Amargatitanis (meaning "Amarga giant") is a genus of sauropod dinosaur; a type of large, long-necked quadrupedal herbivore from the Barremian-age; Lower Cretaceous; from the La Amarga Formation of Neuquén, Argentina. The holotype, MACN PV N53, which was collected in March 1983 by José Fernando Bonaparte, consists of two tail vertebrae, a right ischium, and a partial right hindlimb. A 2016 re-evaluation by Pablo Ariel Gallina re-classified Amargatitanis as a dicraeosaurid.
Description[]
As a dicraeosaurid, Amargatitanis would have resembled better known members of the family such as Dicraeosaurus and Amargasaurus, which had shorter necks than most other sauropods and long neural spines extending from the vertebrae of the neck and trunk. It was a small sauropod, with one study estimating its mass at 11.406 metric tons (12.573 short tons), slightly larger than the same study's estimate for Amargasaurus of 10.195 metric tons (11.238 short tons). Mass estimates for Amargasaurus have been noted to vary widely depending on the method used, and studies using other methods, not yet applied to Amargatitanis, have found Amargasaurus to weigh 3.304 metric tons (3.642 short tons) to 4.376 metric tons (4.824 short tons).
From what is known of the caudal (tail) vertebrae of Amargatitanis, they generally resemble those of other dicraeosaurids. The centra (or "bodies") of these vertebrae are typical of flagellicaudatans, with gently concave anterior (front) faces and flat posterior (backside) faces. The prezygapophyseal centrodiapophysial fossae, which are deep depressions on the anterior surface of the transverse processes of the caudal vertebrae found in most diplodocoids and some macronarians, differ from other sauropods in that they contain a thin vertical lamina (sheet of bone). The caudal vertebrae of Amargatitanis resemble those of Pilmatueia, but not most other dicraeosaurids, in lacking ventrolateral ridges. The ischium generally resembles that of other flagellicaudatans, although it resembles the brachiosaurid Giraffatitan in that much of its posterior margin is straight.
The hind limb bones generally resemble those of other dicraeosaurids. The femur is distinctive in that it is much wider at its proximal (upper) end than at its distal (lower) end, whereas in other sauropods, including Dicraeosaurus, both ends are approximately equal in width. A similar condition may have been present in another dicraeosaurid, Pilmatueia. As in other dicraeosaurids, the lateral (outer) border of the femur is gently curved and lacks the distinct lateral bulge characteristic of titanosauriforms. The tibia has a low cnemial crest, similar to that of Dicraeosaurus and Amargasaurus and unlike the higher cnemial crest found in most macronarians. The posterior fossa of the astragalus differs from other sauropods in being deep and crescent-shaped, and in the arrangement of the foramina (openings) within it. The distal end of the first metatarsal has an oval shape, rather than being constricted in the middle to form distinct medial and lateral condyles as in Dicraeosaurus. The metatarsal has a distinct posterolateral (pointing both to the side and backwards) projection, as in other flagellicaudatans.
Classification[]
Apesteguía originally hypothesized in 2007 that Amargatitanis was a member of Titanosauria, a group of large, macronarian sauropods, based on features of the femur and scapula. However, two later papers argued that these titanosaurian traits were instead a misinterpretation of broken elements. In 2012, D'Emic in turn regarded Amargatitanis as a nomen dubium and that the fossils could not be from the same individual, making it a chimera. A 2016 study by Pablo Gallina found that characteristics such as the lack of a lateral bulge on the femur and presence of procoelous vertebrae (centra being concave at the front and convex at the back) meant Amargatitanis belonged to the family Dicraeosauridae. This claim was supported by phylogenetic analyses conducted by Gallina and later studies, which typically found Amargatitanis at the base of the family. In 2022, researcher Guillermo Windholz and colleagues argued that South American dicraeosaurids formed a clade based on their biogeography and results of phylogenetic analyses, with Amargatitanis being especially closely related to Pilmatueia and Bajadasaurus. They also hypothesized that Dicraeosauridae originated in North America, with the earliest known genera being Suuwassea and Smitanosaurus.
Bajpai and colleagues, in 2023, recovered Amargatitanis as an advanced dicraeosaurid in polytomy with Pilmatueia and a group containing Brachytrachelopan, Dicraeosaurus, and the contemporary Amargasaurus.
Appearance in other media[]
Jurassic Park[]
- Amargatitanis is mentioned in the database of Amargasaurus in Jurassic World Evolution 2.
 |
Read more Amargatitanis on Jurassic Park Wiki |
References[]
- https://ui.adsabs.harvard.edu/abs/2007GondR..12..533A
- https://www.researchgate.net/publication/300420946_Reappraisal_Of_The_Early_Cretaceous_Sauropod_Dinosaur_Amargatitanis_Macni_Apesteguia_2007_From_Northwestern_Patagonia_Argentina
- https://deepblue.lib.umich.edu/bitstream/handle/2027.42/94293/j.1096-3642.2012.00853.x.pdf;jsessionid=3448CA0A3C2388D9E12DDABF05201DB7?sequence=1
- https://docentes.fct.unl.pt/sites/default/files/omateus/files/mannion_et_al_2013_sauropod_lusotitan_portugal.pdf