Longisquama wings

Everyone agrees
that the anterior half of Longisquama is known because it is plainly visible. Everyone agrees that a pair of forelimbs is visible. Sharov (1970) illustrated fingers, but was stymied from completing that task because the two hands are preserved one on top of the other with the fingers intermingled. You can see that chaotic preservation here.

DGS
(digital graphic segregation) is a useful method to segregate one Longisquama hand from another and fingers from one another. Once that is done, phalangeal lengths can be matched for validity and accuracy. Ultimately a reconstruction can be produced (Fig. 1). It is readily apparent that the in situ chaos as preserved is difficult to trace, but not impossible. Anyone can do it with enough resolution and patience.

Figure 1. Longisquama left and right manus traced using DGS then reconstructed (below). This is a very large hand for a fenestrasaur and manual digit 4 is oversized, as in pterosaurs.

Figure 1. Longisquama left and right manus traced using DGS then reconstructed (below). This is a very large hand for a fenestrasaur and manual digit 4 is oversized, as in pterosaurs. Yes, membranes are preserved trailing the manus, just as plumes and other membranes are preserved elsewhere.

The importance of overcoming a chaotic preservation
to retrieve an orderly reconstruction is well illustrated by this example (Fig. 1). The fact that corresponding phalanges on both hands are equal in length self-validates the tracing. Here the phalanges are numbered and their images were copied and pasted to produce the reconstruction. Also note the shapes of the scapula and coracoid, perfect for flapping. There’s a nice sternal complex in there too. Only fenestrasaurs, including pterosaurs, have those.

The size of the manus,
relative to the humerus and antebrachium, the proportions of the phalanges, the presence of a trailing membrane and of preaxial carpals (including a pteroid) all indicate a close relationship to pterosaurs and other fenestrasaurs. No other tetrapods share these traits.

Figure 2. Click to animate. Longisquama flapping and wagging its tail.

Figure 2. Click to animate. Longisquama flapping and wagging its tail.

Scientists have been looking
for a non-flying reptile with large hands that could be a pterosaur ancestor. This is it (fig. 2), only the fingers are a little curled up and relative to the torso the entire forelimb is short, as in the sister to Longisquama, Sharovipteryx.

References
Peters D 2000.
 A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Sharov AG 1970. A peculiar reptile from the lower Triassic of Fergana. Paleontologiceskij Zurnal (1): 127–130.

Reconstructing Sharov’s Longisquama

My detractors often point to my discovery of the second half of Longisquama as pure fantasy.

So let’s pretend
that the back half of Longisquama was never present in the fossil. Pretend, like Jimmy Stewart in a Wonderful Life, that I was never born.

Now the onus
goes back to all the pterosaur workers who still refuse to examine the very pterosaurian traits of Longisquama, as traced by Sharov (1970, Fig. 1). Those traits are still there, whether I point them out or not.

Figure 1. Longisquama as traced by Sharov 1970. Workers have been searching for the predecessor of pterosaurs. Why didn't they look here?

Figure 1. Click to enlarge. Longisquama as traced by Sharov 1970 above, reconstructed below using DGS to move Sharov’s lines around. Workers have been searching for the predecessor of pterosaurs. Why don’t they look here? According to Sharov Longisquama has a sternal complex (he saw the displaced, fused clavicles, but not the sternum they rimmed), antorbital fenestra, long 4th finger (the actual 4th finger is much longer) and membranes trailing the forelimbs, not to mention a strap-like scapula and elongate coracoid. What more could you want? Alongside, not to scale, long-necked Sharovipteryx and short-necked MPUM6009, a basal pterosaur. Yellow displaced “plumes” are actually the tibia and femur, so the hind legs have been seen, just misidentified.  Those two bumps on the head are really a displaced parietal rimming upper temporal fenestrae. A little more resolution would clear this up.

So many fantasy creatures
have been built around the idea of Longisquama (just Google it), but no one has taken Sharov’s blueprint and put the bones back into their in vivo positions — until now (Fig. 1). When you repeat this experiment, you will also get something that can be input into phylogenetic analysis. And the rest (the blue areas) can be guesstimated based on phylogenetic bracketing. Almost all other artists put much smaller hind limbs on Longisquama, but that’s not what close relatives have (Fig. 1).

Like a basal pterosaur Longisquama has this suite of characters:

  1. an antorbital fenestra
  2. a large orbit
  3. multicusped teeth
  4. short neck (eight cervicals)
  5. 9th vert has short rib, 10th vert has rib that contacts sternal complex
  6. strap-like scapula
  7. narrow coracoid
  8. sternal complex (clavicles wrapped around sternum + interclavicle)
  9. parallel ulna and radius
  10. asymmetric manus with short digit 5
  11. structured membrane trails forelimb (proto-wing)
  12. small membrane precedes forelimb (proto-propatagium)

Everything else we’ll call guesswork
based on phylogenetic bracketing, which is, by definition, extremely conservative. Phylogenetic bracketing gives Longisquama long hind limbs, uropatagia, an attenuated tail and a short mt5 + elongated p5.1, just like it’s sisters.

