Liaodactylus, a new gnathosaurine pterosaur

Figure 1. Liaodactylus (in color in in situ compared to Gnathosaurus.

Figure 1. Liaodactylus (in color in in situ compared to Gnathosaurus. The portion of the rostrum above the antorbital fenestra remains unknown. A short crest may or may not have been present.

Liaodactylus primus (Zhou et al. 2017) was considered the earliest filter-feeding pterosaur. Here it nests with the Solnhofen specimen of Gnathosaurus. Distinctly, Liaodactylus has short premaxillary teeth and longer dentary teeth than maxillary teeth. The skull was small, only half the length of Gnathosaurus, but with similar proprotions. The jugal was not elevated and so did not shrink the orbit.

FIgure 2. Subset of the large pterosaur cladogram focusing on the clade Dorygnathia and the clade within it, the Ctenochasmatidae.

FIgure 2. Subset of the large pterosaur cladogram focusing on the clade Dorygnathia and the clade within it, the Ctenochasmatidae. Here Liaodactylus nests as a sister to Gnathosaur, a basal ctenochasmatid.

Zhou et al. did not provide
a specimen-based phylogenetic analysis. but used only one taxon for each genus and so missed out on the gradual accumulation of traits that nested Liaodactylus with Gnathosaurus. Instead they nested it with Ctenochasma.

Zhou et al. used the data matrix
of Andres, Clark and Xu 2004, which nested Kryptodrakon as the basalmost pterodactyloid. As we learned earlier, those authors reconstructed the few bits and pieces of Kryptodrakon as a small Pterodactylus-like pterosaur, when it should have been reconstructed as a larger, but very gracile Sericipterus, which was found in the same deposits, but would not have made so many headlines.

References
Andres B, Clark JM and Xu X 2010.A new rhamphorhynchid pterosaur from the Upper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs, Journal of Vertebrate Paleontology 30: (1) 163-187.
Andres B, Clark J and Xu X 2014. The Earliest Pterodactyloid and the Origin of the Group. Current Biology (advance online publication)
DOI: http://dx.doi.org/10.1016/j.cub.2014.03.030
Zhou C-F, Gao K-Q, Yi H, Xue J, Li Q and Fox RC 201. Earliest filter-feeding pterosaur from the Jurassic of China and ecological evolution of Pterodactyloidea. R. Soc. open sci. 4: 160672. http://dx.doi.org/10.1098/rsos.160672

 

Dr. David Unwin on pterosaur reproduction – YouTube

Dr. David Unwin’ talk on pterosaur reproduction 
was recorded at the XIV Annual Meeting of the European Association of Vertebrate Palaeontologists, Teylers Museum, Haarlem, Netherlands and are online as a YouTube video.
Dr. Unwin is an excellent and engaging speaker.
However, some of the issues Dr. Unwin raises have been solved at www.ReptileEvolution.com
The virtual lack of calcite in pterosaur eggs were compared to lepidosaurs by Dr. Unwin, because pterosaurs ARE lepidosaurs.  See: www.ReptileEvolution.com/reptile-tree.htm
Lepidosaurs carry their eggs internally much longer than archosaurs, some to the point of live birth or hatching within hours of egg laying. Given this, pterosaurs did not have to bury their eggs where hatchlings would risk damaging their fragile membranes while digging out. Rather mothers carried them until hatching. The Mrs. T external egg was prematurely expelled at death, thus the embryo was poorly ossified and small.
Dr. Unwin ignores the fact that hatchlings and juveniles had adult proportions as demonstrated by growth series in Zhejiangopterus, Pterodaustro and all others, like the JZMP embryo (with adult ornithocheirid proportions) and the IVPP embryo (with adult anurognathid proportions).
Dr. Unwin also holds to the disproved assumption that all Solnhofen sparrow- to hummingbird-sized pterosaurs were juveniles or hatchlings distinct from any adult in the strata. So they can’t be juveniles (see above). Rather these have been demonstrated to be phylogenetically miniaturized adults and transitional taxa linking larger long-tailed dorygnathid and scaphognathid ancestors to larger short-tailed pterodactyloid-grade descendants, as shown at: www.ReptileEvolution.com/MPUM6009-3.htm
Thus the BMNH 42736 specimen and Ningchengopterus are adults, not hatchlings. And the small Rhamphorhynchus specimens are also small adults.

What is Orientognathus? Nest it with Changchengopterus and Sordes.

