Fossils in Southwestern Pennsylvania
The rocks in southwestern Pennsylvania contain a wide variety of invertebrate, vertebrate, plant, and trace fossils.
The following is a systematic overview of the types of fossils that may be found. It is by no means meant to be inclusive.
Invertebrate Fossils
| Phylum Cnideria (corals):
Only one genus of coral is found in the marine rocks in southwestern Pennsylvania: Figure from Moore and others (1952). Lophodophyllidium (Stereostylus) |
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| Phylum Bryozoa: Only two genera of bryazoa are commonly found in the marine rocks of southwestern Pennsylvania. Figure from Wagner and others (1970). Rhombopora Septopora |
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| Phylum Brachiopoda: A wide variety of brachiopods are found in the marine rocks. Figures from Moore and others (1952) and Wagner and others (1970).
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| Spiriferid articulate brachiopods Composita (middle figure) Crurithyris (5a-c bottom figure) Hustedia (5a-c top figure) Neospirifer (1a-c, 2a-b bottom figure) Punctospirifer (4a-b top figure) |
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| Rhynchonellid articulate brachiopods Wellerella (2a-c) |
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| Orthid articulate brachiopods Rhipidomella (2a-b, 4a-b) |
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| Lingulid inarticulate brachiopods Lingula |
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| Phylum Mollusca: A wide variety of mollusca from three subphyla are found in both the marine and non-marine rocks. Figures from Moore and others (1952), Harper (1990), and Wagner and others (1970).
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| Pelecepoda Acanthopecten (23, top figure) Astartella (not shown) Aviculopecten (14a-b, top figure; 12, bottom figure) Chaenomya (15a-b, top figure) Clinopistha (12a-b, top figure) Dunbarella (not shown) Edmondia (9a-b, top figure) Lima (7, top figure) Nucolopsis (6a-b, top figure) Nuculana (4a-b, botom figure) Orthomyalina (24, top figure) Palaeolima (not shown) Palaeoneila (1, top figure) Parallelodon (10, top figure) Phestia (not shown) Pseudomonotis (8, bottom figure) Schizodus (5, bottom figure) Septimyalina (not shown) Solemya (not shown) Wilkingia (not shown) |
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| Cephalopoda Brachycycloceras Domatoceras Eoasianites Liroceras Metacoceras Mooreoceras Pseudorthoceras Tainoceras |
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| Phylum Echinodermata:
Echinoderms may be found in the marine rocks in the area. Figures from Harper (1990). Crinoid columnals Delocrinus Endelocrinus Syntomaspina |
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| Phylum Arthropoda:
Uncommon trilobites may be found in the marine limestone units such as the Pine Creek and Woods Run. Top figure (from d'Invilliers and Lyman, 1895). Fragments of insects may be found in the nonmarine shales, particularly the roof shales of coals (Harper, 1990) (top two figures, from d'Invilliers and Lyman (1895). Look particularly at:
Ostracodes are common to abundant in nearly all of the non-marine limestones. They are very small however, generally less than 1-2 mm across. Bottom two figures (from Moore and others, 1952). For a good summary of ostracodes visit: http://www.uni-muenster.de/GeoPalaeontologie/Palaeo/Palbot/seite7.html
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Vertebrate Fossils
| Teeth, spines,
bones, and scales The teeming life in the shallow seawater and the fresh- brackish water lakes is evidenced by common teeth, spines, and scales. These are generally quite small (less than 1 cm) but large teeth (up to 2-3 cm) may be found. Top figure from Harper (1990). Bottom two figures from d'Invilliers and Lyman (1895). Occasional fish bones may be found, particularly in the non-marine Duquesne limestone, which has yielded bones of lungfish Monongahela and Sagenodus (Harper, 1990) Other remains, such as bones of amphibians and reptiles, are very uncommon by may be found with careful searching. Although nearly any non marine formation may yield vertebrate fossils, places to begin to look include (based on Harper, 1990):
VERY IMPORTANT: If you should be fortunate enough to find vertebrate fossils, please contact The Carnegie Natural History Museum as they may be extremely important from a scientific standpoint.
