Both of Us Saw the Same Fossil Under the Microscope and Came to Different Conclusions

Dr. Chris Bennett and I both attended the Second Pterosaur Symposium in Munich in 2007. There we both got to see his second “Anurognathus“(Bennett 2007) [that I call the flat head specimen] under the microscope. He reported the wings included only three phalanges and terminated where the third phalanx appeared to end in a splintered point (Fig. 1, square outline). I said the wing phalanges clearly continued beneath the matrix.

Which one of us was right?
You be the judge.

The left foot of the flathead anurognathid. The

Figure 1. The left foot of the flathead anurognathid. The square surrounds the wingtip according to Bennett 2003). The left circle surrounds the reappearance of m4.3 as it enters the valley created by preparators exposing the foot. The right circle is the tip of m4.3 as it reappears briefly at the surface. M4.4 is really hard to see. Tiny rises in the surface of Solnhofen formation fossils indicate to preparators where to dig.

The specimen is small, about the size of a hummingbird. The third wing phalanx has the thickness of a needle. Please note that the surface of this fossil is orange, but where preparators have excavated the stone turns white.

Inside the square
Bennett (2008) determined that the wing had only three phalanges [terminating in the square outline], slightly dug out by the preparator. If it looks to you like there is a splinter of wing phalanx in that area, I agree with you. Under close inspection it looks like a needle going into an arm for the Red Cross. As you can see, most of the rest of wing phalanx three (m4.3) lies above the surface, surrounded by orange matrix. At the so-called “tip” it begins to be buried. I think the preparators did not dig far enough toward the tibia to expose more phalanx.

Inside the left circle
The preparators dug very deep to expose the left foot. When they removed the matrix they (according to the evidence) came across the rest of wing phalanx three then removed it, perhaps by accident, leaving what looks like the hollow end of a tiny sewer pipe exposed in a creek outcrop. If you see two hollow bones one atop the other, that might be due to crushing or to the presence of m4.4 lying alongside it, buried a little deeper or shallower.

Inside the right circle
On the other side of the “dig,” in line with the rest of the straight phalanx three, at about 10 o’clock within the circle, there is a small bone, likely the tip of phalanx three (see fig. 3 for more detail).

The flathead pterosaur interphalangeal joint 4.3/4.

Figure 2. The flathead pterosaur interphalangeal joint 4.3/4. This image was turned black and white in preparation for publication that never happened. A. Hollow phalanx 3 broken where the preparators dug out the foot. B. The distal tip of m4.3 and the proximal tip of m4.4. Its direction is interpreted here as oriented back toward the tibia, but it may be oriented back toward m4.3. It does appear to be completely disarticulated.

Where is wing phalanx 4?
That’s a good question. Both m4.4s are deep and very hard to see. So I tried to anticipate where they might be. I found the medial end of left m4.4 and it indicates the rest of m4.4 might have been oriented proximally (Fig. 3), as is common in anurognathids, or disarticulated flush against m4.3. Manual4.4 could lie beneath or largely beneath the tibia (Fig. 3 – wait 2 seconds for each change). The curve behind the ankle could be m4.4 or a uropatagium. Or both. The right wingtip appears on the left side of the pelvis at the acetabulum.

Flathead anurognathid GIF animation.

Figure 3. Flathead anurognathid GIF animation. Every 2 seconds the over layer shows my interpretation of wing soft tissue in accord with all other pterosaurs. It also illustrates the likely position of wing phalanx 4 based on the few clues available. If it doesn’t animate, click on it.

What about the other wing?
The right wing provides similar clues in lengths echoing the left wing. It may be more difficult to determine due to its greater depth and the interference of the tiny tail. The tip appears by the left acetabulum. By the way, I used a photograph with 10x the resolution seen here.

While we’re here
Note the wing membrane has a narrow chord that approaches then curls away from the elbow, as in ALL other pterosaurs. It does not extend directly to the tibia with a deep chord.

Addendum
As anyone who has ever eaten chicken knows, bones typically break and splinter at mid shaft, not at the tips. There is no ever so slightly expanded tip (interphalangeal joint) present in the black square, only shaft. All other anurognathids (see them and their links here), have four wing phalanges. The wing membrane does not point to the broken splinters, as if it were a wing tip, but maintains a substantial chord at the splinters as if it continued on further. In short, all the evidence in the fossil and in other anurognathids points to a typical wing with four phalanges. 

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 2007. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.

3 thoughts on “Both of Us Saw the Same Fossil Under the Microscope and Came to Different Conclusions

  1. Square: Excavation around the phalanx tip, regardless of preparation (this is common of Solnhofen fossils, and does not require a preparator to trench around fossil inclusions). The excavation indicates no bone continues beyond the point in the immediate vicinity.

    Circle near to square (extensor side of pes): Partially formed from wall of trench around pes, meaning that the feature is partially artificial. The rest is a blemish as a result of discoloration of the limestone matrix, a common enough feature when you look elsewhere around the same slab.

    Circle afar from square (plantar side of pes): Same as before: Blemish. Easily confusable, as you want to extend the phalanx or infer there is another, and it is conveniently placed. You fail to note, however, that the blemish is a longitudinal feature, and isolated (in circle) a small section of it, while ignoring the rest, which is about the length of the pes itself and continues in a trajectory quite unlike your implied shape.

    Limestone has an irregular texture, which forms features not unlike that of surficial geological features. One can easily use this slab and invent continental coastlines, or islands, and pretend that it is a map. But it’s a map where nothing is real but the included object, the preserved skeleton.

  2. Nice try, Jaime, except that m4.4 always ends in an expanded tip, an interphalangeal joint not seen in the splinters. And remember, I saw it under a microscope and it enters the matrix like a submarine submerging. AND… all anurognathids have four phalanges.

    • The tip “is expanded,” it is not a “joint” without direct evidence of an actual synovial soft-tissue or actual bone on that end. You’ve not found a single “actual bone” that is incontrivertible, that isn’t you making fake shapes on the slab in Photoshop.

      It’s really simple, Dave: If there was an actual bone there, and you weren’t trying to invent phalanges that have managed to distort themselves BENEATH not just the bones but sections of limestone, we wouldn’t be having this discussion. It would be clear, and we’d instead be having a discussion like we had with what that thing is in the skull of Bellubrunnus, in interpreting a bone feature. You are instead trying to say this thing “is a bone” because you cannot see it directly and instead imply it is there using unequivocal limestone blemishes.

      And instead of dealing with my indentification, which just so happens to coincide with Bennett’s, you ignore it. Let’s just say that was my pessimistic prediction of your response.

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 )

Google photo

You are commenting using your Google 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 )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.