Scotland's biggest horse mussel bed and a "faceless and brainless" fish-like creature were recorded during government-backed surveys last year, BBC News reported last Thursday.
Several rare species were recorded. Off the west coast, fan mussels were found. Growing to up to 48cm long, the mussels are Scotland's largest sea shell, the report said.
The Scottish government said the prehistoric "faceless and brainless" amphioxus was recorded off Tankerness on Orkney.
It said the rarely-seen species was regarded as a modern representative of the first animals that evolved a backbone.id.
With a nerve cord down its back, the fish does not have a clearly defined face or brain, BBC News said.
The largest horse mussel bed in Scotland was recorded near Noss Head in Caithness. The molluscs stabilise seabeds, which in turn provides habitat for other species, and can live up to 50 years.
Other finds included flame shell beds in Loch Linnhe in Argyll and new communities of northern feather star off the Sound of Canna.
Environment Secretary Richard Lochhead described the finds as "weird and wonderful," BBC News said.