Sharov’s traits alone
are enough to call this specimen out as the best candidate for pterosaur kinship — and yet — it’s been ignored and dismissed for forty years — even with that PR bump in 2000 and 2002. With such data widely available, does anyone else think it is very odd that professionals who write pterosaur books (Wellnhofer, Witton and Unwin) and other professors (Bennett, Padian, Hone, etc. etc.) claim we don’t know the ancestry of pterosaurs? Or am I the only one who finds this odd and unsettling?

I can understand why they would ignore me, a published amateur widely despised and ridiculed. But why ignore Sharov?

Evidently it’s a mind set.
And it’s hard to break, even with Sharov’s own images. He saw what I saw. I just added details.

New tracings of Longsiquama

Figure 2. Click to enlarge. New tracings of Longsiquama (B) soft tissues and (C) bones.

If you want to learn more details about the Longisquama fossil, find them here.

 

Figure 3. Click to enlarge. If you still don't like Longisquama, there's more where that taxon came from. Any one of these will nest closer to pterosaurs than any archosauromorph. Here's Kyrgyzsaurus to scale alongside other basal fenestrasaurs, Cosesaurus, Sharovipteryx and Longisquama. Kyrgyzsaurus likely was a biped with long legs. We know from the shape of its coracoids that it was a flapper.

Figure 3. Click to enlarge. If you still don’t like Longisquama, there’s more where that taxon came from. Any one of these will nest closer to pterosaurs than any archosauromorph. Here’s Kyrgyzsaurus to scale alongside other basal fenestrasaurs, Cosesaurus, Sharovipteryx and Longisquama. Kyrgyzsaurus likely was a biped with long legs. We know from the shape of its coracoids that it was a flapper.

References
Bennett SC 2008. Morphological evolution of the forelimb of pterosaurs: myology and function. Pp. 127–141 in E. Buffetaut & D.W.E. Hone (eds.), Flugsaurier: pterosaur papers in honour of Peter Wellnhofer. Zitteliana, B28.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Senter P 2003. Taxon Sampling Artifacts and the Phylogenetic Position of Aves. PhD dissertation. Northern Illinois University, DeKalb, IL, 1-279.
Senter P 2004. Phylogeny of Drepanosauridae (Reptilia: Diapsida) Journal of Systematic Palaeontology 2(3): 257-268.
Sharov AG 1970. A peculiar reptile from the lower Triassic of Fergana. Paleontologiceskij Zurnal (1): 127–130.

The Passing of Larry Martin, curator, U of Kansas

Larry Martin, paleontologist and curator at the University of Kansas, died recently. Famously, he was a staunch opponent of the birds are dinosaurs hypothesis and was equally famous for saying, “Show me one character that unites birds with dinosaurs!” Larry could always tell you that whatever trait you could think of was also present in another non-dinosaur taxon. In his mind that dissolved your argument. He never seemed to understand it takes a suite of traits, the famous “most parsimonious” placement, that phylogenetic analysis works on, not “one character.” Convergence is so rampant in the Reptilia that a single trait can often be found elsewhere for any taxon.

Even so, Larry was a friendly and outgoing man who always had time to talk in conventions. He appeared on several dinosaur-related TV shows, including the “Four-winged dinosaur” Nova program on Microraptor.

Martin signed Chris Bennett’s PhD dissertation and he had dozens of other students and KU colleagues over the years.

Martin’s reconstruction of Longisquama can be seen here and a model can be seen below. Caption and photo from the Lawrence Journal-World. The model of Longisquama, unfortunately, is totally inaccurate. It’s okay to be a contrarian, like Larry Martin, but you better have great evidence.

Kansas University graduate student Robert Elder holds a model of a longisquama, a feathered reptile that may predate dinosaurs. David Burnham, left, and Larry Martin, curator of vertebrate paleontology, look on. The model is part of a future display about the birth of flight.

Kansas University graduate student Robert Elder holds a model of a longisquama, a feathered reptile that may predate dinosaurs. David Burnham, left, and Larry Martin, curator of vertebrate paleontology, look on. The model is part of a future display about the birth of flight.

I’m glad I met Larry Martin. He will be missed.

https://www2.ljworld.com/news/2013/mar/12/late-ku-paleontologist-martin-brought-prehistoric/

The metatarsus of Longisquama revealed by DGS

Buchwitz and Voigt (2012) reexamined Longisquama’s plumes and determined that they were indeed attached to the dorsal spine (and therefore not coincidental plant material). The closeup photo they provided of purported plume bases is worth discussing, for several reasons.

From Buchwitz and Voigt (2012) purported to be the bases of three dorsal appendages. Actually these are metatarsals.

Figure 1. From Buchwitz and Voigt (2012) purported to be the bases of three dorsal appendages. Actually these are metatarsals 1-3. See figure 2. Their alignment with the vertebrae is, at best, imprecise. The actual plume bases (fig. 2) are below these hollow bony elements. The parallel lines in the upper right corner are aktinofibrils supporting the detached uropatagium.

