| Aeolosaurus | |
|---|---|
 | |
| Life reconstruction ofAeolosaurus rionegrinus | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Titanosauria |
| Clade: | †Lithostrotia |
| Clade: | †Aeolosaurini |
| Genus: | †Aeolosaurus Powell,1987 |
| Type species | |
| †Aeolosaurus rionegrinus Powell, 1987 | |
| Other species | |
| |
Aeolosaurus (/ˌiːoʊloʊˈsɔːrəs/; "Aeolus' lizard") is agenus oftitanosauriansauropoddinosaur from theLate CretaceousPeriod of what is nowSouth America. Like most sauropods, it would have been aquadrupedalherbivore with a long neck and tail.Aeolosaurus is well known for a titanosaur, as it is represented by the remains of several individuals belonging to at least two species. However, like most titanosaurs, no remains of the skull are known.Theholotype ofAeolosaurus rionegrinus consists of a series of seven tailvertebrae, as well as parts of both forelimbs and the right hindlimb. It was discovered in theAngostura Colorada Formation in Argentina, which dates from theCampanian stage of the Late Cretaceous, about 83 to 74million years ago. The speciesA. maximus was transferred over to the new genusArrudatitan in 2021.[1]
This dinosaur is named after theGreek mythological figureAeolus, Keeper of theWinds inHomer'sOdyssey, because of the frequent winds that blow acrossPatagonia, where the remains were found. The generic name also includes theGreeksauros ('lizard'), the traditional suffix used in dinosaur names. Thespecific name (A. rionegrinus), refers to its location, in theRio Negro Province ofArgentina. Both genus and species were named and described by ArgentinepaleontologistJaime Powell in 1987.[2]
Aeolosaurus is a widespread genus of titanosaur known from theLate Cretaceous ofSouth America. Fossils have been collected from theAllen,Angostura Colorada,Lago Colhué Huapí, andLos Alamitos Formations ofArgentina and theSerra da Galga Formation ofBrazil.[3] AllAeolosaurus fossils are from theCampanian andMaastrichtian ages of theCretaceous period.
The type species ofAeolosaurus,Aeolosaurus rionegrinus, was originally named along with the genus in the doctoral thesis of Jaime E. Powell. However, according to the ICZN, names from dissertations are not valid, so it was not formally named until it was published the following year.[2][4] Powell's thesis was ultimately published in 2003, which is sometimes incorrectly cited as having named the genus.[4][5] In 2004,Aeolosaurus andGondwanatitan were recognized as forming a new group of titanosaurs, which was namedAeolosaurini.[6] In 2007, a second species,A. colhuehuapensis was named, also from Patagonia.[7] A third species,A. maximus, was named in 2011.[3]A. maximus was moved to the genusArrudatitan in 2021.
Like all sauropods,Aeolosaurus was a large, long-necked, quadrupedal herbivore.A. rionegrinus was roughly 14 meters (46 ft) long and 6 tonnes (6.6 short tons) in weight according toGregory S. Paul.[8] In 2020 Molina-Pérez and Larramendi gave a larger estimation of 18.1 meters (60 ft) and 14.7 tonnes (16.2 short tons).[9]A. rionegrinus was heavily built for a titanosaur, with limb bones similar in robustness to those ofSaltasaurus.[3]
Aeolosaurs,Aeolosaurus in particular, have very distinctive caudal vertebrae. The genusAeolosaurus is diagnosed by the shared presence of down-curved prezygapophyses on its anterior caudal vertebrae and chevrons from the anterior and middle portions of the tail with concave posterodorsal surfaces that contain double articular facets.[3] The caudal vertebrae ofAeolosaurus and the related genusGondwanatitan share anteriorly-inclined neural spines in the anterior caudal vertebrae.[10] The vertebrae from the middle part of its tail had elongatedcentra.[11]Aeolosaurus had vertebral lateral fossae that resembled shallow depressions.[11] Fossae that similarly resemble shallow depressions are known fromSaltasaurus,Alamosaurus,Malawisaurus, andGondwanatitan.[11] Its middle tail vertebrae'sneural spines angled anteriorly when the vertebrae are aligned.[11] These vertebrae resemble those ofCedarosaurus,Venenosaurus, andGondwanatitan.[11] The tail ofAeolosaurus was apparently curved strongly downward, a trait likely shared with other members of Aeolosaurini.[12] This curvature would likely have led to the posterior portion of the tail being very low to the ground, though likely not touching it. The curved base of the tail may have enabled the m. caudofemoralis longus, which extended from the femur to the tail vertebrae, to exert more force while retracting the hindlimb.[12]
Aeolosaurus, like many lithostrotian titanosaurs, bore osteoderms.[13] However, its osteoderms were unusual and most closely resemble those ofMendozasaurus.[14] As in all osteoderm-bearing titanosaurs, the osteoderms were probably arranged in one or two rows along the flanks.
