The Latest Pterosaur Family Tree (Lü et al. 2012)

A New Pterosaur Tree
In their report on Moganopterus, Lü et al. (2012) nested it (Fig. 1) with Feilongus, another pterosaur with slender teeth and an extraordinarily long rostrum.

Figure 1. Click to enlarge. The Lü et al. (2012) family tree of the Pterosauria. Colors added to clades also recovered by the large pterosaur tree. Arrows point to nestings recovered by the large study that were missed by Lü et al (2012) principally because they did not employ tiny pterosaurs, but were biased towards larger specimens. 33,500 most parsimonious trees resulted.

Several Clades Here Match the Large Pterosaur Study
The Lü et al. (2012) study nested Anurognathids and Dimorphodontids with the Triassic pteorsaurs. Scaphognathus, Dorygnathus, Sordes and Rhamphorhynchus nested together. The Ornithocheirids nested together, as did most of the Tapejarids and Azhdarchids. The Ctenochasmatids nested together as did the Nyctosaurus and Pteranodon. Missing from this study were several dozen key taxa.

Several Clades Don’t Fare So Well
Lü et al (2012) failed to nest Austriadactylus and Raeticodactylus at the base of the Pterosauria. Perhaps that’s because they chose the neutral taxon “OUTGROUP” to root their tree. Were they not happy with the traditional paradigm, the Phytosauria? Rhamphorhynchus, Dorygnathus and Sordes should have nested a little closer to Campylognathoides and Nesodactylus should have nested as the closest sister. Darwinopterus should have nested closer to Pterorhynchus. The Ornithocheirds, Cycnorhyamphids, Pterodactylus and Germanodactylus should have nested closer to Scaphognathus. The Ctenochasmatids and Azhdarchids should have nested closer to Dorygnathus. Not sure how Nyctosaurus + Pteranodon nested so far from Germanodactylus. Why did Tupuxuara and Thalassodromeus nest so far from Tapejara? So many nestings here just don’t make sense. Perhaps that’s why Lü et al. (2012) ended up with tens of thousands of trees, rather than the one (or the few if you include certain largely incomplete taxa) in the large pterosaur family tree.

Getting back to Moganopterus
Moganopterus was correctly nested with Feilongus, but both were incorrectly nested with the ornithocheirds, Boreopterus and Zhenyuanopterus. Even so basal ornithocheirids and cycnorhamphids are close to one another. Cycnorhamphids inexplicably nested farther away alongside the ornithocheird, Cearadactylus, the ctenochasmatids and a large Pterodactylus longicollum.

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
Lü J, Pu H-Y, Xu L, Wu Y-H and Wei X-F 2012. Largest Toothed Pterosaur Skull from the Early Cretaceous Yixian Formation of Western Liaoning, China, with Comments On the Family Boreopteridae. Acta Geologica Sinica 86 (2): 287-293. online.

Moganopterus, the Latest OMG Pterosaur

Lü et al. 2012 recently reported on a new Early Cretaceous pterosaur, Moganopterus zhuiana (Fig. 1). It is the largest toothed pterosaur found to date. And… it’s another one of those gotta-see-it-to-believe-it pterosaurs. The skull was 3/4 of a meter in length! The skull and anterior cervicals were discovered by splitting a plate and counterplate, so each one largely exposes the inside of the skull.

Figure 1. Click to enlarge. Moganopterus, the largest toothed pterosaur. The counterplate has been photographically reversed.

The Lü et al. 2012 abstract:  A new pterosaur Moganopterus zhuiana gen. et sp. nov. is erected based on a complete skull with lower jaws and anterior cervical vertebrae. It is characterized by much elongated upper and lower jaws with at least 62 total, long, curved teeth with sharp tips, a well developed parietal crest extending posterodorsally, forming an angle of 15 degrees with the ventral margin of the skull, the ratio of length to width of cervical vertebrae greater than 5:1. The skull length is 750 mm, and it is the largest toothed pterosaur found so far in the world. Based on this new pterosaur, the Boreopteridae can be divided into two subgroups: Boreopterinae sub-fam. nov. and Moganopterinae sub-fam. nov., which is also confirmed by the phylogenetic analysis.

