Alamosaurus ‭(‬Alamo lizard‭)‬

Short Info

Alamosaurus ‭(‬Alamo lizard‭)‬

Phonetic : Al-ah-moe-sore-us.

Named By : Charles W.‭ ‬Gilmore‭ ‬-‭ ‬1922

Diet : Herbivore

Size : Estimated 20-24 meters long

Type of Dinosaur : Sauropod

Type Species : A.‭ ‬sanjuanensis‭ (‬type‭)

Found in : USA,‭ ‬New Mexico‭ ‬-‭ ‬Ojo Alamo Formation‭ (‬possibly part of the Kirtland Formation,‭ ‬Utah‭ ‬-‭ ‬North Horn Formation and Texas‭ ‬-‭ ‬Black Peaks Formation,‭ ‬El Picacho Formation and Javelina Formation.
Time period: Maastrichtian of the Cretaceous

When it Lived : Early Jurassic, 199-189 million years ago

Alamosaurus (/,ael@moU’so:r@sor “Ojo Alamo lizard”) is an opisthocoelicaudiine genus. titanosaurian sauropod dinosaurs. It is comprised of only one known species, Alamosaurus sanjuanensis, from the late Cretaceous Period of what is today the southern part of North America. A few vertebrae and limb bones show that it had a size similar with Argentinosaurus and Puertasaurus that would make it the biggest dinosaur to be discovered of North America. The fossils found in it have been extracted from a range of rock formations that span the Maastrichtian time period of the Cretaceous’s late period. A few specimens of juvenile Alamosaurus sanjuanensis have been found from just a few meters beneath the Cretaceous-Paleogene line in Texas which makes it one of the last non-avian dinosaurs that remain species.

Alamosaurus was a huge herbivore quadrupedal with an extended neck and tail, and large legs. The body of the animal was at least partially covered in bone armor. In 2012, Thomas Holtz gave a total length of 30 meters (98 feet) or more, and an estimated mass in the range of 72.5-80 tons (80-88 small ton) and more. Although the majority of the remains are young or small adult specimens 3 fragmentary specimens SMP 1625 and VP-1625 as well as SMP VP-1850, and SMP VP-2104, indicate that an adult Alamosaurus might be growing to huge dimensions comparable to the biggest known dinosaurs such as Argentinosaurus that has was estimated to weigh up to 73 metric tonnes (80 small tons). Scott Hartman estimates Alamosaurus, from a massive incomplete tibia, which could be referring to it, as being somewhat smaller at 28-30 meters (92-98 feet) and comparable in the weight of other titanosaurs with massive bodies like Argentinosaurus as well as Puertasaurus. But, he states that for the moment scientists don’t know how the massive tibia is an Alamosaurus or a totally new sauropod species. In the year 2019, Gregory S. Paul estimated the (SMP VP-1625) specimen to be 27 tons (30 short tons) as well as identified a massive partially anterior caudal vertebra, which could indicate that it is an Alamosaurus specimen that is 15 percent bigger and weighs the same as his Dreadnoughtus estimation of 31 tons (34 short tons). In 2020 , Molina-Perez as well as Larramendi determined the dimensions of the largest specimen with a height of 26 metres (85.3 feet) in weight and 38 tonnes (42 short tons (42 short).

Dr. Matt Wedel,, CC BY 4.0, via Wikimedia Commons

While no skull has been discovered, rod-shaped teeth were found in Alamosaurus Skeletons, which could be related to the dinosaur. The vertebrae that were found in the middle of its tail had an elongated centra. Alamosaurus had vertebral fossae lateral to its vertebrae which looked like shallow depressions. Fossae that resemble similarly to shallow depressions have been identified from Saltasaurus, Malawisaurus, Aeolosaurus and Gondwanatitan. Venenosaurus also had depression-like fossae. However, the “depressions” penetrated deeper into the vertebrae. They also split into two chambers and extended deeper into the vertebral columns. Alamosaurus had larger radius as compared to Venenosaurus.

Alamosaurus remains are found across the southwestern United States. The holotype was found during June of 1921 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 with a different meaning) from New Mexico which was deposited in the Maastrichtian phase that was part of the Late Cretaceous Period. Bones have also been found from different Maastrichtian formations, such as that of North Horn Formation of Utah as well as in the Black Peaks, El Picacho and Javelina Formations in Texas. Undescribed titanosaur fossils closely linked with Alamosaurus were discovered within the Evanston Formation in Wyoming. Three articulated caudal vertebrae were found in the area of Hams Fork, and are kept in the Museum of Paleontology, University of California, Berkeley. These specimens are not described.

Smithsonian paleontologist Gilmore first identified the holotype, USNM 1046, a left scapula (shoulder bone) as well as its Paratype USNM 10487, which is a right ischium (pelvic bone) in 1922, and named the species of type Alamosaurus sanjuanensis. Contrary to popular belief the dinosaur isn’t named in honor of it’s home, the Alamo located in San Antonio, Texas, or the battle that was fought there. The holotype that named after it was discovered at the time of its discovery in New Mexico and, at the time of its designation, Alamosaurus had not yet been discovered in Texas. The name Alamosaurus originates in the form of Ojo Alamo, the geologic formation that it was discovered, and was later named for Ojo Alamo, the neighboring Ojo Alamo trading post (since there’s been some controversy over whether it is appropriate to classify the Alamosaurus-bearing rocks as part of the Kirtland Formation or if they should be kept within the Ojo Alamo Formation). The word “alamo” itself is an Spanish word that translates to “poplar” and is used for the local subspecies cottonwood. The term saurus originates by saura (saura), Greek for “lizard” and is the most commonly used suffix in dinosaur names. There is just one species in the genus of Alamosaurus sanjuanensis which is named for San Juan County, New Mexico in which the first remains were discovered.