Difficult to interpret!
Especially when cropped so closely (fig. 2), one set of Longisquama metatarsals is identified here. There are phalanges extending from the tips of these metatarsals (Fig. 4), as well as plumes. The actual plumes (green) are behind (below) these metatarsals. These match the size and proportions of the other metatarsals of Longisquama (fig. 4) and those of sister taxa (fig. 3).

Figure 2. Click to enlarge. Reinterpretation of the bases of the dorsal plumes of Longisquama. These are metatarsals. On the right you'll see those fine parallel lines representing the aktinofibrils of a detached uropatagium (one of two, of course).

Figure 2. Click to enlarge. Reinterpretation of the bases of the dorsal plumes of Longisquama. These are metatarsals 1-4. On the right of each picture you’ll see those fine parallel lines representing the aktinofibrils of a detached uropatagium (one of two, of course), as in Sharovipteryx. DR = displaced dorsal ribs. Ti = tibia (see Fig. 4 for the whole picture).

They’re not plume bases
These elements are aligned with the plumes, but not exactly. And they increase in length laterally. And they overlap. And they have phalanges emanating from them. And they match another set of nearby metatarsals (fig. 4). They’re metatarsals. Take them ‘as is’ and put them into a reconstruction (fig. 3) and you get a nice transition and match between Sharovipteryx and MPUM6009, a basal pterosaur, the phylogenetically bracketing taxa. Longisquama demonstrates how p5.2 and p5.3 merged to become one phalanx in basal pterosaurs. All the PILs (parallel interphalangeal lines) align.

longisquama-foot588

Figure 3. The foot of Longisquama based on the DGS tracing, shares traits with both Sharovipteryx and MPUM6009.

The big picture (click fig 4 to enlarge) tells the tale. The front of Longisquama is undisturbed. So is the tail. It’s the middle that became twisted. That’s why the feet ended up over the vertebral column. The fossil looks like a big post-mortem gas bubble in its belly exploded, or scavengers focused on the soft guts before burial.

Longisquama in situ with metatarsals in color.

Figure 4. Click to enlarge. Longisquama in situ with metatarsals and ribs framed by figure 2 in color. Yes, they are aligned with the bases of the plumes, but also with  the bases of phalanges.

Enlargements of the tracings can be found here.

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
New Scientist article here
Buchwitz M and Voigt S 2012. The dorsal appendages of the Triassic reptile Longisquama insignis: reconsideration of a controversial integument type. Paläontologische Zeitschrift, Issue 3, pp 313-331

The Back Half of Longisquama Recovered by Phylogenetic Bracketing

The back half of Longsiquama is so difficult to see that all prior experts took Sharov’s (1970) word for it, accepting his observation that the back half was missing. I’ll admit (and you’ll see) that even when the parts are delineated and labeled (Fig. 1), it’s hard for the eye to “see” what’s going on here. Skin, hair, membranes, plumes and scales are everywhere and just make the job more difficult. Only DGS (digital graphic segregation) enables one to pick out the crushed (and I do mean CRUSHED) outlines of the formerly missing parts.

New tracings of Longsiquama

Figure 1. Click to enlarge. New tracings of Longsiquama soft tissues and bones digitally segregated. Black squares are for alignment.

Be that as it may…
Let’s assume the back half isn’t there… for argument’s sake. No problem. Believe it or not, there is another way to figure out what the back half of Longisquama looks like without resorting to actually tracing the parts. This method gives strong clues, but without providing 100% assurance. And it’s called…

Phylogenetic Bracketing
Take the more primitive related taxon (Sharovipteryx) and the more derived related taxon (MPUM6009) and see what they do and don’t have in common. The taxon in the middle, Longisquama, should share most of the traits that both of these taxa share. Phylogenetic bracketing can be used to imagine a transitional taxon that we haven’t discovered yet. However, we’re at an advantage with Longisquama. We already know what the skull, forelimbs and upper torso look like. So, here’s where we’ll start (Fig. 2):

 

Figure 2. Origin of pterosaurs and figuring out the back half of Longisquama through phylogenetic bracketing. Gray areas are in question because others have not yet seen them on the slab.

Figure 2. Origin of pterosaurs and figuring out the back half of Longisquama through phylogenetic bracketing. Gray areas are in question because others have not yet seen them on the slab.

Traits shared by Sharovipteryx and MPUM6009 (and therefore likely present in the purportedly missing back half of Longisquama) include the following:

  1. short torso, shorter than or subequal to femur – this trait is actually not present in  Longisquama (Fig. 1), which has a uniquely longer, lemur-like torso, better for leaping than gliding
  2. bipedal configuration (relatively shorter fore limbs than hind limbs)
  3. four or more sacrals
  4. long, attenuated tail with chevrons parallel to centra
  5. elongated anterior ilium
  6. prepubis
  7. femur at least twice as deep as torso
  8. tibia longer than femur
  9. tibia more than twice the length of the pes
  10. simple hinge ankle joint between proximal tarsals (astragalus and calcaneum) and distal tarsals (principally the centralia and distal tarsal 4, but distal tarsal 3 is sometimes present and smaller)
  11. metatarsals increase in length from 1 to 4, but mt5 is less than a quarter of mt4
  12. feet relatively small – this trait is not present in the actual Longisquama, which has larger feet than either sister
  13. pedal digits increase in length from 1 to 5, but p.5.1 is subequal to mt4 in length and and p5.2 is hyperflexed.
  14. uropatagia present

