A New North American Giant

A comparison between Alamosaurus and two South American giants

Alamosaurus sanjuanensis was first discovered in 1922 by a team collecting from the Nasshoibito beds in New Mexico. Since then, many more fragments of this creature have been found, ranging from single bones to partial skeletons. Scientists have long known that it was a giant. Yet calculations based upon the load which its legs could bare showed that Alamosaurus was not quite in the same league as beasts such as Argentinosaurus.

However recent fossil discoveries may put North America back in the game for the largest dinosaurs on Earth, with a new campaign headed by this ancient sauropod. A team of palaeontologists digging at the 69 million year old Ojo Alamo Formation in New Mexico have uncovered two gigantic vertebrae and a single femur. Denver.W.Fowler from the Michigan State University, described the day as a 'killer.' The bones were carried 1.2 miles in 40 degree heat. Transporting the vertebrae alone took a whole day.

The sheer size of the remains was what surprised the team. '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 that Alamosaurus got even bigger, but we didn't imagine that it could get quite this big.' A quick comparison to other North American dinosaurs confirmed that it was the biggest to have ever lived in the USA.

Not only is Alamosaurus now the biggest North American dinosaur, the enormity of the bones makes it comparable to the South American giants such as Argentinosaurus or Ruyangosaurus. 'Increasingly, we're finding that very large or small individuals often look very different, and are often described as different species,' 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.'