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Ancient giant rabbit unearthed in Minorca, Spain

The largest known rabbit once lived on an island in Spain, as much as 5 million years ago. But it did not have floppy ears and could not hop.

Fossil remains of the largest known rabbit, which lived 3 to 5 million years ago, have been discovered on the small island of Minorca off the coast of Spain. This ancient giant, named Nuralagus rex (meaning “Minorcan King of the Rabbits”), would have weighed about 12 kg (about 26 lbs). Its skeletal structure indicates that it was not built to hop like modern-day rabbits, and did not have the heightened sense of smell and excellent vision of its modern-day counterparts.

European rabbit. Image Credit J.J Harrison via Wikimedia Commons.

In the 40 million years of rabbit evolution, most species have remained within the size range found in modern rabbits. The giant rabbit of Minorca is a notable exception. Its enormous size (for a rabbit) may have been due to a lack of predators on the island. This would be a classic example of a principle in evolutionary biology called the “island rule,” which states that animals confined to an island can evolve to get bigger due to an absence of predators, or smaller because of a scarcity of food. Contemporaries of Nuralagus rex, also found in the Minorca fossil record, include a bat, a large dormouse, and a giant tortoise.

When Dr. Josep Quintana of the Institut Català de Paleontologia discovered the fossil remains of the giant rabbit, he realized that he had encountered this creature before. In a press release issued on March 22nd, 2011, he said,

When I found the first bone I was 19 years old, I was not aware what this bone represented. I thought it was a bone of the giant Minorcan turtle!

A femur end fossil found by Josep Quintana in 1989 when he was 19 years old, thought at the time to belong to a giant tortoise. It wasn’t until he discovered the fossil skeleton of Nuralagus rex did he realize that the bone from 1989 also came from a giant rabbit. On the right, for size comparison, is the femur of a European rabbit. Image Credit: Josep Quintana.

A paper about this ancient giant rabbit, written by Quintana and his co-authors Meike Köhler and Salvador Moyà-Solà, was recently published in the Journal of Vertebrate Paleontology.

The fossilized skeleton of Nuralagus rex revealed a lot about the animal in life. Quintana and his colleagues found that it had a short stiff spine, not the long springy spine of modern rabbits that enable them to jump. The ancient rabbit of Minorca could not hop. Rather, it ambled about like a beaver on land. Its claws showed it to be a powerful digger, likely unearthing food such as roots and tubers. The skull revealed small eye sockets and small auditory bullae (a bony capsule enclosing the middle and inner ear), indicating small eyes and poor hearing. Living on an island free of predators, the ancient giant rabbits evolved to lose the acute senses that small rabbits need for vigilance against attackers.

Tibia of Nuralagus rex compared with one from an extinct bovid (cloven-hoofed mammal) from the Balearic islands, and a European rabbit tibia. Image Credit: Josep Quintana.

Nuralagus rex, a giant rabbit that lived between 3 and 5 million years ago, is the oldest known example of the “island rule.” Its unique physiology presents scientists with interesting insights into the evolution and adaptation of mammals in an isolated environment free of predators. Quintana hopes that his giant rabbit will become a mascot of sorts to attract students and visitors to Minorca, an island that’s a popular tourist destination in Europe. There’s no other place that can lay claim to being the home of the largest rabbit that ever existed on the planet.

Artist’s concept of the giant rabbit Nuralagus rex, shown with the modern European rabbit. Image Credit: Meike Köhler.

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