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Trace Fossils
| Tracks, Trails, and Burrows Trace fossils (ichnofossils) record the motion of animals on or through sediment. They are formed as the animal feeds, walks, slithers, burrows, or rests. The type of creature that makes the trace fossils is generally not known, and can be a source of interesting speculation (see note on Casselman Formation footprints below). The following are some common trace fossils to look for Planolites is a simple meandering burrow oriented horizontal or oblique to bedding; it is typically distinguished from Palaeophycus by its lack of a burrow lining. Planolites is interpreted as a feeding burrow made by a worm-like animal. (Information and figure taken from the Trace Fossil Image Database). Zoophycos is a horizontally to obliquely oriented burrow that shows a helical structure as a result of overlapping U-shaped burrows that have spreite between the U's. Zoophycos is interpreted as a systematic feeding burrow where the animal probed into the sediment in a U-shape swath, then repeated the same type of swath adjacent to the previous swath, moving in a clockwise or counterclockwise direction. (Information and figure taken from the Trace Fossil Image Database). Spirorbis sp. is a small worm in a calcareous tube (1 - 2 mms) with a spiral form. It is always attached to some surface, in this case to a little trunk. It was living under water and affixed itself to leaves or branches lying in the water. (Information and image from http://www.xs4all.nl/~steurh/engdier/espirorb.html). Aulichnites are Gastropod grazing traces. These traces are locally abundant. There are many other trace fossils in the rocks including Clionolithes, Concotrema, and Zapfella which are tiny boring found in fossil shells. Although most trace fossils in the area were formed by invertebrate, some footprints have been linked to amphibians or early reptiles. A fossil trackway was recently found in a ripple-marked sandstone surface in the Casselman Formation of northern Cambria County, PA. Marks and others (1999) interpret the tracks to have been made by a giant myriapod (similar to a present-day millipede). Sir Charles Lyell, in a trip through the Pittsburgh area in 1845, reported (Lyell, 1849) seeing rock slabs showing 'air-breathing reptile' footprints on a slab of rock shown to him in Greensburg. The fossils came from a 'stone quarry in Union Township six miles southeast of Greensburg on a farm belonging to Mr. Gallagher.' See photos to the right. If these footprint slabs still exist today is uncertain. |
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Plant Fossils
Fossil plants in the area include trunks, and stems, branches, leaves, fruit or cones, seeds, and roots of many different varieties. Top two figures from Harper (1990). As pointed out by Harper (1990), Although different fossils may bear different names, they commonly represent parts of the same plant. For example, the scale tree Lepidodendron is recognizable by the diamond-shaped pattern on its trunk surface. Other parts of the tree include: Lepidophylloides (the leaves), Stigmaria (the roots), Lepidostrobus (the cone), and Lepidostrobophyllum (the scales of the cone). Other plant fossils that can be found include Sigillaria (scale tree), Cordaites, Calamites (scouring rush), Sphenophyllum (small scouring rush), Psaronius (a true fern, leaves are Pecopteris), Medullosa (a seed fern, leaves are Neuropteris, Alethopteris), and others. The images to the right show the major plants that can be found as fossils in the area, what they looked like, and their basic parts. Figures are from Edmunds and Koppe (1968) and Gillespie and others (1978). For a great site showing a wide variety of the plant fossils found in the Pennsylvanian and Permian rocks go to: http://www.clearlight.com/~mhieb/WVFossils/TableOfCont.html. Plant fossils may be found in nearly all non-marine shales and sandstones. However, Harper (1990) gives several suggestions as to where to look:
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Where to Look for Fossils
Fossils will not occur in all rocks. Fossils that occur in a rock section in one place, may be absent in the same rock section elsewhere. It all depends on the environments the plants and animals lived, and whether or not the remained were preserved. As a help in finding fossils, Cross and Schemel (1956) presented a very concise type stratigraphic section for the Pennsylvanian-Permian rocks in the central Appalachians. It illustrates the types of rock layers found and their outcrop relationships. It also shows the kinds of fossils that may be found in each kind of rock layer. Cross and Schemel's chart is available in the thumbnail below as a jpeg file (nearly 1Mb) or as a pdf file. It would be very useful to take a copy with you into the field.
Fossil Communities
When you examine the fossils that occur together in a particular rock unit, you are really examining the remains of a community or organisms that lived together when the rocks were deposited. At any particular time, there are different communities of animals living in different environments. For example, think about the animals that live in a forest, a salt marsh, and in shallow sea water. Each area will have a different community of organisms that is controlled by the environmental conditions. The study of animals in relation to each other and to their environments is known as ecology. When we study fossil organisms, we study paleoecology. The following illustrations from McKerrow (1978) show how the fossil organisms found in a rock may be used to reconstruct the environment of deposition. The environments shown are similar to, but not exactly the same, as those for some of the rock units in southwestern Pennsylvania. Communities present in the Pennsylvanian Ames marine limestone are summarized by Brezinski (1983) and Saltsman (1986).
