The haul included vertebrae from a crocodile, the Brisbane Times reported.
The first fossils were discovered about two weeks ago in material removed from a hole drilled for a support for a rail overpass in North Brisbane.
At a news conference Tuesday at the work site, Suzanne Miller, head of the Queensland Museum, said the area was low and swampy 50 million years ago. She said in addition to the crocodile, scientists have found the remains of fish, frogs and plants.
"This is utterly unique to science. To find this variety of plants and animals that were alive and co-existing 50 million years ago is phenomenal," Miller said. "Geologically, around the world there will be a lot of interest in the fossils that have been found."