A rare tree frog – the last documented member of a species relatively new to science – has died at the Atlanta Botanical Garden.

The body of the Rabbs’ fringe-limbed tree frog, estimated to be about 12 years old, was discovered in its enclosure Monday morning during a routine daily health inspection.

Staff at the garden nicknamed the long-lived amphibian "Toughie."

Amphibian specialist Leslie Phillips told the Mother Nature Network in 2013 that she was charmed by the frog. “He is just really cool,” Phillips said. “No other frog I have seen is quite like him. He is muscular and has giant webbed feet and big eyes … He is a very handsome frog.”

Scientists estimate that one-third to one-half of amphibian species worldwide are threatened with extinction, many due to habitat loss and diseases such as chytridiomycosis, caused by an aquatic fungal pathogen.

In 2005 the garden, Zoo Atlanta and Southern Illinois University sent a team of scientists to Panama to collect live animals before the chytrid disease struck the area. Among the frogs they brought back to Atlanta was a species of tree frogs (Ecnomiohyla rabborum) new to science, the Rabbs' frog. Identified in 2005 by Zoo Atlanta herpetology curator Joseph Mendelson, it was later named for conservationists George and Mary Rabb. In time, the disease did arrive in Panama, and many of the frogs disappeared.

In 2008 the Garden purchased and outfitted a climate-controlled facility known as the Frog Pod, designed to house the Rabb’s tree frog and other rare amphibians in complete isolation from each other. It is in this facility that the Rabbs’ frog spent the last eight years of its 11-plus year lifespan.

The zoo lost its last remaining Rabbs’ frog, also a male, in 2012.

“Science had a very short window to learn about the species in the wild before this disease struck the only known locality for the frog and the species vanished,” said Mary Pat Matheson, the garden’s president and CEO, adding that the Garden had successfully bred its male with a female but that the tadpoles did not survive.

Because the frog was the last-known living member of the species in captivity, the garden was bound by a standing protocol to recover genetic material from the body, allowing scientists to continue to study the species. That operation made it impossible to determine the cause of death.