Second egg in Momma Darwinopterus?

Figure 1. Darwinopterus pelvic area in situ.

Figure 1. Darwinopterus pelvic area in situ.

Mrs. T, the AMNH specimen of Darwinopterus (Lü et al. 2011a, Figs. 1-3), preserves a well-defined egg just past her  fossilized cloaca, oddly on top of the tail in ventral view. This is the fourth pterosaur egg recognized by paleontologists. The other three, the IVPP specimen, the JZMP specimen and the MHIN specimen (embryo Pterodaustro), preceded it and preserve embryos with well-defined bones and a bit more leathery eggshell.

Figure 2. Pelvic elements colorized. Red-prepubes. Magenta-femora. Green-ilia. Blues-ventral pelvis. Yellow-vertebrae.

Figure 2. Pelvic elements colorized. Red-prepubes. Magenta-femora. Green-ilia. Blues-ventral pelvis. Yellow-vertebrae.

While trying to colorize the pelvic elements (Fig. 2), I came across a smaller oval that did not leave the body (Fig. 3).

Figure 3. Darwinopterus egg (lower left), and possible egg (upper right). What is it really?

Figure 3. Darwinopterus egg (lower left), and possible egg (upper right). What is it really?

I wondered if it was a younger egg? There’s little reason for this. The eggshell, never substantial even in full term embryos, would not have formed at the early stage this size would represent. And the contents of the egg are mostly goo. Nevertheless, the larger more mature and verified egg, has little more substance than the small one.

So, if anyone out there can help with this  I.D., let me know.

References
Lü J, Unwin DM, Deeming DC, Jin X, Liu Y and Ji Q 2011a. An egg-adult association, gender, and reproduction in pterosaurs. Science, 331(6015): 321-324. doi:10.1126/science.1197323

Looking for the Darwinopterus bits’n’pieces

This is a short trip through DGS using the YH2000 specimen of Darwinopterus (more completed than the holotype, but with a poorly preserved skull, (Lü et al. 2009). Crushed flat and spread eagle, one wonders whether this is a ventral or dorsal view. Without a prominent sternal complex and with such dark bones, it’s hard to tell at first glance (Fig. 1).

Figure 1. Darwinopterus as published in Lu et al. 2009.

Figure 1. Darwinopterus as published in Lu et al. 2009.

The first thing we’ll do is play with the exposure to bring out the bones better (Fig. 2). Now we can see the scape are below the ribs.

Figure 2. Darwinopterus again with pelvic and pectoral regions brightened.

Figure 2. Darwinopterus again with pelvic and pectoral regions brightened.

Next we’ll add a layer in Photoshop and colorize the elements we’re interested in.

Figure 3. Bones colorized. Here the left scapulocoracoid is lavender/purple, the right one is magenta.

Figure 3. Bones colorized. Here the left scapulocoracoid is blue, the right one is magenta. Sternal complex in two parts in yellow. Where is the rest of it? For that matter, where is the right coracoid? I think it has drifted below the left scapula. 

The final step ghosts back the original image to bring out the tracings better. There’s the sternal complex, broken in two and tiny. Maybe parts are missing here. Prepubes in pink. One broken. A few drifted ventral pelvis parts here.

Figure 4. Ghosted image to bring out the tracing better. If bones are broken, you have to find both ends.

Figure 4. Ghosted image to bring out the tracing better. If bones are broken, you have to find both ends. One prepubis in pink is complete. The other is broken in two. I think that’s a right ischium beneath the broken prepubis above and a pubis below the proximal prepubis below. Second sacral has a broken tip. 

 

 

The final step is to apply your tracings to a reconstruction.

Figure 5. In situ and reconstruction of the YH2000 specimen of Darwinopterus.

Figure 5. In situ and reconstruction of the YH2000 specimen of Darwinopterus.

Earlier we looked at Darwinopterus here.

References
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B  (DOI 10.1098/rspb.2009.1603.)

Darwinopterus carpus and another 5th manual digit

I appreciate it when authors provide close-ups of the pterosaur carpus. It gives me a chance to once again document the near universal presence of a vestigial manual digit 5 and other ptero traits missed by other workers.

Figure 1. The carpus of Darwinopterus linglongtaenis. Vesitigial digit 5 is scattered on metatarsal 4. The pteroid articulates in the saddle of the radiale. The preaxial carpal articulates on the first distal carpal now fused to the other distal carpals in a syncopal.

