Another look at the smallest adult pterosaur – AND its hatchling

Earlier we looked at the smallest adult pterosaur, B St 1967 I 276 or No. 6 in the Wellnhofer (1970) catalog. Here (Fig. 1) it is compared to an adult leaf chameleon, Brookesia micro, one of the smallest living lizards and to the Bee hummingbird, one of the smallest living birds. Also shown are their hatchlings and eggs.

Figure 1. The smallest of all adult pterosaurs, B St 1967 I 276 or No. 6 in the Wellnhofer (1970) catalog compared to scale with the living leaf chameleon (Brookesia micro) sitting on someone's thumb. Also shown are hypothetical eggs and hatchlings for both. These lepidosaurs had tiny eggs and hatchlings.

Figure 1. The smallest of all adult pterosaurs, B St 1967 I 276 or No. 6 in the Wellnhofer (1970) catalog compared to scale with the living leaf chameleon (Brookesia micro) sitting on someone’s thumb. Also shown are hypothetical eggs and hatchlings for both. These lepidosaurs had tiny eggs and hatchlings, relatively larger in the chameleon, based on pelvis size and average 1/8 size for other pterosaur hatchlings.

 

Traditional paleontologists
don’t buy the argument that No. 6 was an adult, even though it is much larger than the smallest lizard and about the size of the smallest bird. Worse yet, they refused to test it in phylogenetic analysis. So, the  impasse remains.

Figure 2. Smallest known bird, Bee hummingbird, compared to smallest known adult pterosaur, No. 6 (Wellnhofer 1970). Traditional workers consider this a hatchling or juvenile, but in phylogenetic analysis it does not nest with any 8x larger adults.

Figure 2. Smallest known bird, Bee hummingbird, compared to smallest known adult pterosaur, No. 6 (Wellnhofer 1970). Traditional workers consider this a hatchling or juvenile, but in phylogenetic analysis it does not nest with any 8x larger adults. This image is slightly larger than life size at 72dpi. Note the much smaller eggs produced by the tiny pterosaur. 

 

Pictures tell the tale.
You can see for yourself. No. 6 is substantially smaller than other tiny pterosaurs just as the bee hummingbird is substantially smaller than other hummingbirds.The hatchling was substantially smaller than both the leaf chameleon and bee hummingbird hatchlings based on their larger egg size/pelvis opening.

Earlier we looked at isometric growth in several pterosaurs, with hatchlings matching adults in morphology. Earlier we also took note of the danger of desiccation to hatchling pterosaurs until they reached a certain size/volume, so they probably roamed the leaf litter, which is probably when pterosaurs became quadrupeds and developed elongate metacarpals 4x.

References
Hedges SB and Thomas R 2001. At the Lower Size Limit in Amniote Vertebrates: A New Diminutive Lizard from the West Indies. Caribbean Journal of Science 37:168–173.
Wellnhofer P 1970. 
Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

wiki/Pterodactylus

SVP 11 Pterosaur pelvic morphology

Frigot 2015 
provides general information about pterosaur pelves using principal component analysis, similar to that of Bennett 1995, 1996. I hope it works out better for Ms. Frigot.

From the abstract
“Pterosaurs have modified the basic triradiate amniote pelvis, extending the ilium into elongate processes both anterior and posterior to the acetabulum. While pterosaurs are now generally accepted to move quadrupedally on the ground*, many hypotheses exist regarding the diversity of gaits and terrains exploited across Pterosauria and how this may be correlated with the shifts in body plan found at the base of the monofenestratans and of the pterodactyloids. Early attempts to bring comparative anatomy to bear upon the topic have been largely descriptive of pelvic shape across the clade. I attempt to rectify this by providing a geometric morphometric analysis of a phylogenetically diverse sample of pterosaur pelves. Using landmark-based methods, shape was captured at the bone margins and acetabulum, with a view to capturing surfaces available for muscle attachment. These landmarks were analyzed using principal components analysis (PCA). Principal components 1 and 2 distinguish well between genera, reducing possible concerns over the role of taphonomy and ontogeny in determining shape**. It is not apparent whether the lack of a phylogenetic trend across shape space is due to small sample size or a high degree of evolutionary plasticity, highlighting the need for a greater sample size. However, with this support for a biological signal in the data, subsequent steps can be made that focus on biomechanical and locomotor analyses using detailed anatomical observations. We can then try to identify how pelvic disparity might have led to a diversity of locomotor styles in this most unique taxon.”***

