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