Figure 1. Click to enlarge. The carpus of Darwinopterus linglongtaenis. Vesitigial digit 5 is scattered on metatarsal 4. The pteroid articulates in the saddle of the radiale. The preaxial carpal articulates on the first distal carpal now fused to the other distal carpals in a syncopal.

Here digit 5 is scattered, but all the elements are there. In red: distal carpal 5. In green: metacarpal 5. In blue: two proximal phalanges. In amber: a sharp ungual. This matches the pattern seen in basal fenestrasaurs in which manual digit 5 is not a vestige.

Note the pteroid is located in the saddle of the radiale (Peters 2009) and disconnected from the preaxial carpal (both former centralia, having migrated to the medial wrist, convergent with the mammalian prepollex).

References
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29:1327-1330.
Wang X, Kellner AWA, Jiang S-X, Cheng X, Meng Xi and Rodrigues T 2010
. New long-tailed pterosaurs (Wukongopteridae) from western Liaoning, China. Anais da Academia Brasileira de Ciências 82 (4): 1045–1062. pdf online

wiki/Kunpengopterus

Darwinopterus – Rio Ptero Symposium

The Rio Ptero Symposium (May 2013) produced several interesting abstracts. We’ll look at some of those in the next few days.

An abstract by Unwin and Lü (2013) once again promoted Darwinopterus as the pterosaur transitional taxon between early long-tails and later short-tails. They also continued to promote the unfounded hypothesis of modular evolution, which has not been shown in any other lineage or transitional taxon EVER.

Unfortunately, as we learned earlier, in the large pterosaur tree, Darwinopterus did not nest as a transitional taxon, but as a dead-end taxon, producing no derived descendants (but we’ll review that subject below!). Rather, along with Pterorhynchus, Darwinopterus formed a clade close to Scaphognathus and derived from Jianchangnathus (Fig. 1), derived from basal Dorygnathus specimens. Darwinopterus does not nest near any “pterodactyloid”-grade pterosaurs when you increase the number taxa employed.

The many species within the genus Darwinopterus (Fig. 1) are potentially confusing because they all have a long low skull, closer in proportion to “pterodactyloid”-grade pterosaurs and a long neck. However, these traits are also found in the related Pterorhynchus, Kunpengopterus and Wukongopterus.

Ironically, Kunpengopterus (Fig. 1) does not have a longer skull, but rather a smaller, lower skull. Compare it to the big-headed Scaphognathus or Jianchangnathus. However, the neck is relatively elongated compared to ancestor taxa. And the torso is smaller than the others. So it looks like the skull is bigger.

Darwinopterus had a longer skull on a slightly shorter neck. There were other changes postcranially, but all in line with this particular clade. So nothing special or out of the ordinary here. Certainly nothing presaging “pterodactyloids.”

Figure 1. Click to enlarge. All taxa are to scale with one another. Unwin and Lü note a resemblance between Darwinopterus and Germanodactylus. And that is certainly so, but only by convergence. Phylogenetic analysis indicates a closer relationship between the smaller descendants of Scaphognathus, like no. 12, and Germanodactylus. Arrows indicate phylogenetic order. Here the long neck evolved first with a notably smaller skull. Then the skull became longer and larger in the genus Darwinopterus. Lack of reconstructions by Unwin and Lü may prevent them from seeing the subtleties.

Figure 1. Click to enlarge. All taxa are to scale with one another. Unwin and Lü note a resemblance between Darwinopterus and Germanodactylus. And that is certainly so, but only by convergence. Phylogenetic analysis indicates a closer relationship between the smaller descendants of Scaphognathus, like no. 12, and Germanodactylus. Arrows indicate phylogenetic order. Here the long neck evolved first with a notably smaller skull. Then the skull became longer and larger in the genus Darwinopterus. Lack of reconstructions by Unwin and Lü may prevent them from seeing the subtleties.

Unwin and Lü noted resemblance to Germanodactylus rhamphastinus, which is certainly reasonable at first glance.

However a large gamut phylogenetic analysis recovers a different tree, principally because Unwin and Lü refused to include tiny pterosaurs. Many of these are the actual transitional taxa linking four convergent lines of long-tailed pterosaurs to short-tailed pterosaurs, as we learned two years ago in the large pterosaur tree (still standing!). Until tiny pterosaurs are included in phylogenetic analysis, pterosaur workers will continue to be frustrated in the trees they recover and will find false leads, like Darwinopterus.

