Scientists have had to create a new taxonomic family to classify mysterious mushroom-shaped animals discovered near Australia in 1988.

At first believed to be a new type of jellyfish, the unique creatures resemble chanterelle mushrooms and are still puzzling researchers, who don't know anything about the animals' feeding habits or reproduction methods, Live Science reported.

"We don't even know if they're upside down," said lead study author Jean Just, a taxonomist at the Natural History Museum of Denmark, as quoted by Live Science.

Eighteen specimens of the unusual animal have been discovered; Dendrogramma enigmatica and Dendrogramma discoides were captured by a research ship that scooped a mixture of ocean water and sediment deep below the sea's surface.

Dendrogramma has been detailed in a new study published in PLOS ONE.

The sample taken from 3,280 feet down contained the unusual specimens, which are characterized by flat discs that are about half an inch across and hold digestive tubes that bring in nutrients.

When analysis revealed that the animals didn't have stinging cells or other jellyfish properties, scientists knew they had to find a new classification for the unusual sea animals, which measure less than an inch long.

"They lack all of the characteristics that would put them in one phylum or another," Just told Live Science. "I think their closest relatives are probably the Cnidaria [true jellyfish] and the comb jellies, even if we can't place them in either of those phyla."

Even with the new taxonomic family, the creatures are still a mystery to scientists, who don't know anything about their lifestyle or whether or not they attach themselves to the ocean floor.

 "It's a very interesting surprise, and it poses lots and lots of questions," said Simon Conway Morris, a biologist at the U.K.'s University of Cambridge, as quoted by National Geographic.

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