Alamosaurus (meaning "Ojo Alamo lizard") is a genus of titanosaurian sauropod dinosaurs, containing a single known species, Alamosaurus sanjuanensis, from the late Cretaceous Period of what is now southern North America. Isolated vertebrae and limb bones indicate that it reached sizes comparable to Argentinosaurus and Puertasaurus, which would make it the second largest dinosaur known from North America behind Amphicoelias. Its fossils have been recovered from a variety of rock formations spanning the Maastrichtian age of the late Cretaceous period. Specimens of a juvenile Alamosaurus sanjuanensis have been recovered from only a few meters below the Cretaceous-Paleogene boundary in Texas, making it among the last surviving non-avian dinosaur species.
Description[]
Size comparison, showing the scale of three Alamosaurus specimens.
Isolated caudal vertebra of Alamosaurus sanjuanensis from the Naashoibito member of the Kirtland Formation, New Mexico
Alamosaurus was a gigantic quadrupedal herbivore with a long neck and tail and relatively long limbs. Its body was at least partly covered in bony armor. In 2012 Thomas Holtz gave a total length of 30 meters (98 ft) or more and an approximate weight of 72.5–80 tonnes (80–88 short tons) or more. Though most of the complete remains come from juvenile or small adult specimens, three fragmentary specimens, SMP VP−1625, SMP VP−1850 and SMP VP−2104, suggest that adult Alamosaurus could have grown to enormous sizes comparable to the largest known dinosaurs like Argentinosaurus, which has been estimated to weigh 73 metric tons (80 short tons). Scott Hartman estimates Alamosaurus, based on a huge incomplete tibia that probably refers to it, being slightly shorter at 28–30 m (92–98 ft) and equal in weight to other massive titanosaurs such as Argentinosaurus and Puertasaurus. However, he says that at the moment, scientists do not know whether the massive tibia belongs to an Alamosaurus or a completely new species of sauropod. In 2019 Gregory S. Paul estimated the (SMP VP−1625) specimen at 27 tonnes (30 short tons), and he also mentioned a large partial anterior caudal vertebra which suggests an Alamosaurus specimen that is 15 percent dimensionally larger with similar mass to his Dreadnoughtus estimation of 31 tonnes (34 short tons). In 2020 Molina-Perez and Larramendi estimated the size of the largest individual at 26 meters (85.3 ft) and 38 tonnes (42 short tons).
Hypothetical restoration
Though no skull has ever been found, rod-shaped teeth have been found with Alamosaurus skeletons and probably belonged to this dinosaur. The vertebrae from the middle part of its tail had elongated centra. Alamosaurus had vertebral lateral fossae that resembled shallow depressions. Fossae that similarly resemble shallow depressions are known from Saltasaurus, Malawisaurus, Aeolosaurus, and Gondwanatitan. Venenosaurus also had depression-like fossae, but its "depressions" penetrated deeper into the vertebrae, were divided into two chambers, and extend farther into the vertebral columns. Alamosaurus had more robust radii than Venenosaurus.
History[]
Holotype scapula and paratype ischium
Alamosaurus quarry in 2013 compared with 1937, North Horn Formation, North Horn Mountain.
Alamosaurus remains have been discovered throughout the southwestern United States. The holotype was discovered in June 1921 by Charles Whitney Gilmore, John Bernard Reeside and Charles Hazelius Sternberg at the Barrel Springs Arroyo in the Naashoibito Member of the Ojo Alamo Formation (or Kirtland Formation under a different definition) of New Mexico which was deposited during the Maastrichtian stage of the Late Cretaceous Period. Bones have also been recovered from other Maastrichtian formations, like the North Horn Formation of Utah and the Black Peaks, El Picacho and Javelina Formations of Texas. Undescribed titanosaur fossils closely associated with Alamosaurus have been found in the Evanston Formation in Wyoming. Three articulated caudal vertebrae were collected above Hams Fork, and are housed at the Museum of Paleontology, University of California, Berkeley. These specimens have not been described.
Restored Alamosaurus skeletal mount at the Perot Museum.