Babies, Juveniles and Teens
Abstracts are notable for their news value and Unwin and Lü do not disappoint. They tell us that several small to tiny Darwinopterus specimens are now known. According to Unwin and Lü, this growth series “shows, for the first time, how the short tail of pterodactyloids originated. Only 15 vertebrae are ossified in the smallest known individual and these are short and simple” and shorter overall than dorsal+sacral series. In adults, they note, 30 vertebrae are ossified.

Contra Unwin and Lü (2013) there’s is not the first time.
You only have to look at several transitional taxa in the large pterosaur tree to see this happening over and over again. Here, here, here and here are previously known examples. But they have cast a blind eye to these taxa.

This brings up another possibility with regard to little darwinopterids
We know from phylogenetic analysis that pterosaur genetic survival was enhanced by size reduction. We’ve seen it over and over throughout the pterosaur tree. Tiny pterosaur adults survived while their larger ancestors and sisters became extinct.

Here’s where it gets interesting…
It is possible that the tiny pterosaurs associated with the Darwinopterus specimens were small derived adults, not juveniles. This would duplicate the evolutionary patterns we see elsewhere several times within the Pterosauria. I’d sure like to get that data.

If the small darwinopterids were indeed juveniles
they would have to be isometric copies of the adults, based on the evidence we find in known embryos and known juveniles, like Zhejiangopterus, Tapejara, Pterodaustro and Pteranodon. But that’s not how the little darwinopterids were described.

If the small darwinopterids had shorter rostra and shorter tails that would involve allometric changes inside the smaller egg that become fixed upon hatching. Then isometric changes would take over to adulthood. A smaller rostrum on a smaller specimen would indicate a smaller adult, probably with distinct pedal proportions, if they follow basic pterosaur growth patterns. This could turn out to be another Solnhofen!

I have requested Lü for access to the unpublished data to help them sort out the juveniles from the small adults, whatever they may be. This is a job for DGS and phylogenetic analysis not “eyeballing it.”

Reference
Unwin DMW and Lü J-C 2013. The basal monofestratan Darwinopterus and its implications for the origin and basal radiation of pterodactyloid pterosaurs. Rio Ptero Symposium 98-101.

Scathing Book Review – Pterosaurs by Witton (2013) – the Darwinopterus blunder

Earlier we looked at the myth of Darwinopterus as the transitional taxon between long-tailed early pterosaurs and short-tailed later pterosaurs. Actually, several series of tiny pterosaurs (Fig. 5 as an example) fill that role and they do it four times, two out of two distinct Dorygnathus and two out of the smallest Scaphognathus (which is why some tiny pterosaurs have a large eye and short snout).

Remember a good transition consists of a beginning, several middles and an end. The Darwinopterus scenario provides a middle, but no specific beginning or end.

Darwinopterus and associated egg.

Figure 1. Darwinopterus female and associated egg.

Supporting the traditional view, Mark Witton, author of “Pterosaurs“, reports, Darwinopterus incontrovertibly fills a long-standing gap in pterosaur evolution, bridging the morphological distance between early pterosaurs and Pterodactyloidea.”

Incontrovertibly? Not so. Darwinopterus fails when put to several tests (see below).

Witton (2013) also falls off the Darwinian train when he reports, “Rather than demonstrating a bauplan with a smattering of pterodactyloid and non-pterodactyloid features across the entire skeleton, it [Darwinopterus] possess the characteristic skull and neck of pterodactyloid while retaining a body very similar to those of rhamphorhynchid pterosaurs.” This has been called, “modular evolution” and this is the only animal that this bizarre mode of evolution has _ever_ been applied to. Modular evolution creates chimaeras, but that’s _not_ how evolution works!

Long time readers of the Pterosaur Heresies already know the solution to this problem.

According to the results of the large pterosaur tree (now 204 taxa), Darwinopterus nests at the acme of a small clade of darwinopterids including Wukongopterus, Kunpengopterus and Pterorhynchus at its base, all derived from a sister to Jianchangnathus, which also gave rise to Scaphognathus and a long list of tiny and large descendants.

A clade has been erected (Lü, Unwin, et al. 2009) for Darwinopterus + Pterodactyloidea, the “Monofenestrata.” Unfortunately, Darwinopterus does not have a monofenestra. The naris is small, but still visible (Fig. 2), just like Pterorhynchus.

Figure 2. Click to enlarge. Darwinopterus skull with colorized rostral bones. The arrow points to the naris, still present.

Figure 2. Click to enlarge. Darwinopterus skull with colorized rostral bones. The arrow points to the naris, still present. This is just a big, long-necked basal scaphognathid.

