| Ampelosaurus | |
|---|---|
 | |
| Skeleton restoration ofAmpelosaurus atacis | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Titanosauria |
| Clade: | †Lithostrotia |
| Subfamily: | †Lirainosaurinae |
| Genus: | †Ampelosaurus Le Loeuff,1995 |
| Type species | |
| †Ampelosaurus atacis Le Loeuff, 1995 | |
Ampelosaurus (/ˌæmpɪloʊˈsɔːrəs/AM-pi-loh-SOR-əs; meaning "vine lizard") is atitanosauriansauropoddinosaur from theLate CretaceousPeriod of what is nowFrance. Its type species isA. atacis, named by Le Loeuff in 1995. Its remains were found in a level dating from 71.5 million years ago representing the earlyMaastrichtian.
Like most sauropods, it would have had a long neck and tail but it also carriedarmor in the form ofosteoderms. In 2005, over 500 bones have been assigned toAmpelosaurus and 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 toAmpelosaurus probably belong to a second titanosauriantaxon.
Ampelosaurus lived on what was the Ibero-Armorican Island, a landmass including much of present-day France andIberian Peninsula. Histological studies show characteristics related to an island environment such as a slowed growth rate. However, with a size of about 14 m (46 ft) in length for the largest known individual,Ampelosaurus was not an insular dwarf unlike some other Ibero-Armorican titanosaurs likeLirainosaurus andAtsinganosaurus, or the genusMagyarosaurus from the Hateg island.
Several specimens found elsewhere in France and Spain were referred toAmpelosaurus but were later identified as belonging to other titanosaurs.
Ampelosaurus is known by abundant remains from the Bellevue site near the village ofCampagne-sur-Aude in the Upper Aude Valley, inAudedepartment inOccitaniaregion. It was recovered in the lowerlevels of theMarnes Rouges Inférieures Formation, which belong to the earlyMaastrichtianepoch of the LateCretaceous Period, ~ 70 million years ago. These sediments represent an ancientfloodplain with numerousriver channels.[1] Historically, the dinosaurs of the Upper Aude Valley were first reported byPaul Gervais in 1877 from two vertebrae discovered in the commune ofFa. 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 dinosaurs 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 andEspéraza. 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 namedAmpelosaurus atacis by the French paleontologistJean Le Loeuff in a preliminary description published in 1995.[1][2]Ampelosaurus is derived from theGreekαμπελος, "the vine" and theLatinised Greeksaurus, "reptile". Therefore,Ampelosaurus means "vineyard lizard" after the Blanquette de Limoux vineyard. The vineyard is located on the south side of the regionAmpelosaurus was found in. The specific name is based on the Latinatax, the "Aude river".[1] Only one tooth, three articulateddorsal vertebrae (the holotypeMDE-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.[1] Four osteoderms discovered at Bellevue and described in 1994 were also attributed toAmpelosaurus in 1995.[3][1] In 2005, Le Loeuff published a more complete description of the bones discovered since 1989 including a braincase and a rightdentary.[2] 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.[4] Several excavation campaigns were necessary (until 2006) to extract this skeleton.[5] This specimen, which as yet to be described, includes an almost complete disarticulatedskull of which only a few elements are currently on display in theDinosaur Museum of Espéraza.[6][2] 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.[5]
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.[2] 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 genusLirainosaurus.[7] In 2013 Veronica Díez Díaz et al., however, noted that these femora differed fromL. astibiae in several features.[8] 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 genusGarrigatitan from the Upper Campanian ofProvence.[9] The recognition of the presence of a second species of titanosaur at Bellevue in addition toAmpelosaurus 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.[9] 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 ofAmpelosaurus.[10]
The presence ofAmpelosaurus 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 thatAmpelosaurus was known not only from the upper Aude Valley, but also the Petites Pyrénées (Ariège department), and the Chaînon de Saint-Chinian (Hérault department).[11] 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.[12][13] In the same way, in 1999Eric Buffetaut and colleagues attributed toAmpelosaurus atacis teeth and postcranial bones discovered in the Grès à Reptiles formation atCruzy (located in the area called Chaînon deSaint-Chinian) inHérault department.[14] A later study showed that Cruzy's titanosaur teeth are different from those ofAmpelosaurus, and belong to a new taxon whose description is in progress.[15] In 2009, Fernando Barroso-Barcenilla and colleagues reported in the Spanish site of Lo Hueco, inCuencaprovince, the discovery of spatulate teeth with the same morphology as those ofAmpelosaurus.[16] However, the detailed description of the titanosaur teeth from Lo Hueco refuted this interpretation.[17] In 2013, Fabien Knoll and colleagues tentatively attributed toAmpelosaurus sp. a braincase also from the Lo Hueco site.[18] In 2019, Knoll and colleagues finally referred this braincase toLohuecotitan pandafilandi,[19] which was described in 2016 from a postcranial skeleton.[20] Two types of titanosaur braincase are present in Lo Hueco. This attribution to the genusLohuecotitan is based on the fact that the other braincase morphotype was found to be associated with a titanosaur skeleton distinct fromLohuecotitan,[21] and because none of the very abundant titanosaur postcranial remains of Lo Hueco (represented by more than twenty partially articulated skeletons) belong toAmpelosaurus.[20][22]