Smithsonian paleontologist Gilmore originally described the holotype, USNM 10486, a left scapula (shoulder bone), and the paratype USNM 10487, a right ischium (pelvic bone) in 1922, naming the type species Alamosaurus sanjuanensis. Contrary to popular assertions, the dinosaur is not named after the Alamo in San Antonio, Texas, or the battle that was fought there. The holotype, the specimen the name was based on, was discovered in New Mexico and, at the time of its naming, Alamosaurus had not yet been found in Texas. Instead, the name Alamosaurus comes from Ojo Alamo, the geologic formation in which it was found and which was, in turn, named after the nearby Ojo Alamo trading post (since this time there has been some debate as to whether to reclassify the Alamosaurus-bearing rocks as belonging to the Kirtland Formation or whether they should remain in the Ojo Alamo Formation). The term alamo itself is a Spanish word meaning "poplar" and is used for the local subspecies of cottonwood tree. The term saurus is derived from saura (σαυρα), Greek for "lizard" and is the most common suffix used in dinosaur names. There is only one species in the genus, Alamosaurus sanjuanensis, which is named after San Juan County, New Mexico, where the first remains were found.
In 1946, Gilmore posthumously described a more complete specimen, USNM 15660 found on June 15, 1937 on the North Horn Mountain of Utah by George B. Pearce. It consists of a complete tail, a right forelimb complete except for the fingers — which later research showed do not ossify with the Titanosauridae — and both ischia. Since then, hundreds of other bits and pieces from Texas, New Mexico, and Utah have been referred to Alamosaurus, often without much description. Despite being fragmentary, until the second half of the twentieth century they represented much of the globally known titanosaurid material. The most completely known specimen, TMM 43621-1, is a recently discovered juvenile skeleton from Texas, which allowed educated estimates of length and mass.
Some blocks catalogued under the same accession number as the relatively complete and well-known Alamosaurus specimen USNM 15660, and found in very close proximity to it based on bone impressions, were first investigated by Michael Brett-Surman in 2009, to which their proximity was estimated using bone impressions. In 2015, his research reported osteoderms, which is the first occurrence of such in this taxon. The only known crania are teeth[1].
Alamosaurus sp. are known from the Hall Lake Formation, oriented higher in the formation than Sierraceratops, living with triceratopsinins and cf. Tyrannosaurus.[2] The only evidence for A. sp. in Hall Lake is TKM007, a humerus, which has an unknown repository location, as "TKM" refers to the locality it was found at. This large humerus is 96 centimeters long and 45 in width, belonging to the right size. The specimen was very fragmented upon discovery. The massive deltopectoral crest rises above the humeral head and arcs downwards in a rough parallel to the external margin of the shaft, probably somewhat deflecting medially, though this area is extremely eroded. The margin itself is somewhat straight, with a concavity formed by the sharply-sloped internal margin contrasting. The deltopectoral crest is not as large and not as medially deflected as A. sanjuanensis; the observed medial deflection in some Alamosaurus may be due to crushing, however, so it may not be an effective descriptive autapomorphy[3][4].
No skull material is known, except for a few slender teeth.
Reconstructed skeleton
The restored Alamosaurus skeletal mount at the Perot Museum [circular reference] (pictured right) was discovered when a member of an excavation team at a nearby site had to go around a hill to urinate.
Classification[]
Gilmore in 1922 was uncertain about the precise affinities of Alamosaurus and did not determine it any further than a general Sauropoda. In 1927 Friedrich von Huene placed it in the Titanosauridae.
