| Phyllolepida Temporal range:Devonian | |
|---|---|
 | |
| Austrophyllolepis ritchiei andBothriolepis mawsoni | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | †Placodermi |
| Order: | †Arthrodira |
| Suborder: | †Actinolepidoidei |
| Clade: | †Phyllolepida Stensiö 1934 |
| Type species | |
| Phyllolepis concentrica Agassiz 1844 | |
| Families | |
Phyllolepida ("leaf scales") is anextincttaxon of flattenedplacoderms found throughout the world, with fossils being found inDevonianstrata. Like other flattened placoderms, the phyllolepids were bottom-dwellingpredators that ambushed prey. Unlike other flattened placoderms, the phyllolepids were inhabitants of freshwater environments.
Unlike theRhenanida, the armor of the phyllolepids were made of whole plates, rather than numerous tubercles and scales, and unlike thePetalichthyida, the components of the comparatively wide mouth are known. The phyllolepids are considered to have been blind, as the orbits for the eyes are extremely small, so much so as to suggest that the eyes were vestigial, and that they were placed on the sides of the head, as opposed to visually-oriented bottom-dwelling predators, like, saystargazers orflatfish, which have the eyes placed high on top of the head.
Despite having a relatively clear idea of the phyllolepids' lifestyle and anatomy, most fossils consist of fragments of theirthoracic armor, and only twogenera,Phyllolepis andAustrophyllolepis have been thoroughly studied. From the articulation of the thoracic and head plates, it has been suggested that they are either the sister group of orderArthrodira, or are in fact, a group of highly derived arthrodires.
The Phyllolepids are divided into twofamilies, the more primitiveGavinaspididae, represented only byGavinaspis of Early DevonianChina, andPhyllolepididae, which contains all other genera. Barring the ChineseGavinaspis, the cosmopolitanPlacolepis (fossils of which have been found in Australia,Turkey,Venezuela, andAntarctica), and the Euro-North AmericanPhyllolepis, the majority of genera are found in Early to Middle DevonianAustralia. By the Famennian, onlyPhyllolepis survived, and became extinct at the close of the Devonian.
Long, John A.The Rise of Fishes: 500 Million Years of Evolution Baltimore: The Johns Hopkins University Press, 1996.ISBN 0-8018-5438-5
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