More unfortunately, Darwinopterus does not nest near the base of any pterodactyloid-grade pterosaurs in the completely resolved large pterosaur tree. Those taxa that do actually nest at the base of pterodactyloid-grade pterosaurs (in the large pterosaur tree) fulfill Witton’s wish for a smattering of pterodactyloid and non-pterodactyloid features. Those features can be found in tiny pterosaurs (Fig. 5).

 Pterosaur family tree according to Witton (2013). Note all of the suprageneric taxa here! That means Witton does not have to come up with an ancestor to Darwinopterus nor a descendant. The large pterosaur tree provides specific specimens for both.

Figure 3. Pterosaur family tree according to Witton (2013). Note all of the suprageneric taxa here! That means Witton does not have to come up with a specific ancestor to Darwinopterus nor a descendant. The large pterosaur tree provides specific specimens for both.

Let’s put aside all the other problems with Witton’s pterosaur family tree and focus on the Darwinopterus situation.

Here Darwinopterus nests within the Wukongopteridae, a suprageneric taxon. Both the ancestor and descendant taxa are also suprageneric, leaving the transition to and from Darwinopterus rather cloudy. By that I mean, Witton doesn’t tell us which taxa are the direct ancestors and descendants of Darwinopterus. That avoids having to deal with details and data. Actually the original Lü, Unwin et al. (2010) tree generated some 500,000 most parsimonious trees, so from the start there are red flags everywhere with this study and this tree.

By contrast
there’s complete resolution (one tree results) in the large pterosaur tree. It also provides specific taxa (specimens) that nest with Darwinopterus and others that act as transitions to the four pterodactyloid grades. The former clade “Pterodactyloidea” is not monophyletic when tiny pterosaurs are included in analysis, something Witton and his cohorts refuse to do.

For a reminder, here (Fig. 4) are the closest sisters to Darwinopterus and three Darwinopterus specimens. The upper clade of wukongopterids are monophyletic, not transitional. The real story takes place after Scaphognathus with those half-sized descendants (no, they’re not juveniles).

Figure 1. Darwinopterids and their closest sisters in phylogenetic order beginning with Sordes.  Click to enlarge.

Figure 4. Click to enlarge. Darwinopterids (wukongopterids) and their closest sisters in phylogenetic order beginning with Sordes. Kunpengopterus is derived from Pterorhynchus. Darwinopterus and Wukonopterus were derived from Kunpengopterus. So the skull gradually increases in length along with the neck.

And here (Fig. 5)  are some of the transitional taxa arising out of the small Scaphognathus specimens. These tiny pterosaurs are the real transitional taxa. And there’s not just one. There are four series with gradual decreases and gradual increases in size. The hope that there is just one transitional taxon is a myth. The transition is a spectrum of gradual change. The apparent disappearance of the naris likewise had four paths with some reducing the naris and others merging the naris and antorbital fenestra.

Scaphognathians

Figure 5. Click to enlarge. Scaphognathus and its tiny descendants that ultimately gave rise to larger descendants.

Here, using specimens, you can see that every specimen between the large Scaphognathus and the large Germanodactylus are transitional taxa, creating a spectrum, some closer to Scaphognathus and others closer to Germanodactylus. That’s the beauty of using specimens, rather than suprageneric taxa. You get the real picture without any fudging or imagination.

By convergence, Darwinopterus, like the other four gradual transitions, did reduce the naris and elongate the skull and neck. These traits were derived from Pterorhynchus, which already had a reduced naris, then Kunpengopterus, which had a longer skull and longer neck (Fig. 4).

But then Darwinopterus went nowhere. It became extinct. End of story?

Let’s hope.

References
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B  (DOI 10.1098/rspb.2009.1603.)
Lü J, Unwin DM, Deeming DC, Jin X, Liu Y and Ji Q 2011a. An egg-adult association, gender, and reproduction in pterosaurs. Science, 331(6015): 321-324. doi:10.1126/science.1197323
Lü J, Xu L, Chang H and Zhang X 2011b. A new darwinopterid pterosaur from the Middle Jurassic of Western Liaoning, northeastern China and its ecological implicaitions. Acta Geologica Sinica 85: 507-514.
Witton M. 2013. Pterosaurs. Princeton University Press. 291 pages.

wiki/Darwinopterus

Darwinopterus, NOT the Transitional Pterosaur

Google Darwinopterus and you’ll get entries like: “the remarkable transitional pterosaur,” “one hell of an intermediate,” “fills evolution gap.” The news has been out for awhile now. Darwinopterus (Figure 1) has been hailed as the long lost transitional taxon bridging the basal long-tailed pterosaurs and the later short-tailed pterosaurs.