So, add it all up and you get pretty much what I found in Longisquama, sans the torso length, which is uniquely long and lemur-like in Longisquama, and sans the foot size, which is uniquely larger in Longisquama. All prior reconstructions of Longisquama missed the long torso, long hind limbs, pterosaur like pedal digit 5 and attenuated tail. Instead authors imagined a shorter legged, shorter torso, more typically basilisk-like back half, but then none of them imagined that Longisquama was phylogenetically bracketed by Sharovipteryx and pterosaurs with a common ancestor in Cosesaurus.

Then we take the opposite tack: 
Traits that are distinctly different between the bracketing taxa, Sharovipteryx and MPUM6009, include the following:

  1. relative skull size – skull is small in both Sharovipteryx and Longisquama
  2. relative neck length – neck is short in both MPUM6009 and Longisquama
  3. pectoral girdle size – girdle is small in both Sharovipteryx and Longisquama
  4. forelimb size – midway between the vestigial fore limbs of Sharovipteryx and hyper elongated fore limbs of MPUM6009.
  5. The pelvis – was deep with ilial processes diverging at right angles in Longisquama and MPU6009

Dorsal plumes are distinct only on Longisquama
Dorsal plumes, which are secondary sexual traits (not gliding tools), along with the other extradermal membranes (originating with Cosesaurus), were but part of the package when wings developed in Longisquama and pterosaurs to enhance whatever mating ritual was going on with leaps, flapping and extravagant showing off. Matrix impressions indicate that smaller dorsal plumes were also present on MPUM 6009 (fig. 1), the basalmost pterosaur and the one with the longest hind limbs and shortest forelimbs.

Missing from this discussion is Cosesaurus
…which nests as a common ancestor for Sharovipteryx, Longisquama and pterosaurs in that phylogenetic order. The skull, neck and torso proportions of Cosesaurus are closer to pterosaurs than to either Longisquama or Sharovipteryx that diverged along their own morphological directions.

Current interpretation of Cosesaurus.

Figure 2. Current interpretation of Cosesaurus. Note the proportions of the skull, neck and torso are closer to pterosaurs than to either Sharovipteryx or Longisquama.

Inherited traits
Given that Sharovipteryx, Longisquama and pterosaurs (Fig. 2) shared a common ancestor, like Cosesaurus (sharing a quadrant-shaped coracoid, pteroid, sternal complex, antorbital fenestra (without fossa), prepubis, anteriorly extended ilium, 4 or more sacrals, an attenuated tail, elongated p5.1, etc. etc,)… we cam expect than Longisquama shared these traits by inheritance, giving further clues to the back half of Longisquama.

So, even if the back half of Longisquama were NOT present on the slab, the reconstruction  would look much the same, but with a smaller foot and shorter torso than presented here (fig. 1) based on tracing these elements. The manual fingers were also larger on Longisquama. So, phylogenetic bracketing validates the DGS tracings, but the tracings also revealed certain traits not revealed by phylogenetic bracketing. So, there was no “cheating” here, deciding what to trace prior to tracing it on the specimen.

Tomorrow I’ll show you a close-up of four Longisquama metatarsals that were mistaken for plume bases, which they align with.

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.

The origin and evolution of Longisquama “feather-like structures”

 

Figure 1. Click to enlarge. The origin and evolution of Longisquama's "feathers" - actually just an elaboration of the same dorsal frill found in Sphenodon, Iguana and Basiliscus. Here the origin can be found in the basal tritosaur squamate, Huehuecuetzpalli and becomes more elaborate in Cosesaurus and Longisquama.

Figure 1. Click to enlarge. The origin and evolution of Longisquama’s “feathers” – actually just an elaboration of the same dorsal frill found in Sphenodon, Iguana and Basiliscus. Here the origin can be found in the basal tritosaur squamate, Huehuecuetzpalli and becomes more elaborate in Cosesaurus and Longisquama.

A year ago
New Scientist covered a new paper on the dorsal appendages of Longisquama (Buchwitz and Voigt 2012) who wrote in his abstract, “We explain the existing feather similarity by their development from a filamentous primordium and a complex sequence of individual processes, some of which are reminiscent of processes observed in feather development. Such an interpretation is in agreement with a set of homologous mechanisms of appendage morphogenesis in an archosauromorph clade including Longisquama and feather-bearing archosaurs but does not necessarily require that the appendages of Longisquama themselves are feathers or high-level feather homologues.”

Here a larger and more parsimonious phylogenetic analysis
nests Longisquama with fenestrasaur, tritosaur squamates, derived from sisters to Huehuecuetzpalli and Cosesaurus (Fig. 1). With this lineage the origin and the development of the single line of dorsal plumes becomes easy to visualize. They were small originally and, through evolution, became enlarged. Among living reptiles, the tuatara (Sphenodon) and the iguana (Iguana) bear similar and homologous small structures.