Earlier on January 24, 2015 we looked at a description of Orientognathus chaoyngensis (Lü et al. 2015. Fig.1) a new Late Jurassic rhamphorhynchoid pterosaur known then from a series of comparative descriptions only. No images. Now that I’ve seen a low-resolution photograph (Fig. 1), let’s review the data we had to work with on the 24th of January.

Figure 1. Orientognathus in situ, tracing moved to live position, comparisons to sisters Changchengopterus and Sordes.

Figure 1. Orientognathus in situ, tracing moved to live position, comparisons to sisters Changchengopterus and Sordes. Click to enlarge. More resolution is needed to get more out of this. The wings and tail are not very long here. The sternum is a small triangle.

Data provided:

  1. toothless tip of dentary, slightly pointed – True
  2. mc4/humerus ratio = 0.38 – True and precise
  3. ulna < each individual wing phalanx – False, the ulna is quite long
  4. tibia subequal to femur – False, tibia is longer, both tibia are broken.
  5. deltopectoral crest more developed than in Qinlongopterus – True, but not as much as in Sordes.
  6. anterior teeth stouter and longer than in Pterorhynchus – True, but Pterorhynchus has pretty short anterior teeth.
  7. teeth are straight and longer than in Jianchangnathus Subequal actually. 
  8. pteroid/humerus ratio = 0.21; pteroid has expanded distal end True enough (0.23)
  9. larger than other rhamphorhynchine pterosaurs from Late Jurassic NE China (measurements not indicated). Did not check, but seems pretty big (Fig. 1).

The specimen is nearly complete and partly disarticulated. 
The antebrachium (forearm) is broken. Put them back together and that’s a long forearm.

It turns out the the tibia is not equal to the femur in length
So all of the prior candidates become rejects.

Step two: ulna is not smaller than each individual wing phalanx
Orientognathus has a large antebrachium, subequal to m4.2 and longer than m4.1.

Figure 2. The original nesting of Orientognathus from Lü et al. 2014. Note the lack of resolution in that clade. Changchengopterus is not listed, but should be.

Figure 2. The original nesting of Orientognathus from Lü et al. 2014. Note the lack of resolution in that clade. Changchengopterus is not listed, but should be.

Step three: Phylogenetic Analysis
The prior cladogram lost resolution when Orientognathus was added (Fig. 2) .

However
A new analysis of the large pterosaur tree (not yet updated) nests Orientognathus between Changchengopterus and the primitive specimen of Sordes (Fig. 1) with no loss of resolution.

These three (Sordes, Orientognathus and Changchengopterus) are the metaphorical ‘plain brown sparrows’ among pterosaurs from which all later spectacular specimens are derived. It’s that lack of any ‘distinctive’ traits that is actually their own distinctive trait.

Thus Orientognathus is basal to the several specimens of Sordes and the many specimens of Dorygnathus, from which arise darwinopterids (wukongopterids), scaphognathids and ultimately all the pterodactyloids. Orientognathus may have been hard to nest and caused so little stir because it is indeed plesiomorphic. Getting that antebrachium and tibia right would have helped. If anyone has access to high resolution imagery of the skull and foot, that would be very helpful.

References
Lü J, P H-Y, We X-F, Chan H-L and Kundrat GM 2014. A new rhamphorhynchid pterosaur (Pterosauria) from Jurassic deposits of Liaoning Province, China. http://www.biotaxa.org/Zootaxa/article/view/zootaxa.3911.1.7/0

Pterosaur tails tell tales… Unwin et al. 2014 JVP abstract

Unwin et al. (2014)
describe an increasing number of tail vertebrae in a purported ontogenetic series (hatchling to juvenile to adult in a series of purported Darwinopterus specimens.) Although this is unheard of elsewhere among vertebrates, Unwin et al. link this trait to the origin of pterodactyloid-grade pterosaurs. And it should be mentioned that Unwin et al. are the only workers who nest darwinopterids basal to pterodactyloids. Andres nests anurognathids there. Kellner nests Rhamphorhynchus there. I nest tiny dorygnathids and scaphognathids there by convergence (e.g. Fig. 1) four times.