Lü et al. (2012) nested Moganopterus with Feilongus, which was confirmed by the large pterosaur study. Their new pterosaur family tree will be our focus 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
Lü J, Pu H-Y, Xu L, Wu Y-H and Wei X-F 2012. Largest Toothed Pterosaur Skull from the Early Cretaceous Yixian Formation of Western Liaoning, China, with Comments On the Family Boreopteridae. Acta Geologica Sinica 86 (2): 287-293. online.

What Drives the Elongation of the Metacarpus in Pterosaurs?

In several clades of pterosaurs the metacarpus became elongated. We looked at this phylogenetically earlier in an 8-part series on pterosaur fingers starting here. Generally an elongated metacarpus is seen as a synapomorphy of the old “Pterodactyloidea,” but it is more complicated than that. We’ll look at each elongation event clade by clade. I don’t think anyone has tackled this subject yet, hence the lack of references below.

Figure 1. Protoazhdarchids

Clade 1 – The Proto-azhdarchids
In Pterodactylus? spectabilis, n1, the metacarpus was not elongated. Rather the forearm was shortened with respect to the ancestral sister Dorygnathus (SMNS 50164). In the next taxon, Beipiaopterus, the metacarpus was genuinely elongated. (We looked at this yesterday.) So what happened here?

Beipiaopterus was several times larger overall with a longer tibia, as long as the glenoid-acetabula length.  Beipiaopterus was the first of the stork-like taxa with an elongated neck and more gracile proportions. Still the metacarpus was only half the tibia length. The next taxon after Beipiaopterus, n44, was much smaller overall, but had the proportions of an azhdarchid with a hyper-elongated metacarpus, slightly longer than the tibia. It is likely that Beipiaopterus was a sideline in the lineage between n1 and n44. That means the hyperelongation of the metacarpus occurred in relatively small pterosaurs with very tiny and likely grounded hatchlings.

Figure 2. Protoctenochasmatids

Clade 2 – The Proto-ctenochasmatids
In St/Ei I  the pattern of metacarpal elongation was similar. Overall St/Ei I was much smaller than its phylogenetic predecessor, Dorygnathus R156, which also had a much longer forearm. Two intervening taxa, D. purdoni and Angustinaripterus, are known only by skulls. The ctenochasmatid clade achieved its greatest metacarpal length with Gegepterus, which had stork-like proportions overall. The total length of the tibia is unknown. Other ctenochasmatids, like Ctenochasma and Pterodaustro, did not greatly elongate the metacarpus. Neither became subequal to the tibia. The Pterodaustro embryo, interestingly enough, had a relatively shorter metacarpus than the adult with a longer humerus and more robust forearm, but smaller fingers. Is this a clue that forelimb proportions changed slightly during ontogeny?

Figure 3. Tiny scaphognathids

Clade 3 – The Post-Scaphognathids
The lineage of cycnorhamphids and ornithocheirids includes several tiny pterosaurs derived from a series of ever smaller Scaphognathus specimens. The first in this lineage to sport an elongated metacarpus was Gmu-10157 with a metacarpus just short of the tibia and ulna length. So, once again metacarpal elongation occurred first with the tiny pterosaurs and their grounded hatchlings. In this clade, Cycnorhamphus had the longest metacarpus and tibia. The ornithocheirids never developed a hyper-elongated metacarpus. Basal ornithocheirids  had a relatively longer metacarpus compared to the ulna. The forearm elongated in derived forms, so the metacarpus appeared to be relatively shorter. The length of the tibia was shorter in succeeding ornithocheirids, then became more elongate, relative to the metacarpus in the most derived ornithocheirds. Matching its adult sisters, the hatchling ornithocheirid had a metacarpus to match its forearm length, but a much longer tibia was present.

