalia may be a basal saurischian or a prosauropod. The others are basal saurischians.”

* these are false nestings according to the tree topology of the large reptile tree.

University of Bristol
“Those archosaurs most closely related to the dinosaurs are forms such as Marasuchus. The detailed evolutionary relationships are still debated, but by the late Triassic, several early theropods are known, as the dinosaurs rapidly diversified. These dinosaurs, such as Eoraptor, Coelophysis and Herrerasaurus were all carnivores, and, despite their diversity, were quite rare at this time.”

Natural History Museum of Los Angeles County
“The ancestry of dinosaurs can be traced back some 230 million years ago to the Late Triassic. All dinosaurs belong to a group of reptiles called archosaurs-a group that also includes crocodiles and a variety of Mesozoic reptiles (pterodactyls and others) that are often misinterpreted as dinosaurs. The anatomical characteristics of both the earliest known dinosaurs and their archosaurian relatives suggest that the common ancestor of all dinosaurs was a small bipedal predator, which had forelimbs shorter than hind limbs. This ancestor was probably similar to the 235-million-year-old Lagosuchus from Argentina, pictured below.

“From the most primitive Triassic forms to the most advanced ones of the latest Cretaceous, all dinosaurs share defining traits that distinguish them from their closest archosaurian relatives. Among these innovations, the femur (or upper leg bone) developed a distinct head for a tied attachment into a hollow hip socket. These and other changes resulted in a hind limb that was tucked directly underneath the body, providing upright, pillar-like support of the body and also enhancing locomotive abilities. The changes that led to the erect posture of dinosaurs from the sprawling posture of their reptilian predecessors had a profound effect on the evolutionary success of these animals. These transformations may have also been coupled with the evolution of a higher metabolism (a step towards warm bloodedness) that endowed them with a greater capacity for sustained activities such as running.”

Genesis park genesispark.com
“The Bible states that on the fifth day of creation God created great sea monsters and flying creatures. This would have included the great swimming and flying reptiles (like the plesiosaur and pterosaur creatures mentioned at our Genesis Park website). On the sixth day God created the land animals, which would have included all of the dinosaur kinds (Genesis 1:20-25).”

YouTube
Brief Lecture on the Origin of Dinosaurs – one commenter correctly noted, “This doesnt (sp) explain the actual origin of dinasaurs (sp) like the title states.”

The origin and evolution of dinosaurs Paul Sereno
Annual Review of Earth and Planetary Sciences
Vol. 25: 435-489 (Volume publication date May 1997)

“Phylogenetic studies and new fossil evidence have yielded fundamental insights into the pattern and timing of dinosaur evolution and the emergence of functionally modern birds. The dinosaurian radiation began in the Middle Triassic, significantly predating the global dominance of dinosaurs by the end of the period. The phylogenetic history of ornithischian and saurischian dinosaurs reveals evolutionary trends such as increasing body size. Adaptations to herbivory in dinosaurs were not tightly correlated with marked floral replacements. Dinosaurian biogeography during the era of continental breakup principally involved dispersal and regional extinction.”

American Museum of Natural History
Strangely, they don’t have an online account of dinosaur origins.

ReptileEvolution.com
Meet a long list of the best known taxa preceding dinos, the advent of dinos and see their family tree here and here. More specifics here (Fig. 1).

Figure 1. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Figure 1. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor. Read more at reptileevolution.com

The Dinosaur Heresies NYTimes Book Review from 1986

the_dinosaur_heresies200Now almost 30 years old, here’s something you might like to read (perhaps again?).
This is the NY Times book review of Dr. Robert Bakker’s ‘The Dinosaur Heresies’ from 1986. You can read the complete original here. I went to the prophesies below and marked them with a [+] or a [-] for those supported today or not and for those that are still questionable: [?].

BOOKS OF THE TIMES;
Dinosaur Mysteries
By MICHIKO KAKUTANI
Published: November 8, 1986

THE DINOSAUR HERESIES. New Theories Unlocking the Mystery of the Dinosuars and Their Extinction. By Robert T. Bakker. Illustrated. 481 pages. William Morrow & Company. $19.95.