From the Unwin et al. 2104 abstract:
“The evolution of pterodactyloids from basal pterosaurs in the Early-Middle Jurassic involved a complex series of anatomical transformations that affected the entire skeleton. Until recently, almost nothing was known of this major evolutionary transition that culminated in the Pterodactyloidea, a morphologically diverse and ecologically important clade that dominated the aerial environment throughout the mid-late Mesozoic. The discovery of Darwinopterus, a transitional form from the early Late Jurassic of China, provided the first insights into the sequence of events that gave rise to the pterodactyloid bauplan and hinted at an important role for modularity, but was largely silent regarding the anatomical transformations themselves, or the evolutionary mechanism(s) that underlay them. A series of recent finds allowed us to construct a complete postnatal growth sequence for Darwinopterus. By comparing this sequence with those for Rhamphorhynchus and Pterodactylus, pterosaurs that phylogenetically bracket Darwinopterus, it is possible to map key anatomical transformations such as the evolution of the elongate, complex tail of basal pterosaurs into the short, simple tail of pterodactyloids. In Darwinopterus hatchlings the tail is shorter than the dorsal-sacral series (DSV) and consists of around 18 simple vertebral ossifications. The tail is longer (1-2 x DSV) in juveniles and has a normal complement of about 30 caudals, but only reaches its full length (2-3 x DSV) and complexity in adults. Basal pterosaurs largely conform to this pattern, although some species, including Rhamphorhynchus, have longer tails with up to 40 caudals. Generally, the tail of adult pterodactyloids, including Pterodactylus, resembles that of Darwinopterus hatchlings (≤18 ossified vertebrae; tail ≤0.7 x DSV; vertebrae simple, blocky), but occasionally develops a little further (e.g. in Pterodaustro) corresponding to the condition seen in early juveniles of Darwinopterus and paralleling the developmental pattern observed in long-tailed pterosaurs. The short tail of adult pterodactyloids, and anurognathids, basal pterosaurs that also have relatively short tails, appears to be neotenic, resulting from a sharp decrease in growth rate compared to the rest of the skeleton. This mechanism, heterochrony acting upon a distinct anatomical module to effect a large-scale morphological transformation, can be applied to other modules to generate the derived features (e.g. elongate neck and metacarpus, reduced fifth toe) that typify the pterodactyloid bauplan.”

Problem #1
Among professional pterosaur workers, only Unwin et al. nest Darwinopterus as the stem pterodactyloid. No one else does. Andres nests anurognathids with pterodactyloids. Kellner nests Rhamphorhynchus with pterodactyloids. Readers of this blog and reptile evolution.com know that when you add the sparrow- to hummingbird-sized Solnhofen pterosaurs, you get four clades of pterodactyloid-grade pterosaurs.

Figure 1. Scaphognathians to scale. Click to enlarge.

Figure 1. Scaphognathians to scale. Click to enlarge.

Problem #2
Are the specimens truly juvenile Darwinopterus? Or do they represent smaller genera or species, perhaps closely related, or not? Currently no two Darwinopterus specimens are conspecific. No two are identical. See them here. By comparing purported Rhamphorhynchus and Pterodactylus juveniles to putative adults I’m afraid Unwin et al. are playing with a pack of Jokers. Those smaller specimens are distinct species and genera, as recovered in the large pterosaur tree. Everyone should know by now that pterosaur juvenile pterosaurs are isometric matches to their adult counterparts, from several well-known examples. Any differences in Darwinopterus likewise mark phylogenetic, not ontogenetic differences.

Problem #3
Rhamphorhynchus and Pterodactylus only phylogenetically bracket Darwinopterus if the inclusion set is reduced to these three taxa. Otherwise they nest several nodes away from each other with lots of intermediate taxa as you can see here.

Problem #4
Unwin et al. claim the caudal count increases with maturity in Darwinopterus (18 in hatchlings, 30 in juveniles and adults). Put these into a cladogram and they probably become disparate taxa. Where else does the vertebral count nearly double during ontogeny? Nowhere. Those caudal counts for the larger specimens have to be estimates. Not every tail is complete. It appears as if the caudal count could vary among the larger specimens as well.

Problem #5
I see no mention of a phylogenetic analysis with regard to the various Darwinopterus specimens. This is a problem as Unwin et al. do not want to test their observations with the only method known to lump and split taxa. In the large pterosaur tree IVPP V 16049 nests with YH2000. 41H111-0309A nests with ZMNH M 8782. All four Darwinopterus taxa nest as a sister clade to Kunpengopterus + Archaeoistiodatylus and this combined clade is a sister to Wukongopterus, then the PMOL specimen of Changchengopterus, then Pterorhynchus. This major clade nests between Dorygnathus and Scaphognathus, both of which ultimately give rise to the two pairs of basalmost pterodactyloids.