Figure 4. Click to enlarge. Scaphognathus and its descendants demonstrating the elongation of the metacarpus immediately following the smaller specimens of Scaphognathus.

Clade 4 – More Post-Scaphognathids: Ornithocephalids
The lineage of Pterodactylus and Germanodactylus (with all of its many descendants) originated with a sister to Gmu-10157, the tiny pterosaur, Ornithocephalus. Thus clades 3 and 4 likely had a single common ancestor as yet undiscovered. In this clade the hyperelongation of the metacarpus occurred with Eopteranodon and Eoazhdarcho, two stork-like taxa often mistaken for azhdarchids, and perhaps convergently, Nyctosaurus and Pteranodon. I wonder if these two were derived from long-legged taxa, like Eopteranodon, that reduced their hind limb length? Or did they never have long legs and simply developed elongated metacarpals from the likes of Muzquizopteryx and the SMNK-PAL specimen of Germanodactylus? The skulls seem to point to the latter hypothesis, which would make Eopteranodon and Eoazhdarcho offshoot cousins of these two lineages. The juvenile Pteranodon had a hyperelongated metacarpus.

The Evidence in Summary
Apparently there are two stages to metacarpal elongation. The first occurs among tiny pterosaurs in which the metacarpus elongates to 3/4 or so of the tibial length. The second sometimes, but not always, occurs in larger pterosaurs, in which the metacarpus elongates to at least the tibial length, which is sometimes, but not always also elongated.

That’s evolution for ya.

Guesswork
An elongated metacarpus and tibia impart a stork-like appearance to the pterosaurs that have these traits and the best guess is a stork-like lifestyle was their niche. In Pteranodon and Nyctosaurus this was not the case as these albatross-like soarers developed their long wings by elongating their metacarpus. The first appearance of an elongated metacarpus in tiny pterosaurs and presumably their hatchlings might have provided limbs that had more similar proportions, perhaps for added efficiency during terrestrial locomotion. This efficiency would have been lost in Pteranodon and Nyctosaurus in which the metacarpus was much longer than the tibia.

Nothing about metacarpal elongation in the literature, hence no references.

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.

A New Sister for Huanhepterus

One of the strangest pterosaurs of all is also the least known. All I know about Huanhepterus (Dong 1982, Fig. 1) is found in Wellnhofer’s 1991 Encyclopedia, a photograph of the rostrum and a line drawing of the reconstructed post-crania. No one has told me they have seen the post-crania first-hand. A trip to China to see the post-crania wasn’t productive in that regard.

Even so, taking the data at hand, I originally nested Huanhepterus with the flightless pterosaur, Sos 2428, n57, derived from n44 and n42. The basic problem was a reversal to the shorter metacarpus condition. That autapomorphy was bothersome enough to recheck the clade. Good thing I did. I found some errors in Beipiaopterus, a road-kill skeleton I had reconstructed many years ago. Now the two are sisters and the reversal is gone.

Figure 1. The ancestry of Huanhepterus. It retained a relatively short metacarpus inherited from Beipiaopterus and Pterodactylus? spectabilis. Cope's Rule in action here, but not just prior to P? spectabilis, a tiny pterosaur following a mid-sized one, Dorygnathus.

A New Reconstruction for Beipiaopterus
Beipiaopterus was the problem. Several years ago, I had misinterpreted several traits. Now with corrections in place, Beipiaopterus becomes a sister to Huanhepterus and the short metacarpus autapomorphy goes away. Thereafter in this clade all taxa had a much longer metacarpus, including the flightless pterosaur, Sos 2428, the protoazhdarchids (n44 and n42) and the azhdarchids.

