The Langobardisaurus Pteroid and Preaxial Carpal

The right manus of Langobardisaurus tonelloi.

Figure 1. Click to enlarge. The right manus of Langobardisaurus tonelloi. Left: Reconstructed. Middle: In situ. Right: Interpretation of elements in situ. Here a case can be made for the appearance of the pteroid and preaxial carpal, derived from the two former centralia. And if those are not bones but holes leading to the white matrix, no problem. No change either way to the family tree. Hard to tell when things are disarticulated like this. Or are they?

Peters (2009) described the pteroid and preaxial carpal of Cosesaurus, first viewed and illustrated (but misidentified) by Ellenberger (1993). Langobardisaurus nested in the large reptile tree as a sister to Cosesaurus, so it seemed appropriate to look for these bones in Langobardisaurus, a taxon we earlier noted had a similar pterosaur-like pectoral girdle, although the design is more primitive than in Cosesaurus and derived along its own way with enlarged clavicles.

In situ
The Langobardisaurus tonelloi skeleton is complete  and articulated. The manus is also complete and articulated, but some carpal elements were shifted (the loose ones) as well as the ungual of digit 5, which drifted closer to the tip of digit 4. The preaxial carpal and pisiform have drifted the least of the other carpals. The loose pteroid (in red, Fig. 1), drifted a little further. It has the same check mark shape seen in Cosesaurus, Sharovipteryx, Longisquama and pterosaurs.  And if those are not bones but holes leading to the white matrix, no problem. No change either way to the family tree. That simply means Langobardisaurus had no ossified centralia, like Tanystropheus, Tanytrachelos and Huehuecuetzpalli, the last of which had a completely unossified wrist. The lack of ossification is what enabled the centralia to migrate.

The ulna and radius have been slightly broken during crushing. The pteroid, lying atop the ulna, was previously overlooked. I found it, along with all the other listed details, using the much derided DGS technique employing Adobe Photoshop. In reality, I just looked more closely than others had done before. I also understood what to look for because I had reconstructed relatives.

Reconstruction
The distal carpals needed very little restoration. DC3 and 4 rotated as a set. The proximal carpals were strongly attached to the radius and ulna. The former centralia, the preaxial carpal and pteroid, were restored to the positions they have in Cosesaurus. Otherwise there is no room for them in the central carpus. In Sphenodon the medial centralia is pointed but straight. In Langobardisaurus the pteroid is check-marked shaped, as in Cosesaurus and pterosaurs. The pteroid and preaxial carpal, even in pterosaurs, have loose connections and commonly drift.

Langobardisaurus tonelloi

Figure 2. Langobardisaurus tonelloi. Looks more and more like a long-necked cosesaur.

Bipedalism and Flapping
Both Cosesaurus and Langobardisaurus have traits found in bipeds (Renesto, Dalla Vecchia and Peters 2002), although more developed in Cosesaurus (Ellenberger 1993, Peters 2000 a, b, 2002), supported by occasionally bipedal tracks, Rotodactylus, that match their manus and pedes. Both Cosesaurus and Langobardisaurus have a pterosaur-like pectoral girdle  distinct from their quadrupedal kin. Such a pectoral girdle suggests a flapping ability, as in pterosaurs. This secondary sexual character and behavior was a precursor to flight, but in the case of Langobardisaurus and Cosesaurus, it was just an attention-getting behavior, which reached an acme with Longisquama. Bipedalism lifts the manus off the substrate and permits evolutionary changes not associated with terrestrial locomotion.

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
Ellenberger P 1993Cosesaurus aviceps . Vertébré aviforme du Trias Moyen de Catalogne. Étude descriptive et comparative. Mémoire Avec le concours de l’École Pratique des Hautes Etudes. Laboratorie de Paléontologie des Vertébrés. Univ. Sci. Tech. Languedoc, Montpellier (France). Pp. 1-664.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters, D. 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330.
Muscio G 1997. Preliminary note on a specimen of Prolacertiformes (Reptilia) from the Norian (Late Triassic) of Preone (Udine, north-eastern Italy). Gortania – Atti del Museo Friulano di Storia Naturale 18:33-40
Renesto S 1994. A new prolacertiform reptile from the Late Triassic of Northern Italy. Rivista di Paleontologia e Stratigrafia 100(2): 285-306.
Renesto S and Dalla Vecchia FM 2000. The unusual dentition and feeding habits of the Prolacertiform reptile Langobardisaurus (Late Triassic, Northern Italy). Journal of Vertebrate Paleontology 20: 3. 622-627.
Renesto S, Dalla Vecchia FM and Peters D 2002. Morphological evidence for bipedalism in the Late Triassic Prolacertiform reptile Langobardisaurus. Senckembergiana Lethaea 82(1): 95-106.

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