What is "phyllolepididae"

Phyllolepididae is one of two families of phyllolepid placoderms. The family, as a whole, is believed to be descended from the Chinese placoderm, '' Gavinaspis ''(which forms the other, monotypic family, "Gavinaspididae"). All but two genera are, more or less, restricted to freshwater habitats of the Early to Middle Devonian of Australia. By the Frasnian, the genus Placolepis would spread throughout the world, with fossils being found in Australia, Turkey, Venezuela, and Antarctica, and by the start of the Famennian, phyllolepids would become extinct in Australia (then eastern Gondwana), with only species of Phyllolepis surviving in freshwater environments of Europe and North America.

With the exception of Yurammia. all phyllolepids have distinct ornamentation consisting primarily of concentric rings.