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
Dong Z-M 1982. On a new Pterosauria (Huanhepterus quingyangensis gen.et. sp.nov.) from Ordos, China. Vertebrata Palasiatica 20(2):115-121.
Lü J-C. 2002. Soft tissue in an Early Cretaceous pterosaur from Liaoning Province, China. Memoir of the Fukui Prefectural Dinosaur Museum 1: 19-28.
Lü J-C 2003. A new pterosaur: Beipiaopterus chenianus, gen. et sp. nov. (Reptilia: Pterosauria) from Western Liaoning Province, China. Memoir of the Fukui Prefectural Dinosaur Museum 2: 153-160.

wiki/Huanhepterus
wiki/Beipiaopterus

Caelidracones?

Unwin (2003) erected the clade Caelidracones to include Anurognathus, Quetzalcoatlus, their most recent common ancestor and all of its descendants. Essentially this was intended to include all employed pterosaurs except Preondactylus and the Dimorphodontidae (Dimorphodon and Peteinosaurus). Unfortunately the large pterosaur study found all three outgroup taxa to be ingroups within the Caelidracones.

Characters purportedly uniting members of the Caelidracones include: 1) Quadrate inclined anteriorly (mandible articulation anterior to squamosal articulation); 2) Ulna longer than tibia. 3) Fibula less than 80% the length of the tibia. 4) Ilium preacetabular process longer than the postacetabular process.

1) The quadrate is inclined anteriorly in Longisquama, an outgroup taxon to the Pterosauria and MPUM 6009, the basalmost pterosaur. Dimorphodon had a similar incline. Other inclinations are derived. Anurognathus and all other anurognathids had a vertical or posterior lean quadrate.

2) A shorter ulna than tibia does define basal fenestrasaurs and MPUM 6009, but thereafter the ulna is not shorter than the tibia. There is a reversal to a shorter ulna in Preondactylus through Carniadactylus, all are basal protoanurognathids.

3) The fibula is always subequal to the tibia in pterosaurs, unless it they are fused together. Sometimes the lower fibula is unossified, but the tarsal articulation is still present.

4) The ilium anterior process is always longer than the posterior process in all fenestrasaurs starting with Cosesaurus – except in Preondactylus, Peteinosaurus, the IVPP embryo and a few later pterosaurs.

Unwin (2003) had the opportunity to test fenestrasaurs as outgroup taxa, but has generally refused to acknowledge my contributions to the study of pterosaurs – with one exception: he credited Peters (2000) for defining the Pterosauria as Preondactylus, Quetzalcoatlus their last common ancestor and all of its descendants, a definition that needs to be updated by replacing Preondactylus with MPUM 6009.

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
Unwin DM 2003. On the phylogeny and evolutionary history of pterosaurs. pp. 139-190. — in Buffetaut, E. & Mazin, J.-M., (eds.): Evolution and Palaeobiology of Pterosaurs. Geological Society of London, Special Publications 217, London, 1-347.

Breviquartossa?

In his early phylogenetic analysis of the Pterosauria, Dr. David Unwin (2003) invented a clade called Breviquartossa to include Rhamphorhynchus, Quetzalcoatlus, their last common ancestor and all of its descendants (Rhamphorhynchidae +”Pterodactyloidea”). Traits include: 1) the ventral margin of the skull curves downward caudally. 2) loss of ‘coronoid’ eminence on caudal end of mandible. 3) Development of a mandibular symphysis (fusion of the mandibles) and 4) forms more than 30% of the mandible length. 5) Loss of heterodonty in the mandibular dentition. 6) Metacarpals 1-3 of equivalent length. 7) Short metatarsal 4.

Unwin (2003) commented about the possible inclusion of Campylognathoides with Rhamphorynchus, which is supported by the large pterosaur study. Unwin (2003) called this more inclusive clade Lonchognatha.

