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PALEONTOLOGY ARTICLE

Birdsong Shale Fossils
By MIKE BALDWIN

10.10.2006 -- The Birdsong Shale of Vulcan Quarry, Parsons, Tennessee consists of alternating layers of bluish-green clay shale and calcareous [limy] shale beds. The majority of these shale beds are two to three inches thick, although some may be as thick as eight inches. Birdsong Shale, as a whole, is 25-40 feet thick but can reach a thickness of 60 feet.1

Birdsong Shale is very fossiliferous in Vulcan Quarry. You should be able to find a number of fine specimens from this location, including corals, brachiopods, gastropods, nautiloids, bryozoans, and an abundance of crinoids [mostly stems]. On a recent field trip to Vulcan Quarry, a softball-sized crinoid calyx [head] was found. Although a large number of trilobites are believed to have inhabited the Ross Shelf [location of Birdsong Shale] during the Devonian Age, few intact trilobite fossils can be found there. Trilobite specimens tend to be very fragile and fragmentary,
suggesting that many trilobites may not have survived the fossilization process.1

Phacops
Image courtesy of the National Audubon Society
Field Guide to North American Fossils

The Phacops [pictured above] was widespread throughout North America during the Devonian Age and is often beautifully preserved.2  With close examination and determination, you may find a trilobite or two in Vulcan Quarry. The three zones of the Birdsong Shale were named from the dominant fossil types seen within them. The zones are: [1] Trilobite Zone–approximately 22 feet thick; [2] Bryozoan Zone–6 feet thick; and [3] Brachiopod Zone–33 feet thick.1

For fossils found in Vulcan Quarry, your specimen card should contain the following information:
[01] Specimen Name
[02] Site: Vulcan Quarry [Parsons TN]
[03] County/State: Decatur/Tennessee
[04] Formation: Ross
[05] Member: Birdsong Shale
[06] Epoch: Lower Devonian [408-387mya]

What I would like to do now is give you a look at some of the specimens to be found in the Birdsong Shale.

ANTHOZOA
Streptelasma strictum1

Conical-shaped coralla [coral] which had a funnel-shaped gullet leading from the mouth to a large central cavity which worked like a stomach. It had tentacles like a hydra.3

FAVOSITES
Favosites conicus1
Favosites foerstei1

Tubulate corals [honeycomb corals] range from small sheets to massive domes. The walls are thin, perforated by small pores. They lived in shallow water.4

TRILOBITES
Dalmanites retusus1
Paciphacops logani1

Most trilobite fossils have lost the appendages. These structures do not preserve well. The name trilobite means "three-lobed ones." I might be interpreted as threeparts consisting of head, body, and tail. But, in fact, the name actually refers to parts that run lengthwise and are separated by furrows, not joints. These grooves divide every
trilobite into an axial lobe in the middle and two pleurae– one at each side of the body.

GASTROPOD
Platyceras1

The sea snail spent most of their lives in particular resting-places. Playceras clung to the sides or tops of crinoids so tightly that the gastropods even left marks upon their hosts.3

BRYOZOA
Intrapora puteolata1

Bryozoans are extremely abundant, occuring in vast numbers either indepentdently or attached to other fossils, however they are difficult to identify without using a microscope.1

BRACHIOPOD
Leptaena1

This brachiopod has a shell with a semi-circular outline, with prominent auricles and a straight hinge line. The ornament consists of numerous very fine, clustered ribs, and strong, concentric wrinkles.4

BRACHIOPOD
Dicoelosia1

This brachiopod has a characteristic bi-lobed, near triangular outline. The hinge line is of variable width, but is generally short. Numerous fine ribs diverge near the front of the shell. Dicoelosia attached to bryozoans in shallow to mid-depth water.4

NAUTILOID
Michelinoceras [Orthoceras]

All long, straight cephalopods with simple siphuncles used to be called Orthoceras. Many of the North American cones are now called Michelinoceras. The shell of the Michelinoceras is shaped like a slowly tapering cylindrical cone and is made up of closely spaced concavoconvex chambers, joined together by a centrally placed tube called the siphuncle.4

CRINOID
Scyphocrinites stellatus1

Crinoids, called sea lilies, are a complex and beautiful group of stalked echinoderms. Most fossil crinoids were stemmed. The stem was attached by roots to the sea floor or to other animals or plants. The stem bore a crown consisting of a theca [calyx] covered with plates and 5 or more arms [brachia].2 Most beds of crinoidal limestone
consist mainly of broken stems and few calyxes, which may mean that mature crinoids broke loose from their stems and drifted away.3

Works Cited:
1. Kieran Davis; The Paleobiogeography and Palaeoenvironment of the Birdsong Shale (Ross Formation, Lower Devonian, Tennessee; Report
Presented to Coventry University, School of Natural and Environmental Science; April, 1996

2. Ida Thompson; National Audubon Society Field Guide to North American Fossils; Alfred A Knopf, Inc.; New York; 1996

3. Patricia V. Rich, Thomas H. Rich, Mildred A. Fenton, and Carroll L. Fenton; The Fossil Book: A Record of Prehistoric Life; Dover Publishing, Inc.; Mineola, New York; 1996

4. Cyril Walker and David Ward; Fossils: Eyewitness Handbook; Dorling Kindersley, Inc., New York; 1992

Images on this page courtesy of Index Fossils of North America by Hervey W. Shimer and Robert R. Shrock [1959]; The Fossil Book: A Record of Prehistoric Life; Fossils: Eyewitness Handbook