Ampelosaurus ( ; meaning "vine lizard") is a titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now France. Its type species is A. atacis, named by Le Loeuff in 1995. Its remains were found in a level dating from 71.5 million years ago, representing the early Maastrichtian.
Ampelosaurus would have had a long neck and tail — like most sauropods — but it also carried armor in the form of osteoderms. In 2005, over 500 bones had been assigned to Ampelosaurus. Additional material has been found since, including a partially articulated skeleton with skull, which makes it one of the best known dinosaurs in France. However, recent studies suggest that the type locality is not a monospecific titanosaur bone bed and that part of the bones attributed to Ampelosaurus probably belong to a second titanosaurian taxon.
Ampelosaurus lived on what was the Ibero-Armorican Island, a landmass including much of present-day France and Iberian Peninsula. Histological studies show characteristics related to an island environment such as a slowed growth rate. However, with a size of about in length for the largest known individual, Ampelosaurus was not an insular dwarf unlike some other Ibero-Armorican titanosaurs like Lirainosaurus and Atsinganosaurus, or the genus Magyarosaurus from the Hateg island.
Several specimens found elsewhere in France and Spain were referred to Ampelosaurus but were later identified as belonging to other titanosaurs.
Discovery and naming
Ampelosaurus is known by abundant remains from the Bellevue site near the village of Campagne-sur-Aude in the Upper Aude Valley, in Aude department in Occitania region. It was recovered in the lower levels of the Marnes Rouges Inférieures Formation, which belong to the early Maastrichtian epoch of the Late Cretaceous Period, ~ 70 million years ago. These sediments represent an ancient floodplain with numerous river channels.
Historically, the dinosaurs of the Upper Aude Valley were first reported by Paul Gervais in 1877 from two vertebrae discovered in the commune of Fa. The first discoveries of dinosaur bones at Campagne-sur-Aude date back to the beginning of the twentieth century, but they remained isolated and were quickly forgotten. It was not until 1982 that dinosaur's localities of the Upper Aude Valley were rediscovered by local amateurs, Pierre Clottes and Christian Raynaud, following the accidental discovery of a fossil bone in Campagne-sur-Aude by a hunter a year earlier. Clottes and Raynaud mainly discovered caudal vertebrae and limb bones during simple surface collecting carried out at several sites around the villages of Campagne-sur-Aude and Espéraza.
In 1989, the first systematic excavations carried out by professional paleontologists began on the main site, located at the Bellevue farm. Several excavation campaigns brought to light numerous bones of an unknown sauropod. This new dinosaur was named Ampelosaurus atacis by the French paleontologist Jean Le Loeuff in a preliminary description published in 1995. Ampelosaurus is derived from the Greek αμπελος, "the vine" and the Latinised Greek saurus, "reptile". Therefore, Ampelosaurus means "vineyard lizard" after the Blanquette de Limoux vineyard. The vineyard is located on the south side of the region Ampelosaurus was found in. The specific name is based on the Latin atax, the "Aude river". Only one tooth, three articulated dorsal vertebrae (the holotype MDE-C3-247), and the neural spine of another dorsal vertebra were illustrated, whereas the material known at that time also included other dorsal and caudal vertebrae, ribs, chevrons, limb bones, shoulder and pelvis bones, from several individuals. Four osteoderms discovered at Bellevue and described in 1994 were also attributed to Ampelosaurus in 1995.
In 2005, Le Loeuff published a more complete description of the bones discovered since 1989 including a braincase and a right dentary. In 2001 was found a relatively complete skeleton of a young adult about 10 m long, nicknamed "Eva" after the name of Eva Morvan the student who discovered the first elements. Several excavation campaigns were necessary (until 2006) to extract this skeleton. This specimen, which has yet to be described, includes an almost complete disarticulated skull of which only a few elements are currently on display in the Dinosaur Museum of Espéraza. In 2007, the remains of a larger specimen were discovered, including a sternal plate, a scapula, a 1.20 m femur, a pubis, a caudal vertebra and a chevron.
For more than twenty years, Ampelosaurus atacis was considered the only titanosaur present at Bellevue. Observed differences in long bones proportions have been interpreted as examples of individual variations. However, in 2012, a morphometric study of titanosaur femurs from France and Spain suggested the presence of three morphotypes at Bellevue, one of which was tentatively assigned to the genus Lirainosaurus. In 2013 Veronica Díez Díaz et al., however, noted that these femora differed from L. astibiae in several features.
In 2021, Díez Díaz and colleagues also agree on the existence at this site of a second titanosaur but find it more similar to the genus Garrigatitan from the Upper Campanian of Provence. The recognition of the presence of a second species of titanosaur at Bellevue in addition to Ampelosaurus atacis creates a high level of uncertainty in the attribution to one or the other of these species of isolated remains found at this site. Díez Díaz et al. thus underline the need to revise all the titanosaur bones found at Bellevue to clarify their taxonomy.
