Flugsaurier 2018: Anurognathid JPM 2012-001

Updated April 1, 2021
with hi-rez data from Zhou et al. 2021 and a new name for this specimen, Sinomacrops. See that data in part 1 here and part 2 here.

Flugsaurier 2018 part 3
Since the purpose of the symposium is increase understanding of pterosaurs, I hope this small contribution helps.

Lü et al. 2018 report on two new and unnamed anurognathid pterosaurs
from China. I’m guessing the one featured today has been known for six years based on its number: JPM-2012-001.

Figure 1. Larger image of Sinomacrops in situ with DGS tracing of the bone and soft tissue elements. See figure 3 for skull tracing. Note the wing membrane is just like that found in all other pterosaurs, enabling wing folding that minimizes membrane exposure and keeps the wing taut between only two points, the wing tip and elbow. PhD pterosaur workers prefer the bat-wing model despite having never seen even one example that was not subsequently invalidated.
Figure 2. Sinomacrops skull interpretations using traditional pen and ink vs. DGS, a technique in use here since 2003 and promoted to pterosaur academics back then. Now many other paleo workers are coloring bones in situ, but few to no other pterosaur workers do this. Note the ?po is here identified as the squamosal. The ‘scr'(scleral ring) is part pterygoid, part ectopalatine. The la/na is the ascending process of the maxilla. The ‘j’ jugal is the dentary.
Figure 3.The second half of the DGS method is to create a rough rconstruction from traced elements, avoiding the mishaps that occur with freehand drawings. Here the bones themselves determine the shape of the skull and width of the palate
Figure 4. Left: Life restoration of Sinomacrops from Wei et al. 2019 filled with problems. Center: Skeletal of Sinomacrops from fossil tracings. Right: Anurognathus holotype for comparison to scale. Note the smaller feet and more robust humerus in Sinomacrops.

According to Lü et al. 2018
“Based on body morphologies, anurognathid pterosaurs can be classified into two subgroups: long-tailed anurognathids (length ratio of tail to femur is greater or equal to 1) and short-tailed anurognathids (length ratio of tail to femur is smaller than 1).” The JPM specimen is a long-tailed type.

The second Chinese anurognathid, BPMC-0009,
is not shown in its entirety in Lü et al. 2018. Rather the authors focus on the tiny fourth phalanx at the wing tip (which also includes an ungual!). Lü et al. 2018 report, “The extremely reduced wing phalange 4 (its length is 4.6mm) may indicate that the so-called three wing-phalanged pterosaurs: Anurognathus (Bennett, 2007) and Beipiaopterus (Lü, 2003) may be caused by extremely reduced wing phalanx 4 and this phalanges did not preserve, and the expanded distal end of the wing phalanx 3 perhaps confirm this possibility (this distal of wing phalanx 4 is sharp and pointed).”

Unfortunately,
the basal azhdarchid, Beipiaopterus, has four wing phalanges. So does the flathead anurognathid SMNS 81928(not congeneric with the holotype Anurognathus), which also has four wing phalanges. See them in situ here and here. All anurognathids have four wing phalanges. Regarding BPMC-0009Jeholopterus also has a relatively small m4.4, so it may be related to the BPMC-0009 specimen. We’ll have to see the complete specimen to make that determination.

Not listed by the authors,
the UNSM 93000 specimen of Nyctosaurus does have only three wing phalanges, discussed earlier here.

The JPM specimen
has a long tail —but it nests with the short tailed Anurognathus (holotype, Fig. 3). So there goes the earlier Lü et al. hypothesis about splitting anurognathids. Under the Lü et al. hypothesis, you will have to know that every tiny caudal bone was on the matrix surface, preserved and able to be seen. Think how easy it would be for such tiny, pollen-sized, distal caudals to be buried… or lost during taphonomy. Besides, no one wants to pull a Larry Martin, splitting or lumping taxa based on one  trait. Use all 180+ traits in the large pterosaur tree (LPT). And make reconstructions to test your observations!

Figure 1. Clck to enlarge and animate. Here the buried wing phalanges are shown along with more tail vertebrae and wing membranes. Boosting the contrast brings some close-to-the-surface parts to more prominence.

Figure 4. Clck to enlarge and animate. Here the buried wing phalanges are shown along with more tail vertebrae and wing membranes. Boosting the contrast brings some close-to-the-surface parts to more prominence.

Anurognathids have a long history
of bad reconstruction. So does Anurognathus. Note, as in Vesperopterylus and all other anurognathids (Fig. 5), there is no trace of a giant scleral ring in the anterior half of the JPM specimen skull (Figs. 1–3, contra Bennett 2007 and the current fashion among pterosaur workers and artists). Rather, and just like related Dimorphodon, the antorbital fenestra is quite large and the orbit is right behind it.

Figure 1. Anurognathid skulls in phylogenetic order.

Figure 5. Anurognathid skulls in phylogenetic order. None have a giant sclerotic ring in the anterior of the skull. Rather, all have a large antorbital fenestra.

Like the holotype Anurognathus,
(Fig. 3) the JPM-2012-0001 specimen has longer dentary teeth (deeper than the mandible), an antorbital fenestra taller than the orbit (convergent with azhdarchids and tapejarids), a tiny metacarpus and a long list of other shared traits. The JPM specimen is more gracile overall, with smaller feet, more slender wing finger, a larger sternal complex and a shorter, taller skull.

References
Bennett SC 2007. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.
Lü J-C, Zhou X-Y, Liu C-Y and Sun D-Y 2018.
Chinese anurognathid pterosaurs. Flugsaurier 2018: the 6th International Symposium on Pterosaurs. Los Angeles, USA. Abstracts:63-65.

https://pterosaurheresies.wordpress.com/2014/02/13/anurognathid-eyes-the-evidence-for-a-small-sclerotic-ring/

A new anurognathid, Sinomacrops, traced and reconstructed

Sinomacrops part 2: more problems and insights

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.