Mr. [not Dr.?] Bakker has a quirky, free-floating imagination, and in the course of this book – which is generously illustrated with his own charming sketches – he raises many offbeat questions: Were changes in dinosaur eating patterns responsible for the evolution of flowering plants? [+] Did pink pterodactyls exist? [?] What sort of lips did dinosaurs have? [+] Could a human being beat a tyrannosaurus at arm wrestling? [?]

Mr. Bakker, the adjunct curator at the University Museum in Boulder, Colo., has published many papers in the field of vertebrate paleontology, and his book stands as an informative layman’s introduction to the wonderful world of dinosaurs while at the same time making an impassioned case for his own – sometimes heretical – views on their endurance and extinction. ”I’d be disappointed,” he writes, ”if this book didn’t make some people angry”; and given the often fiercely polarized world of vertebrate paleontology, he’s unlikely to be let down.

As Mr. Bakker sees it, dinosaurs have been given a bad rap over the years as ”failures in the evolutionary test of time” – portrayed as small-brained, cold-blooded sluggards who couldn’t ”cope with competition from the smaller, smarter, livelier mammals.” Such portraits, he suggests, are unfair as well as scientifically inaccurate: in the first place, dinosaurs dominated history for 130 million years [+] – a remarkably long period of time that attests to a decided ability to survive (the human species, in contrast, has only been around for 100,000 years). And while Mr. Bakker acknowledges that dinosaurs were probably not brilliant thinkers [+], he makes a persuasive argument for their physiological adaptability and their prodigious energy [+] – he even speculates that tyrannosaurus could gallop about at speeds approaching 45 miles an hour.  [-] 

Much of ”The Dinosaur Heresies,” in fact, revolves around the question of whether the animals were cold-blooded (and more closely related to reptiles) or, as Mr. Bakker contends, warm-blooded (and more closely related to mammals and birds) [+]. While he occasionally stops to summarize opposing viewpoints, he is less interested in presenting an objective overview of the field than in mustering evidence to support his own theories.

He argues that gizzards and large digestive tracts in [some] dinosaurs would have compensated for their weak teeth [+], enabling them to eat high quantities of land plants, necessary to support a high metabolic rate. He argues that birds and pterodactyls – both of which would have had to evolve high-pressure hearts and lungs before flight could have been achieved  [+] – descended from dinosaurs  [+] [-], and that it’s not unlikely that these ancestor dinosaurs were already equipped for high metabolism [+]. He argues that the dinosaurs’ ”adaptations for sex and intimidation” – horns, head-butting armor and all manner of bony frills -suggest that they led active, aggressive lives, uncharacteristic of lethargic, cold-blooded animals  [+]. He argues that the growth rate of dinosaurs more closely resembles that of mammals than reptiles [+]. And, finally, he argues that dinosaurs’ porous bone tissue indicates the sort of high blood-flow rate usually associated with warm-blooded creatures [?].

On the question of the dinosaurs’ demise, Mr. Bakker sides with those paleontologists who discount new theories of mass extinction caused by some sort of cosmic catastrophe – he cites evidence suggesting the extinctions occurred not during a single ”doomsday” period but over tens of thousands of years [+] [-] [?]. In his view, the development of new sorts of dinosaurs and other animals, combined with changes in the physical and genetic environment, gradually led to their doom [+] [-].

On a side note:
I liked Dr. Bakker’s quote about making some people angry with his novel ideas based on overlooked data.

On another side note:
like our antiquated notions about dinosaurs from over 30 years ago, pterosaurs today have been given a bad rap. They are still portrayed as ungainly quadrupeds, bound by membranes that tied their legs together and tied their wings to their ankles (along with a long list of other false paradigms). The data deniers, unfortunately, are still out there, thinking that if they just turn a blind eye toward certain data and hypotheses they will go away.

As everyone knows,
this blog, Pterosaur Heresies, was intended to approach data with the same verve and testing of false traditions that Dr. Bakker demonstrated.