Buchwitz reported in New Scientist, “The strange skin appendages of Longisquama are neither scales nor feathers,” says Michael Buchwitz of the Freiberg University of Mining and Technology, Germany. “They are perhaps linked to the early evolution of dino and pterosaur fuzz, though. Longisquama‘s skeleton is too incomplete to work out its exact evolutionary position, but Buchwitz says the little reptile was probably part of the lineage that gave rise to pterosaurs, crocodiles, dinosaurs and birds. Many of these groups later evolved their own skin appendages, including filaments on pterosaur wings, quills on the tails of some plant-eating ornithischian dinosaurs, and the proto-feathers of theropod dinosaurs. Longisquama shows that evolution was experimenting with the genes that gave rise to feathers long before any of these animals appeared on the scene.”

Tomorrow we’ll take a close look at the metatarsus of Longisquama courtesy of Buchwitz and Voigt (2012).

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
New Scientist article here
Buchwitz M and Voigt S 2012. The dorsal appendages of the Triassic reptile Longisquama insignis: reconsideration of a controversial integument type. Paläontologische Zeitschrift, Issue 3, pp 313-331

The skull of Longisquama documented

Yesterday we looked at the sternal complex and pectoral girdle of Longisquama (Sharov 1970). Today we’ll look at the controversial skull. Like the shoulder region, the skull is also covered in skin and scales and maybe… could those be long strands of ptero-hairs (pycnofibers) around the neck? You tell me. If you haven’t bought into the rest of the homologies I presented earlier, you won’t buy into the integumentary homologies. (sigh)

The skull of Longisquama in situ.

Figure 1. The skull of Longisquama in situ. The premaxilla and anterior dentary are largely missing. Otherwise crushing has shifted all the elements, even the transverse palatal and parietal elements, to the parasagittal plane (see figure 2). Also, note the sclerotic ring always gets crushed into the plane of the disk, never, as Bennett (2007) mistakenly reports in his anurognathid, on edge. Sharp-eyed observers should be able to see the windpipe.

In situ the overall shape of the skull is apparent, as are the scleral rings and teeth. For me the antorbital fenestra is clearly visible, though covered with tendrils of integument and underlain with palatal elements (Fig. 2), but for other workers, Like Senter, it is not so apparent, but note his lack of detail (Fig. 2). Note the rich crest of soft tissue arising from the frontals, which produces the longest overlooked plume, along with the gular sac in the throat region.

Do you see an antorbital fenestra? Several, but not all prior workers join you if so.

The skull of Longisquama has portrayed by other workers and as documented here.

Figure 2. The skull of Longisquama has portrayed by other workers and as documented here. The parietal is rotated, giving the impression of two crests. The occiptal region is folded in like a playing card. The antorbital fenestra reveals rotated palatal elements as shown in the reconstruction. Note the more or less cartoony aspects of the prior reconstructions, all lacking the precision and detail of the present tracing (produced with DGS) and the reconstruction, which puts the elements back together in three dimensions with a minimum of distortion.

Yes, the skull is messy,
and skin/scales/fibers obscure much, but the skull is largely complete. A reconstruction of the elements recovers a very pterosaur-like skull that also harkens back to the skull of the ancestral Cosesaurus. Some of the teeth are multicusped. The orbit is large. The palatal view suggests that Longisquama may have enjoyed binocular vision with that narrow snout and wide cranium. Such vision would have been appropriate for a lemur-like leaping reptile, however this is not a trait that basal pterosaurs inherited. The rotated parietals produce the illusion of a double crest, but the reconstruction removes the illusion. The rotated occipital bones help determine the width of the skull. Prior workers did not put the crash scene back together again, but took appearances as is, ignoring the occipital bones, and others. The vestigial quadratojugal extends from the jugal toward the quadrate without making a firm connection to it, again, as in pterosaurs and kin going back to Macrocnemus.

*
I did not put my earlier published interpretations (Peters 2000, 2002) of Longisquama here because they have been shifted to my trash pile in favor of this interpretation, produced with more understanding and a better eye for what lurks there. If anyone wants to talk about how I reconstruct Longisquama, do not rummage through my trash as Darren Naish did in last year’s critique. This is the most recent work. This would have been published several years ago, but reviewers blackballed it for the usual reasons.

If – just – the skull or – just – the skull and forequarters were known,
Longisquama would still nest with Cosesaurus, Sharovipteryx, Kyrgyzsaurus and basal pterosaurs. The rest of the anatomy cements those relationships.

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.

For those interested, PterosaurHeresies gets between 200 and 400 hits per day with about half that many unique visitors. The Lesothosaurus is a rhynchosaur post stands out as a recent exception with twice those numbers.

