Serikornis: Pre-bird or flightless bird?

Several authors have wondered over the years
how we might be able to tell (or nest) a flightless post-Archaeopteryx  bird from a flightless pre-Archaeopteryx troodontid. Earlier we nested a very large flightless sapeornithid bird, Jianianhualong, distinct from its original nesting as a troodontid. So it can be done.

Figure 1. Serikornis and Jurapteryx (Archaeopteryx) recurva to scale. These two nest as sisters in the LRT. The larger Serikornis was non-volent.

Lefèvre et al. 2017 bring us
a new Late Jurassic ground-dwelling theropod from China, Serikornis sungei (Figs. 1–3; PMOL-AB00200; 50 cm in length) that they nested with the derived troodontid, Eosinopteryx. They reported, “The plumage of this new specimen brings new information on the structure and function of the feathers in basal paravians and consequently on the early evolution of flight.”

By contrast
in the large reptile tree (LRT, 1050 taxa) Serikornis nests strongly with the Eichstätt specimen of Archaeopteryx, aka Jurapteryx recurva. That Solnhofen bird has large wing and tail feathers. The latest Jurassic, earliest Cretaceous formations from which Serikornis came are chronologically appropriate to this relationship. Apparently taxon exclusion by the Lefèvre team is the cause of the disparate nestings.

Figure 2. Serikornis in situ, with original drawing, skull under DGS and reconstructed.  As you can see, the metatarsus was feathery, not scaly, and the wing feathers were reduced. The teeth were longer, curved and sharper.  DGS did a pretty good job with the skull. 

As earlier authors have noted
the most likely time for an early volant bird to go back to flightlessness is when they are still not very good at flight. And that seems to be the case here. Serikornis probably got too big to fly. And its teeth were larger, opposite the general trend for volant birds. And so its flight feathers, like those of any number of extant and extinct flightless birds, became less able to perform aerial duties.

What about that short coracoid?
It is not long and strap-shaped, a common shape in flapping tetrapods. The coracoids in the Eichstätt specimen are lost in a crack so coracoids could not be scored for that Solnhofen bird. That short coracoid of Serikornis must have been a reversal, an atavism. That happens. It’s only one trait out of 228.

Maybe a sternum was overlooked.
The two putative coracoids (Fig. 3) do not have the same outline. So I wonder if one of them was a sternum? Certainly part of the large furculum is buried.

Figure 3. Serikornis pectoral girdle. Here one of the putative coracoids is rei-dentified as a sternum rotated from its in vivo position. A tiny portion of the bottom coracoid peeks out (in indigo).

At first I scored Serikornis
by copying the row for Eosinopteryx then renaming it. Soon distinct scores started appearing. The list became long. PAUP nested Serikornis apart from Eosinopteryx, among the very early birds and with Jurapteryx recurva, close to the base of the clade that includes all extant birds.

An abbreviated list of birdy traits in Serikornis include:

1. orbit in the posterior half of the skull
2. ascending process of premaxilla extends to frontals
3. tail longer than presacral spine
4. that long gracile pubis
5. fibula poorly ossified to absent at mid length
6. metatarsal 5 lacking phalanges

So the claim to fame for this taxon
should have been yet another one of the earliest flightless birds –- not a transitional troodontid documenting the advent of flight feathers. These flight feathers were on their way out, not on their way in.

References
Lefèvre U, Cau A, Cincotta A, Hu D-Y, Chinsamy A, Escuillié F and Godefroit P 2017. A new Jurassic theropod from China documents a transitional step in the macrostructure of feathers. Sci Nat 104:74. DOI 10.1007/s00114-017-1496-y

to soon yet for a Wikipedia article

Shringasaurus: new rhynchocephalian lepidosaur with horns

Sengupta, Ezcurra and Bandyopadhyay 2017 bring us
a new, very large, horned rhynchocephalian lepidosaur, Shringasaurus (Fig. 1). Unfortunately, that’s not how the Sengupta team nested it (due to the sin of taxon exclusion, see below). Even so, there is consensus that the new taxon is closely related to the much smaller Azendohsaurus (Fig. 1).