Or was it?

Pterosaurs, the flying reptiles of the Mesozoic, have been known for over 200 years, but until recently no taxon has been put forth as the transitional “link” between the primitive short-handed, long-tailed forms and the more derived long-handed, short-tailed ones. Lü et al. (2009) claimed to fill that gap with an unusual pterosaur, Darwinopterus modularis, which appeared to combine traits from both groups.

The skull and neck were described as “typically pterodactyloid,” while the remainder of the skeleton was considered “identical to that of basal pterosaurs.” This specimen was used to support the hypothesis of “modular evolution” in which the transition from basal to derived pterosaurs was posited to proceed in two phases: (1) skull and neck followed by  (2) post-cervical axial column, limb girdles and limbs.

Darwinopterids

Figure 1. Click to enlarge. Some of the several Darwinopterus specimens now known.

Four big problems arose from the Lü et al. (2009) study: 
1.The cladistic results were not robust. There were no distinct sister taxa and there was a great loss of resolution at the Darwinopterus node. No sequence of basal taxa in the Lü et al. (2009) analysis documented a gradual accumulation of Darwinopterus characters. Instead, four proximal sister taxa nested in an unresolved clade and one of those included four sister taxa in an unresolved clade. Similarly, three derived clades without resolution nested as sisters. A fine mess! And not the way evolution works!

2. The gamut of included taxa was not sufficiently broad ( = inclusive) to recover a single tree result matching evolution’s own single tree. Instead 500,000+ trees were recovered! Such loss of resolution provides little to no recoverable data. Missing from the inclusion set were all the tiny pterosaurs (skulls smaller than 2 cm in length, Figure 3) because they were traditionally considered juveniles and thus unworthy of inclusion. Also missing were several specimens considered congeneric with others but were distinct in several regards.

3. Evolution does not otherwise proceed in modules. Most fossil vertebrates can be identified by just a skull, tooth, pes or pelvis, but “modular evolution” would play havoc with this, creating chimaeras with the head of one taxon on the torso of another, as imagined in Darwinopterus by Lü et al. (2009). There is another, more parsimonious, explanation (see below).

4. Lü et al. (2009) used more than one specimen to score Darwinopterus, Scaphognathus and other pterosaurs. In Darwinopterus, the YH skull was a third longer with a larger antorbital fenestra, smaller orbit and deeper skull. Such characters change scores. Lü et al. (2009) also incorrectly scored several taxa (details on request).

Here’s how to solve all four problems at once:
Increase the size of the cladistic study inclusion set (Figure 4).

I added Darwinopterus to a cladistic analysis of 170 taxa (152 pterosaurs + 18 outgroup taxa, Figure 4)). These were tested against 185 characters. That analysis employed three times the number of taxa employed by Lü et al. (2009) against fifty percent more characters. While the Lü et al. (2009) resulted in 500,000+ trees, my analysis recovered a single tree in which there was not one, but four “pterodactyloid”-grade clades (not including the darwinopterids/wukongopterids). Completely unexpected, but it makes sense when you look at the details in each of the lineages. This new family tree goes a long way to explaining many of the mysteries surrounding pterosaurs.

Darwinopterus and kin nesting between Sordes and Scaphognathus

Figure 2. Nesting between Sordes and Scaphognathus were Pterorhynchus, Kunpengopterus, Darwinopterus and Wukongopterus (not shown), taxa with a longer skull, a longer neck and a reduced to absent naris..

Darwinopterus nested as the sister to Wukongopterus (Wang et al. 2009). Both nested as sisters to Kunpengopterus (Wang et al. 2010) and Pterorhynchus (Czerkas and Ji 2002). This clade nested between Sordes and Scaphognathus (Figure 2.), far from any of the actual transitional pterosaurs (see below). Lü et al. (2009) included Pterorhynchus in their analysis, but they did not score 27 percent of the characters. Of the remaining 80 characters 19 were scored differently in Darwinopterus and Pterorhynchus. Of these 19, I found 10 scores to be valid. Two of these described the longer rostrum in Darwinopterus. Three described the absence of a distinct naris in Darwinopterus. Of the remaining 9 characters all were incorrectly scored. (Details on available on request.)

