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.

Advertisements

10 thoughts on “Jianchangopterus – a very ‘rhamphy’ pterodactylid

  1. I showed the original to one of my anatomy students. She was unable to replicate your findings of a long tail. In fact she identified a short tail, tentatively, preserved above the wing fingers with no congruence to your model at all. She also disagreed with your pelvic reconstruction.
    This single-blind test of your DGS method is especially interesting as I gave her no knowledge of where the image came from. I simply put the original cropped pelvis/hindlimb photo on and said, “Does this animal have a tail? If so where and how long?” I oriented her with the legs and pelvis and provided no additional clues about where to look.
    Main comments that were developed: “I can’t see much because it is so pixelated,” and after being shown your reconstruction, “What actual evidence does he have?” and, “I could photoshop a tail onto a human skeleton and say it had one but that doesn’t mean it is true.”
    Closing thought from my student, “I need more than photoshop evidence to support your hypothesis before I consider it valid.”

  2. If you’re looking at the Pterodactylus, remember what you’re seeing is a thin layer of matrix overlying the actual bones, which remain buried. Very common among Solnhofen animals, what you first find is a rise in the shape of an animal in the otherwise level matrix. That’s how they know precisely where to excavate. Here the tail has not been excavated. One other point, you can’t expect a novice to see this. You have to expect a long tail given phylogenetic bracketing or proximity. As mentioned above, I’m encouraging the excavation of ptero tails until you get to the very last caudal, which is rarely done.

    I should add, based on NB’s comment, by ‘novice’ I mean someone not familiar with Solnhofen fossils and how they are discovered and exposed.

    • I’m not going to comment on the Pterosaur (I think Rob Gay’s post illustrates quite well what’s wrong). However I am going to say I am a bit shocked to see you write “you can’t expect a novice to see this”
      Not only does this come across as an extremely arrogant and insulting way to talk about someone whose abilities you have no idea of (particularly when this “novice” is someone actually going through anatomy training!!!). But isn’t the entire point behind this website that a novice with no preconceptions can notice stuff that the “biased” expert can miss??!! You yourself could be classed as a novice (indeed you repeatedly refer to yourself as an amateur) and yet you repeatedly go toe to toe with experts in their field and claim to spot stuff they haven’t noticed.
      Yet here a “novice”, given no information on the specimen, but with actual education in anatomy, disagreed with your interpretation and your response is “you can’t expect a novice to see this.”

      Also, are we still going to write “Modular evolution doesn’t happen” even after our last discussion? Are we going to ignore decades of evidence from neontogey and palaeontology, from molecular biology, developmental biology and anatomy, because David Peters doesn’t like a couple of the examples and so claims the whole idea is wrong?

    • Response from my student.
      “If it hasn’t been excavated and other specimens show a short tail [my note: we looked at other pterosaur skeletons after I had posted the previous comment] then why would you think it is long? Until it is excavated why not assume that its tail is short? What is giving you the idea that it has a long tail besides your own photoshop reconstructions? Why would this creature need a long tail? What is the purpose?”

      • Vestiges don’t have a purpose. Long tails disappear slowly in evolution. It doesn’t happen overnight. With regard to other specimens (if you could be specific, that would help), sure the tail becomes very short in several specimens, especially in Pterodactylus. Assumptions, of course, are not scientific. However, phylogenetic bracketing and proximity is scientific. I already mentioned earlier that “what is giving me the idea” is a tell tale rise in the matrix, which is what Solnhofen preparators count on to guide their air scribes, as mentioned earlier. It might be helpful to see some pre- and post prep fossils so you get the idea.

  3. Neil, by novice of course I mean someone who has not looked at pterosaurs for years as I have. Anatomy training doesn’t prepare you for Solnhofen fossils. Only working with Solnhofen fossils does that. That’s the experience you need. And let’s face it, even there the bulge created by skulls and torsos is going to be much more evident than a string of tiny tail verts. Please don’t blame me for noticing something that others have overlooked, especially when proof of same comes in the examples of Jiangopterus, Dendrorhynchoides (the holotype and referred specimens), Pterodaustro, etc. Please again note that the proximal tail bones disappear beneath the femur of the AMNH specimen of Pterodactylus. That tells you that the tail is beneath the matrix surface at that point. Let’s get out the digging tools and excavate where I have marked, then we’ll know whether or not I was correct. I’m only applying the same skills that Solnhofen preparators use. I encourage them to keep digging until the last caudal is exposed and then a little beyond, just to be sure.

    With regard to modular evolution, if it were true in the case of Darwinopterus, then phylogenetic analysis would indicate that pterosaurs derived from it would continue to finish what changes it started. That doesn’t pan out in the large pterosaur tree. Other pterosaurs make more parsimonious transitional taxa.

    • If you don’t like modular evolution in Darwinopterus and this taxon, than say you don’t like it in Darwinopterus and this taxon. Don’t claim it doesn’t exist.

      And I’m not going to argue about this pterosaur as I know very little about pterosaur anatomy. I was objecting to your assumption about the student’s novice status counting against her opinion, when you’ve (rightly) decried such presumption throughout this blog. Comments stand on their merit, not on the fact that she’s a student and therefore you think she doesn’t have the knowledge to disagree with you. All her comments have merit, particularly “I can’t see much because it is so pixelated”. That’s what I was blaming you for; saying “Please don’t blame me for noticing something that others have overlooked” is a ridiculous (and some might say petulant) comment.

      • Not petulant. You’re reading this wrong. The entire ‘reason for being’ for the website and blog is to notice what others have overlooked, either by observation of the fossil or by inclusion in phylogenetic analysis. Several times such observations have been confirmed by others. A suggestion to ‘keep digging’ until one finds the tip of the tail is a valid suggestion. I’m merely showing where to dig. And phylogenetic proximity adds to the possibilities. An anatomy student cannot be expected to read vague bulges in matrix without some experience at doing so. I’m not putting that person down, just noting that the skill set is different. No alternate imagery was presented, btw.

        With regard to crushed skulls and other previously indecipherable roadkills, even I cannot eyeball these fossils. Anyone interested in doing so has to go through the DGS process, one bone at a time, making mistakes along the way and testing those bone identifications in three view reconstructions that fit established morphological patterns. Perhaps the process is more difficult than you would like it to be, but there you have it. While others draw vague outlines around suspected skulls, I dive in and decipher them when possible. I hope you’re not angry with my methods because I try harder or attempt more precision. And, no doubt, I do make mistakes, most of which I discover without outside help. I could always use outside help, but specific drawings with valid identifications come in extremely rarely.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s