Figure 1. Shringasaurus to scale with Azendohsaurus. Line art modified from Sengupta et al. Color added here. Note the anterior lappet of the maxilla over the premaxilla. The supratemporal  (dark green) remains.

From the abstract:
“The early evolution of archosauromorphs (bird- and crocodile-line archosaurs and stem-archosaurs) represents an important case of adaptive radiation that occurred in the aftermath of the Permo-Triassic mass extinction. Here we enrich the early archosauromorph record with the description of a moderately large (3–4 m in total length), herbivorous new allokotosaurian, Shringasaurus indicus, from the early Middle Triassic of India. The most striking feature of Shringasaurus indicus is the presence of a pair of large supraorbital horns that resemble those of some ceratopsid dinosaurs. The presence of horns in the new species is dimorphic and, as occurs in horned extant bovid mammals, these structures were probably sexually selected and used as weapons in intraspecific combats. The relatively large size and unusual anatomy of Shringasaurus indicus broadens the morphological diversity of Early–Middle Triassic tetrapods and complements the understanding of the evolutionary mechanisms involved in the early archosauromorph diversification.”

Allokotosauria
Shringasaurus was nested in the clade, Allokotosauria, According to Wikipedia, “Nesbitt et al. (2015) defined the group as a  containing Azendohsaurus madagaskarensis and Trilophosaurus buettneri and all taxa more closely related to them than to Tanystropheus longobardicus, Proterosuchus fergusi, Protorosaurus speneri or Rhynchosaurus articeps.” This definition was based on the invalidated hypothesis that rhynchosaurs and allokotosaurs were close to the base of the Archosauriformes as the addition of more taxa will demonstrate. Basically this clade equals Trilophosaurus, Azendohsaurus and now Shringasaurus. In the large reptile tree (LRT, 1049 taxa) this clade nests between Sapheosaurus + Notesuchus and Mesosuchus + Rhynchosauria all nesting within Sphenodontia (=  Rhynchocephalia), so they are all lepidosaurs. All you have to do is add pertinent taxa to make this happen in your own phylogenetic analysis.

Figure 2. Scene from the 1960 film, The Lost World, featuring a giant iguana with horns added presaging the appearance of Shringasaurus.

Coincidentally the 1960 film,
The Lost World featured an iguana made up with horns similar to those of Shringasaurus.

References
Sengupta S, Ezcurra MD and Bandyopadhyay S 2017. A new horned and long-necked herbivorous stem-archosaur from the Middle Triassic of India. Nature, Scientific Reports 7: 8366 | DOI:10.1038/s41598-017-08658-8 online here.

No Wiki page yet.

Professor TR Holtz on Dinosaur Classification

An Albert Einstein anecdote is appropriate to today’s discussion. 
One of his students staood up 15 minutes into an exam saying, “The questions in this year’s exam are the same as last year’s exam.” Einstein replied, “Don’t worry; the answers are different this year.”

It’s got to be difficult telling students
how basal dinosaurs are related. The answers are different this year. Do they traditionally split into Saurischia and Ornithischia? Or do ornithischians nest with theropods, as Baron, Norman and Barrett 2017 proposed a few months ago. Or do they split into Theropoda and Phytodinosauria, as recovered here in the large reptile tree (LRT)?

Dr. Thomas R. Holtz (U of Maryland, PhD from Yale U) is often seen on TV and YouTube as a popularizer/explainer of all things dinosaur. Recently he uploaded a web page that showed several options for dinosaur and outgroup relations. This was part of his lecture series.

Holtz reports,
“Dinosauria is comprised of three major clades: Ornithischia, Sauropodomorpha, and Theropoda. Traditionally, sauropodomorphs and theropods were recognized to form a clade Saurischia. However, recent discoveries have reduced the support for this hypothesis, and alternative relationships are possible.”

Things would be easier and more logical
if Holtz knew the precise outgroup for the Dinosauria. Unfortunately he does not. He bought into the Avemetatarsalia hypothesis, when that was invalidated 17 years ago (Peters 2000).