*That’s traditional thinking. Many pterosaur tracks indicate bipedal locomotion.
**Ontogeny does not change pelvis shape because pterosaurs grew isometrically.
***So, sorry… no taxa or conclusions here.

References
Frigot RA 2015. The pterosaurian pelvis. An anatomical view of morphological disparity and implications for for locomotor evolution.

Trees of Life: Birds and Pterosaurs

Yale’s Richard Prum recently announced that the Tree of Life of Birds is almost complete. A genomic analysis of 198 species of birds was published in the Oct. 7 edition of the journal Nature. Prum reported, ““In the next five or 10 years, we will have finished the tree of life for birds.” I presume that means fossil taxa will also be included and scored by morphological traits because genes (genomic traits) are not available.

It is not the first time…
Trees of Life for Birds were announced earlier here, here, here and here.

Having been through a similar study, I support all such efforts. AND I will never attempt to add any but a few sample birds to the large reptile tree. Others have better access to specimens and they have a big head start on the process.

Unfortunately,
some workers have ignored the pterosaur tree of life. Recently Mark Witton ignored isometric growth patterns in pterosaurs to agree with Bennett (2013) that the genus Pterodactylus includes tiny short-snouted forms, mid-sized long-snouted forms (including the holotype, of course) and large small-heron-like forms. Witton reports, “Speaking of adulthood, it was also only recently that we’ve obtained a true sense of how large Pterodactylus may have grown. We typically imagine this animal as small bodied – maybe with a 50 cm wingspan – but a newly described skull and lower jaw makes the first unambiguous case for Pterodactylus reaching at least 1 m across the wings (Bennett 2013).”

We looked at Bennett’s paper earlier in a three part series that ended here. The taxon Witton refers to is actually just a wee bit larger than the holotype and is known from a skull, so wingspread can only be guessed. The tiny short-snouted forms are actually derived from the short-snouted scaphognathids as shown here.

The Pterodactylus lineage and mislabeled specimens formerly attributed to this "wastebasket" genus

Figure 1. Click to enlarge. The Pterodactylus lineage and mislabeled specimens formerly attributed to this “wastebasket” genus. Others have split the largest specimens of Pterodactylus from the others without employing a phylogenetic analysis.

You might recall
that one of the largest complete Pterodactylus specimens (Fig. 1) recovered by the large pterosaur tree was mistakenly removed from this genus and lumped with Ardeadactylus, a basal pre-azhdarchid, all without phylogenetic analysis.

Agreeing with Bennett,
Witton deletes some taxa that actually belong to this genus, while accepting others that do not belong, all based on eyeballing specimens without a phylogenetic analysis that includes a large gamut of specimens (that does not delete the tiny forms). Eyeballing taxa is not the way to handle lumping and splitting. Phylogenetic analysis is. We looked at the Pterodactylus wastebasket problem here.

References
Bennett  SC 2012 [2013]. New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus. Paläontologische Zeitschrift (advance online publication) doi: 10.1007/s12542-012-0159-8
http://link.springer.com/article/10.1007/s12542-012-0159-8

News on the Origin of Pterosaurs on YouTube

I just uploaded a pterosaur origins video on YouTube. Click here to view it.

Click to view this "Origin of Pterosaurs" video on YouTube.

Click to view this “Origin of Pterosaurs” video on YouTube. 17 minutes long. 

Back to Cuspicephalus: Germanodactylid? or Wukongopterid?

