Alamosaurus

## AlamosaurusOjo Alamo Lizard

**Life Expectancy** of at least 70 years

 **Main** Segments

MainSegments

***“ These Alamosaurs are a hundred feet long, and weigh some 80 tonnes. They are the largest dinosaurs on the continent. So huge that no predator can tackle them. ”***

― **David Attenborough**, *North America*
***Alamosaurus*** (Ojo Alamo lizard) is a genus of titanosaurian sauropod dinosaur that lived in the Javelina Formation of Texas and the Ojo Alamo Formation of New Mexico, USA, 70 - 66 million years ago, during the Maastrichtian stage of the Late Cretaceous Period.

## Description

### Size and Physique

*Alamosaurus* is one of the largest known sauropods of North America. Standing at least 11 meters (36 feet) tall, 30.5 meters (100 feet) long, and weighing 80 metric tons (88 short tons), it rivals the size of the biggest sauropods like *Argentinosaurus*, which lived in Argentina, South America around 97 - 92 million years ago. Despite its large size, *Alamosaurus* is armored with osteoderms, a trait seen in titanosaurs, the existence of this bony defense confirmed by a discovery in 2015. As a sauropod, the species is believed to have a long lifespan, with one individual in North America stated to be at least 70 years old.

### Prehistoric Planet's Depiction

*Main: *Alamosaurus* on Prehistoric Planet*

Main: *Alamosaurus* on Prehistoric Planet

*Alamosaurus* appears in the first segment of North America, which shows a herd of them traveling by the coast of the Western Interior Seaway. A 70 year-old member of the herd eventually collapses and succumbs to old age, and its corpse becomes the subject of dispute for carnivores that came to scavenge the carcass, from troodontids and *T. rex* to a pair of *Quetzalcoatlus*. *Alamosaurus*, along with the other titanosaurs of the series, are also the subject of the Prehistoric Planet: Uncovered segment "How Did Dinosaurs Get So Big?"

## Habitat

*Main: Javelina Formation*

Main: Javelina Formation

***“ The coast of the vast, inland sea that almost splits North America in half. Here in the south, as the tide falls, giants are drawn to the shoreline. ”***

― **David Attenborough**, *North America*
*Alamosaurus* lived 70 - 66 million years ago in the Javelina, Black Peaks, and El Picacho Formations in Texas, the Ojo Alamo Formation in New Mexico, and the North Horn Formation in Utah, USA, alongside animals like *Quetzalcoatlus* and *Tyrannosaurus*. It is believed that the regions it inhabited were semi-arid inland plains. While *Alamosaurus* appears to be mostly confined to the southwestern areas of the US, indeterminate titanosaur remains have supposedly been found in the Evanston Formation in Wyoming, though more recent studies are unable to confirm that these fossils are indeed those of *Alamosaurus*.

### Origin

Most North American dinosaur species are known to have come to and from Asia. *Alamosaurus* is peculiar in that it is the only known sauropod in North America after 30 million years of complete sauropod absence. Hence, the mysterious origin of *Alamosaurus* is a significant aspect of it, subject to continuous debate.

One theory is that the species (or at the very least, its ancestors) immigrated from South America on the same land bridge that hadrosaurs traveled to reach South America, though this theory is challenged by the fact that the "bridge" between North and South America may not have been a single, unbroken strip of land, but a series of islands, thus making the crossing of the sauropods problematic, with their large size making island rafting a less-feasible means of reaching North America.

The alternate theory is that they came from Asia instead, given its close relationship with *Opisthocoelicaudia* of Mongolia, though this does not take into account that *Alamosaurus* is also closely related to *Pellegrinisaurus* of Argentina, that the land bridge of Beringia (which connects Asia and North America) would have been inhospitable to titanosaurs due to the being closer to the poles, and that there are no traces of Late Cretaceous sauropods in Northern Laramidia (since if *Alamosaurus* or its ancestors came from Asia, the titanosaur would have passed through areas near or within the more northern areas of Laramidia like the Hell Creek, Lance, and Scollard Formations, leaving behind a population of subspecies or something that evolves into another, distinct sauropod species).

The third theory, the idea that sauropods that lived in North America for the past 30 million years prior *Alamosaurus* were simply not preserved well, is considered unlikely. As of 2021, the belief that *Alamosaurus* (or its ancestors) immigrated from South America is the most supported theory, and is in fact mostly considered the only viable explanation of their existence on the southern end of Laramidia.

## Behavior

***“ Some live to a great age. This male is around 70 years old. Many in the herd are likely to be his offspring. But his long life is now coming to an end. His immense body is beginning to fail him. He may not survive the night. ”***

― **David Attenborough**, *North America*
*Alamosaurus* is depicted traveling in herds that consist of related individuals, offspring of some of the older members. Given how sauropods were likely not as complex as birds (with some species, like crows and magpies, even holding what appears to be funerals) or elephants (which possess greater brain-to-body ratios and also mourn their dead), these family ties do not seem to matter the herd's members. When one of them succumbs to old age and dies, the rest of the herd continues on with their migration with not a glance back, prioritizing their journey and search for resources.

## References

### General

1. ↑ 1.0 1.1 Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. ISBN 0-520-24209-2.
2. ↑ 2.0 2.1 The sauropod dinosaur *Alamosaurus* from the Upper Cretaceous of the San Juan Basin, New Mexico
3. ↑ 3.0 3.1 Stratigraphic Distribution of Sauropods in the Upper Cretaceous of the San Juan Basin, New Mexico, with Comments on North America's Cretaceous 'Sauropod Hiatus'
4. ↑ 4.0 4.1 Holtz Dinosaur Genus Appendix
5. ↑ Dinosaur Facts and Figures. The Sauropods and Other Sauropodomorphs
6. ↑ Osteoderms of the Titanosaur Sauropod Dinosaur *Alamosaurus sanjuanensis* Gilmore, 1922
7. ↑ A re-evaluation of the 'mid-Cretaceous sauropod hiatus' and the impact of uneven sampling of the fossil record on patterns of regional dinosaur extinction
8. ↑ 8.0 8.1 Climatic constraints on the biogeographic history of Mesozoic dinosaurs
9. ↑ Magpie Death Ritual
10. ↑ Rare Video Shows Elephants 'Mourning' Matriarch's Death

### Prehistoric Planet

1. ↑ 1.0 1.1 1.2 1.3 1.4 As stated in North America.