Scientific name Gargantuavis philoinos Rank Genus | Species †G. philoinos Phylum Chordata | |
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Similar Patagopteryx, Samrukia, Enantiornis, Avisaurus, Vorona | ||
The giant bird gargantuavis a case of insular evolution in late cretaceous europe
Gargantuavis is a genus of extinct avialan stem-birds containing the single species Gargantuavis philoinos. G. philoinos lived during the late Cretaceous period in what is now southern France. Its fossils were discovered in the Marnes Rouges Inferieures Formation, which has been dated to roughly 70 million years old. A large avialan, Gargantuavis was flightless, occupying an ecological niche somewhat similar to that of modern ratites or more primitive theropods. It is possible that some of the fossil eggs found in the region, usually attributed to non-avialan dinosaurs, actually belong to this bird.
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Discovery
The first Gargantuavis fossil was found in 1995 in Var, France. This first specimen, a partial set of pelvic vertebrae (synsacrum), was uncovered near the village of Fox-Amphoux in a paleontological excavation. Several other specimens were later found further west, in the villages of Villespassans, Cruzy, and Campagne-sur-Aude, providing enough fossil material to describe and name the species in 1998. The species name G. philoinos, meaning "wine lover", was chosen because several of these first Gargantuavis bones were found in and around vineyards and wineries.
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), illia (hip bones), and at least one partial femur (upper leg bone), which was referred to the species based on the fact that it seems to fit well with the hip. A neck vertebra has also been referred to Gargantuavis.
Other than its large size, the most unusual feature of Gargantuavis was its pelvis. The pelvis of Gargantuavis 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. In addition to their unusual width, which prevented the two ilia from meeting at the front of the pelvis, the acetabulum, or hip socket, of Gargantuavis was set close to the front, rather than closer to the middle of the pelvis.
Some researchers have suggested that Gargantuavis was not a stem-bird at all, but rather a giant pterosaur. However, when this idea was tested by studying the form and internal structure of the bones, its identity as an avialan was supported.
Ecology
During the time period in which Gargantuavis lived, the region of southern France where its fossils are found was part of a large island in the prehistoric Tethys Sea. The rock formations that have yielded Gargantuavis fossils have also produced abundant remains of fish, turtles, crocodylomorphs, pterosaurs, sauropods, ankylosaurians, ornithopods, and theropods, including other early avialans, like enantiornithes. Abundant fossils of the ornithopod Rhabdodon, and the lack of any hadrosaurid fossils, have been used as index fossils to roughly date these formations to the early Maastrichtian age. Gargantuavis seems to have been an uncommon part of the fauna in its region. Despite numerous digs at sites where its bones have been found since its discovery, most have yielded only single specimens.