Updated July 1, 2021
with new data provided by Dalla Vecchia 2021.
Yesterday we looked at Bergamodactylus wildi, the basalmost pterosaur, newly named by Kellner (1995). In that same paper Kellner also named Austriadraco dallavecchiai (BSp 1994 I51) a small Triassic pterosaur known from scattered bits and pieces. Among those pieces is a mandible (Fig. 1) with an apparent mandibular fenestra. Earlier Nesbitt and Hone (2010) attempted to show that pterosaurs were archosauriforms based on this autapomorphy (not found in other pterosaurs). Both of the above papers considered the mandible preserved in lateral view, contra the original interpretation by Wellnhofer (2001) of a medial view.
Austriadraco had a hole preserved in the mandible.
The question is, was that extra bone (in light blue, just anterior to the glenoid) not found in other pterosaurs, the displaced lid for the mandibular fenestra? Or was there yet another unexposed bone that shifted position, as shown in Dimorphodon, that would have acted like a lid for that hole? In any case, the reality of that fenestra in situ is not in doubt. What is in doubt is the reality of that fenestra in vivo.
if the mandible of Austriadraco is exposed in medial or lateral view? Here are some questions you might ask a researcher, one who has actually seen the fossil.
- Does the coronoid have a substantial exposure below the rim of the mandible?
- Is there a concave pocket for insertion of the jaw muscles in the surangular?
- Does the articular have a broad or narrow presence?
- Do you see the dentary foramina (fo) that Kellner reported?
- Does the articular have a deep or shallow glenoid (pocket) for reception of the quadrate?
- Does the dentary have a long low shelf below a long concavity?
- Does the splenial have a large exposure?*
- Does the angular extend posteriorly medial to the articular?
- Is the exposed surface of the articular generally convex or concave?
All four above named paleontologists
have seen the specimen first hand, but it was three to one against a medial exposure. Which side are you on? (and don’t forget, you’re using DGS to make your decision).
* I don’t think Wild illustrated this one correctly based on the data in the photograph (Fig. 1).
Austriadraco nests with
Seazzadactylus (Fig. 3) in the large pterosaur tree (LPT, 245 taxa). Descendants include the rest of the pterosaurs. None of these have a lateral mandibular fenestra. Neither does Eudimorphodon. Phylogenetic bracketing indicates: no lateral mandibular fenestra.
Dalla Vecchia FM 2009. Anatomy and systematics of the pterosaur Carniadactylus (gen. n.) rosenfeldi (Dalla Vecchia, 1995). Rivista Italiana de Paleontologia e Stratigrafia 115 (2): 159-188.
Kellner AWA 2015. Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa. Anais da Academia Brasileira de Ciências (2015) 87(2): (Annals of the Brazilian Academy of Sciences) Printed version ISSN 0001-3765 / Online version ISSN 1678-2690.
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225-233.
Wellnhofer P 2001. A Late Triassic pterosaur from the northern calcareous Alps. In: Sabatier P., Ed. 2003. Two Hundred Years of Pterosaurs. Toulouse, Laboratoire de Géologie sédimentaire et Paléolontologie, Université Strata Série 1-11: 99–100.