Cape Town - A team of cave divers exploring an underwater cave in the Dominican Republic has discovered a fossilised tibia of a monkey that scientists said is about a million years old, embedded in the limestone rock of the cave.
Cave divers Cristian Pittaro, Phillip Lehman, Dave Pratt, and Victoria Alexandrova were responsible for this find within Padre Nuestro Cave on the island of Hispaniola.
The island in the Greater Antilles belongs jointly to the Dominican Republic and Haiti.
Today these caves are underwater, making them a challenging environment in which to hunt for fossils.
Foremost South African researcher Dr Robyn Pickering, of the University of Cape Town’s Department of Geological Sciences, is a prominent member of the team of scientists who tested the specimen to determine its age.
In an article in the Journal of Human Evolution, the team said they used three-dimensional geometric morphometrics to confirm that the fossil tibia did indeed belong to Antillothrix bernensis, a primate that they now believed existed on Hispaniola “relatively unchanged” for over a million years.
They calculated the age of the fossilised tibia using the uranium-series technique, a dating system based on theories around the rate of decay of uranium and other radioactive isotopes such as thorium from specimens over time in a closed system.
This monkey, roughly the size of a small cat, was believed to have been tree-dwelling and living largely on a diet of fruit and leaves.
Pickering, a lead researcher involved in the dating of the limestone surrounding the fossils, said scientists had long been puzzling over the age of primate fossils from this region – since the days of early evolutionary theorists Charles Darwin and Alfred Wallace.
“The presence of endemic new world monkeys on islands in the Caribbean is one of the great questions of bio-geography and now, knowing the age of these fossils, changes our understanding of primate evolution in this region,” she said.
“Our analysis of the fossils shows that Antillothrix existed on the island of Hispaniola for over a million years relatively unchanged morphologically.”
Researchers Professor Alfred Rosenberger and Dr Siobhán Cooke, of Brooklyn College, part of the City University of New York, and Northeastern Illinois University, have been working in the Dominican Republic since 2009, searching for rare fossil remains of endemic mammals.
Their aim was to investigate how these animals were adapted to their unique, island environments.
“Prior to our discoveries in Altagracia we knew almost nothing, even though this species was first described by Renato Rímoli back in 1977,” said Cooke.
Then, to determine how the monkey adapted to its environment, Dr Melissa Tallman and her student Andrea Morrow, from the 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 allowed the comparison of relatively young examples of Antillothrix bones to the newly discovered million year old specimens.
At the University of Melbourne, Dr Helen Green and Pickering worked in the state of the art Isotope Chronology Laboratory, where they measured the levels of uranium, thorium and lead present in the limestone rocks today, using the results to calculate the age.
Cape Argus