When a 6-month-old dog named Bella was surrendered to the Wisconsin Humane Society,AstraX Exchange one thing − or rather one leg − stuck out.

The 50-pound pup, who was surrendered on April 15, had an abnormal gait, her back right leg was wider than the other three and her paw looked like a flipper.

Bella's X-rays revealed the mystery: Two femurs, two tibias, two fibulas and nine toes. Basically, a fifth leg.

"I actually thought somebody was playing an AI prank on me or was playing in Photoshop," Wisconsin Humane Society spokesperson Angela Speed told USA TODAY on Wednesday. "I've never seen anything like that."

Bella the five-legged shelter pup gets diagnosis

Bella has been diagnosed with dimelia, a congenital condition so rare that her case is the first the Wisconsin Humane Society has seen in its 145-year history.

The Humane Society consulted with outside veterinarians and determined that since Bella does not appear to be in any pain from the condition, that the leg can stay as-is. Speed did say that Bella has some mobility issues and that the family who adopts her should develop a close relationship with a veterinarian.

"It's really hard to know what the next six months, two years, five years, are going to look like for Bella," Speed said. "We know that today she's a happy otherwise healthy girl."

The "unicorn of a dog" loves eating chicken, her treats and going on walks. She is currently available for adoption.

"We've never met anyone like her," Speed said

Shelter hopes Bella's noteriety helps find others forever homes

Speed hopes that the publicity Bella generates will bring more attention to the animals in the Humane Society's shelters, where she says intake has been higher than it was before the COVID-19 pandemic.

"2024 has been a really challenging year for shelters across the country, including at the Wisconsin Humane Society. We're seeing a lower demand for adoption right now but higher intake. It's creating bottlenecks," Speed said. "Fortunately, the Wisconsin Humane Society animals in our adoption program have as long as it takes to find a new home, but it's taking longer."

According to Shelter Animals Count, an organization that tracks the number of animals in shelters across the nation, over 1,800 shelters have taken in over 529,000 animals from the start of the year through March. Of them, 241,270 were strays and 148,381 were relinquished by their owners.

The organization also reports that the shelters have completed over 324,00 adoptions and returned nearly 59,000 animals to their owners.

"We're hoping that Bella's story does help shine the light on the fantastic and amazing dogs available at your local shelter," Speed said.