Earlier we looked at the gracile skull of Cuspicephalus which nested with Germanodactylus B St 1892 IV 1 in the large pterosaur tree.

Today we revisit this taxon after the publication of Witton et al. 2015, which attempted to related Cuspicephalus to Darwinopterus and the wukongopterids.

Cuspicephalus scarfi

Figure 1. Cuspicephalus scarfi. Click to enlarge. Note the round exoccipital process at the back of the skull. Germanodcatylids have these. Wukongopterids do not. Witton thinks that bone is an artifact.

I have rarely seen a paper with such a bogus foundation…

  1. Witton et al. support the ‘modular’ evolution of pterosaurs at the base of the Pterodactyloidea. Earlier we learned that with the simple addition of taxa (which other workers continue to avoid) there are four origins for pterodactyloid-grade pterosaurs, all following phylogenetic miniaturization, a process that happens often in reptile evolution. We also learned that there is no such thing as ‘modular’ evolution with half the body evolving and waiting for the other half to catch up. In the case of wukongopterids, the other half never developed pterodactyloid-grade traits. Wukongopterids were a terminal taxon. The non-modular evolution of long tails to short tails happened several other times at several other nodes in the pterosaur cladogram (including in the anurognathids).
  2. With several distinct genera and specimens now nesting close to Darwinopterus robustus within the Wukongopteridae, no attempt was made to figure out which of these specimens were more basal and which were more derived — as shown in the large pterosaur tree.
  3. Witton et al. support a monophyletic “Monosfenestrata” which, to them, includes pterodactyloids + wukongopterids, a tree topology that is not supported by any other published studies. In the large pterosaur tree, wukongopterids, like anurognathids, convergently developed some pterodactyloid-grade traits and not others, then left no descendants.
  4. Witton et al. did not produce their own skull tracings, but rely on cartoonish and inaccurate versions of prior work by others (apparently often by Bennett 1996). Few to no skull sutures are shown and certain inaccuracies are present.
  5. Witton et al. are not critical of the cladistic work of others (Andres et al., 2014; (Lü et al., 2010; Tischlinger and Frey, 2014), nor do they offer support for the matrix they preferred (Unwin 2003). Seems less scientific than one would like to see here. Or did they not want to do the work? Or make enemies?
Figure 2. Cuspicephalus compared to Darwingopterus and to Germanodactylus, all to scale.

Figure 2. Cuspicephalus compared to Darwingopterus and to Germanodactylus, all to scale. Click to enlarge. The large reptile tree nests Cuspicephalus with Germanodactylus. Witton et al. report a closer relationship to Darwinopterus. The presence of large exoccipital ‘ears’, an extended cranium, a pointed rostrum, a pointed ventral orbt, an alignment of the rostral crest and antorbital fenestra anterior margin all argue for the present hypothesis. The longer antoribital fenestra developed by convergence in Darwinopterus and Cuspicephalus.

Granted,
wukongopterid skulls are indeed very similar to those of germanodactylids (Fig. 2). Both clades also offer a wide variety of shapes and sizes.

With regard to a key trait
in Cuspicephalus scarfi (MJML K1918) from Witton et al. 2015: The exoccipital processes are unexpanded: they look relatively large on MJML K1918, but this is largely an artefact of distortion around the occipital region, and they are not as prominent as those of Germanodactylus or dsungaripterids.

Actually
in Cuspicephalus the exoccipitals are just as big, if not bigger relative to skull height (Fig. 2).

