A Darwin man thought he had made a grisly find when he came across what appeared to be a severed human finger on a beach, but it turned out to be a mysterious plant instead.

The man was walking his dog along the beach at Lee Point, north of Darwin, when the animal took an interest in the object.

The man feared he had discovered the remains of a murder victim and quickly called Northern Territory Police.

Watch Commander Brendan Lindner said officers were initially unsure about what the man had found.

"They played it safe and treated it as though it were human remains," he said.

The finger was sent for forensic examination, but preliminary testing proved inconclusive and it was sent to pathology for analysis.

"In the meantime, the attached photo did the rounds amongst Casuarina Police Station officers attached to Patrol Group 5 (PG5), with officers evenly split during debate at the end of shift as to whether the finger was real or not," Watch Commander Lindner said.

Those who argued it was fake won the day, with the pathologist determining the finger was actually plant material.

Police have now been left wondering what the doppelganger digit really is.

"None of us on PG5 are botanists or marine biologists, so the best we can come up with is Alcyonium digitatum, otherwise known as 'dead man's fingers'," Watch Commander Lindner said.

That species is a type of coral, but according to the World Register of Marine Species it is only found in the northern hemisphere.

For now no-one is sure what the plant is, but Watch Commander Lindner said the investigation was now finalised and the suspicious pinky would be disposed of.