Phyllolepida

Taxobox
name = Placodermi
fossil_range = Devonian
status = Fossil

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image_caption = "Austrophyllolepis ritchiei" and "Bothriolepis mawsoni"
regnum = Animalia
phylum = Chordata
subphylum = Vertebrata
infraphylum = Gnathostomata
classis = Placodermi
classis_authority = McCoy, 1848
subdivision_ranks = Orders
subdivision =
Arthrodira † (?sister or containing group)

Phyllolepida †

The order Phyllolepida ("leaf scales") was an order of flattened placoderms found throughout the world, with fossils being found in Devonian strata. Like other flattened placoderms, the phyllolepids were bottom-dwelling predators that ambushed prey. Unlike other flattened placoderms, the phyllolepids were inhabitants of freshwater environments.

Unlike the Rhenanida, the armor of the phyllolepids were made of whole plates, rather than numerous tubercles and scales, and unlike the Petalichthyida, the components of the extraordinarily wide mouth are known. The phyllolepids are considered to have been blind, as the eyes are extremely small, so much so as to suggest that they were vestigial, and that they were placed on the sides of the head, as opposed to visual bottom-dwelling predators, like, say stargazers or flatfish, 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 their thoracic armor, and only two genera, "Phyllolepis" and "Austrophyllolepis" 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 order Arthrodira, or are in fact, a group of highly derived arthrodires.

References

Long, John A. The Rise of Fishes: 500 Million Years of Evolution Baltimore: The Johns Hopkins University Press, 1996. ISBN 0-8018-5438-5