reconstruction of Phyllolepis Side and top vies of Phyllolepis rossimontina ©

Phyllolepis rossimontina (placoderm)

fossil of phyllolepisPlates from the Phyllolepis. The image is approximately 6 cm wide. (Photo courtesy of Ted Daeschler, ANS).

One nearly complete individual and numerous isolated plates have been found in the shallow channel margin facies of Red Hill. Additional plates have also been found in the floodplain pond facies. The nearly complete specimen is now known as Phyllolepis rossimontina. The specific identities of the isolated plates are uncertain.

Phyllolepis belongs to the placoderm family Phyllolepidae (=leaf scale), which has been variously been placed within their own order, the Phyllolepida (= leaf scale), or within the Arthrodira. These flattened fishes have large plates on the head and the trunk and are easily distinguished from other placoderms by the patterns of raised ridges on these plates. The earliest records of phyllolepids come from the Middle Devonian of Antarctica and Australia, and extend their range to Western Europe, Greenland and North America during the Famennian (Late Devonian). Most phyllolepids ranged from 40-50 cm in length.

Most phyllolepids are known only from the plates of their head and thorasic shields. However, an exceptionally well preserved specimen of Austrophyllolepis (from Australia) has allowed a greater understanding of these unusual fishes. They were either blind or has greatly reduced vision. On the other hand they had an exceptionally well developed system of sensory-line canals, which may have been sensitive to minute changes in water pressure or electical fields. Dr. John Long of the Western Australian Museum has speculated that these fishes were ambush predators that would lie in wait in bottom sediments for unsuspecting prey. Their long and apparently powerful tails would presumably provide the rapid burst of speed required for capturing such prey.

Two groenlandaspid placoderms, Groenlandaspis pennsylvanica and Turrisaspis elector have also been recovered from Red Hill. You can also learn more about placoderms.

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Books:
Carroll, R. L. 1988. Vertebrate Paleontology and Evolution. New York: W. H. Freeman & Co.
Janvier, P. 1996. Early Vertebrates. Oxford: Claredon Press.
Long, J.A. 1995. The Rise of Fishes: 500 Million Years of Evolution. Baltimore and London: John Hopkins Univ. Press.
Scientific Papers:
Lane, J.A. and R.J. Cuffey. 2005. Phyllopepis rossimontina sp.nov. (Placodermi) from the uppermost devonian at Red Hill, north-central Pennsylvania. Revista Brasileira de Paleontologia 8(2): 117-126.
Stensiö, E.A. 1969. "Elasmobranchiomorphi. Placodermata. Arthrodires." In: J. Piveteau (ed.) Traité de Paléontologie 4(2):71-692. Paris: Masson S.A.
Image Credits:
The reconstruction of Phyllolepis is copyrighted © 2002, Dennis C. Murphy. (See Terms of Use.) It's based on Long (1995) and Stensiö (1969).

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