In 1959, fossils of 4 distinct types of fish were discovered south of Alice Springs, in the heart of the Australian continent. They were entombed in marine sandstones, laid down in a shallow sea about 500 million years ago. It was not until the 1960s that these remains were recognized as belonging to the earliest known vertibrates.
The name of Arandaspis was given to the best-preserved specimens. This was coined to celebrate the aboriginal Aranda tribe of the area, and to reflect the fish's bony head covering--in Greek aspis means "shield."
Arandapsis had a streamlined, deep- bodied shape. With no fins to stabilize it, it would have swum in an erratic, tadpolelike style. Its lower body was covered in oblique rows of small bony scales, each shaped like a cowrie shell, and decorated with pointed tubercles, which must have given the skin a rough, abrasive texture, like that of a shark.
The front of the body was encased in a head shield, made from 2 large plates of thin bone--a deep, rounded ventral (underside) plate and a flatter dorsal (topside) plate. There were openings for eyes, nostrils and the single pair of gill apertures on either side. Deep grooves in the shield marked the position of lateral line canals--the organs in a fish that sense vibrations.
Arandaspis' jawless mouth was on the underside of its head, suggesting that it may have fed on or near the seabed. Like other heterostracans, there were probably small, movable plates inside its mouth equipped with ridges of dentine. These could have formed a flexible pair of "lips," capable of scooping or sucking up particles of food from the mud.
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