The 14 squat, lumpy handfishes grow fin tips so splayed that the fish look as if they're walking on humanlike hands.
Females of the other group, including handfishes, grow lump-style ovaries, and fertilized eggs get days of parental tending.
It was one of the first Australian fishes discovered by science: the only known specimen of the smooth handfish and one of three handfishes collected in 1802 during a French expedition led by Captain Nicolas Baudin.
Handfishes are small, often colourful or patterned, benthic fishes that tend to 'walk' on hand-like pectoral fins rather than swim.
Despite this interest, and conservation concerns for some species, classification of handfishes has been confused, largely due to their rarity and a lack of specimens.
Gledhill says handfishes are extremely vulnerable to environmental change--pest species, pollution, siltation, fishing, rising sea temperatures and coastal development--due to their scarcity, patchy distribution, low breeding rates and poor dispersal capabilities.
The CSIRO review of the handfishes has raised concerns about the decline of at least two more handfish species, the red handfish and Ziebell's handfish, and exposed a paucity of information about the abundance, distribution and biology of the broader handfish family.
The scientists spent many months among preserved handfishes for the review, applying a mix of intuition, stringent technique and forensic inquiry.
They also examined scientific and historical references to handfishes and their classification, and discovered similarities between a handfish from the Great Australian Bight and a 50-million-year-old fossil at the Pesciara Cave deposits at Monte Bolca in Northern Italy.
Our theory is that handfishes were once fairly widespread but patchily distributed, before being subjected to broad scale extinction events, possibly in the Tertiary period,' Last says.