In the LRT
Crocodylomorpha and Poposauridae are successively more distant outgroups to the Dinosauria. In Holtz’s view crocs are distantly related with a common ancestor close to Euparkeria. Pterosaurs, Lagerpeton, Lagosuchus and Silesaurus are closer relatives. In the LRT pterosaurs are lepidosaurs, Lagerpeton is a sister to Tropidosuchus and Lagosuchus is a theropod and Silesaurus is a poposaur.

Holtz also believes in the clade Ornithodira
even though that was also invalidated 17 years ago (Peters 2000). Holtz reports, “Unfortunately, at present we have no pterosaur-lineage animals which are not already highly derived for flight, so we can’t yet trace the transformations from walking to flying in this group.” This is wrong. Peters 2000 listed a half dozen taxa with a gradual accumulation of pterosaur traits, even when tested against archosaurs. The concept of the clade Ornithodira survives to this day due to taxon exclusion. And Peters exclusion, even published work in academic journals. Apparently no one wants to test what happens when various tritosaurs are entered into the taxon list.

Holtz believes that very small dinosaurormphs
left footprints in the Early Triassic. This was invalidated earlier here.

Holtz believes that dinsoauromorphs

1. had a parasagittal stance with erect hind limbs, but several clades develop this
2. had simple hinge ankle joints, but both mammals and tritosaur lepidosaurs had this
3. had a digitigrade posture, but both mammals and tritosaur lepidosaurs had this

See what happens
when Holtz tries to pull a “Larry Martin“? Larry would have given the same answers with a wry smile. Holtz needs to base his conclusions on a large gamut phylogenetic analysis that considers all possible candidates, not a short list of convergent traits.

Holtz mentions Nyasasaurus
an incomplete taxa considered a Middle Triassic dinosaur. Here it compares well with the basal popoaur, Turfanosuchus, only much larger.

Phytodinosauria
Holtz reports, “No recent computer-generated phylogenetic analysis has supported [Phytodinosauria]. This is wrong. The LRT recovered the clade Phytodinosauria six years ago. Holtz also reports, “but possible support for this arrangement may exist in the enigmatic Chilesaurus.” Yes. And you heard that first here two years ago.

Holtz lists
several Late Triassic dinosaurs of uncertain position.

In the LRT
none of the taxa listed by Holtz nests in an uncertain position… and he would discover that, too, if he also ran a large gamut phylogenetic analysis. He has access to all the literature and specimens, more so than I do. Instead of leaving dinosaur origins as a big question for his students, Holtz could find out for himself and provide an unequivocal answer. This is science. Anyone can do it, whether PhD or independent researcher.

References
Baron MG, Barrett PM 2017. A dinosaur missing-link? Chilesaurus and the early evolution of ornithischian dinosaurs. Biol. Lett. 13: 20170220. http://dx.doi.org/10.1098/rsbl.2017.0220 pdf online
Baron MG, Norman DB, Barrett PM 2017. A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature 543:501–506.
Peters D 2000b. A reexamination of four prolacertiforms with implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293–336.

Turtle origins: Pappochelys STILL not the best candidate

Schoch and Sues 2017
bring us more details about Pappochelys, and pull a ‘Larry Martin‘ or two to force fit this taxon into a false narrative: the origin of turtles story. What little they report and show is indeed intriguing. What more they don’t report and show invalidates their hypothesis. A wider gamut phylogenetic analysis has the final say.

As a reminder,
many paleontologists try to find one, two or a dozen traits that look like they link one taxon to a clade, but avoid testing those hypotheses in a wide gamut phylogenetic analysis, like the large reptile tree (LRT, 1048 taxa). This technique of force-fitting and ignoring other candidate sisters never turns out well. It’s not pseudoscience, but it does remind one of early attempts at flying that did not include sufficient power, rudders, ailerons and horizontal stabilizers. Those attempts were all doomed to crash.

A wide gamut phylogenetic analysis
remains the only tool that always delivers a correct tree topology because  taxon exclusion is minimized. The LRT worked with Diandongosuchus. It worked with Lagerpeton. It worked with Chilesaurus. It worked with turtles, whales and seals. And it worked with pterosaurs. The LRT works!

