A new type of tarantula has been discovered in the Northern Territory's Judburra Gregory National Park by a PhD student from Adelaide.

The University of Adelaide's Sophie Harrison discovered the hairy, silvery brown specimen last week while on a survey expedition in the park, about 360km south of Darwin.

"As we were strolling along with our volunteers, we saw this beautiful big burrow dug into the ground," Ms Harrison told 105.7 ABC Darwin.

"It was a big pit in the ground that came up to my knees. Lo and behold, at the bottom, was a beautiful greyish brown tarantula."

Ms Harrison and expedition leader Dr Robert Raven almost immediately knew they had discovered a new specimen because the tarantula, which has a stocky build and is smaller than a human palm, has markedly unusual characteristics.

"It's got a unique arrangement of mouth parts, so we could see it was different to anything else described," she said.

The expedition group went on to find 10 specimens of the tarantula, which is yet to be named, and Ms Harrison had her picture taken with the discovery.

"It was quite placid. We got it out and had a hold, and it was happy to roam around, and it wasn't aggressive," she said.

But she was "not 100 per cent sure" what would have happened had it bitten her.

"Generally, tarantulas related to this one will cause about six to eight hours' vomiting and nausea. If it bit a dog or a cat, we'd expect it to be fatal," she said.

The tarantula has been taken to be milked so that its venom can be properly studied and proved to be of a genus, the sub-class above species, that is entirely new to science.

Eels and other spiders also discovered

Mr Harrison is studying trapdoor spiders for her PhD but has not always been so comfortable holding arachnids.

"It was a little creepy [at first], but now I've dug out that many of them, it doesn't bother me anymore," she said.

The burrow of the new genus of tarantula discovered by Ms Harrison. ( Supplied: Sophie Harrison )

The expedition, which involved Indigenous rangers and volunteer field assistants from a mining company, discovered six other spiders while in Judburra Gregory National Park.

Five of the new spider species were discovered in just one day, including the new tarantula and a saddle-kneed trapdoor spider, named due to the brownish red markings on its "knees".

The group also found an existing species of eel previously not known to exist in the park's river.

The park's 1.3 million hectares are home to 15 threatened species, including the purple-crowned fairy wren and a critically endangered type of snail.