References
Sharov AG 1970. A peculiar reptile from the lower Triassic of Fergana. Paleontologiceskij Zurnal (1): 127–130.

wiki/Longisquama

Longisquama Pectoral Girdle and Sternal Complex Documented

In my efforts to help explain the relationship of the lepidosaur tritosaur fenestrasaur, Longisquama (Sharov 1970) to basal pterosaurs I present a pair of images (Figs. 1, 2) designed to illustrate just where the pectoral elements are. Admittedly these elements are difficult to pick out at first glance. So these are for those naysayers who often say, “I can’t see what you’re seeing!!” Here’s why:

Longisquama in situ. See if you can find the sternal complex, scapula and coracoid before looking at figure 2 where they are highlighted.

Figure 1. Click to enlarge. Longisquama in situ. See if you can find the sternal complex, scapula and coracoid before looking at figure 2 where they are highlighted.

The trouble
with seeing the bones of Longisquama is they are largely covered with scales and skin. That’s just a fact we need to embrace. Longisquama has more dermal and extra dermal tissue preserved than most other Mesozoic fossils. In such cases DGS (digital graphic segregation) really becomes a powerful tool, finding bones beneath the skin.

 

Figure 2. Click to enlarge. Longisquama ghosted out with DGS, other than the sternal complex (interclavicle+clavicles + sternum), scapula and coracoid.

Figure 2. Click to enlarge. Longisquama ghosted out with DGS, other than the sternal complex (interclavicle+clavicles + sternum), scapula and coracoid.

Here the affinities with pterosaurs are quite clear
Everyone has seen the horse-shoe-shaped clavicles, but few have recognized that they overlap medially and frame the sternum AND are surmounted by keeled interclavicle with crossbars that accommodate the quadrant-shaped ventral coracoids. (Whew!) This is the standard morphology of the classic pterosaur sternal complex (Wild 1993). Even the overall shape is identical to that in the basal pterosaur, MPUM6009 (Fig. 3). Only the fenestrasaurs, Cosesaurus, Sharovipteryx and pterosaurs share all these traits. In most derived pterosaurs the stem of the coracoid does indeed straighten out more, if you’ve noticed the difference.

Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex.

Figure 3. Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex. The quadrant-shaped coracoid is the remnant and result of the anterior fenestra of the coracoid enlarging to the posterior rim, which is the only part that remains.

Still finding it difficult to spot some of these elements?
Then I encourage you to more closely examine the specimen itself or high resolution photos and become acquainted with sister taxa that will prepare you for what you should be looking for. I know that sounds self-fulfilling, but if you know that most tetrapods have four limbs you don’t stop at three. It’s the same thing at this point. Also see this page on ReptileEvolution.com for the same images of Longisquama (Figs. 1, 2) presented on a mouseover.

Flapping
Earlier we discussed the evolution of the sternal complex and pectoral girdle in fenestrasaurs (Fig. 3) and its role in flapping on a bipedal frame. That’s why these elements are so distinctly shaped, approaching the morphology of birds by convergence. The coracoid no longer slides against the interclavicle and sternum as in more primitive quadrupedal lizards.

Front Half Only
Even if only the front half of Longisquama was known (Sharov, 1970; Fig. 1), this would still be enough to cement Longisquama to pterosaurs. Adding the back half and fingers just puts frosting on the cake.

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
Sharov AG 1970. A peculiar reptile from the lower Triassic of Fergana. Paleontologiceskij Zurnal (1): 127–130.
Wild R 1993. A juvenile specimen of Eudimorphodon ranzii Zambelli (Reptilia, Pterosauria) from the upper Triassic (Norian) of Bergamo. Rivisita Museo Civico di Scienze Naturali “E. Caffi” Bergamo 16: 95-120.

wiki/Longisquama

Pterosaurs landing in trees – part 3 – Longisquama

Earlier we demonstrated pterosaurs grappling tree trunks and perching on tree branches. Today we’ll report on the origin of this behavior in Longisquama (Fig. 1).

Figure 1. Longisquama on a tree trunk.

Figure 1. Longisquama on a tree trunk.

My What Long Fingers You Have Grandma!
The origin of tree clinging likely occurred in sister to Longisquama, the current outgroup for the Pterosauria. The fingers of Longisquama were larger than those of any pterosaur. Fingers one through three and five became smaller as the wing finger, #4, became larger.

The PILs Have Something to Say
In Longisquama the PILs of manual digit 4 were not aligned with those in digits 1-3. This indicates they no longer worked as a set and that metacarpal 4 + digit 4 likely were rotated into the plane of the wing, as in pterosaurs. This means, like pterosaurs, Longisquama was able to flex (or hyperflex) digit 4 in the plane of the wing and while clinging to trees, the wing would have created yet one more display trait, opening and closing tangential to the diameter of the tree trunk. Pterosaurs emphasized the wings and de-emphasized the dorsal frill.

Short Arms
The relatively short arms of Longisquama meant that the long legs had to crouch more, which created a pre-loaded spring ready to release for the next leap/glide. The arms lengthened in pterosaurs.

Finger 4 – Not Quite Ready for Flight, but Great Looking!
Before finger 4 became large enough to support gliding and flapping flight it served as yet ANOTHER decoration on Longisquama, already at no shortage for display traits. As in pterosaurs, finger four was free to flex in the plane of the wing, on a tangent to the diameter of the tree (Peters 2002). I did not realize at the time of that publication how large the fingers of pterosaur predecessors, like Longisquama, had become.