In the large pterosaur tree
Cuspicephalaus nests with B St 1892 IV 1, n61 in the Wellnhofer (1970) catalog, which nests with two headless taxa, Wenupteryx (MOZ 3625) and the so-called “Crato azhdarchide (SMNK PAL 3830)”

From Witton et al. “Our assessment suggests that wukongopterid skulls can be distinguished from other Jurassic monofenestratans by not only lacking the well-documented cranial  synapomorphies of pterodactyloid clades, but also through a unique combination of characters (Darwinopterus, Gemanodactylus and Cuspicephalus = D, G and C):

  1. Striated bony crest lower than the underlying prenarial rostrum, with sloping anterior margin – actually lower in G.
  2. Anterior crest terminates in the posterior region of the prenarial rostrum, closer to the anterior border of the nasoantorbital fenestra than the jaw tip – note the crest starts more anteriorly in D
  3. Reclined, but not sub-horizontal, occipital regions leans more in G.
  4. Piriform (pear-shaped) orbitbut in G and C the orbit is sharply angled ventrally
  5. Convex anterodorsal orbital marginmore convex in G + C.
  6. Short nasal processonly in D.
  7. Unexpanded exoccipital processesonly in D.
  8. Concave dorsal skull surfacenot on G, D or C.
  9. Straight ventral skull surfacepresent on G, D and C.
  10. Nasoantorbital fenestra over 50% of jaw length – on D and C
  11. Small, equally sized alveoli – only on C, larger teeth on D and G.
  12. First alveolus pair located on anterior face of jaw, with mandible over-bitten by first premaxillary tooth pair – present on G, D and C
  13. Regular tooth spacing – only on D
  14. Interalveolar spacing generally greater than tooth length – only on D
  15. Dentition extends under anterior half of the nasoantorbital region – only on G and C
  16. Relatively slender, sharply pointed conical teeth – only on C.

Chronology
Cuspicephalus is Kimmeridgian (Late Jurassic) in age. So is Germanodactylus (Kimmeridigian/Tithonian). Darwinopterus is late Middle Jurassic (Bathonian/Oxfordian) in age. No wukongopterids are found in Late Jurassic deposits. So far…

I can see why there is confusion here. 
The skulls are very similar in overall morphology. But the weight of evidence appears to lend weight to a Germanodactylus relationship for Cuspicephalus. If Witton et al. had made more precise tracings and reconstructions, if they had used a valid tree topology that included tiny pterosaurs, if they had not discounted the presence of exoccipital processes on Cuspicephalus, then I think they would have come up with a nesting that echoed that of the large pterosaur tree.

An outlandish suggestion based on a cladogram
We have a large germanodactylid skull without a body (Cuspicephalus) and we have a large germanodactylid post-crania without a skull (the Crato Azhdarchide). Although they are separated somewhat in time, they are sister taxa. Wonder how well the real skull and real post-crania would match up with these two…

Diopecephalus = P. longicollum = Ardeadactylus. Normannognathus is in the box in the lower left.

Figure 3. Witton et al. also attempted to resolve the relationships of Normannognathus without success. Here it is in the box at lower left. Phylogenetic analysis nests it with Diopecephalus = P. longicollum = Ardeadactylus.

Normannognathus
Witton et al. also considered the problem of the placement of Normannognathus (Fig. 3). Earlier we looked at the phylogenetic relationships of Normannognathus (Buffetaut et al. 1998;  MGC L 59’583) known from a toothy, curved rostrum and crest. While Witton et al. considered the problem too difficult to solve, several years ago Normannognathus was matched to the big Pterodactylus longicollum (SMNS-56603, No. 58 of Wellnhofer 1970), which was not considered by Witton et al.

References
Andres B, Clark J, Xu X. 2014. The earliest pterodactyloid and the origin of the group. Current Biology 24: 1011-1016.
Bennett SC 1996. Year-classes of pterosaurs from the Solnhofen limestones of Germany: taxonomic and systematic implications. Journal of Vertebrate Paleontology 16:432–444.
Lü JC, Unwin DM, Jin X, Liu Y, Ji Q. 2010. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society B 277: 383-389.
Tischlinger H and Frey E 2014. Ein neuer Pterosaurier mit Mosaikmerkmalen basaler und pterodactyoider Pterosaurier aus dem  Ober-Kimmeridgium von Painen (Oberpfalz, Deutschland) [A new pterosaur with moasic characters of basal and pterodactyloid Pterosauria from the Upper Kimmeridgian of Painten (Upper Palatinate, Germany)]. Archaeopteryx 31: 1-13.
Witton MP, O’Sullivan M and Martill DM 2015. The relationships of Cuspicephalus scarfi Martill and Etches, 2013 and Normannognathus wellnhoferi Buffetaut et al., 1998 to other monofenestratan pterosaurs.

