reconstruction of Holoptychius Holoptychius sp. ©

Holoptychius sp. (lobe-fin fish)

fossil scaleFossil scale of Holoptychius sp. Photo courtesy of Ted Daeschler, ANS.

The distinctive scale of this large lobe-fin fish has recently been found at Red Hill. Evidently rare at the site, Holoptychius fossils are common in Late Devonian rock elsewhere in Pennsylvania, and, along with the antiarch placoderm Bothriolepis, are characteristic of fossiliferous localities belonging to the Sherman's Creek Member of the Catskill Formation.

The scarcity of Holoptychius and apparent absence of Bothriolepis —the most common vertebrate fossil in the Catskill Formation— at Red Hill suggest significant sedimentological or paleoecological differences between it and other Catskill localities. One consideration is that the Sherman's Creek Member is interpreted to be estuarine in origin, whereas Red Hill appears to have been a non-tidal and freshwater environment. On the other hand, both Holoptychius and Bothriolepis are frequently collected in freshwater localities throughout the world. In fact, either or both of these taxa were found in association with other Late Devonian tetrapods from freshwater localities (i.e., with Acanthostega, Ichthyostega, Obruchevichthys, Ventastega).

Holoptychius is a widely distributed member of the Porolepiformes, a group of medium to large lobe-fins primitively related to lungfishes; Porolepis, Glyptolepis and Laccognathus are also members of this group. Porolepiforms were present in some marine deposits, but were most common in estuarine and freshwater habitats. Their sluggish appearance has led some scientists to conclude they were ambush predators.

Other lobefins, including an unidentified lungfish, a juvenile rhizodont (c.f., Sauripterus), Red Hill rhizodont, Red Hill megalichthyidid, and Hyneria lindae were also found at Red Hill. You can also learn more about lobe-fin fishes.

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Fenton, C.L. and M.A. Fenton. 1958. The Fossil Book: A Record of Prehistoric Life. Garden City, New York: Doubleday & Company, Inc.
Janvier, P. 1996. Early Vertebrates. Oxford: Claredon Press
Long, J.A. 1995. The Rise of Fishes: 500 Million Years of Evolution. Baltimore & London: John Hopkins Univ. Press.
Scientific Papers:
Maisey, J.G. 1996. Discovering Fossil Fishes. New York: Henry Holt & Co.
Image Credits:
The reconstruction of Holoptychius is copyrighted ©. (See Terms of Use.) It was based on Fenton and Fenton (1958).

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