Like most sauropods,Ampelosaurus would have had a long neck and tail, but it also carriedarmor in the form ofosteoderms 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 15–16 m (49–52 ft) in length and about 8 metric tons (8.8 short tons) in body mass.[1][23] In 2022, Vila and colleagues assign a size of 13.9 m (46 ft) long and a weight of 9.98 metric tons (11.00 short tons) for the largest individual based on the femurMDE-C3-174 (Vila et al. Supplementary Information).[24]Ampelosaurus atacis is known from many unattached bones andteeth. It is one of the best-known dinosaurs fromFrance.[1] It is considered to be a dwarf sauropod by Coriaet al. (2005) because it has a smaller size in comparison with its ancestors.[25] However, according to Klein et al. (2012),Ampelosaurus is not an insular dwarf since its adult size is much greater than that ofEuropasaurus orMagyarosaurus.[26]
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 southernFrance have been assigned toA. atacis. In 2023 Vila and colleagues increase this number to 1400 dinosaur bones known at Bellevue, the majority belonging to titanosaurs.[10] 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, allowingAmpelosaurus 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.[4][6][2] All the material has been assigned toA. atacis, the observed differences in the proportions of limb bones being at the time interpreted by Le Loeuff as related to individual variation.[2] In 2023 however, examination of the material by Vila et al. revealed that many of the bones assigned toAmpelosaurus 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 ofAmpelosaurus.[10] The description ofAmpelosaurus below is provisional since some specimens referred to it may belong to another species.[10]
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 differentiateAmpelosaurus fromMagyarosaurus andLirainosaurus, both of which are also from Europe. The teeth are different from the two later genera asAmpelosaurus has teeth that are roughly cylindrical in the top with thin expansions at the bottom. They are 21 millimetres (0.83 in) high and about 6 millimetres (0.24 in) 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.[2] The teeth, have a general morphology similar to titanosauriansAntarctosaurus 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.[2]
Thescapula was found attached to a coracoid. In the longer direction, the bone is 72 centimetres (28 in) long. The blade of the scapula, contrary to titanosaurs, is triangular, larger closer to the base. The blade narrowsdistally instead of showing an expansion. Differing fromMagyarosaurus andSaltasaurus, the scapula does not have the dorsal crest at the base of the scapular blade. The shape of the coracoid is quadrangular,[1] and the coracoid has a thickened cranial margin.[2]
Ampelosaurus is also known from apubis, about 75 centimetres (30 in) long. It has a strong distal expansion, that is similar to a titanosaur fromBrazil, and a large foramen. Contrary to the South American titanosaurs, theilium does not have an expansion on the side. Theischium, known from a shaft, is unexpanded distally and very well developed. It is also very flat.[2] An incompleteradius is also known. It lacks the proximal and distal ends, and possesses a very prominent ridge along it.[2] The largest and best-preserved specimens are both ulnas. The right ulna has a total length of 395 millimetres (15.6 in). The right ulna is small and slender, is missing anolecranon, and has a well-marked ridge. The left ulna is larger, with a length of 725 millimetres (28.5 in).[2] The ulna has a deep radial fossa.[27]
About 27 femora are known from Bellevue, making them the most common bone, most of them more-or-less complete. They are very flat craniocaudally but otherwise, lack any unusual features.[2] In a study of its bone physiology, it was found that the maximum known femur length was 1,100 millimetres (43 in), which is much larger than previously known (802 millimetres (31.6 in)). That means, that the ancestorsAmpelosaurus were slightly smaller than itself.[26] 18 humeri are also known,[2] but none of them approach the size of the largest femur. The humeri do not have a freemedullary cavity.[26] The humeri are robust, about 63 centimetres (25 in) long, with very expanded distal and proximal ends.[2]
Three different types of osteoderms have been recovered at Bellevue. Two with large spines have been uncovered. At the base of each spine, which is about 12 centimetres (4.7 in) tall, are two large foramina. The internal faces are all concavo-convex and have a ridge opposite the spine. In side view, they have two sections, a low half that progressively thickens, and a spine.[2]