New discoveries bring new insights.

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
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.

The Evolution of the Pterosaur Palate – part 1

Not much attention has been paid to the pterosaur palate.
Ever since Williston (1902) and continuing through Huene 1914, Wellnhofer (1978, 1991) and Bennett (1991, 2001a,b), the solid palatal plate in pterosaurs has been considered the palatine (Fig. 1). That’s the tradition and that’s the paradigm – but that’s wrong.

Scaphognathus palate

Figure 1. Click to enlarge. (Left) The traditional reconstruction of the palate of the pterosaur Scaphognathus (Wellnhofer 1978) in which the palatal shelf is considered the palatine bone. (Right) The heretical and recently vindicated reconstruction of the palate in which the palatine is fused to the ectopterygoid creating a L-shaped bone, the ectopalatine. The medial extent of the maxillary palate shelf is unknown. 

Not the Palatine, the Maxilla!
Virtually ignored, Newton (1888), Seeley (1901 and Woodward (1902) reported that the solid palatal plate was an outgrowth of the maxilla, not the palatine. Unfortunately, I did not know that when I reported (in Peters 2000) that the palatal plate actually originated from the maxilla. (Thought I had discovered something!) The much smaller palatine and ectopterygoid were fused to form a single L-shaped element, the ectopalatine. This was due to an ancestry among fenestrasaurs and Macrocnemus, rather than archosaurs. Even that was largely ignored until…

Reinterpretation and Vindication
Osi et al. (2010) reported, “The hard palate is formed by the extensive palatal plate of the maxilla and not by the palatine as has been generally reconstructed.”  This was well demonstrated by a 3D Dorygnathus skull (Fig. 2).

Palate of the WDC specimen of Dorygnathus

Figure 2. The Osi et al. (2010) WDC 3-D Dorygnathus palate. Click to enlarge. The non-fusion of the palatine and ectopterygoid might have signaled ontogenetic immaturity, but the specimen is half again larger than other Dorygnathus specimens. The original interpretation of the premaxilla was based on the break at mid maxilla, not the sutures, which are revised at right. The purported foramen incisivum is not found in other pterosaurs. It represents missing vomer bone. 

The Origin and Evolution of the Palatal Elements in Basal Pterosaurs
To trace the origin of the palatal elements in pterosaurs we go back to Lacertulus, a basal tritosaur from the Late Permian (Fig. 3. Lacertulus had round wide jaws with large wide elements with no maxillary component.

In Huehuecuetzpalli (Fig. 3) the snout was narrower and so were all the palate elements. In Macrocnemus, narrower still. In Tanystropheus, not so narrow, but the interpterygoid vacuity was narrow. In both of these the palatine barely contacts the ectopterygoid.

In Cosesaurus (Fig. 3) the vomer teeth were probably absent (hidden in the fossil). In Sharovipteryx the ectopterygoid and palatine were both straight and fused. The rostrum in Longisquama was narrowed and the palatal elements were reduced.

The evolution of the pterosaur palate

Figure 3. The evolution of the pterosaur palate from basal tritosaur ancestors. Note the fusion of the palatine and ectopterygoid creating the ectopalatine in adults. The non-fusion of these elements in figure 1 may represent an ontogenetic character. Not sure. Vomers in green. Palatines in blue. Pterygoids in orange. Ectopterygoids in magenta. The latter two elements are fused in Longisquama and most pterosaurs. The medial extent of the maxillary palate processes and the width of the rostral portion of the skull is unknown in specimens exposed in lateral view.

Figure 3. The evolution of the pterosaur palate from basal tritosaur ancestors. Note the fusion of the palatine and ectopterygoid creating the ectopalatine in adults. The non-fusion of these elements in figure 1 may represent an ontogenetic character. Not sure. Vomers in green. Palatines in blue. Pterygoids in orange. Ectopterygoids in magenta. The latter two elements are fused in Longisquama and most pterosaurs. The medial extent of the maxillary palate processes and the width of the rostral portion of the skull is unknown in specimens exposed in lateral view.

In the basal pterosaur, MPUM 6009, the palate did not become so narrow. Like Sharovipteryx, the anterior pterygoid was more robust, forming a “head” and the posterior portion was quite gracile. Other pterosaurs had more gracile palatal elements. A maxilla palatal process leading from the base of the ascending process connects to the palatine portion of the ectopalatine.

The solid portion of the palate
The evolution of the maxillary process of the palate would probably come later in the evolution of pterosaurs (Fig. 1), appearing in Rhamphorhynchus and, by convergence, in Dorygnathus and other pterosaurs derived from this genus or by convergence after Scaphognathus. Due to crushing, etc. the medial extent of the maxilla toward the vomers is difficult to gauge in most Triassic and early to mid-Jurassic pterosaurs, other than anurognathids) which we’ll cover in a future blog.