in 1946 Gilmore postedhumously reported a complete and more extensive specimen of USNM 15660, discovered on the 15th of June in 1937 at the North Horn Mountain of Utah by George B. Pearce. It has a full tail, right forelimb that is complete, minus fingers, that later studies revealed that they do not ossify in the Titanosauridae as well as the two ischia. Since the time, a myriad of fragments and pieces of Texas, New Mexico, and Utah have been identified as Alamosaurus and often with no details. Although they were fragmentary, up to in the latter half of 20th century, they were the majority of the titanosaurid fossils. The most widely known piece, TMM 43621-1, is the most recent discovery of a juvenile skeleton found in Texas that allowed for educated estimations of the length and mass.

The blocks, which are catalogued in the same accession numbers as the comparatively extensive and famous Alamosaurus sample USNM 15660, as well as found close to it, based on bone impressions, were initially studied by Michael Brett-Surman back in the year 2009. Then, in the year 2015, Brett-Surman revealed that the blocks had osteoderms, which was the first evidence of their presence on Alamosaurus.

There is no skull material to be found with the exception of some slender teeth.

Gilmore during 1922 was unsure regarding the exact affinities between Alamosaurus and was unable to find it more than an overall Sauropoda. In 1927, Friedrich von Huene placed it within the Titanosauridae.

Alamosaurus was, in all likelihood an advanced, or derived part of Titanosauria however, its connections within the group aren’t always clear. The problem is further complicated by a few researchers who have rejected the term Titanosauridae and substituting them with Saltasauridae. One major analysis unites Alamosaurus with Opisthocoelicaudia in a subgroup Opisthocoelicaudiinae of the Saltasauridae. Another analysis that is more thorough finds Alamosaurus as an ancestor taxon of Pellegrinisaurus and Pellegrinisaurus, both genera situated outside Saltasauridae. Other scientists have also noticed certain similarities between those of the saltasaurid Neuquensaurus along with The Brazilian Trigonosaurus (the “Peiropolis titanosaur”) that are used in numerous morphological and cladistic analysis of titanosaurians. A study released in the year 2016 in 2016 by Anthony Fiorillo and Ron Tykoski suggests that Alamosaurus was an ancestral sister taxon of Lognkosauria and consequently to other species like Futalognkosaurus as well as Mendozasaurus and was outside of those of the Saltasauridae (possibly being descendant from close relatives with the Saltasauridae) Based on synapomorphies in cervical vertebral morphologies and two cladistic studies. The study also suggests that the people who inherited Alamosaurus came in South America, rather than Asia.

Alamosaurus fossils are primarily discovered in the Naashoibito members from the Ojo Alamo Formation (dated to approximately 69-68 millions of years) as well as in the Javelina Formation although the exact age of the former has been difficult to establish. A young specimen of Alamosaurus has been found to be in the Black Peaks Formation, which lies over the Javelina in Big Bend, Texas, and is located on the Cretaceous-Paleogene border. The Alamosaurus specimen was believed to be just a few metres below the boundary and has been dated at 66 million year ago. However, the exact location where the boundary is located within this region is unclear. Only one site in the Javelina Formation has so far provided the right rock types that can be used for radiometric dating. The outcrop, which is located in the middle of the formation approximately 90 meters (300 feet) below the K-Pg boundary , and within the local area that contains Alamosaurus fossils measured up to 69.0+-0.9 millennia old as of the year 2010. Based on this date, in conjunction with a measured age from the Aguja Formation as well as the probable place of the boundary of the KPG within the Black Peaks Formation, the Alamosaurus fauna appears to have existed from 70-66 million year ago. beginning with the first records of Alamosaurus close to the bottom of the Javelina formation and the most recent close to the K-Pg border within the Black Peaks Formation.

Skeletal components of Alamosaurus are one of the most well-known Late Cretaceous dinosaur fossils found in the United States Southwest and are currently used to determine the species of the time and location which is called”the “Alamosaurus fauna”. The south region area of Late Cretaceous North America, the transition from Edmontonian into the Lancian stage of the fauna is more dramatic than during the northern part of. Thomas M. Lehman describes the process in terms of “the abrupt reemergence of a fauna with a superficially ‘Jurassic’ aspect.” These species are dominating by Alamosaurus and are populated by Quetzalcoatlus within Texas. The Alamosaurus-Quetzalcoatlus association probably represent semi-arid inland plains.

Alamosaurus’ appearance Alamosaurus could be an indication of an event of immigration that originated from South America. Alamosaurus emerges and establishes itself within its surroundings very quickly and quickly, which could support the notion that it was born as a result of an immigration event. Others have suggested the possibility that Alamosaurus was an Immigrant from Asia. However, those who disagree with the theory of immigration point out that people living in an upland ecosystem such as Alamosaurus have a higher chance of being more endemic than coastal species and have less of a chance to cross the waters of. Additionally, Early Cretaceous titanosaurs are well-known, which means that North American potential ancestors for Alamosaurus existed before.

Source: Wikipedia