Let’s just make this short and painful
Schoch and Sues ignored:

1. the sister of Pappochelys in the LRT, Palatodonta
2. other proximal relatives of Pappochelys in the LRT, Diandongosaurus, Anarosaurus, Palacrodon and Majiashanosaurus
3. the sister to hard shell turtles in the LRT, Elginia
4. the sister to soft shell turtles in the LRT, Sclerosaurus
5. basalmost hard shell turtles in the LRT, Niolamia and Meiolania.
6. the proximal relatives of Eunotosaurus in the LRT, Acleistorhinus, Delorhynchus, Australothyris and Feeserpeton.

Figure 1. Shoch and Sues cladogram of turtle origins. Look at that loss of resolution! Gliding kuehneosaurs nest between aquatic taxa? Really? Add about 300 taxa and let’s see if this tree resolves itself. 

Schoch and Sues employed only 29 taxa
many of which were suprageneric, compared to 1048 specimens in the LRT. Schoch and Sues lament, “the currently available data fail to support any of the three more specific hypotheses for the diapsid origins of turtles (sister group to Sauria, Lepidosauria or Archosauria, respectively). We found no support for earlier hypotheses of parareptilian relationships for turtles hypothesized by Laurin & Reisz (1997) and Lee (1997), respectively, nor for the hypothesis that captorhinid eureptiles were most closely related to turtles (Gaffney & McKenna 1979; Gauthier et al. 1988).” Schoch and Sues published a cladogram (Fig. 1)  in which the following taxa could not be resolved:

1. Acerosodontosaurus (swimming diapsid)
2. Kuehneosauridae (gliding lepidosauriforms)
3. Claudiosaurus (swimming diapsid)
4. ‘Pantestudines’ = Eunotosaurus, Pappochelys, Odontochelys, Proganochelys (turtles and turtle mimics)
5. Trilophosaurus + Rhynchosauria + Prolacerta + Archosauriformes (a paraphyletic mix)
6. Squamata + Rhynchocephalia (terrestrial lepidosaurs)
7. Placodus + Sinosaurosphargis + Eosauropterygia (swimming enaliosaurs)

In other words
Schoch and Sues have no idea how these taxa are related to each other. Their data fails to lump and separate 29 taxa completely. They report, “[Papppochelys] shares various derived features with the early Late Triassic stem-turtle Odontochelys, such as T-shaped ribs, a short trunk, and features of the girdles and limbs.” See what I mean about pulling a ‘Larry Martin’? They’re trying to save their hypothesis by listing a few to many traits. Unfortunately Schoch and Sues do not have the data that documents this suite is unique to Pappochelys and turtles. Actually these traits are found elsewhere within the Reptilia and sometimes several times by convergence.

Figure 2. Pappochelys comes to us from several specimens, all incomplete and all disarticulated. These are the pieces of the skull we will use in Photoshop to rebuild the skull. Schock and Sues made a freehand cartoon, a practice that needs to be discouraged. They had the nasals backwards and the lacrimal upside down and labeled a prefrontal. The failed to recognized the quadratojugal. And they changed the squamosal. The postorbital looks to be so fragile that the orbit might instead have been confluent with the lateral temporal fenestra.

Freehand reconstructions
Shoch and Sues created their reconstructions not by tracing bones, but freehand. That never turns out well. They created cartoon bones and modified them to be what they wanted them to be when they could have used Photoshop and real data.

Figure 3. In dorsal view Shoch and Sues compared Pappochelys to Odontochelys and Proganochelys, but deleted the more primitive Eunotosaurus. And it’s easy to see why. Eunotosaurus has wider ribs than its two purported successors. That and the LRT tell you its not a turtle, but a turtle mimic. Note the inaccuracy Schoch and Sues applied to their Odontochelys. The version from ReptileEvolution.com appears in frame 2 of this GIF animation. Since Pappochelys is know from 4 or more scattered and incomplete specimens, we really don’t know how many dorsal ribs it had.

Why didn’t they show Eunotosaurus
(in Fig. 3)? This turtle mimic has wider and more extensive dorsal ribs. That could be one reason. We’re all looking for a gradual accumulation of traits and Eunotosaurus, one of many turtle mimics, does not provide the primitive state.