 

 

Jianchangopterus – a very ‘rhamphy’ pterodactylid

Jianchangopterus zhaoinanus (Li and Bo 2011, YHK-0931) is a small, complete and crushed Middle Jurassic pterosaur from Liaoning, China. Originally it was described as a scaphognathine pterosaur (Fig. 1) close to Sordes. At first glance, it might be appear to be one. It had short legs, short hands, a longish tail and sharp teeth. What it doesn’t have is a distinct primary naris with a strong maxillary ascending process. So, this is could be VERY interesting, with a little bit of this, and a little bit of that…

So what is it?
An example of modular evolution?

No. 
Modular evolution doesn’t happen. Phylogenetic analysis sorts these sorts of things out. Evolution changes every part of the body, even if just a little bit.

A transitional taxon?
Well, every pterosaur, except terminal taxa, can be considered transitional between its ancestral and derived kin. But in this case Jianchangopterus is not transitional between rhamphs and pterodacs.

Figure 1. Jianchangopterus in situ. It is small, has a long tail, but it nests at the base of the Pterodactylus clade, between Ningchengopterus and the Painten pterosaur, neither of which expose the mid to distal tail. Figure 1. Jianchangopterus in situ. It is small, has a long tail, but it nests at the base of the Pterodactylus clade, between Ningchengopterus and the Painten pterosaur, neither of which exposes the mid to distal tail.

Figure 1. Jianchangopterus in situ, both plates superimposed. It is small, has a long tail, but it nests at the base of the Pterodactylus clade, between Ningchengopterus and the Painten pterosaur, neither of which expose the mid to distal tail. Manual 4.4 is very thin, folded back against m4.3 here in one wing, less folded on the other wing.

What analysis recovers
when you add this taxon to the large pterosaur tree, you find that Jianchangopterus nests between Ningchengopterus and the Painten pterosaur, in their own clade at the base of the genus clade Pterodactylus (Fig. 2). Outgroups to these two clades include Ornithocephalus and two tiny Solnhofen pterosaurs (n9 and n31). The outgroup to all three clades is SMNS81775, a very tiny pterosaur, that I know from a skull drawing only. It has a large orbit, short rostrum and short antorbital fenestra.

Let’s delete all Pterodactylus to see what happens
And the outgroups too. Results: Jianchangopterus nests in the same spot. It doesn’t shift toward any scaphognathines.

Sometimes what is obvious STILL needs to be examined
Lu and Bo looked at certain obvious traits in Jianchangopterus (tail, metacarpus, tooth number, etc.) and decided it was closest to Sordes, which they considered a scaphognathid. It is not. And neither is Jianchangopterus. Shifting Jianchangopterus to Sordes adds 40 steps to the most parsimonious score. Eyeballing a specimen, even following ‘the rules’ regarding certain traits still takes a back seat to phylogenetic analysis.

It’s all in the details…
and the taxa one includes, as I’ve harped on constantly.  On that point, Lu and Bo were not aware of the Painten pterosaur when they published. And they failed to mention Ningchengopterus.

Figure 2. Jianchangopterus between Ningchengopterus and the Painten pterosaur. Note in Jianchangopterus the metacarpus is relatively shorter, especially relative to the ulna. The cervicals are more robust and relatively a little shorter. This is a reversal that makes Jianchangopterus more rhamph-like. You can't eyeball these things. You have to let the matrix and computer recover the relationships.