Alamosaurus was in any case an advanced, or derived, member of the group Titanosauria, but its relationships within that group are far from certain. The issue is further complicated by some researchers rejecting the name Titanosauridae and replacing it with Saltasauridae. One major analysis unites Alamosaurus with Opisthocoelicaudia in a subgroup Opisthocoelicaudiinae of the Saltasauridae. A major competing analysis finds Alamosaurus as a sister taxon to Pellegrinisaurus, with both genera located just outside Saltasauridae. Other scientists have also noted particular similarities with the saltasaurid Neuquensaurus and the Brazilian Trigonosaurus (the "Peiropolis titanosaur") which is used in many cladistic and morphologic analyses of titanosaurians. A recent analysis published in 2016 by Anthony Fiorillo and Ron Tykoski indicates that Alamosaurus was a sister taxon to the Lognkosauria and therefore to species such as Futalognkosaurus and Mendozasaurus and lay outside the Saltasauridae (possibly being descended from close relations to the Saltasauridae), based on synapomorphies of cervical vertebral morphologies and two cladistic analyses. The same study also suggests that the ancestors of Alamosaurus hailed from South America, rather than Asia.[1]
Paleoecology[]
Restoration of Alamosaurus (background) and other dinosaurs from the Ojo Alamo Formation
Fossils are most often seen in the Naashoibito Member, Ojo Alamo Formation, which is 68-69 million years old and in the Javelina Formation, though this age is harder to determine. A specimen from the Black Peaks Formation overlies the Javelina and straddles the Chicxulub impactor event, whicht the specimen hailing from 66 million year-old sediments just meters below this boundary. Only one section of the Javelina is available for radiometric dating, providing an age of 69 million years ago. Using the underlying Aguja Formation, this suggests an Alamosaurus fauna lasting 66-70 million years, with occurrences near the base of the Javelina and just below the K-Pg boundary in the Black Peaks. The Alamosaurus fauna provides skeletal components of this taxon so frequently it is used to define faunal relations across the United States. The Edmontonian-Lancian transition was described by Lehman to be very dramatic in the south, introducing typical "Jurassic"-like animals. It is commonly found with Quetzalcoatlus, with this combination likely suggesting a semi-arid inland plains environment. This taxon may have immigrated in from South America during this time, which is supported by a supposed dominance occurring quickly. Some suggest ancestry with Asia, though this is not supported by its upland nature suggests it to be endemic rather than coastal species and tend to be less adept at crossing bodies of water. Additionally, Early Cretaceous titanosaurs are already known, which may indicate potential ancestors in North America. It coexisted with "Alamotyrannus", Ojoraptorosaurus. Gryptosaurus alsatei, cf. Kritosaurus, Glyptodontopelta, cf. Torosaurus utahensis, Bravoceratops, Ojoceratops, Quetzalcoatlus, rays, fish, amphibians, lizards, turtles and multituberculates in the American southwest[1].
JPInstitute.com Description[]
A large member of the long-necked sauropod family, Alamosaurus was one of the last of these huge plant-eaters to live in what is now the United States. It is related to the titanosaurs, which were common in South America in the Cretaceous period.
It is an example of the re-introduction of the sauropods to North America from South America during the later part of the Cretaceous. It is the only known North American sauropod from the Late Cretaceous.
Appearance in other media[]
Jurassic Park[]
- Alamosaurus appears as a skeleton along with the Tyrannosaurus rex skeleton in the Visitor Center of Jurassic Park. Towards the end of the film, it was destroyed in the battle between the Tyrannosaurus rex, Rexy, and the Velociraptor pack, led by The Big One.
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Read more Alamosaurus on Jurassic Park Wiki |
We're Back! A Dinosaur's Story[]
- It appeared in the children's book We're Back! A Dinosaur's Story.
Links[]
References[]
- https://eartharchives.org/articles/remember-the-alamosaurus-america-s-armored-dinosaur-titan/index.html
- https://www.nhm.ac.uk/discover/dino-directory/alamosaurus.html
- https://www.nps.gov/bibe/learn/nature/alamosaurus.htm
- https://www.austintexas.gov/sites/default/files/files/Dino_PDF.pdf
- https://kidadl.com/dinosaur-facts/alamosaurus-facts
- https://en.m.wikipedia.org/wiki/Alamosaurus
- ↑ 1.0 1.1 1.2 Cite error: Invalid
<ref>tag; no text was provided for refs namedwikipedia: - ↑ https://www.sciencedirect.com/science/article/abs/pii/S0195667121002822?via%3Dihub
- ↑ https://geoinfo.nmt.edu/publications/periodicals/nmg/6/n4/nmg_v6_n4_p72.pdf
- ↑ https://equatorialminnesota.blogspot.com/2021/01/your-friends-titanosaurs-331-alamosaurus-new-mexico.html