The holotype specimen ofA. atacis is a group of three connecteddorsalvertebrae. Cervical vertebrae are uncommon from Bellevue and most of them are poorly preserved.[2] The vertebrae areopisthocoelous, with centra that lengthen toward the rear.Neural spines have been preserved on the vertebrae, and they face toward the rear. Two dorsal vertebrae were preserved with a complete, but very crushedneural arch, a neural spine with a characteristic shape: it is very widened distally and narrows downwards. The vertebrae also have an internal structure that is spongy, with very large cells.[1] The caudal vertebrae are all stronglyprocoelous and are compressed on the sides. The neural spines of the caudal vertebrae are very narrow and very tall and point toward the rear. The middle caudal vertebrae are more compressed on the sides that the others. Also, the centrum of middle caudal vertebrae is longer proportionally.[1] Two sacral vertebrae were known from Bellevue. They are poorly preserved, and are thought to belong to a juvenile. A complete sacrum was also found in 2002.[2]
This set of characters was identified by Le Loeuff in his description ofAmpelosaurus to distinguish it from all other genera: teeth that weakly spatulate; alaterally widening distal extremity of neural spines on the dorsal vertebrae; neural arch of the dorsal vertebrae inclining strongly towards the rear; the lack of a distal expansion on the scapular blade; the presence of a light,ventral crest on top of the scapula; the presence of plate, bulb, and spine shaped osteoderms;[1] and, in 2005, Le Loeuff added that the constriction of the neural spine on the dorsal andcervical vertebrae was also probably a characteristic ofAmpelosaurus.[2]
Characteristics of the tail vertebrae and the presence of osteoderms indicate thatAmpelosaurus belongs toLithostrotia, a group ofderived titanosaurians which also includesAlamosaurus andSaltasaurus.[28] Many other paleontologists have classifiedAmpelosaurus as belonging to Titanosauria,[29]Saltasauridae,[27] andTitanosauridae.[1][25][30][31]Ampelosaurus may have an uncertain classification, but it is clearly a titanosaur, with many features found in titanosaurs.[1]
More recently,Ampelosaurus has been put in a clade with other French and Spanish titanosaurs from the late Campanian to Maastrichtian, which was namedLirainosaurinae by Díez Díazet al. in2018.Ampelosaurus nested as sister taxon toAtsinganosaurus also from France, and the entire clade was placed in between the taxa commonly classified asSaltasauridae and taxa normally in eitherAeolosaurini orLognkosauria.[32]
Ampelosaurus seems to have grown in a way similar to more basal sauropods. After a certain point in itsdevelopment, the microscopic material of the bone became very different from more basalSauropoda.Ampelosaurus grew more slowly once the bone microstructure became unique among sauropods. AlthoughDiplodocoidea and basalMacronaria also show an increase in bone growth and a decrease in growth rate around the presumed onset of sexual maturity, it is much more gradual thanAmpelosaurus. The process of growing, which in other sauropods started around sexual maturity, was clearly delayed inAmpelosaurus. The period of growth after sexual maturity seems to be shortened inAmpelosaurus and is dominated by slow bone building instead of fast growth.[26] Growth marks are generally rare in sauropods or appearing only late in ontogeny, if at all. The lack of growth marks is suggestive of fast and continuous growth in sauropods, which supports the hypothesis that they achieved large body size through because of fast growth.[26]Ampelosaurus does not show growth marks on any bone sample. This is unusual to be found with the apparently reduced growth rate and high level of bone growth seen in it, as those features are often associated with the occurrence of growth marks.[26]
EFS, a system found on the surface of bones, is thought to show a growth plateau which indicates that maximum body size and skeletal maturity is reached in an individual.Ampelosaurus has not been known to have EFS, found on most non-titanosaurian sauropods.Magyarosaurus, a closely related titanosaur,Lirainosaurus, a titanosaur related to saltasaurids,Alamosaurus, a saltasaurid, andPhuwiangosaurus, a very basal titanosaur, were also found to have lacked EFS. However, the basalmacronarianEuropasaurus has been shown to have had EFS, so it was likely just titanosaurians that did not have them. The outer edge of the bones, were EFS would have been found, was well-preserved, and still lacked any fossilized proof of them being present forAmpelosaurus. However, in the PLoS ONE study that found the lack of EFS, the larger specimens were not tested, soAmpelosaurus might have had EFS. This is characteristic of titanosaurs, as diplodocoids and basal macronarians seem to have EFS. A majority of allAmpelosaurus specimens have been found with secondary osteons placed densely in the inner regions of bones, and lightly in outer regions. The osteon orientation found inAmpelosaurus of osteons not only facing across the bone is not typical ofNeosauropoda. Also, there is no medullary cavity in any bones ofAmpelosaurus.Ampelosaurus seems to have had many ontogenetic stages in its life based on its bone histology.[26]
