The Evolution of Anurognathid Skulls

Sometimes its good to just get a bunch of sister taxa all together
Here I present a selection of anurognathid skulls, plus some precursors including Dimorphodon. No one else has reconstructed the whole set of anurognathid skulls. Reconstructing all of them permits side-by-side comparisons to discover and weed out autapomorphies that may represent mistakes and help characterize their traits and evolutionary patterns. Plus you finally get to see what they really looked like!

What Made Anurognathids Unique
was the orientation of their nares, or nose holes. Here (Fig. 1), following the results of the large study, a selection of skulls illustrates how the naris moved anteriorly and rotated vertically during the evolution of anurognathids.

Bennett’s Attempt
In his first attempt at reconstructing an anurognathid skull, Bennett (2007) botched it, creating a “monster’ (Fig. 1) with giant eyes in the front of the skull, having a small antorbital fneestra and a broad parietal, bearing no resemblance to sister taxa. This was discussed in more detail earlier here.

 

Figure 1. Anurognathid skulls in phylogenetic order.

Figure 1. Anurognathid skulls in phylogenetic order.

Kellner’s Hypothesis
Kellner (2003) considered the terminal naris of anurognathids to be a primitive feature, relating it to non-pterosaur archosauriforms that also had a terminal (over the premaxillary teeth) naris. Unfortunately no other character traits were shared and Kellner never reconstructed an anurognathid skull. Rather he based his interpretation of Anurognathus on Wellnhofer’s early efforts which did not illustrate the posterior skull.

The Special Naris of Anuros Starts with GLGMV0002
Dimorphodontids split from eudimorphodontids with the appearance of GLGMV0002, which had a relatively larger naris. Dimorphodon took this to an extreme. It’s difficult to gauge the size of the naris in Peteinosaurus, but in the IVPP embryo, the naris is smaller, but rotated vertically.

Wider and Wider Premaxilla
In Dendrorhynchoides the premaxilla started to become much wider along with the rest of the skull. The flathead anurognathid, SMNS 81928, took this to its first extreme. Anurognathus had a similar premaxilla, but on an elongated maxilla.

Transverse Premaxilla – Anteriorly Oriented Nares
The last three anurognathids had nares that faced anteriorly, unlike any other pterosaur. The CAGS specimen was the most primitive of these.  Batrachognathus was similar but had a narrower nasal, which rotated the orbits anteriorly giving it binocular vision, like an owl. Jeholopterus, the vampire pterosaur, also had binocular vision. Distinct from other anurognathids, Jeholopterus had an upturned premaxilla bordered by twin fangs able, by virtue of their length and upturned orientation, to pierce the hides of dinosaurs. Unlike other anurognathids, the mandible tip rose to meet the upturned premaxilla.

We know of no other anurognathids more derived than Jeholopterus, but keep looking for them. Anurognathids are relatively rare in any case. Jeholopterus could represent the end of anurognathids. Or there could be more discoveries yet to come.

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.
Döderlain L 1923Anurognathus ammoni, ein neuer Flugsaurier. Sitzungsberichte der Königlich Bayerischen Akademie der Wissenschaten, zu München, Mathematischen-physikalischen Klasse: 117-164.
Kellner AWA 2003. Pterosaur phylogeny and comments on the evolutionary history of the group. In: Buffetaut E. & J-M. Mazin, Eds. Evolution and Palaeobiology of Pterosaurs. London, Geological Society Special Publication 217: 105–137.
Wellnhofer P 1975a-c. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33.Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.

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