It’s interesting to see the accumulation of the Unwin’s Breviquartossa traits in the transition between Campy and Rhamph. 1) The caudal descent of the skull occurs not as an abrupt drop-off in Rhamphs, as in Anhanguera, but as a gradual curve anterior to the orbit in R. muensteri that straightens out below the orbit. 2) The presence of a ‘coronoid’ eminence on the caudal mandible seems to be present only on Eudimorphodon. Otherwise I don’t see it on Campylognathoides. 3) Fused mandibles do appear on the most primitive Rhamphs and by convergence in the most primitive Dorygnathus. 4) However, fusion of more than 30% of the mandibles does not occur in the most primitive of either genus, but only on derived specimens. 5) Loss of heterodonty in the mandibular dentition is indeed present in Rhamphorhynchus, but not in Scaphognathus or Dorygnathus. Rather it is emphasized famously in certain specimens. The giant teeth of Rhamphorhynchus should not be homologized with small teeth of derived pterosaurs, even though they are all relatively similar in size. 6) Metacarpal 1 remains shorter than the others in basal  Rhamphs, Sordes, Dorys and Scaphos. 7) Metatarsal 4 was distinctly shorter in Campylognathoides and the larger Rhamphs, but not the small ones. All four metatarsals were nearly all the same length in azhdarchids, ctenochasmatids and shenzhoupterids in three convergent reversals.

Anyway…
The Breviquartossa/Lonchognatha is just barely an invalid clade because it excludes all the Eudimorphodon specimens. Better to call this clade the Eudimorphodontia, which includes all pterosaurs but the Dimorphodontia and the basalmost pterosaurs. Both Campylognathoides + Rhamphorhynchus descend from one Eudimorphodon and all the descendants of Sordes + Dorygnathus descend from another Eudimorphodon specimen according to the large pterosaur tree.

At the base of the Breviquartossa is where the loss of resolution is highest in Unwin (2003) and in the Darwinopterus study (Lü et al. 2009) based on it. Here’s where multiple specimens of Scaphognathus, Rhamphoryhchus, Dorygnathus and the others would have changed Unwin’s tree.

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
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.)
Unwin DM 2003. On the phylogeny and evolutionary history of pterosaurs. pp. 139-190. — in Buffetaut, E. & Mazin, J.-M., (eds.): Evolution and Palaeobiology of Pterosaurs. Geological Society of London, Special Publications 217, London, 1-347.

A Competing Pterosaur Tree – Andres, Clark and Xing 2010

One of the most recent competing pterosaur trees was published recently by Andres, Clark and Xing (2010, Fig. 1).

Figure 1. Pterosaur tree from Andres, Clark and Xing 2010. Color added. This tree differs from all others by nesting anurognathids with derived pterosaurs ("pterodactyloids").

Some Good Pairings
The Andres, Clark and Xing (2010) paper sought to nest a partial skeleton, Sericipterus and it is basically correctly nested here. In the large pterosaur study Sericipterus nested close to the Uppsala specimen of Dorygnathus (R 156), in the lineage of Harpactognathus and Angustinaripterus, but not quite there. The anurognathids are all nested together. Sordes nests as a sister to Scaphognathus not far from Dorygnathus. The outgroup taxa, Ornithosuchus, Herrerasaurus and Scleromochlus correctly nest together. Campylognathoides is close to Sordes which is more or less correct, but missing some intervening taxa.  Peteinosaurus and Dimorphodon are correctly nested as sisters. Eudimorphodon and Austriadactylus are correctly nested as sisters.

Figure 2. Odd and improbable pairings recovered in the Andres, Clark and Xing (2010) tree.

Some Unusual and Improbable Pairings
Andres, Clark and Xing (2010) found Scleromochlus and Preondactylus to be sisters. Since Scleromochlus has tiny hands and lacks a pedal digit 5 and Preondactylus has an enormous wing finger and an elongate pedal digit 5, among dozens of other differences noted here, this relationship seems improbable and is not supported on the large reptile tree. This by default nesting is probably due to a lack of lepidosaur tritosaur fenestrasaurs in the mix, which would have produced a better set of outgroup taxa with a gradually accumulating list of pterosaurian traits missing in the Scleromochlus/ Herrerasaurus/  outgroup.