Figure 2. Jianchangopterus between Ningchengopterus and the Painten pterosaur. Yes, it looks superficially like a basal “rhamph.” But phylogenetic analysis separates the homoplasies from the homologies. Note in Jianchangopterus the metacarpus is relatively shorter, especially relative to the ulna. The cervicals are more robust and relatively a little shorter. This is a reversal that makes Jianchangopterus more rhamph-like. You can’t eyeball these things. You have to let the matrix and computer recover the relationships.

So what about that long tail?
Neither Ningchengopterus nor the Painten pterosaur expose a long tail, either because the plate is broken or the tail is beneath matrix. The outgroups all have a long tail. They also have a longer metacarpus especially relative to the ulna. This is evolution at its best. Nothing proceeds in a straight line. At every generation some are taller, some have longer hands, others have shorter hands.

Figure x. When you compare the three specimens of Sordes to the three jianchangopterids the purported similarities to Sordes start to fade. Shifting Jianchangopterus to Sordes adds 40 steps.

Figure 3. When you compare the three specimens of Sordes to the three jianchangopterids the purported similarities to Sordes start to fade. Shifting Jianchangopterus to Sordes adds 40 steps. The 36 specimen of Sordes nests closer to the Donau Dorygnathus than to the other two Sordes specimens which were themselves basal to Dorygnathus.

 

What about the most basal Pterodactylus?
Here the more derived AMNH1942 specimen of Pterodactylus (n20 in the Wellnhofer 1970 catalog. Fig. 3), the most basal taxon in the Pterodactylus genus clade, also seems to have a very long, but faint tail, largely hidden below a dusting of matrix.

Figure 3. Pterodactylus AMNH1942 with tail traced.

Figure 3. Pterodactylus AMNH1942 with tail traced. Note the tail goes below the leg at the knee, then reappears near the wingtips and trails toward the feet. The matrix itself is filled with organic shapes and what appears to be a tail could be one of these. However, the undisputed long tail of Jianchangopterus adds credence to this interpretation.

Clearly  a robust tail disappears beneath the femur. What we see of the rest of the tail could be organic shapes, which are also all around the matrix. But then with a sister taxon like Jianchangopterus with an undisputed long tail, this deserves further investigation.

Figure 5. Pterodactylus AMNH1942 without the tracing.

Figure 5. Pterodactylus AMNH1942 without the tracing. No doubt the tail disappears behind the femur. Further investigation is needed to find the rest of the tail and expose it on the surface.

More derived Pterodactylus specimens had a short tail.  No doubt about that.
So the tail became further reduced in derived members of this clade. There has been a long-standing assumption that Pterodactylus had a short tail. That assumption really has to be tested by exposing that last caudal vertebra. That hasn’t always (has never) been done. So we might be living under a false paradigm. Jianchangopterus provies a clear clue that the old paradigm needs to be examined in greater detail and with greater certainty.

The short hand
The metacarpus/ulna ratio is very small/short in Jianchangopterus. Phylogenetic analysis demonstrates that this single trait is a reversal from a larger ratio. Don’t think it can’t happen. Evolution works the way it works, and not always in a straight line.

Transitional taxa
We’ve seen several contenders for the transition taxon between rhamphs and pterodacs.

Darwinopterus had a short hand and long tail, but a long skull and neck, but it nests on the rhamph side not anywhere near any of the four pterodac origin/transition points.

Rhamphodactylushad a long skull, short tail and long hands. It nests on the pterodac side of one divide.

Kryptodrakon was a misread large but gracile dorygnathid.

Only the tiny Solnhofen pterosaurs provide concrete evidence for four gradual transitions, each to their own pattern.

Getting back to Jianchangopterus
Lü and Bo report, “the lateral surface of the premaxilla and maxilla have horizontal laminations.” This is what I’ve been reporting, this is the anterior jugal laminated to these underlying bones.

Lü and Bo report, “the maxilla bears a distinct recess (representing the antorbital fossa).” This may not be true. IMHO, what Lu and Bo see is IMHO is a medial sheet of bone dividing the left and right rostra, common to many pterosaurs.

