North America’s Largest Dinosaur Discovered

Montana State University’s  Museum of the Rockies  and the State Museum of Pennsylvania have made BIG news. The largest dinosaur to ever be discovered in North America has been found in New Mexico according to a publication of  Acta Palaeontologica Polonica where  MSU researcher, Denver Fowler along with Robert Sullivan, of Harrisburg PA, made the revelation of their massive find. Pictured below, you can see the  badlands’  conditions of the Naashoibito beds in San Juan, New Mexico, where the discovery was made.

Sullivan and Fowler
Sullivan and Fowler Working in the Naashoibito Beds - Courtesy

The bones were of a saurapod called the Alamosaurus. It was a long-necked dinosaur that lived in the Southwestern part of the U.S. about 69 million years ago. The Alamosaurus isn’t new to researchers however, the sheer size of this particular specimen is what sets it apart from the pack.

“We used to think that a fully grown  Alamosaurus  measured around 60 feet long and weighed about 30 tons; but a 2009 study by another MSU researcher, Dr. Holly Woodward, found that a femur thought to belong to an adult was still growing,” Fowler said. “This told us thatAlamosaurus  got even bigger, but we didn’t imagine that it could get quite this big.”

Now that they have compared the fragmentary remains to that of its South American cousin, the Argentinosaurus, it is estimated that this heavy hitter could have been as much as 70 tons! The team collected two vertebrae and a femur. Just to give you an idea of how enormous this find was, it took most of a day for the team to carry the collection 1.2 miles back to camp. In the image below, you can see a reconstructed vertebrae and how large in scale this creature was in comparison to humans.

Nate Carroll stands beside the reconstructed vertebrae he sculpted along with Liz Freedman, a doctoral student in Jack Horner's paleontology lab. - Courtesy of MSU website.

One thing this discovery reveals is the importance of continued research. It is apparent now that many of the assumptions about the Alamosaurus were based on immature remains. Fowler and his team hope that they can get back to New Mexico in hopes of finding a more complete specimen. Unfortunately, to date there have only been  fragmentary  discoveries of the Alamosaurus.  Fowler said. “Our findings show that  Alamosaurus  was originally described based on immature material, and this is a problem as characteristics that define a species are typically only fully gained at adult size. This means that we might be misinterpreting the relationships of  Alamosaurus  and possibly other sauropod dinosaurs too.” Though Fowler’s teams have made significant discoveries, a big challenge they have is to try to make super size discoveries with a small team of two or three people.

If you would like to follow the research from the Horner Paleo Lab at the Museum of the Rockies, go to their  Facebook  page or

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Darrin Jenkins

Darrin is an IT manager for a large electrical contractor in Louisville KY. He is married and has 3 kids. He loves helping people with their technology needs. He runs a blog called Say Geek!