Figure 4. From two years ago. Pappochelys compared to placodont sister taxa and compared to the Schoch and Sues reconstruction, which appears to have several scale bar errors and underestimated the number of dorsal vertebrae. So few ribs and vertebrae are known for Pappochelys that their order, size and number could vary from that shown here. 

The ‘Probably’ weasel word
Pappochelys is not known from any complete or articulated fossils. Even so Shoch and Sues report, “The vertebral column of Pappochelys comprises probably eight cervical, probably nine dorsal, two sacral, and more than 24 caudal vertebrae.” This is wishful thinking… They should have said ‘unknown’ not ‘probably’.

Dredging up false data to support a diapsid relationship
Schoch and Sues reference Bever et al. (2015) when they show a Eunotosaurus juvenile purportedly lacking a supratemporal and in its place, an upper temporal fenestra. Earlier that ‘missing’ supratemporal was identified as a nearby bump on the cranium of the juvenile.

Gastralia
Turtle ancestors in the LRT have no gastralia. So the origin of the plastron is still not known. According to Schoch and Sues, “The gastralia of Pappochelys are unique in their structure and arrangement.” Unfortunately Palatodonta is only known from cranial remains.    All other proximal relatives in the LRT have slender gastralia, not broad like those in Pappochelys. Some Pappochelys gastralia are laterally bifurcated, similar to the plastron elements in Odontochelys. That’s intriguing, but ultimately yet another Larry Martin trait. What we’re looking for is maximum parsimony, a larger number of traits shared by sister taxa and proximal relatives than in any other taxa.

Scapula
The Pappochochelys scapula is dorsally small and slender, like those of other placodonts and basal enaliosaurs. Shoch and Sues compared it to the basal turtle scapula, which is relatively much larger. Comparable pectoral elements are documented in the outgroups Bunostegos and Sclerosaurus, but these were ignored by Shoch and Sues. We don’t know of any post-crania for the hard shell turtle sister, Elginia, which might or might not have had a Meiolania-like carapace.

Shoch and Sues made some great observations,
but they kept their blinders on with regard to other candidates. A wide gamut analysis really is the only way to figure out how taxa are related to one another. Hand-picking traits and cherry-picking a small number of taxa is not the way to understand turtle origins. However, once relationships are established and all purported candidates are nested in a large gamut analysis, THEN it’s great to describe and compare how various parts of verified sister taxa evolved.

The LRT
nests turtles with pareiasaurs. Hardshell turtles arise from the mini-pareiasaur Elginia to Niolamia. Softshell turtles arise from the mini-pareiasaur Sclerosaurus to Odontochelys. Pappochelys nests with Palatodonta at the base of the Placodontia.

References
Bever GS, Lyson TR, Field DJ and Bhular B-A S 2015. Evolutionary origin of the turtle skull. Nature published online Sept 02. 2015.
Schoch RR and Sues H-D 2017. Osteology of the Middle Triassic stem-turtle
Pappochelys rosinae and the early evolution of the turtle skeleton. Journal of Systematic Palaeontology DOI: 10.1080/14772019.2017.1354936

Tulerpeton restoration

A reconstruction
puts the in situ bones back into their in vivo places.

A restoration
imagines the bones and soft tissues that are missing from the data. Adding scaled elements from a sister taxon is usually the best way to handle a restoration as we await further data from the field.

Figure 1. Tulerpeton restored based on the bauplan of Silvanerpeton and to the same scale.

We looked at
Tulerpeton, the Upper Devonian taxon known chiefly from its limbs, earlier. I reconstructed the limbs several ways, but did not attempt a restoration. Here (Fig. 1) that oversight is remedied based on the bauplan of Viséan sister, Silvanerpeton, also nesting at or near the base of the Reptilia (only amnion-layered eggs determine reptile status).

Among the overlapping elements,
in Tulerpeton the pectoral girdle and forelimbs are larger. An extra digit is present laterally.