The long tail, clearly laid out on this specimen, takes one positive step to confirm my earlier observations of similar longish, very thin tails on other pterodactyloid-grade pterosaurs.

Reference
Lü J and Bo X 2011. “A New Rhamphorhynchid Pterosaur (Pterosauria) from the Middle Jurassic Tiaojishan Formation of Western Liaoning, China”. Acta Geologica Sinica85(5):977–983.

New basal pterodactyloid(?) Kryptodrakon = Sericipterus, a dorygnathid

The big news this morning:
Andres, Clark and Xu (2014) have claimed to discover the earliest known pterodactyloid (Middle/Late Jurassic, Shishugou Formation in Xinjiang, China).They wrote: “We report here the earliest pterosaur with the diagnostic elongate metacarpus of the Pterodactyloidea, Kryptodrakon progenitor, gen. et sp. nov., from the terrestrial Middle-Upper Jurassic boundary of Northwest China. Phylogenetic analysis confirms this species as the basalmost pterodactyloid.”

Andres reported, “In paleontology, we love to find the earliest members of any group because we can look at them and figure out what they had that made the group so successful.” 

If it is one, it’s a big one!
Wingspan estimates are over a meter.

That big size is the red flag
Of course, this flies in the face of the large pterosaur tree, which recovered four origins for pterodactyloid-grade pterosaurs at about this same time, and they were all tiny. Andres, Clark and Xu did not include these tiny pterosaurs in their phylogenetic analysis.

Figure 1. The bits and pieces of Kryptodrakon assembled into a Pterodactylus bauplan, from Andres, Clark and Xu 2014.

Figure 1. The bits and pieces of Kryptodrakon assembled into a Pterodactylus bauplan, from Andres, Clark and Xu 2014.

It’s always difficult to reassemble bits and pieces,
but not impossible. Andres, Clark and Xu did that above (Fig. 1), using a small Pterodactylus as their bauplan or blueprint.

There’s an alternate bauplan available
and it’s also from the same Shishugou Formation. Sericipterus is a very large and gracile dorygnathid (Fig. 2). When you put the bones of Krypodrakon on top of the bauplan for Sericipterus you find a good match. 

Figure 2. The bone bits of Kryptodrakon placed on the bauplan of the giant dorygnathid, Sericipeterus, also from the Shishugou Formation. There's a good match here.

Figure 2. Here the bone bits of Kryptodrakon are placed on the bauplan of the giant dorygnathid, Sericipeterus, also from the Shishugou Formation. There’s a good match here. Perhaps Kryptodrakon is a junior synonym for Sericipterus, filling in some of its missing pieces.

And suddenly that “long metacarpus” is not so long anymore. Notably, Sericipterus had gracile wing bones, and that proved confusing to Andres, Clark and Xu. “Thinner” can sometimes be confused with “longer” unless you know what the bauplan is.

But wait, there’s more.
Compare the metacarpus of Kryptodrakon with its dorsal rib and the metacarpus doesn’t look so long anymore. The same holds for the distal carpal, scapula, humerus and wing joint scraps. They’re all too big for that metacarpus to be “elongate.”

A more parsimonious solution
Kryptodrakon and Seripterus are both from the same formation. They are the same size, and their bones have the same shape (so far as can be told from available scraps). We also know from a larger phylogenetic analysis that includes tiny pterosaurs that basal pterodactyloid-grade pterosaurs were all tiny and Kryptodrakon was big.

Therefore,
the more parsimonious solution is to consider Kryptodrakon a junior synonym for Sericipterus, a giant dorygnathid, not a pterodactyloid.

One more thing
Andres, Clark and Xu were also the discoverers and authors of Sercipterus, the only other pterosaur found in the Shishugou Formation.

Sorry to throw cold water on this.
But testing for parsimony is good Science.

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

Read more: Science_News