Scientists have dated the fossilised remains of an extinct monkey found in an underwater cave in the Caribbean. Researchers discovered a shin bone belonging to the Hispaniola monkey in the Altagracia Province, Dominican Republic, in 2009.

The remains of Antillothrix bernensis were embedded in limestone rock and dated using the Uranium-series technique. The Hispaniola monkey is thought to have gone extinct in the 16th century. The exact cause of the extinction is unclear, but it was probably related to the settlement of Hispaniola - now known as the Dominican Republic - by Europeans in 1492 after its discovery by Christopher Columbus. By analysing the fossilised bone’s shape, experts confirmed that the fossilised tibia did belong to Antillothrix bernensis. Experts at Grand Valley State University used a specialised technique to model the three-dimensional shape of the monkey’s leg bone. This helped them to reconstruct how the small primate might have moved about in its environment and enabled them to compare relatively young examples of Antillothrix bones to the newly discovered million-year-old specimen. Scientists found that the creature’s morphology or body shape had not changed much over the million or so years it had been in existence. The monkey, roughly the size of a small cat, was tree-dwelling and lived largely on a diet of fruit and leaves.

Dr Helen Green of Melbourne University’s School of Earth Sciences, a lead researcher involved in the dating of the limestone surrounding the fossils, said the the age of primate fossils from this region has puzzled scientists since the days of Darwin and Wallace.

‘The presence of new world monkeys on the Caribbean islands is one the great questions of bio-geography and our work on these fossils shows Antillothrix existed on Hispaniola relatively unchanged for over a million years.

‘By establishing the age of these fossils we have changed the understanding of primate evolution in this region,’ said Dr Green.

Professor Alfred Rosenberger of City University New York, who helped recover the bones after they had been found in 2009, and Dr Siobhán Cooke of Northeastern Illinois University, have been working in the Dominican Republic since 2009. They have been searching for rare fossil remains of endemic mammals - creatures who are found in only isolated pockets of the world - to investigate how the animals adapted to their unique, island environments.

‘Very little was known about the native monkey from this island,’ said Dr Cooke. ‘Prior to our discoveries in Altagracia we knew almost nothing, even though this species was first described by Renato Rímoli back in 1977.’ The paper was published in the Journal of Human Evolution.