Aeolosaurus is most closely related to the generaGondwanatitan andPanamericansaurus.[15][16] Together withGondwanatitan, it defines the cladeAeolosaurini.[6] The twoAeolosaurus species fromArgentina,A. rionegrinus andA. colhuehuapensis, appear to be more closely related to each other than to the Brazilian speciesA. maximus.[3]
The classification ofAeolosaurus and its relatives is heavily based on features of the tail vertebrae, which are the only bones preserved in most aeolosaurs.[3]
Aeolosaurus has been included in several cladistic analyses. The phylogeny of Aeolosaurini here is based on Gallina and Otero 2015, with the application of clade names according to their phylogenetic definitions.[3][6][16][17][18]
There are currently two named valid species ofAeolosaurus, as well as several specimens that have been referred to the genus but not given a species. In addition,Gondwanatitan faustoi, the closest known relative of the genus, has been proposed to represent an additional species ofAeolosaurus, asAeolosaurus faustoi.[19] However,Gondwanatitan is typically considered a distinct genus.[4]
Another specimen, described in 1993, consists of five tail vertebrae, and some bones from the forelimb andpelvis. Since there are two rightulna (forearm) bones, the specimen must consist of at least two individuals. These bones were also associated with twoosteoderms, or bonyarmor plates, providing evidence that this dinosaur was armored. This specimen is from theAllen Formation of Rio Negro, dating back about 70 to 68 million years ago to the middleMaastrichtian stage. While this specimen bears features that characterize the genusAeolosaurus, it is from a younger time period and shows enough differences that the authors recognized it as a possible second species.[13] Additional material from the same quarry, described in 2013, shows that the quarry contained the remains at least three individuals ofAeolosaurus.[21]
Another partial skeleton, including four more tail vertebrae and material from both limbs on the left side of the body, was described in 1997. This was recovered from theLos Alamitos Formation of Rio Negro, which falls between the other two dates. This specimen was also referred to the genusAeolosaurus, but not to the speciesA. rionegrinus, and may represent a third species.[22]
However, since the genusAeolosaurus is not well known, the authors chose not to formally name either of these possible new species. For now, they are both simply known as "Aeolosaurus sp." Future discoveries may give scientists more information on variation within the genus, and show that all of the above specimens belong toA. rionegrinus, or that they merit being formally named.
A middle caudal vertebra from theSerra da Galga Formation, CPP 248, cannot be evaluated for any diagnostic features of the genusAeolosaurus.[4] However, because it clearly does not belong toGondwanatitan, it is most likely that this vertebra representsAeolosaurus, a genus otherwise unknown from theSerra da Galga Formation.[3]
Another series of 15 tail vertebrae was assigned toAeolosaurus in the original description, but it was later determined that the series does not belong to this genus, as it lacks several features found in the other specimens ofAeolosaurus.[2][13]
Aeolosaurus lived during theCampanian andMaastrichtian ages of theLate Cretaceous and shared its environment withhadrosaurs.[3][5] The unnamedAllen Formation species ofAeolosaurus inhabited an environment that it shared with five other species of titanosaur, includingRocasaurus muniozi, as well as hadrosaurs and ankylosaurs.[21]
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