Andres, Clark and Xing (2010) found Dimorphodon and Campylognathoides to be sisters. Here Eudimorphodon and several other taxa bridge this morphological gap.

Andres, Clark and Xing (2010) nested Preondactylus, Dimorphodon apart, but the large study found them to be sisters.

Andres, Clark and Xing (2010) found Anurognathus to nest with Sordes and with Pterodactyloidea (here represented by Pterodactylus), but these taxa were widely separated in the large study. Andres, Clark and Xing (2010) determined that no maxillary ascending process could be identified in Jeholopterus and Batrachognathus, creating a confluent naris and antorbital fenestra. This is incorrect as shown here and here. Much of this mistake can be laid on the earlier misinterpretation by Bennett (2007) of the antorbital fenestra as the orbit in the flathead anurognathid.

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
Andres B, Clark JM and Xing X 2010. A new rhamphorhynchid pterosaur from theUpper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs, Journal of Vertebrate Paleontology 30: (1) 163-187.
Bennett SC 2007. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.

The Azhdarchoidea?

The Azhdarchoidea (Unwin 1995) is a putative clade of derived pterosaurs created to unite the Azhdarchidae (Quetzalcoatlus and kin) with the Tapejaridae (Tapejara and kin). Characters uniting taxa within this putative clade include: 1) Orbit positioned lower than dorsal rim of nasoantorbital fenestra; 2) Manual 4.2 more than a third shorter than m4.1.

Is Azhdarchoidea a Valid Clade?
The tall antorbital fenestra either unites Chaoyangopterus with Huaxiapterus (Fig. 1) or this trait developed by convergence. Manual 4.2 is indeed only 2/3 the length of m4.1 in Chaoyangopterus, but m4.2 is a bit too long (82%) in Huaxiapterus. Manual 4.2 is likewise less than 2/3 of m4.1 in the tiny pterosaur, n42. In Tapejara m4.2 is also a bit too long, but 2/3 the length of m4.1 in other tapejarids, such as Tupuxuara.

Figure 1. Click to enlarge. Putative members of the Azhdarchoidea include Chaoyangopterus and Huaxiapterus (red arrows). The larger study found no clade uniting just the Azhdarchidae and the Tapejaridae. Instead n42 was found to be basal to azhdarchids and Germanodactylus cristatus n61 was found to be basal to tapejarids.

Similarities
It’s easy to see several similarities in azhdarchids and tapejarids, including the elongated metacarpus, the depth of the suborbital jugal, the depth of the mandible at mid length, and the short m4.4. Unfortunately many other distinctions separate these two taxa in the larger pterosaur tree.

Distinctions
In dorsal view, the azhdarchid mandible has parallel sides ending in a rounded tip. In tapejarids and germanodactylids the mandible is sharp with a tooth at its tip. A posterior cranial crest is present in tapejarids and germanodactylids, but not in azhdarchids. The antorbital fenestra extends for 2/3 of the rostrum in tapejarids and germanodactylids, not in azhdarchids. The number of dorsal vertebrae is smaller in azhdarchids and protoazhdarchids. The pedal phalangeal ratios are more similar in protoazhdarchids and azhdarchids than in tapejarids. Similar pedal phalangeal proportions unite germanodactylids and tapejarids.

Figure 2. Left to right, Eopteranodon, Wellnhofer's No. 13 and Aurorazhdarcho, sisters that nest far from the Azhdarchidae.

A Basal Azhdarchoid?
Aurorazhdarcho (Frey, Meyer and Tischlinger 2011, Fig. 2) was promoted as the basalmost azhdarchoid. Unfortunately no phylogenetic analysis was published. Here, in the large pterosaur tree, Aurorazhdarcho nested with other stork-like pterosaurs, Eopteranodon and Eoazhdarcho, at the base of Nyctosaurus + Pteranodon, distinct from both the Tapejaridae and the Azhdarchidae.

