Biology of Australia

The fauna of Australia

Porolepiformes  

These were relatively large predatory fish from the Devonian. They had a worldwide distribution, being most common in Middle to Late Devonian freshwater deposits. The scales of this form give them their name, the cosmine-covered scales had rows of pores. Other features characterise these fish, a broad head, small eyes, in the cheek they had a prespiracular bone, and the large fangs had a special style of infolding of the enamel and dentine - called a dendrodont tooth structure. They had a large whorl of stabbing teeth at the front of the jaw. It is  believed that most porolepiforms were ambush predators, based on the body and tail.

The oldest known porolepiform, Porolepis, was found in Spitsbergen and western Europe. It grew to about 1.5 m, had a thick cosmine cover on all its bones and scales, and the eyes were very small. It has been assigned to the family Porolepidae, together with some other forms known only from fragmentary bones, Most Middle and Late Devonian porolepiforms are placed in the family Holoptychiidae, because they have round scales and lack cosmine. In the Early Devonian seas and in-shore environments, Porolepis was among the largest predators. Their appearance seems sluggish, though they were probably more efficient than the primitive placoderms and acanthodians with their heavy armour that they probably preyed on.

Sources & Further reading

1. John A Long The Rise of Fishes - 500 Million years of Evolution, University of New South Wales Press, 1995

Links

New Onychodontiform (Oeteichthyes; Sarcopterygii) from the lower Devonian of Victoria, Australia