In 2023, at the Annual Conference of the European Association of Vertebrate Palaeontologists, Bernat Vila and colleagues presented preliminary results of a comprehensive study of the abundant titanosaur remains from Bellevue which confirms the presence at this locality of a new titanosaur species whose description is in progress. This study will also lead to an emended diagnosis of Ampelosaurus.
Purported Ampelosaurus remains from other localities The presence of Ampelosaurus has also been reported in other parts of southern France, as well as in Spain, but their identification has so far been shown to be erroneous (or has not been demonstrated in the case of the Labarre sandstone formation). In a short note published in 1998, Jean Le Loeuff stated that Ampelosaurus was known not only from the upper Aude Valley, but also the Petites Pyrénées (Ariège department), and the Chaînon de Saint-Chinian (Hérault department). However this has never been confirmed by a publication. Previously, Le Loeuff had recognized the presence of two different titanosaurs in the Grès de Labarre formation (Ariège) based on two different types of caudal centra and two very different tibiae. But he then considered that, given the fragmentary nature of the material, the specimens should be considered indeterminate titanosaurs. In the same way, in 1999 Eric Buffetaut and colleagues attributed to Ampelosaurus atacis teeth and postcranial bones discovered in the Grès à Reptiles formation at Cruzy (located in the area called Chaînon de Saint-Chinian) in Hérault department. A later study showed that Cruzy's titanosaur teeth are different from those of Ampelosaurus, and belong to a new taxon whose description is in progress. In 2009, Fernando Barroso-Barcenilla and colleagues reported in the Spanish site of Lo Hueco, in Cuenca province, the discovery of spatulate teeth with the same morphology as those of Ampelosaurus. However, the detailed description of the titanosaur teeth from Lo Hueco refuted this interpretation. In 2013, Fabien Knoll and colleagues tentatively attributed to Ampelosaurus sp. a braincase also from the Lo Hueco site. In 2019, Knoll and colleagues finally referred this braincase to Lohuecotitan pandafilandi, which was described in 2016 from a postcranial skeleton. Two types of titanosaur braincase are present in Lo Hueco. This attribution to the genus Lohuecotitan is based on the fact that the other braincase morphotype was found to be associated with a titanosaur skeleton distinct from Lohuecotitan, and because none of the very abundant titanosaur postcranial remains of Lo Hueco (represented by more than twenty partially articulated skeletons) belong to Ampelosaurus.
Description
Like most sauropods, Ampelosaurus would have had a long neck and tail, but it also carried armor in the form of osteoderms 25 to 28 cm long. The four osteoderms found have three different morphologies, they are plate, bulb, and spine-shaped. Ampelosaurus is thought to have measured in length and about in body mass. In 2022, Vila and colleagues assign a size of long and a weight of for the largest individual based on the femur MDE-C3-174 (Vila et al. Supplementary Information). Ampelosaurus atacis is known from many unattached bones and teeth. It is one of the best-known dinosaurs from France. It is considered to be a dwarf sauropod by Coria et al. (2005) because it has a smaller size in comparison with its ancestors. However, according to Klein et al. (2012), Ampelosaurus is not an insular dwarf since its adult size is much greater than that of Europasaurus or Magyarosaurus.
Skeleton
Ampelosaurus is one of the most completely known titanosaurian sauropods from Europe. Since 1989, over 500 bones discovered at the Upper Cretaceous Bellevue locality of southern France have been assigned to A. atacis. In 2023 Vila and colleagues increased this number to 1400 dinosaur bones known at Bellevue, the majority belonging to titanosaurs, likely including at least two species. An abundant amount of well-preserved elements have been uncovered at Bellevue. In the original description, only a tooth and some vertebrae were examined. In 2005, a complete description was made by Le Loeuff of all known material, allowing Ampelosaurus to be much better understood. In 2001 a partially articulated skeleton was found, including a disarticulated skull. This specimen, nicknamed "Eva", has not yet been described. All the material has been assigned to A. atacis, the observed differences in the proportions of limb bones being at the time interpreted by Le Loeuff as related to individual variation. In 2023 however, examination of the material by Vila et al. revealed that many of the bones assigned to Ampelosaurus belong to a distinct titanosaur making it uncertain the assignment of isolated bones to either of these two species. This study will lead to the erection of a new titanosaur species and to emended the diagnosis of Ampelosaurus. The description of Ampelosaurus below is provisional since some specimens referred to it may belong to another species.
A. atacis is known from a few, well-preserved teeth and some cranial material, a tooth of which was described in its original description. The teeth differentiate Ampelosaurus from Magyarosaurus and Lirainosaurus, both of which are also from Europe. The teeth are different from the two later genera as Ampelosaurus has teeth that are roughly cylindrical in the top with thin expansions at the bottom. They are high and about wide. Those expansions give its teeth a slight constriction between the root and the crown. The teeth are also quite different from the peg-like teeth of titanosaurids. The teeth, have a general morphology similar to titanosaurians Antarctosaurus and a braincase from Dongargaon. Another skull was described from southern France, but showed some differences, meaning there could have been at least two different titanosaurians in France during the Late Cretaceous.