New Openings?
The new premaxillary openings discovered by Osi et al. (2010) were indeed novel with regard to Dorygnathus, but were also found in Rhamphorhynchus muensteri by convergence (Fig 4). They do not represent vomernasal organs, but are new structures. Only higher scleroglossan lizards have vomernasal openings. No other such openings have been reported in pterosaur ancestors or other pterosaurs. Longisquama (Fig. 2) may have had something similar my convergence (this is educated guesswork). In any case they were secondarily developed in all cases and not related to or pinched off from the choanae.

Various pterosaur palates

Figure 4. Comparing pterosaur palates. Left to right: the new WDC Dorygnathus, Rhamphorhynchus muensteri, Cacibupteryx and Dorygnathus purdoni. The pterygoid extends a process to the jugal in three of these taxa, but such a process is otherwise rare in pterosaurs.

The Fragile Stem-like Portion of the Palate
As the maxillary portion of the palate expanded, the posterior elements (palatine and ectopterygoid) become more or less smaller in all pterosaurs (Fig. 4). More later on these derived taxa.

Problems with the Supplementary Material in Osi et al. (2010)
1. Comparisons were only made to archosaurs when in fact no line up of archosaurs documents a gradual increase in pterosaurian characters. They report: “Hone and Benton (2007, 2008) provided new evidence to support the origin of the Pterosauria within Archosauria and we follow their definition here.” Unfortunately, Hone and Benton made their test by omitting the data from Peters, 2000, omitting the two fenestrasaurs closest to pterosaurs and scoring the other two for only a quarter of their available characters. Their so-called ‘test’ was no test at all, but elimination of the competition and a foregone conclusion with only one possible outcome.

Reinterpretation of purported premaxilla in Dorygnathus

Figure 5. Here I reinterpret more bones in this purported premaxilla of the WDC 3-D Doryganthus of Osi et al. (2010). Purple = maxilla. Green = vomer. Pink = nasal.

2. Osi et al. (2010 fig. 3) is a multiview photo of the premaxilla of the new specimen  (Fig. 5). Unfortunately the authors failed to recognize the pmx/mx suture essentially extending from the antorbital fenestra not quite to tooth #4. So a healthy portion of the maxilla is present here laminated to the pmx. The break occurred at the narrowest portion below the naris.

3. The sagittal rdge (SI) in the pmx is the paired, fused, anterior vomers.

4. Considering the proportions of the very elongate premaxilla, longer than in any other Dorygnathus of which I am aware, and as long as the maxilla, this is probably a derivation of Dorygnathus and sufficiently distinct to merit its own genus. I would encourage the authors to erect a new genus and perform a phylogenetic analysis of all known Dorygnathus specimens to confirm the new specimen’s closest relations. There is an unrecognized variety in Dorygnathus that needs to be explored. I don’t think this specimen is basal to any known taxa, which all have a relatively shorter premaxilla.

5. Their figure 9 misidentified the entire broken rostrum of Gnathosaurus as the premaxilla, when it should have included only the first four teeth and a long premaxillary ascending process.

6. Paradoxically, and contra the evidence of their specimen, the hypothetical  reconstructions in their figure 11 separate the palatine from the ectopterygoid, giving each a separate articulation on the pterygoid for no apparent reason, other than following the pattern seen in crocodilians. These two elements were in direct contact and fused in many taxa.

7. Figure 11 also purports to extend the premaxilla in “(B) pterodactyloid pterosaurs” to include over a dozen teeth. This is also wrong. The premaxilla in all pterosaurs includes up to 4 teeth, no more.

8. In their figure 11 the authors should have reconstructed the posterior vomers lateral to the anterior pterygoids, not medial to them. They had it right in their figure 8.

9. The authors ascribe a lateral pterygoid process contacting the jugal to all basal pterosaurs, but this process is restricted to certain Rhamphorhynchus and certain Dorygnathus by convergence.

We’ll look at anurognathid palate tomorrow…

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 1991. Morphology of the Late Cretaceous Pterosaur Pteranodonand Systematics of the Pterodactyloidea. [Volumes I and II]. – Ph.D. thesis, University of Kansas [Published by University Microfilms International/ProQuest].
Bennett SC 2001a, b. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part I and 2. General description of osteology. – Palaeontographica, Abteilung A, 260: 1-153.
Newton ET 1888. On the skull, brain and auditory organ of a new species of pterosaurian (Scaphognathus Purdoni) from the Upper Lias near Whitby, Yorkshire. Philosphoical Transaction of the Royal Society, London 179: 503-537.
Osi A, Prondvai E, Frey E and Pohl B 2010. New Interpretation of the Palate of Pterosaurs. The Anatomical Record 293: 243-258.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Seeley HG 1901. Dragons of the air. An account of extinct flying reptiles. – London, Methuen: 1-240.
Wellnhofer P 1978. Pterosauria. Handbuch der Paläoherpetologie, Teil 19.– Stuttgart, Gustav Fischer Verlag: 1-82.
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs. London, Salamander Books, Limited: 1-192.
Williston SW 1902. On the skull of Nyctodactylus, an Upper Cretaceous pterodactyl. Journal of Geology 10:520–531.
Woodward AS 1902. On two skulls of Ornithosaurian Rhamphorhynchus. Annals of the Magazine Natural History 9:1.