The end of the Cretaceous Period gave rise to some of the most impressive dinosaurs of the entire age of dinosaurs, with many evolutionary lines changing into new forms right up to the K/Pg extinction. The Alamosaurus is one such fascinating example. Reaching a length of 85 feet and a weight of at least 30 tons, Alamosaurus was the largest dinosaurs to ever stride across North America.

This dinosaur has been discovered in Late Cretaceous deposits, with some just feet below the iridium layer of the K/Pg extinction boundary. Its habitats contained freshwater swamps and woodlands of angiosperm trees. Horned ceratopsids and swift raptors roamed the forest floor, while the massive Quetzalcoatlus soared through the sky. Even the feared Tyrannosaurus stomped through this land. Alamosaurus straddled these two ecosystems, navigating through flooded plains on its massive legs or reaching high with its neck to devour flowering plants atop trees. The presence of Alamosaurus in this wooded environment allows paleontologists to reconstruct the formation's interconnected flora and fauna.

This specimen is a fossil fragment of an Alamosaurus sanjuanensis, the only known species of the genus, found in the Javelina Formation of West Texas. This 66-million-year-old Cretaceous Period deposit is a lesser-known sister site to the Hell Creek Formation further north and offers an exciting new world of dinosaurs to discover. Within its fossil beds are obscure creatures, further expanding our understanding of what the dinosaur era’s end looked like.

All specimens measure between 0.75-1" and are enclosed in an acrylic specimen jar with a removable top which arrives in a handsome, glass-topped riker box case measuring 4x3x1". It comes complete with a informational card that serves as our statement of authenticity.

This specimen is an extraordinary piece and invites you to ponder life at the end of the age of dinosaurs. You can learn more about Alamosaurus and find more authentic dinosaur fossils below!

In the final years of the dinosaur age, the ground shook under the weight of a giant. Other creatures would hear this titan approach before they saw it, but once they knew it was coming, there was only one place to look: up It was the Alamosaurus, the last of the great sauropods and the largest dinosaur ever discovered in North America. With a tip-to-tail length of 26 m (85 ft), Alamosaurus was truly a sight to behold, provided you would not mind craning your neck.

Like some other titanosaurs, Alamosaurus sported osteoderms: scale-like armor that protected these giants from attack. A discovery in 2009 of an osteoderm fossil definitively proved their presence on Alamosaurus after 90 years of debate, allowing paleontologists to chart Alamosaurus’ relationship to the other taxa in the titanosaur family tree. Unfortunately, osteoderms fossilize poorly and have irregular shapes, making identification difficult, but their appearance with Alamosaurus is further proof
of how formidable these sauropods were.

Alamosaurus was the only titanosaur that lived in North America, dominating the delta ecosystems that it lived in. Fossils of the sauropod have been found along the junction between the Aguja and Javelina Formations in West Texas, dating to the end of the Cretaceous, from 84 to 66 million years ago. At this time, a prehistoric ocean known as the Western Interior Seaway cut the North American continent in two, with West Texas on its western coast. This gave birth to a wildly diverse environment that Alamosaurus called home.

After its migration into North America, Alamosaurus stood as the largest dinosaur on the continent, but its reign was ended by the Cretaceous–Paleogene extinction. Alamosaurus remains have been found just a few feet below the K-Pg boundary, a thin strip of iridium leftover from the meteorite impact. Because of its young age, there are comparably few Alamosaurus fossils to study, but every specimen of this creature found testifies to its massive size and its place as one of the last sauropods on Earth.