Possible Solution 
I noted earlier that the Darwinopterus clade left no descendants. They also did not produce any small taxa like Dorygnathus and Scaphognathus did. Other workers thought the smaller Scaphognathus specimens were juveniles, despite the morphological differences. I can only wonder if the same situation is happening in the Darwinopterus clade? Perhaps what the Unwin team found are the smaller specimens previously missing from their clade branch. Even so, and sadly, this clade was not able to survive into the Cretaceous, small or not, because no known Cretaceous pterosaurs share darwinopterid traits. They are all accounted for with presently known tiny ancestors.

References
Unwin D, Lü J-C, Pu H-Y, Jim X-S  2014. Pterosaur tails tell tails of modularity and heterochrony in the evolution of the pterodactyloid bauplan. JVP 2014 abstracts

‘Aerodactylus’ nests with Pterodactylus antiquus. It’s not a new genus.

A recent online paper in PLOS by Vidovic and Martill (2014) proposed that the BSP AS V 29a/b specimen (n15 in the Wellnhofer 1970 catalog, Figs. 1-5) formerly attributed to Pterodactylus scolopaciceps (Meyer 1860) was actually more closely related to Cycnorhamphus. They gave it a new name, “Aerodactylus.

I know this sounds technical. I’ll make it simple with pictures and links.

From their abstract:
A cladistic analysis demonstrates that Aerodactylus is distinct from Pterodactylus, but close to Cycnorhamphus Seeley, 1870, Ardeadactylus Bennett, 2013a and Aurorazhdarcho Frey, Meyer and Tischlinger, 2011, consequently we erect the inclusive taxon Aurorazhdarchidae for their reception.

BSP AV S 29a/b, formerly attributed to Pterodactylus, Vidovic and Martill rename Aerodactylus. Scale bar = 2cm.

Figure 1. BSP AV S 29a/b, formerly attributed to Pterodactylus, Vidovic and Martill rename Aerodactylus. Scale bar = 2cm. Upper image distorted to match lower image. Looks like it is swimming or walking.

The BSP specimen is gorgeous and complete.
It looks like quadrupedal in situ (Fig. 1). I’m happy to take this opportunity to finally create a reconstruction (Fig. 5) and add it to the large pterosaur tree (not updated yet), especially considering the current drama brought on by this change of genus.

Unfortunately,
my results do not support the Vidovic and Martill (2014) results. In the large pterosaur tree BSP AS V 29a/b is recovered as a sister to the original pterosaur, the first one ever described, Pterodactylus antiquus (Figs. 3, 4).

The authors also have the traditional mindset, falsified several times recently.
From their abstract:
“The majority of pterosaur species from the Solnhofen Limestone, including P. scolopaciceps are represented by juveniles. Consequently, specimens can appear remarkably similar due to juvenile characteristics detracting from taxonomic differences that are exaggerated in later ontogeny.”

The authors fail to recognize the several juveniles that are not morphologically different than adults here, here, here and here, along with the three embryos that are not different from adults here, here and here.

Okay, so let’s take a look at the contenders.
Vidovic and Martill (2014) nested BSP AS V 29 a/b with the their purported cycnorhampid Gladocephaloideus (Fig. 2, and why was it not mentioned in the abstract?)

Here three pterosaurs considered sisters by Vidovic and Martill 2014 are shown to scale. In the large pterosaur tree, these taxa do NOT nest together. It is clear to see they are not closely related.

Figure 2. Click to enlarge. Here three pterosaurs considered sisters by Vidovic and Martill 2014 are shown to scale. In the large pterosaur tree, these taxa do NOT nest together. It is clear to see they are not closely related. These specimens show variety, not similarity.

In Evolution
there is supposed to be a gradual change from one taxon to another. Sister taxa should share a long list of traits. Here (Fig. 2) they don’t.

Here are the competing contenders
It turns out that this Pterodactylus, BSP AS V 29a/b, really IS a Pterodactylus. It shares many more traits with its sisters (Fig. 3).

Figure 3. Click to enlarge. The large pterosaur tree nests these three taxa together. So this Pterodactylus really is a Pterodactylus.

Figure 3. Click to enlarge. The large pterosaur tree nests these three taxa together. So this Pterodactylus really is a Pterodactylus, just a distinct species. These specimens show similarity, with a little variety.

What a mess!
And why? What was it about this very run-of-the-mill pterosaur made anyone think it was anything but what it is, a Pterodactylus.

Figure 4. Subset of the large pterosaur tree, with the BSP specimen added.

Figure 4. Subset of the large pterosaur tree, with the BSP AS V 29a/b specimen added.