The Actual Transitional Taxa
There were four transitional lineages (see below and Figure 4) that produced four convergent clades of “pterodactyloid”-grade pterosaurs, none of which came close to including Darwinopterus. At the bases of the four pterodactyloid-grade clades were four separate series of tiny pterosaurs, smaller than their predecessors and smaller than their successors. Each sequence documented a gradual transition from basal to derived.  Two arose from distinct Dorygnathus specimens. Two arose from the small Scaphognathus specimens (Figure 3).

The descendants of Scaphognathus.

Figure 3. Click to enlarge. The descendants of Scaphognathus. Note the size reduction followed by a size increase.

The widely-held hypothesis that small, short-rostrum pterosaurs were juveniles of larger forms is falsified by this study. Those tiny pterosaurs had a short rostrum because their ancestors within Scaphognathus also had a short rostrum. Other tiny pterosaurs did not have a short rostrum. They were basal to other clades leading to the azhdarchids and to the ctenochasmatids. If the tiny pterosaurs were juveniles, they should have nested with their parents, as in Pterodaustro.

Remember: pterosaurs were derived from a clade of lizards that grew isometrically, not allometrically. Juveniles were close matches to adults. This is never more clear than when looking at pterosaur embryos here, here and here. Even the Darwinopterus embryo was the spitting image of its mom, with a long rostrum and tiny eyes.

Pterosaur family tree

Figure 4. Click to enlarge. The family tree of the Pterosauria.

Other pterosaurs also had tiny transitional taxa. Between Campylognathoides and Rhamphorhynchussize reduction is documented. Preceding Nyctosaurus and Pteranodon a small taxon appears.

The fact that pterosaurs reduced their size during morphological transitions indicates that size reduction was a survival technique producing new morphologies (and sizes!) to keep genetic lineages from going extinct. Eudimorphodontids, dimorphododontids, dorygnathids, campylognathids and rhamphorhynchids did not survive into the Cretaceous, but their reduced descendants did. Thereafter size increases created some of the most spectacular forms now known. The tiny scaphognathids and dorygnathids were their common ancestors. This new heretical hypothesis of pterosaur relations plays havoc with traditional hypotheses, including the one invoking Cope’s rule by Hone and Benton (2007).

So what was Darwinopterus, if not a transitional pterosaur?
Sadly, Darwinopterus and Wukongopterus produced no known descendants. They were derived pterorhynchids about the same size as others. In the context of their phylogenetic nesting, both Darwinopterus and Wukongopterus inherited their so-called “basal” traits from a sister to Pterorhynchus, which also had a rather short metacarpus, long tail, long pedal digit 5 and long tail. The elongation of the skull and reduction of the naris were well underway in Pterorhynchus. The elongation of the neck was relatively slight. These traits were convergent with those in “pterodactyloid”-grade pterosaurs. A sister taxon, Wukongopterus, did not have an elongated neck. Kunpengopterus had a longer neck, but not an elongated skull (see above).

As always, I encourage readers to see the 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:
Czerkas SA and Ji Q 2002. A new rhamphorhynchoid with a headcrest and complex integumentary structures. In: Czerkas SJ ed. Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum:Blanding, Utah, 15-41. ISBN 1-93207-501-1. 
Hone and Benton 2006. Cope’s Rule in the Pterosauria, and differing perceptions of Cope’s Rule at different taxonomic levels. Journal of Evolutionary Biology 20(3): 1164–1170. doi: 10.1111/j.1420-9101.2006.01284.x
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B  (DOI 10.1098/rspb.2009.1603.)
Lü J, Unwin DM, Deeming DC, Jin X, Liu Y and Ji Q 2011a. An egg-adult association, gender, and reproduction in pterosaurs. Science, 331(6015): 321-324. doi:10.1126/science.1197323
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605
Wang X, Kellner AWA, Jiang S and Meng X 2009. An unusual long-tailed pterosaur with elongated neck from western Liaoning of China. Anais da Academia Brasileira de Ciências 81 (4): 793–812.
Wang X, Kellner AWA, Jiang S-X, Cheng X, Meng Xi & Rodrigues T 2010. New long-tailed pterosaurs (Wukongopteridae) from western Liaoning, China. Anais da Academia Brasileira de Ciências 82 (4): 1045–1062.
Zhou C 2009. New material of Elanodactylus prolatus Andres & Ji, 2008 (Pterosauria: Pterodactyloidea) from the Early Cretaceous Yixian Formation of western Liaoning, China.Neues Jahr. Geo. Paläo. Abh. (DOI: 10.1127/0077-7749/2009/0022.)