Re: [dinosaur] Gargantuavis pelvis from Maastrichtian of Romania (not ornithurine bird)

[Tim Williams <tijawi@gmail.com>]

Amazing. It'd be a shame if _Gargantuavis_ is ever sunk into _Elopteryx_. Considering how fragmentary the _Elopteryx_ holotype is, this should probably be a non-starter.

This sentence got me thinking: "Judging from the elongated shape of the preserved caudal vertebrae, _Balaur_ had a long tail (Cau et al., 2015) and, if avian, it is therefore outside Pygostylia, the clade including short-tailed birds."

Pygostylia contains short-tailed birds - but there's no reason why it should contain *only* short-tailed birds.

The length of the tail (and whether or not it es a pygostyle) does not directly determine if _Balaur_ (or _Gargantuavis_ or _Elopteryx_) is a member of Pygostylia or not. Membership of this clade is not dependent on whether the taxon has a pygostyle. Pygostylia is node-based, and anchored in _Confuciusornis_ (e.g., Turner et al., 2012; Hartman et al., 2019).  As such, membership of Pygostylia depends on a taxon's phylogenetic position relative to _Confuciusornis_ and crown birds, not on the presence of a pygostyle. Some topologies recover the long-tailed _Jeholornis_ inside Pygostylia. There's even a suggestion that _Balaur_ may be closely related to the volant _Jinguofortis_, which has a pygostyle (http://theropoda.blogspot.com/2018/09/balaur-un-jinguofortisidae-gigante.html) I don't know how the putative _Balaur_-_Gargantuavis_-_Elopteryx_ clade impacts on this hypothesis.

It's likely that the pygostyle evolved multiple times within avialan theropods, making any apomorphy-based definition of Pygostylia impractical. In one way it's unfortunate that "Pygostylia" was chosen as a clade, since the name tends to give the impression that a critter must have a pygostyle in order to be a pygostylian. _Balaur_ etc could theoretically be a pygostylian (i.e. a member of Pygostylia) without a pygostyle.

On Tue, Oct 15, 2019 at 5:34 AM Ben Creisler <bcreisler@gmail.com> wrote:

Ben Creisler

bcreisler@gmail.com

A new paper:

Gerald Mayr, Vlad Codrea, Alexandru Solomon, Marian Bordeianu & Thierry Smith (2019)
A well-preserved pelvis from the Maastrichtian of Romania suggests that the enigmatic Gargantuavis is neither an ornithurine bird nor an insular endemic.
Cretaceous Research (advance online publication)
doi: https://doi.org/10.1016/j.cretres.2019.104271
https://www.sciencedirect.com/science/article/pii/S0195667119302289

We describe a well-preserved pelvis from the Maastrichtian SÃnpetru Formation of the HaÅeg Basin in Romania. The fossil closely resembles the pelvis of Gargantuavis philoinos from the Ibero-Armorican Peninsula, but differs in a smaller size and a few morphological features. It constitutes the first record of Gargantuavis outside the Ibero-Armorican Island and is more complete than any of the previously known Gargantuavis pelves. The new fossil allows the recognition of characteristics previously unknown for Gargantuavis. These include the presence of large supratrochanteric processes, the absence of a widened midsection of the synsacrum (which indicates the absence of a glycogen body), and the absence of fusion between the pelvic bones at the level of the acetabulum. The latter two features suggest that Gargantuavis is not closely related to the Ornithurae and the taxon may even fall outside the Ornithothoraces, the clade including Enantiornithes and Ornithuromorpha. Recognition of Gargantuavis in the fauna of the HaÅeg Island is of particular significance, because various theropods have been described from the Upper Cretaceous of Romania. The Romanian pelvis is of similar-size to Elopteryx nopcsai, which was described as avian and is based on hindlimb elements, and it also shows some similarities to the pelvis of the unusual theropod Balaur bondoc. The new fossil furthermore disproves the hypothesis that the flight capabilities of Gargantuavis were lost in an insular environment of the Ibero-Armorican Island, and raises the possibility that Gargantuavis, Elopteryx, and Balaur belong to a distinctive theropod clade of the Late Cretaceous European archipelago.

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