Home | Exhibits | Life Through Time Exhibit | Devonian

Artists conception of ostracoderm fish in a Devonian sea.

(From Louis Pirson and Charles Schuchert, A Text-Book of Geology. John Wiley & Sons, NY: 1920)

Silurian

Devonian 408,000,000 to 360,000,000 years ago

Mississippian

The Devonian* saw the peak of marine faunal diversity during the Paleozoic Era.  New predators such as sharks, bony fishes and ammonoids ruled the oceans. Trilobites continued their decline, while brachiopods  became the most abundant marine organism. A wonderful assemblage in the collection has fragments of trilobite (Phacops rana milleri), brachiopod (Sulcoretepora deissi) and bryozoan fossils, all replaced with pyrite. Oceanic conditions and biological richness resulted in the greatest production of carbonate during the Paleozoic Era.

On land, vascular plants flourished and forests became established. Land animals such as scorpions, spiders,  and wingless insects began to thrive. Tetrapods  first evolved into land animals before the end of this Period.

Sea levels were exceptionally high during the Devonian, giving a widespread equable climate for most of the Period. However, the Late Devonian saw glaciations occur in the south polar area of Gondwana. Most of the modern continental  plates were grouped together in one hemisphere of the Earth.

* The Devonian was named for strata in Devon, England by Sedgewick and Murchison in 1839.

Devonian Animal (Metazoan) Fossils
Trilobites (ToL: Trilobites<Arthropoda<Ecdysozoa<Bilateria<Metazoa<Eukaryota)
	Trilobites: Though declining in numbers, trilobites continued in importance and reached their greatest size during this Period. A number of small specimens are housed in this case: Basidechenella rowi, Phacops rana milleri, Trimerus vanuxemi, Huntonia oklahomae, and Phacops sp.
Echinoderms (ToL: Echinodermata<Deuterostomia<Bilateria<Metazoa<Eukaryota)
	Brittle stars (Ophiuroidea) are represented by  a specimen of  furcaster sp. on a rock slab.
	Crinoids (Crinoidea). Two Devonian crinoids represent the echinoderms: the delicate Bactrocrinus nanus and the basket-like Arthroacantha carpenteri.
Vertebrates (ToL: Vertebrata<Chordata<Deuterostomia<Bilateria<Metazoa<Eukaryota)
	Placoderms: This extinct group of armored fish is represented by  fossil skin from Coccosteus sp. Dunkleosteous, represented on the mural and by a cast of a skull hanging above the cases, reached lengths of up to 30 feet. (Mural)
Mollusks (ToL: Mollusca<Lophotrochozoa<Bilateria<Metazoa<Eukaryota)
	Gastropods (Gastropoda). Two snails are displayed: the slipper shaped Platyceras carinatum and Platyceras rarispinum. Both are replaced with pyrite.
	Cephalopods (Cephalopoda) are represented in this display by a pyrite replaced ammonoid, Tornoceras uniangulare. Some of the outer shell has broken away revealing the chambered structure. Manticoceras sp. shows some of the beautiful patterns cephalopod fossils are known for.
Brachiopods (ToL: Brachiopoda<Lophotrochozoa<Bilateria<Metazoa<Eukaryota)
	Brachiopods reached their widest diversity and greatest abundance during the Devonian. Some brachiopods are long and thin such as Mucrospirifer grabaui , or the three specimens of Mucrospirifer prolificus (edge, top, top). Paraspirifer bownockeri is deeply grooved on one valve, with a corresponding ridge on the other. Brachiopods or their shells were often used as a substrate by other organisms: A fossil of Aulopora microbuccinata is covered with a coral. Another brachiopod, Mucrospirifer mucronatus, is encrusted with bryozoans (see below). A specimen  of Orthospirifer cooperi has another type of brachiopod, Phloihedron sp.  growing on it Another Philohedron sp. (top and edge views) shares its brachiopod substrate with some coral.
	Two specimens  are displayed to show some of the distinctive internal anatomy, including the coiled lophophore supporting structure (click the engraving to the left), of the brachiopod Paraspirifer bownockeri : with one valve removed, with partial shell removal as seen from the hinge and from one end. Two specimens of Pseudoatrypa devoniana, (top, top) are each excellent examples of pyrite replacement.
Moss Animals (ToL: Bryozoa<Lophotrochozoa<Bilateria<Metazoa<Eukaryota)
	Unknown bryozoans completely encrust the shell of a brachiopod, Mucrospirifer mucronatus. A fossil bryozoan, Sulcoretepora deissil, exhibiting pyrite replacement is prominant in our assemblage.
Corals (ToL: Cnidera<Metazoa<Eukaryota)
	Devonian colonial corals are represented here by Hexagonaria , a Petosky stone (Hexagonaria), a fragment of a tetracoral and by two specimens of the the tabulate coral Favosites turbinatus (end of cornucopia-shaped coral cut and polished to show inner structure), Favosites turbinatus, and another tabulate or chain coral, Halicites. Finally, the tabulate coral Aulopora microbuccinata covers a brachiopod shell. Solitary corals appear as the red horn coral Lophophyllum, the horn coral Heliophyllum sp., and as white shapes in a slab of black stone.
Sponges (ToL: Porifera<Metazoa<Eukaryota)
	Sponges: Two fragments of glass sponge are displayed.

The engravings are from Dana, James D. (1870) Manual of Geology, Le Conte, Joseph (1898) A Compend of Geology, Grabau, Amadeus (1901) Guide to the Geology and Paleontology of Niagra Falls, Shimer, Hervey (1914) An Introduction to the Study of Fossils or Pirson, Louis and Charles Schuchert, A Text-Book of Geology. (1920).

Case Index

Life Through Time Mural

Geological Timeline

Last modified 29 January 2007 | ©1998, HSU NHM