Re: Gladocephaloideus, Ardeadactylus and Aurorazhdarcho
In the large pterosaur tree, Gladocephaloideus nests with Gegepterus within the Ctenochasmatoidea.

Ardeadactylus nests with Huanhepterus and other proto-azhdarchids. Pterodactylus longicollum is not related, but nests on the other side of the Pterodactylus antiquus holotype (Fig. 4). Yes, this genus generally gets bigger as members become more derived.

Aurorazhdarcho nests with Eoazhdarcho and Eopteranodon at the base of Nyctosaurus + Pteranodon.

So none of these taxa are really related to one another.

Getting back to the juvenile problem
Vidovic and Martill (2014) considered the SMF R 4072 specimen to be a juvenile Pterodactylus. However in phylogenetic analysis, it nests at the base of Germanodactylus. The fear of adding tiny Solnhofen specimens to phylogenetic analysis is unwarranted. A tree that includes them has been on the web for three years. And juvenile pterosaurs identical to parents are well known, but ignored.

The authors had direct access to the specimens and I did not. 
I hope you see that direct access to the specimens is no guarantee of validity. Conversely, lack of direct access to the specimens is no hinderance to critical observation.

The authors thanked, Chris Bennett (Fort Hayes), David Hone (London), and Dino Frey (Karlsruhe) ‘for the useful comments made during the project.’ And this is why I have trouble getting pterosaur papers published.

I hope now you can appreciate when I say the world of pterosaur study is like a funhouse mirror where everything is distorted and, in this case at worst, makes no sense, yet is supported by professional workers.

And let’s leave on a good note

Figure 5. Pterodactylus specimen BSP AS V 29a/b reconstructed. Soft tissue shows where the naris opens.

Figure 5. Pterodactylus specimen BSP AS V 29a/b reconstructed. Soft tissue shows where the naris opens. Presumeably the small hole at the front of the antorbital fenestra. But there is a larger hole further back! This specimen has the usual wingtip claw, fifth toe claw and fifth manual digit. It may also have a few more ribs than usual, which might go along with the smaller pelvis.

BSP AS V 29 a/b is a premiere specimen.
It looked so much like other Pterodactylus ()Fig. 3) that I ignored it until now. A bit of soft tissue fills most of the antorbital fenestra leaving a small hole up front (the naris?) and a larger hole further back. The sternum is smaller relative to the humerus than in other Pterodactylus specimens. The twin teeth at the mandible tips are easy to see. These fuse to become one sharp tooth in germanodactylids and their descendants. There is nothing about this specimen that says it is anything but a Pterodactylus.

After this paper, Hermann von Meyer must be rolling over in his grave.

References
Vidovic SU and Martill DM 2014. Pterodactylus scolopaciceps Meyer, 1860 (Pterosauria, Pterodactyloidea) from the Upper Jurassic of Bavaria, Germany: The Problem of Cryptic Pterosaur Taxa in Early Ontogeny. PLoS ONE 9(10): e110646. doi:10.1371/journal.pone.0110646

 

Ikrandraco avatar – a new pterosaur & DGS reveals a few more bones

A recent paper
by Wang et al. (2014) described a wonderful new Chinese ornithocheirid, Ikrandraco avatar, with a crest below the mandible, not above the rostrum. Actually two specimens were found with slightly different preservations.

Figure 1. Click to enlarge. Ikrandraco avatar skull. As originally traced (below) with DGS (above).

Figure 1. Click to enlarge. Ikrandraco avatar skull. As originally traced (below) with DGS (above).

This wonderful new ornithocheirid (not a pteranodontoid) from the Jiufotang formation (Early Cretaceous). The authors report, “We propose that this pterosaur fed on fishes from nearby freshwater lakes by flying low over the water, capturing its prey by lowering the mandible in the water, being capable of a reduced and temporary skimming. We also propose that it had a more developed throat pouch then in other pterosaur species.”

The mandible was quite sharp. The rostrum was not. Oddly the teeth appear to have emerged from the sides of the rostrum and mandible. The alveoli were like portholes on a ship’s hull.

Figure 2. Ikrandraco in situ. Below as originally traced. Above with femur, tibia, pelvis and tail traced and manual 4.4 identified (not a rib).

Figure 2. Ikrandraco in situ. Click to enlarge. Below as originally traced. Above with femur, tibia, pelvis and tail traced and manual 4.4 identified (not a rib).

