A 360-million-year-old species of fish with elegant needle-like spines, previously unknown to science, has been discovered in a fossil-rich deposit on the outskirts of Grahamstown.

The find was made by palaeontologist Robert Gess who has been working on the site which was exposed by a 1985 cutting to re-route the N2 around the town.

The deposit, a thick band of shale, marks the location of a brackish prehistoric estuarine lagoon, and has yielded a wealth of plant material, fish and fragments of a metre-long water scorpion.

These creatures were swimming in the warm, placid waters of the lagoon 120 million years before the first dinosaurs made their appearance on earth.

The shale is extremely fragile, and Gess' main tool has been a penknife, with which he systematically prises layers apart, centimetre by centimetre, or even millimetre by millimetre.

The specimens themselves are often so soft that even using a paintbrush to clean them can cause damage. Gess discovered the fish in 1999, but scientific convention prevented him from formally announcing his find until publication in a scientific journal of a descriptive paper this year.

The fish, named Diplacanthus acus, is only 10cm long but the distinctive narrow spines on its back and stomach make it almost 15cm from top to bottom.

--Sapa