Big Joe (dinosaur)

Big Joe is the most complete and best-preserved Allosaurus fossil known to date. First described as Allosaurus fragilis newer studies showed that the fossil belongs to Allosaurus jimmadseni an older species of the Allosaurus genus.^[1] The large theropod dinosaur lived around 155 Ma ago in the Late Jurassic on a North American flood plain,^[2] it’s powerful hind limbs, sharp claws and serrated teeth, made it an apex predator of its ecosystem.^[3]

Big Joe

Big Joe on display at Knuthenborg Safaripark
Common name	Big Joe
Species	Allosaurus
Place discovered	Wyoming, United States
Date discovered	2015
Discovered by	Brock Sisson

With 95% of its skeleton preserved and rare skin imprints, Big Joe is today's best-preserved Allosaurus fossil found. Therefore, it offers scientists a rare opportunity to study its anatomy and growth to understand A. jimmadseni role in the Late Jurassic ecosystem.^[1][4]

Discovery

The fossil was discovered in 2015 by Brock Sisson and colleagues in the State of Wyoming in what was once the sandbank of a river.^[1] It took 10 men 18 months to finally free Big Joe from the sandstone he was encased in.^[5]

Portions of Big Joe’s skin and scales have also been preserved as impressions. The impressions are unique among dinosaurs and were described by palaeontologist Dr. Mark Loewen as being similar in appearance to that seen on the underside of snakes.^[1]

Fossil characteristics

Big Joe is measured at 9 meters (30 feet) long and 2.2 metres (10 feet) tall, and weighed approximately 1.5 tons which means that he represents one of the largest Allosaurus that has ever been found.^[1]

Big Joe is estimated to have died at around 30 years old, based on a count of the lines of arrested growth (LAGs) present in a bone that was broken during fossil preparation. This discovery makes him the oldest Allosaurus to have ever been histologically sampled.^[1]

The skeleton itself contains a few injuries. First, the calf and shin are fused together with ankle bones, indicating recovery from an injury.^[1] This may have taken place due to a fight with another predatory dinosaur or a failed hunt.^[6] The extent of healing indicates Big Joe survived long after this injury occurred.^[1] In addition, there is an infection on the head and the teeth show signs of disease.^[6]

Exhibition

As of February 2025, Big Joe is part of the Museum of Evolution inside the Knuthenborg Safaripark.^[7] The fossil is part of a newly built exhibition which opened to the public on the 9th of April 2023, after initially arriving with several other prehistoric fossils from the Permian like Dimetrodon.^[2] Visitors can see the fossil in the Dinosaur Era of the Museum together with other dinosaur fossils such as the world's biggest dinosaur skull belonging to the Torosaurus Adam.^[7]