References
Clack JA 1994. Silvanerpeton miripedes, a new anthracosauroid from the Visean of East Kirkton, West Lothian, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences 84 (for 1993), 369–76.
Coates MI and Ruta M 2001 2002. Fins to limbs: What the fossils say. Evolution & Development 4(5): 390–401.
Lebedev OA 1984. The first find of a Devonian tetrapod in USSR. Doklady Akad. Navk. SSSR. 278: 1407–1413.
Lebedev OA and Clack JA 1993. Upper Devonian tetrapods from Andreyeva, Tula Region, Russia. Paleontology36: 721-734.
Lebedev OA and Coates MI 1995. postcranial skeleton of the Devonian tetrapod Tulerpeton curtum Lebedev. Zoological Journal of the Linnean Society. 114 (3): 307–348.
Mondéjar-Fernandez J, Clément G and Sanchez S 2014. New insights into the scales of the Devonian tetrapods Tulerpeton curtum Lebedeve, 1984. Journal of Vertebrate Paleontology 34:1454-1459.

wiki/Silvanerpeton
wiki/Tulerpeton

There’s nothing special about Henosferus

The incisors are not too big
or weird or crowded (Fig. 1), the canine just rises above the rest of the teeth, there are only 5 premolars all standard-shaped, and only three molars, all standard-shaped. The dentary definitely formed the main jaw joint and the post-dentary bones must have been tiny.

Figure 1. Henosferus mandible restored by Rougier et al. 2005 from several broken specimens.

…and that’s why
Henosferus ( Rougier et al. 2007; Middle Jurassic) makes a good candidate for basalmost mammal. There are too few traits here to add it to the large reptile tree (LRT). Frankly, I’m eyeballing this restoration. It compares well with Juramaia (Fig. 2) without the odd molars and incisors. 

Figure 2. Juramaia (Late Jurassic, 160 mya) is more completely known and nests between monotremes and therians (marsupials + placentals).

Henosferus is traditionally considered
a member of the Australosphenida, a group of mammals that include monotremes, and other taxa known chiefly from scraps. Vincelestes sometimes makes this list, but in the LRT it nests as a carnivorous marsupial.

References
Luo Z-X, Yuan C-X, Men Q-J and JiQ 2011. A Jurassic eutherian mammal and divergence of marsupials and placentals. Nature 476: 442–445. doi:10.1038/nature10291.
Rougier, GW, Martinelli AG, Forasiepi AM and Novacek M J 2007. New Jurassic mammals from Patagonia, Argentina : a reappraisal of australosphenidan morphology and interrelationships. American Museum novitates, no. 3566. online here.

wiki/Juramaia
wiki/Henosferus

You heard it here first: Chilesaurus is a basal ornithischian confirmed.

Figure 1. Chilesaurus and kin, including Damonosaurus and basal phytodinosauria.

Figure 2. Look familiar? Here are the pelves of Jeholosaurus and Chilesaurus compared. As discussed earlier, this is how the ornithischian pelvis evolved from that of Eoraptor and basal saurorpodomorpha.

A new paper by Baron and Barrett 2017 confirms Chilesaurus (Fig. 1) as a basal member of the Ornithischia, not a bizarre theropod. As long time readers know, this was put online two years ago (other links below) in this blog.

Unfortunately, the authors don’t have an understanding of the interrelationships of phytodinosaurs, even though they report, “For example, Chilesauruspossesses features that appear ‘classically’ theropod-like, sauropodomorph-like and ornithischian-like…” Nor did they mention the sister taxon, Jeholosaurus (Fig. 2).

Remember,
discovery only happens once.
More on this topic later.

This note went out this morning:
Thank you, Matthew,
for the confirmation on Chilesaurus.
In this case, it would have been appropriate to include me as a co-author since I put this online two years ago.

https://pterosaurheresies.wordpress.com/2015/04/28/chilesaurus-new-dinosaur-not-so-enigmatic-after-all/
http://www.reptileevolution.com/reptile-tree.htm
http://www.reptileevolution.com/chilesaurus.htm

References
Baron MG, Barrett PM 2017. A dinosaur missing-link? Chilesaurus and the early evolution of ornithischian dinosaurs. Biol. Lett. 13: 20170220. http://dx.doi.org/10.1098/rsbl.2017.0220 pdf online

Best regards,