Ampelosaurus atacis is only known with certainty at the base of the Marnes de la Maurine Member of theMarnes Rouges Inférieures Formation in the Upper Aude Valley in southwestern France (Aude department).Ampelosaurus was also reported in other localities in France and Spain (notably Massecaps and Lo Hueco) but these specimens were found to belong to different titanosaurs. The age of the Marnes Rouges Inférieures Formation, which is divided in four members, extends from the lateCampanian, 75 million years ago (for the Marnes Rouges de Campagne Member dated bypalynology), to the end of the earlyMaastrichtian, 70 million years ago (for the Poudingue Fleuri Member).[33]Magnetostratigraphic studies indicate an age of 71.5 million years (top of chron C32n.1n) for the localities of the basal part of the Marnes de la Maurine Member (including the Bellevue locality), which corresponds to the early Maastrichtian.[34] At that time Europe was anarchipelago made up of islands of varying sizes and changing geography over time.Ampelosaurus roamed the vast plains of the Ibero-Armorican Island, an emergent landmass made up of much of the present dayFrance andIberian Peninsula.[35] The sediments of the Marnes Rouges Inférieures Formation consist ofmudstones,sandstones,conglomerates, andsiltstones, of fluvial and alluvial origin.[34]
Fauna associated withAmpelosaurus atacis included another yet unnamedtitanosaur,[10] theornithopodRhabdodon priscus (represented by teeth, jaws, and postcranial bones),[2][36] an indeterminatenodosauridankylosaur (known only by dermal scutes),[2] an indeterminateDromaeosauridae ( represented by teeth),[2] the giant ground birdGargantuavis philoinos,[37] an undeterminedpterosaur,[38][39] the turtlesFoxemys mechinorum (known by an incomplete skull and shell elements)[40] and a new yet unnamedcompsemydid (one skull and an isolated costal plate),[41] an undescribedallodaposuchideusuchian (represented by many elements including a complete skull showing similarities withMusturzabalsuchus andAllodaposuchus subjuniperus),[42] and fisches (alepisosteid and thecoelacanthAxelrodichthys megadromos).[2][43] Dinosaurs eggshells and nests are also present in the Marnes de la Maurine Member. They are represented by the oospeciesCairanoolithus roussetensis,C. dughii, andMegaloolithus siruguei in the lower part,M. siruguei andMontanoolithus labadousensis in the middle part,M. siruguei andM. mamillare in the upper part.[34]Fusioolithus baghensis is recorded in the Poudingue Fleuri Member.Megaloolithus andFusioolithus are titanosaur eggs.[44][45] The oogeneraCairanoolithusandMontanoolithus are referred respectively to nodosaurids and dromaeosaurids.[46][47] A few invertebrate and plant remains are also known. The macroflora, notably found at Bellevue, is represented by leaves of palm trees and cycads, as well as fragments ofangiosperm wood from trees 10 to 15 m high.[48]
Titanosaurians were a flourishing group of sauropod dinosaurs during Cretaceous times. Fossils of titanosaurians have been found on all continents and their remains are abundant in a number of Late Cretaceous sites. Titanosaurian sauropods were among the most common dinosaurs in the ibero-Armorican island during the Campanian-Maastrichtian times. In this island a shift in the dinosaur fauna known as the Maastrichtian Dinosaur Turnover is observed in which a late Campanian-early Maastrichtian pre-turnover dinosaur fauna was replaced by an early-late Maastrichtian post-turnover assemblage. Concerning the titanosaurs the pre-turnover assemblage included small-sized species such asAtsinganosaurus andGarrigatitan (latest-middle Campanian to early-late Campanian in age) from southeastern France (Bouches-du-Rhône department) andLirainosaurus (latest Campanian in age, 72 to 73.5Ma) from north-central Spain (Burgos province,Treviño enclave), and moderate-sized forms such asLohuecotitan (late Campanian-early Maastrichtian) from central Spain (Cuenca province) andAmpelosaurus (early Maastrichtian 71.5 Ma) from southwestern France (Aude department). The post-turnover assemblage is dominated by larger forms such asAbditosaurus (mid-early Maastrichtian, 70.5 Ma) from northeastern Spain (Lleida province). The latter is closely related toGondwanan titanosaurs and does not show reduced growth rate or reduced body size, two common traits found in pre-turnover titanosaurs assemblages. It belongs to a distinct immigrantclade of large titanosaurs that reached the Ibero–Armorican island during the early Maastrichtian, being a member of the post-turnover titanosaurian assemblage of this island. This dispersal event from the southern landmasses, probablyAfrica, took place probably during the called KMa2 regressive event (which occurred about 70.6 million years ago during the Lower Maastrichtian), aeustatic event that affected the central Tethyan margin and northern Africa.[49][24]
