Gargantuavis (meaning 'gargantuan bird') is an extinct genus of large, primitive bird containing the single species Gargantuavis philoinos.[
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Its femur shows that it was a form rather than cursorial, not adapted for running.
Discovery
The first Gargantuavis fossil was found in 1995 in Var, southeastern France. This first specimen, a fragmentary set of pelvic vertebrae (synsacrum), was uncovered near the village of Fox-Amphoux in a paleontological excavation and described by French paleontologists Eric Buffetaut and Jean Le Loeuff, who noted the synsacrum's similarity to that of modern birds.
Gargantuavis specimens are known from six localities in Europe:
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The Bastide-Neuve locality, near Fox-Amphoux (Var), yielded the initial specimen reported in 1995, two other partial pelvic fragments (BN 758 and BN 763) described in 2015, and a possible rib fragment found in association with BN 763.
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The Bellevue locality, near Campagne-sur-Aude (Aude), yielded another partial pelvis (MDE C3-525), which was deemed the holotype in the 1998 description of the genus.
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The Combebelle locality, near Villespassans (Hérault), yielded a large femur lacking the distal end (MDE A-08), which was referred to the genus in its initial 1998 description.
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The Montplo-Nord locality, near Cruzy (Hérault), yielded a single neck vertebra (MC-MN 478) which was referred to the genus in 2013.
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A quarry near the village of Laño in northern Spain (Condado de Treviño) yielded a partial syncranum (MCNA 2538) described in 2017, the only specimen known outside of France.
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The Sânpetru Formation of Romania–what was Hațeg Island–yielded a garguntuaviid pelvis in 2019, identified as cf. Elopteryx. Its discovery here revises earlier ideas of the bird being endemic to the Ibero-Armorican Island.
Description
Though Gargantuavis is only known from a few isolated fossil bones, some information about its life appearance and ecology have been inferred by studying their details. Gargantuavis is known from several specimens representing a few limited parts of the skeleton: synsacra (the fused vertebrae above the hip),
Other than its large size, the most unusual feature of Gargantuavis was its pelvis. It was originally reported to be extremely wide, like that of a moa, though a better preserved specimen described in 2015 showed that this interpretation was due to crushing in the original. The hips of Gargantuavis, while still broad, were narrower and more bird-like than originally thought.
Paleoecology
During the Late Cretaceous, Europe was an archipelago. Southern France and north-western Spain where its fossils are found was part of the large Ibero-Armorican island in the prehistoric Tethys Ocean.
Since no skull remains have been found, the diet of the animal is uncertain.
Bone histology showed that Gargantuavis had a rapid early growth followed by an extended period (of at least 10 years) of slow cyclical growth before to attain skeletal maturity. A similar pattern is known in extinct Moa and in the extant kiwi, which are also insular birds. The titanosaur Ampelosaurus, found together with Gargantuavis in the Bellevue site, shows also a reduction in its growth rate, possibly linked to some environmental pressure like periodic food shortages. This is supported by Sedimentology and Mineralogy studies which indicate episodes of semi-arid and strongly seasonal climate during the Late Cretaceous in Southern France.
Classification
The systematic position of Gargantuavis with other birds is uncertain because of the fragmentary nature of its remains.[ Some researchers suggested that Gargantuavis was not a stem-bird at all, but rather a giant pterosaur,][Mayr, G., 2009. Paleogene fossil birds. Berlin, Springer.] but this was rejected based on the presence of more bird-like conditions.
However, the discovery of a pelvis from what was Hațeg Island shows trochanter on the femora, a lack of a glycogen body, and a lack of fusion of the pelvic bones around the hip socket, meaning it was not closely related to Ornithurae, and likely not even a member of Ornithothoraces which includes modern birds and their closest ancestors. The archaic Hațeg avian theropods Elopteryx and Balaur bondoc bear some similarity to Gargantuavis remains, which may indicate the three form some clade native to the Late Cretaceous European archipelago, though they have ambiguous affinities.[ This was questioned by other authors, and it is claimed that it was a basal ornithurine, at an evolutionary level similar to that of Hesperornithes,]
