Dalla Vecchia 2021 provides his new revision
of the small, Late Triassic pterosaur, Austriadraco (Figs. 1–5; Wellnhofer 2001, Kellner 2015) known from completely disarticulated and scattered remains of a single specimen on five contiguous blocks of matrix. It is reconstructed here (Fig. 1) for the second time based on Dalla Vecchia’s 2021 data. An earlier reconstruction (now replaced) mistakenly had a 2x larger jugal, probably due to scale bar issues. Dalla Vecchia and earlier authors (see below) did not provide a reconstruction.
From the abstract:
“Several skeletal elements preserved in the holotype and only specimen of the pterosaur Austriadraco dallavecchiai Kellner, 2015 (uppermost Triassic, Austria) have not been identified or have remained undescribed in previous works. They include important elements for the systematic and phylogenetic studies such as the femur, premaxillae and maxillary teeth. The broad bone initially considered the sternal plate is plausibly formed by the fused frontals, as already suggested by some authors.”
We don’t call that a ‘sternal plate’ in pterosaurs. Ever since Wild 1994 pterosaurs and their fenestrasaur ancestors have had a sternal complex created by the fusion or, in this case, the partial fusion of two clavicles, an interclavicle and sternum. In Austriadraco this rhomboid to triangular element (Fig. 2) is not a pair of fused frontals, but a sternal complex, as Wellnhofer originally labeled the element. Overlooked sternal ribs are also associated and identified here for the first time. With Dalla Vecchia’s excellent closeup photos now we know why this complex element appeared to have two sternal crista. Those are slightly disarticulated anterior clavicles, slightly separated from the anterior process of the cruciform interclavicle during taphonomy. See the sternal complex of another Late Triassic pterosaur, Bergamodactylus (Fig. 3, MPUM 6009), for a similar triangular morphology.
An actual frontal appears in situ close to the slender coracoid portion of the scapulocoracoid in Austriadraco. It was misidentified by all prior workers as part of a very wide coracoid.
From the abstract, continued:
“The diagnosis of Austriadraco dallavecchiai is amended on the basis of new information. The close relationship of Austriadraco dallavecchiai to Seazzadactylus venieri from the uppermost Triassic of Friuli (north-eastern Italy) is further supported by the morphological similarity between the two taxa (e.g. they share similar postorbital process of the jugal and dorsal process of the surangular).”
In the large pterosaur tree (LPT, 258 taxa) Austriadraco also nests with Seazzadactylus (Fig. 5) based on all the scoreable traits.
The sternal complex/frontal controversy provided by Dalla Vecchia 2021:
“Sternal plate or fused frontals? The rhomboid bone preserved closed to the left humerus and right scapulocoracoid has been identified as a sternum by Wellnhofer (2003), but it was later referred to as the fused frontals by Bennett (2015: 801) and Kellner (2015: 674). Dalla Vecchia (2014: 88) adopted the identification as a sternum as “provisional”. Wellnhofer (2003: 14) opted for the identification as a sternum because “in its general shape it agrees well with the sternum of the juvenile specimen of E. ranzii described by Wild (1994)”. However, he was probably influenced by the close association of the one with the dorsal vertebrae and ribs, shoulder girdle elements and humeri in BSP 1994 I 51 and because of its superficial similarity to the triangular or rhomboidal sternal plates of Dorygnathus (see Wiman 1925: fig. 7; Padian 2008a: fig. 20).”
Superficial? General shape? Surprisingly these professional workers did not trace the sternal complex elements in sufficient detail (Fig. 2) to cite Wild 1994, who first dissected the parts.
Dalla Vecchia 2021 continues:
“The identification as fused frontals is plausible because of the morphological resemblance to
the fused frontals of the Jurassic non-monofenestratan pterosaur Allkaruen koi (see Codorniú et al. 2016: fig. 1b).”
Ummm. Alkareun koi is a Middle Jurassic relative of the highly derived ctenochasmatid, Pterodaustro. It is probably not the best taxon to compare with a tiny Late Triassic pterosaur, especially when the element in Austriadraco is a sternal complex, not a fused frontal.
Dalla Vecchia 2021 continues:
“This explains the presence of the paired narrow processes, which would be an unusual
feature in a pterosaur sternum. Bennett (2015: 801) identified those processes as
the lacrimal processes of the frontals.”
Those processes are indeed unusual. We’ve all been wondering about them for nearly twenty years. Finally, thanks to photos published in Dalla Vecchia 2021 we can see the details necessary to reconstruct these slightly disarticulated elements as clavicles. The keyword ‘clavicle’ does not appear in Dalla Vecchia 2021.
Dalla Vecchia 2021 continues:
“In dorsal and ventral view, the fused frontals have concave lateral margins, because they form the upper margin of the orbits.”
That’s often called confirmation bias, and we’re all subject to that foible. Ultimately, the details are important and the details were overlooked by previous workers. Another Late Triassic tiny pterosaur, Bergamodactylus has a similar triangular sternal complex (Fig. 3). The keyword ‘Bergamodactylus‘ does not appear in the Dalla Vecchia text, only in the citations.
Remember the pterosaur mandible fenestra myth?
That belongs to Austriadraco, too. Nesbitt and Hone (2010) misinterpreted a mandibular fenestra in Austriadraco. They did not notice the displaced bone that would have covered it in vivo. They also thought the exposure was lateral rather than medial.
Kellner (2015) agreed this was a mandible in lateral view with a fenestra. That is wrong, as shown below in comparison to closely related Eudimorphodon, which preserves two mandibles, one in lateral view, one in medial view. Only the medial view has the same depression and bone morphology we also see in Austriadraco (Fig. 4).
Dalla Vecchia 2021 mistakenly accepted the presence of an “external mandibular fenestra” not shared with any other pterosaurs along with the aforementioned “frontal with short anterior processes” not shared with any other pterosaurs. So, maybe a DGS tracing and reconstruction could have helped. For now, these two myths of unique traits are going to continue unabated in the literature.
The above authors all have an agenda:
to keep pterosaurs somehow close to dinosaurs and archosaurs, trying to keep this third myth alive. These authors keep trying, but end up failing and faltering. That’s why this blogpost is here: to show the evidence for mistakes and help readers dismiss these myths.
Austriadraco dallavecchiai
(Wellnhofer 2001, 2003; Kellner 2015; Dalla Vecchia 2021; BSp 1994 I51, Late Triassic ~210mya) was a tiny pterosaur sister to Seazzadactylus. It was a tiny adult based on similarly-sized relatives. Kellner (2015) provided a new name, Austriadraco, to this specimen originally identified as a Eudimorphodon variant without a phylogenetic analysis.
References
Dalla Vecchia FM 2021. A revision of the anatomy of the Triassic pterosaur Austriadraco dellavecchiai Kellner, 2015 and of its diagnosis. Rivista Italiana di Paleontologia e Stratigrafia (Research in Paleontology and Stratigraphy) 127(2): 427-452.
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.
Wellnhofer P 2003. A Late Triassic pterosaur from the Northern Calcareous Alps (Tyrol, Austria). In: Buffetaut E., Mazin J.-M. (Eds) – Evolution and palaeobiology of pterosaurs. Geological Society of London, Special Publications, 217: 5-22.
Wild R 1994. A juvenile specimen of Eudimorphodon ranzii Zambelli (Reptilia, Pterosauria) from the upper Triassic (Norian) of Bergamo. Rivisita Museo Civico di Scienze Naturali “E. Caffi” Bergamo 16: 95–120.
The Pterosaur Heresies 