| Ligabuesaurus | |
|---|---|
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Somphospondyli |
| Genus: | †Ligabuesaurus Bonaparte et al., 2006 |
| Type species | |
| Ligabuesaurus leanzai Bonaparte et al., 2006 | |
Ligabuesaurus is agenus ofsomphospondylansauropod from theEarly CretaceousLohan Cura Formation of what is nowArgentina. Thetype species,Ligabuesaurus leanzai, was described in 2006, based on a partial skeleton with a skull. The generic name,Ligabuesaurus, honorsGiancarlo Ligabue, while thespecific name,leanzai, honors the geologist Dr. Héctor A. Leanza, who discovered the skeleton in the Lohan Cura Formation.[1]
The prominent Argentine paleontologistJosé F. Bonaparte led expeditions throughout northwesternPatagonia during the late 1990s and early 2000s. One of these expeditions, in 1997, examined a site called Cerro de los Leones, which is 10 km (6.2 mi) to the West ofPicún Leufú. This locality is part of the Cullín Grande Member of the Lohan Cura formation. This expedition led to the excavation of the enigmatic and controversialsauropod genusAgustinia. Additional remains of sauropods were found at a nearby quarry by the geologist Dr. Héctor Leanza and were collected between 1998 and 2000.[1] One of these additional skeletons would eventually be prepared and stored at theBernardino Rivadavia Natural Sciences Argentine Museum inBuenos Aires.[2]
These additional remains, which included the specimen MCF-PHV-233, would eventually be described and named in 2006 by José Bonaparte, Bernardo González Riga, and Sebastián Apesteguía. MCF-PHV-233 was made theholotype of the new speciesLigabuesaurus leanzai. In 2014, the remains were returned to theCarmen Funes Museum inPlaza Huincul, where they were originally reposited after their excavation but before preparation.[1] In 2022, a second skeleton was referred, specimen MCF-PHV-228.[3] A third skeleton was recovered from the same locality, but it was not referred toLigabuesaurus due to a lack of overlapping material.[1]
Jose Bonaparte and colleagues describedLigabuesaurus as a large saurpood, although they did not provide any specific estimates of its full size in the description itself. Thefemur of the holotype is 166 cm (5.45 ft) long and thehumerus is slightly shorter at 149 cm (4.89 ft).[1]Gregory S. Paul suggested a full size of 18 m (59 ft) long and 20 tons.[4] Rubén Molina-Pérez and Asier Larramendi suggested a similar estimate of 18.7 m (61 ft) long, 4.4 m (14 ft) tall at the shoulder, and a smaller mass of only 14.5 tons[5] In their full osteology ofLigabuesaurus in 2022, Flavio Bellardini and colleagues estimated its mass as being between 17 and 29 tons based on the circumference of thefemur andhumerus.[2]
The holotype ofLigabuesaurus, MCF-PHV-233, consists of a partialmaxillary bone with ten associated teeth, sixcervical anddorsal vertebrae, parts of a few ribs, bothscapulae, the lefthumerus, parts of the right humerus, four leftmetacarpals, and most of the right hindlimb including an incompletefemur,tibia,fibula,astragalus, fivemetatarsals, and several associated pedalphalanges. From these remains, Bonaparte and colleagues were able to differentiateLigabuesaurus from all other sauropods based on several characteristics of the vertebrae including the presence of anteroposteriorly narrow neural spines, relatively short pedicels on the neural arches, and the presence of uniquelaminae on the posterior cervical vertebrae.[1] The full osteology, published in 2022, provided a revised diagnosis, which included several of the same autapomorphies with additional details from referred specimens.[2]
In 2022, the holotype relceived a full osteological description by a team of authors including Flavio Bellardini, Rodolfo Coria, Diego Pino, Guillermo Windholz, Mattia Baiano, and Augustin Martinelli. They referred additional specimens from the same locality toLigabuesaurus. These included MCF-PVPH-261, which consists of several vertebrae from the neck and upper back, bothcoracoids, most of the hips, and several leg bones. More fragmentary specimens referred to the genus included MCF-PVPH-228 (several vertebrae, a scapula and some ribs), MCF-PVPH-908 (a single dorsal vertebra), and MCF-PVPH-744 (a single tooth). Although these elements were found relatively far apart from one another, the lack of repeated elements led Bellardini and colleagues to suggest that all specimens were from a single individual. The physical separation of the remains and any distortions in the shape and size of symmetrical elements were the result oftaphonomy.[2]
In their original description ofLigabuesaurus, Bonaparte and colleagues assigned it to theTitanosauria, but did not conduct a thorough examination of its relationships with the other members of Titanosauria.[1] The interrelationships of titanosaurs and their close relatives have been a subject of considerable academic debate, partially due to the fragmentary nature of many titanosaur specimens. Subsequent analyses have recoveredLigabuesaurus as a non-titanosaur member ofSomphospondyli. Philip Mannion and colleagues conducted a comprehensive analysis of all known members ofTitanosauriformes. This analysis recoveredLigabuesaurus as being a close relative ofAndesaurus, which, per the definition of Titanosauria (the least-inclusive clade containing bothAndesaurus andSaltasaurus), would makeLigabuesaurus and its close relatives true titanosaurs.[6] In their osteology ofLigabuesaurus published in 2022, Flavio Bellardini and colleagues recovered the genus once again as a non-titanosaurian somphospondylian.[7]
TheLohan Cura Formation, where all remains ofLigabuesaurus were found, is composed mainly ofsiltstones andsandstones, which means the environment was likely heavily irrigated byrivers. This is further supported by the prevalence of a variety ofturtle fossils.[8] Remains from othersauropods are also common including the rebbachisauridsLimaysaurus andComahuesaurus, and the enigmatic genusAgustinia. Pterosaur teeth belonging toornithocheiromorphs have also been found here.[9]
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