The authors were able to identify the tiny metatarsals and sacrum, but overlooked the tibia, femur, pelvis and tail, shown here (Fig. 2). And yes, that fossil is no closer to me than half a world away. I wouldn’t have looked fro the tibia and femur, but there was the metatarsus, all by itself, lined up with a crack that split the tibia. What I see of the bones are either impressions of bones that were once there, or they remained buried, just below the surface.

Figure 3. DGS restores the known elements to a more in vivo pose of Ikrandraco.

Figure 3. DGS restores the known elements to a more in vivo pose of Ikrandraco. The tiny premaxilla had tiny teeth. Rather than having a nice anhanguerid-like rake and spoonbill, this pterosaurs evolved a very narrow set of jaws. The deep angle of the quadrate absorbed shocks as the lower jaw slid through the water. 

The authors considered this an adult individual based on the fusion of the extensor tendon, but that is a phylogenetic feature shared with several ornithocheirids, large and small.

Other ornithocheirids can be seen here for comparison. Most have longer teeth. Wang et al. (2014) nested Ikrandraco with Nurhachius and Istiodactylus among pterosaurs known from more than just scraps. I haven’t done the work, but that seems reasonable, except that the orbit doesn’t have the keyhole shape. Among pterosaurs with rostral crests and large round orbits, we look to Criorhyrhynchus and Coloborhyrhynchus, which are related to istiodactylids. Unfortunately the authors nested ornithocheirds derived from a sister to sharp-snouted Pteranodon from the Late Cretaceous. That doesn’t make sense. The large pterosaur tree derives ornithocheirids from scaphognathids, sisters to cycnorhamphids and Yixianopterus is a basal ornithocheirid (not included in Wang et al. (2014).

The Ornithocheiridae.

Figure 4. The Ornithocheiridae. Click to enlarge and expand. Look for the taxon that shares the most traits with Ikrandraco. In size Ikrandraco was relatively small, about as tall as Boreopterus. 

 

 

 

References
Wang X, Rodrigues T, Jiang S, Cheng X and Kellner AWA 2014. An Early Cretaceous pterosaur with an unusual mandibular crest from China and a potential novel feeding strategy. Scientific Reports 4 : 6329, pp. 1-9. | DOI: 10.1038/srep06329

The JZMP embryo and its adult sister taxa

Currently the only known embryo/adult pterosaur pairing is in the genus Pterodaustro. Unfortunately, not much has been made about the allometry/isometry in the growth patterns of this genus, even though the data is available. The best data, unfortunately, is right here, rather than in an academic journal. Adults are 8x larger than hatchlings and ontogeny is chiefly isometric (as shown most clearly in Zhejiangopterus) and other pterosaurs like Ptweety the Pteranodon.

For the other two embryos, the IVPP embryo and the JZMP embryo we currently do not have congeneric adults and have to look to sister taxa or simple isometry to estimate the adult proportions and traits.

Today we’ll look at the sister taxa of the JZMP embryo (Fig. 2).

Figure 1. The closest sisters to the JZMP embryo, a basal ornithocheirid without an adult skeleton known for it.

Figure 1. The closest sisters to the JZMP embryo, a basal ornithocheirid without an adult skeleton known for it. Click to enlarge. This is not the phylogenetic order. Yixianopterus is the most primitive. Then the JZMP embryo followed by the smaller forms. These are followed by the boreopterids. 

Generally what we find at clade bases is a gradual increase in size from tiny ancestors. While we do have a tiny ancestor in Pterodactylus(?) pulchellus, we don’t have a gradual increase from that point forward. Yixianopterus the basalmost ornithocheirid, is large AND primitive. The JZMP embryo as an adult, was similar in size to Yixianopterus, but twice as tall as Haopterus and two Lebanon basal ornithocheirids. Click here to see a phylogenetic lineup of ornithocheirids and their outgroup.

Given these various sizes in basal ornithocheirids, and no gradual increase in size, one wonders if Haopterus and the Lebanon ornithocheirids are juveniles. Finding lots of larger congeneric taxa would be helpful. Checking out the annular rings in their long bones would also give clues.

The alternative, that the small ornithocheirids are adults, might represent the next phase in derived ornithocheirid evolution, in which the wings get longer and the feet get smaller, among other traits, which appears to be the case in the Lebanon ornithocheirids.

References
Ji Q, Ji S-A, Cheng Y-N, You HL, Lü J-C, Liu Y-Q and Yuan CX 2004. Pterosaur egg with leathery shell. Nature 432:572.