Non-marine bivalve community. Inhabited shallow waters which spread over extensive areas after the flooding of coal forests. Brackish water.
Mud community. Inhabited shallow marine waters with a moderate clastic influx.
Composita community. Inhabited marine water with calcite mud deposition.
References (used and other helpful sources of information)
Unfortunately, most of these resources are out-of-print. I would suggest looking for used copies through the the Advanced Book Exchange, AddAll, or Ebay auctions.
For additional references of paleontological studies see page 162 of Schultz (1999).
Bartlow, J. A., editor, 1975, Proceedings of the First I. C. White Memorial Symposium "The Age of the Dunkard," West Virginia Geological Survey, 352 p.
Brezinski, D. K., 1983, Developmental Model for the Appalachian Basin marine Incursion: Northeastern Geology, v. 5, p. 92-99.
Burns, J., 1991, Fossil Collecting in the Mid-Atlantic States, Johns Hopkins Press, Baltimore, 201 p.
Cross, A. T., and Schemel, M. P., 1956, Geology and Economic Resources of the Ohio River Valley in West Virginia, Part I: Geology of the Ohio River Valley in West Virginia, West Virginia Geological Survey, Volume XXII, 149 p.
d'Invilliers, E. V., and Lyman, B. S., 1895, A Summary Description of the Geology of Pennsylvania, Volume III Part II Describing the Bituminous Coal Fields and the New Red of Bucks and Montgomery Counties, Pennsylvania Geological Survey, p. 2153 - 2588.
Edmunds, W. E., and Koppe, E. F., 1968, Coal in Pennsylvania, Pennsylvania Geological Survey Educational Series No. 7, 29 p.
Gillespie, W. H., Clendening, J. A., and Pfefferkorn, H. W., 1978, Plant Fossils of West Virginia, West Virginia Geological Survey Educational Series ED-3A, 172p.
Harper, J. A., 1990, Fossil Collecting in the Pittsburgh Area, Pittsburgh Geological Society Guidebook, 50 p.
Hoskins, D. M., 1969, Fossil Collecting in Pennsylvania, Pennsylvania Geological Survey Bulletin G 40.
Hoskins, D. M., 1999, Common Fossils of Pennsylvania, Pennsylvania Geological Survey Educational Series 2, 19 p.
LaRocque, A., and Marple, M. F., 1965, Ohio Fossils, Ohio Geological Survey Bulletin 54, 152 p.
Leighton, H. 1945, The Geology of Pittsburgh and its Environs: A Popular Account of the General Geological Features of the Region: Carnegie Institute Press, 2nd edition, Pittsburgh, PA , 80p.
Lyell, C., 1849, A Second Visit to the United States of North America, John Murray, London, 2 volumes, 368 and 385 p.
Marks, W. J., Marks, R. I., and Pompa, A. M., 1999, Problematic Tracks in the Casselman Formation of Cambria County, Pennsylvania Geological Survey Pennsylvania Geology v. 29, n. 2/3, p. 2-6.
McKerrow, W. S., 1978, The Ecology of Fossils, M.I.T. Press, Cambridge, Massachusetts, 384 p.
Moore, R. C., Lalicker, C. G., and Fischer, A. G., 1952, Invertebrate Fossils, McGraw-Hill Book Company, Inc., New York, 766 p.
Read, C. B., and Mamay, S. H., 1964, Upper Paleozoic Floral Zones and Floral Provinces of the United States. United States Geological Survey Professional Paper 454-K, 30 p.
Saltsman, A. L., 1986, Paleoenvironment of the Upper Pennsylvanian Ames Limestone and associated rocks near Pittsburgh, Pennsylvania: Geological Society of America Bulletin, v. 97, p. 222-231.
Schultz, C. H., editor, 1999, The Geology of Pennsylvania, Pennsylvania Geological Survey Special Publication 1, 888p.
Shimer, H. W., and Shrock, R. R., 1944, Index Fossils of North America, The M.I.T. Press, Cambridge, Massachusetts, 837 p.
Wagner, W. R., and others, 1970, Geology of the Pittsburgh Area: Pennsylvania Geological Survey General Geology Report G 59, 145p.