Researchers have discovered two new species of jellyfish off Western Australia's northwest coast. One is particularly peculiar: It's larger than its cousins, doesn't have tentacles and is, according to the discoverer, extremely venomous.

The Keensingia gigas, a type of Irukandji jellyfish, was found by the director of Marine Stinger Advisory Services, Lisa-ann Gershwin. Such jellyfish are normally the size of a fingernail, but these measure the length of an arm. 

In addition, its apparent lack of tentacles has stumped Gershwin, as jellyfish require tentacles to catch prey.

The Keesingia gigas jellyfish. (John Totterdell/MIRG Australia)

"I think it's probably a fairly tame explanation," she told The Guardian. "I just don't know what it is." 

The Keesingia gigas is just one of the many strange species found in Australia, land of megadiversityBelow, a rundown of some species found in the continent in the past year, ranked by least to most interesting:

5. The Tandanus Tropicanus Catfish

Discovered: July 2014

TropWater/James Cook University

A special North Queensland catfish named Tandanus tropicanus is notable for its cylindrical-like look. Its fleshy body curves into an eel-like shape toward its tail. That said, it's one of "possibly a hundred" new freshwater fish species that could be found in Northern Australia, according to discovery co-author Dr. Damien Burrows of James Cook University.

4. The Blotched Boulder Frog

Discovered: March 2013

AFP Photo/Conrad Hoskin (James Cook University)

Here's another Queensland find: a frog that requires rain to feed and breed. Found in the "lost world" of a rainforest in northern Queensland, the frog has been isolated for millions of years, researchers said, and has adapted to its boulder-filled habitat by burrowing deep into the boulder fields, emerging only when its raining.

3. Unnamed Humpback Dolphins

Discovered: October 2013

REUTERS/Will Burgess WB/TC

Scientists with the Wildlife Conservation Society found new humpback dolphins living off the northern coast of Australia in 2013, though the "discovery" is more a debate over taxonomy: Howard Rosenbaum, director of the WCS ocean giants program, explained the organization has been examining differences between dolphins and through genetic analysis, realized some species significantly differed from each other.

"One of the reasons we're finding new species is because we're finding new tools," Martin Mendez, assistant director for the Latin American and Caribbean program at WCS, told National Geographic. "Genetics opens a new window into these kinds of questions."

2. The Cape Melville Leaf-Tailed Gecko

Discovered: March 2013

Similar leaf-tailed geckos from Madagascar. (REUTERS)

Discovered alongside the aforementioned frog, the Cape Melville Leaf-Tailed Gecko is exactly what it sounds like: a gecko with what looks like a leaf for a tail. 

"The Cape Melville Leaf-Tailed Gecko is the strangest new species to come across my desk in 26 years working as a professional herpetologist," Patrick Couper, curator of reptiles and frogs at Queensland Museum, told CNN. "I doubt that another new reptile of this size and distinctiveness will be found in a hurry, if ever again, in Australia."

1. The Black-Tailed Antechinus

Discovered: February 2014

Gary Cranitch/Queensland Museum

The antechinus are known for their amazing sex drive. No, we're not kidding: Males are known to die from stress after over-enthusiastic marathon mating sessions.

"What they do is just competitively mate, so they mate for a very long time, like 12 to 14 hours, some of the species," biologist Diana Fisher from the University of Queensland told Australia's ABC News. "They do it over and over and over - they're very promiscuous. There's this huge intense mating season going on for about two weeks."

The newest species of the antechinus were found in the Gold Coast and "follow the typical pattern of antechinus," according to Queensland University of Technology's Dr. Andrew Baker, who noted that the new additions are "quite striking."