The Benefit of a Larger Family Tree
Here again the benefit of a larger family tree permits an entire suite of traits, from head to toe, define cladistic relations. More taxa is the key to understanding, as any paleontologist will tell you, except when dealing with pterosaur relations [sarcasm]. Not sure why other paleo scientists refuse to expand their taxon list to match mine.

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
Frey E, Meyer CA and Tischlinger H 2011. The oldest azhdarchoid pterosaur from the Late Jurassic Solnhofen Limestone (Early Tithonian) of Southern Germany. Swiss Journal of Geosciences 104 (Supplement 1): 35–55. doi:10.1007/s00015-011-0073-1.
Unwin DM 1995. Preliminary results of a phylogenetic analysis of the Pterosauria (Diapsida: Archosauria); pp. 69-72 in Sun, A. and Wang, Q.-Y. (eds.), Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, short papers. China Ocean Press, Beijing.

wiki/Azhdarchoidea 

The Monofenestrata?

When Darwinopterus was first described (Lü et al. 2010) it was promoted as the transitional taxon uniting basal long-tailed pterosaurs with derived “pterodactyloid” pterosaurs, those with a united naris and antorbital fenestra. The Monofenestrata was a clade invented to include Darwinopterus and its kin along with traditional “pterodactyloids.” It has come to be accepted among pterosaur workers.

Unfortunately the original phylogenetic analysis (Lü et al. 2010) was poorly resolved, especially so at the transition point.

A larger pterosaur tree, including many more taxa, resolved the issue and found that Darwinopterus and kin nested with Pterorhynchus and this clade became extinct afterwards, leading to no other so-called “pterodactyloids.” In fact there were four convergent origins to the various “pterodactyloid” clades, not just one, as demonstrated by the large pterosaur study. These were derived from Dorygnathus and Scaphognathus (itself derived from Dorygnathus, too).

So, by this definition, the Monofenestrata is polyphyletic (not monophyletic) and therefore it has no value.

The enlargement of the skull in the Darwinopterus/Pterorhynchus clade along with the reduction and disappearance of the naris was convergent with the other four “pterodactyloid”-grade clades. Hence the confusion built on hope, perhaps for fame or resolution, not a comprehensive fully-resolved phylogenetic analysis.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
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.

wiki/Monofenestrata

The Largest Rhamphorhynchus Specimens

Conspecific?
Bennett (1975) determined that all Rhamphorhynchus specimens were conspecific with the various sizes and shapes representing the two genders and juveniles. More recently Prondvai et al (2012) followed this hypothesis in their bone histology study. Previously we looked at the smallest Rhamphs and determined that none resembled known larger specimens enough to consider them juveniles of same. Today we’ll look at the largest Rhamphs to determine if any of them might be considered conspecific.

Figure 1. A sampling of the largest Rhamphorhynchus specimens to scale. If Bennett (1995) and Prondvai et al. (2012) are correct, then these specimens should look conspecific. But they don't. The smaller ones would be juveniles and n81 would be the only fully mature individual. That doesn't make sense. It doesn't take a detailed view to see they are as different from one another as various species or even genera of birds.

So, Which of These Are Juveniles?
Above (Fig. 1) are shown several of the largest Rhamphorhynchus specimens. If these are all conspecific then the individual variation extends throughout the skeleton to the pedal phalangeal ratios. Like Pteranodon, Pterodactylus and several other purported genera, this clade needs a complete revision, looking at and reconstructing individuals.

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 1995. A statistical study of Rhamphorhynchus from the southern limestone of Germany: year classes of a single large species. Journal of Vertebrate Paleontology 69: 569–580.
Prondvai E, Stein K, Ösi A, Sander MP 2012. Life History of Rhamphorhynchus Inferred from Bone Histology and the Diversity of Pterosaurian Growth Strategies. PlosOne. online pdf