DINOSAUR FOOTPRINTS FROM A COAL MINE IN EAST-CENTRAL UTAH
LEE R. PARKER AND ROBERT L. ROWLEY, JR.
Natural casts of dinosaur footprints removed from the Price River Coal Company mine roof.
Thousands of natural casts of dinosaur footprints occur in the roof
surface of a mine in an Upper Cretaceous coal in east-central Utah.
Ninety three have been removed for study. They range in length from 28
to 87.5 cm. Most are three-toed forms; only two types are four-toed.
About 14 dinosaur taxa were probably responsible for producing the
specimens in the collection. These tracks were made by animals which
walked in the peat on the surface of a swamp; their footprints were
filled by mud, silt or sand during the flooding of a local river. Most
footprints are very broad with short thick toes, apparently
well-adapted for walking on soft peat. Some footprint casts become
loose in the mine roof and can fall, creating a hazardous condition for
miners, especially in the case of tracks weighing up to 140 kg. In
order to collect quality tracks, they must be chiseled from the roof
rock matrix. Footprints from coal mines are well-known in central Utah
and are displayed in front of the homes of miners and also in some
For twelve years one of us (Rowley) has been able to examine thousands
of natural casts of dinosaur footprints as they occur in the roof
surface of the Price River Coal Company mine in Spring Canyon, west of
Helper, Utah. Ninety three have been removed for further study. This
report briefly describes the conditions involved in the formation and
collection of these dinosaur footprint casts and illustrates 14 types
which have been collected.
footprints occur in the mine roof surfaces as protrusions which hang
down from the roof, sometimes as far as 30 cm. They often occur in
trackways made by bipedal animals or are positioned around tree bases;
some times the tracks are over the top of woody litter or tree roots,
indicating that the animals had been walking on that material as it
occurred on the swamp forest floor. Frequently, the roof surface is so
covered with them that one track oversteps another, similar to tracks
of livestock in a corral (Peterson 1924, Parker and Balsley 1989 and in
prep.). Because of overstepping or incomplete depression of the foot
into the peat, few tracks are of the "exhibit" quality which is
desirable for removal. The sediment which filled in the original
footprints is usually a light-colored fluvial shale or siltstone. The
lower surfaces of most tracks are partially or completely covered with
a thin layer of hard vitreous coal or a fine-grained carbonaceous
siltstone, both of which have a highly polished slickenside-like
occurrence of natural casts of dinosaur foot prints from coal mines is
well-known locally. It is common to see them displayed as a front yard
ornament at miners' homes or as conversation pieces in reception areas
of some businesses in the cities of Helper and Price. Since they can be
as long as 1 m and weigh hundreds of kilograms, they are an impressive
College of Eastern Utah Prehistoric Museum in Price has a good display
of several track types. It also contains a part of the W. D. Wilson
collection of many types and sizes (Lockley 1986). A collection of 30
tracks, described by Strevell (1932), is housed at the Utah State
Natural History Museum, University of Utah, in Salt Lake City (Frank L.
De Courten pers. comm. 1986). However, the largest collection of fossil
footprint casts from coal mines of the Rocky Mountain area in terms of
variety and total specimen numbers is the one illustrated in this
report (made by Rowley). It numbers nearly 100 specimens, and includes
14 different footprint morphotypes. Other museums which we know to have
one or several specimens include: The American Museum of Natural
History, New York; California Polytechnic State University, San Luis
Obispo; The Field Institute of Natural History, Chicago, Illinois;
Louisiana Polytechnic Institute, Ruston; New Mexico Museum of Natural
History, Albuquerque; Peabody Museum of Natural History, New Haven,
Connecticut; The Museum of Western Colorado, Grand Junction; San Diego
Museum of Natural History, San Diego, California; The Smithsonian
Institution, Washington, D.C.; The South Dakota School of Mines and
Technology, Rapid City; University of Pennsylvania, Philadelphia
(Strevell 1932); University of New Mexico, Albuquerque (Ratkevich 1976)
and Utah State University, Logan (Peterson 1924).
Geologic Setting and Paleoecology
The Castlegate D Seam which the Price River Coal Company is mining is
one of several coals in the Upper Cretaceous (Campanian) Blackhawk
Formation (Doelling 1972). It was developed from a peat-forming swamp
on the upper surface of the sheet-like sands of the Aberdeen Member.
This member represents one of several major deltas in the formation
which prograded into the Cretaceous epicontinental seaway and allowed
the development of brackish and freshwater swampy environments when
subaerial surfaces occurred (Balsley and Parker 1983).
living on the swamp surface made deep footprints into the peat. Before
they became obliterated by the rebounding peat, a local river flooded
and deposited overbank sediment into the swamp, filling the footprints
and thus preserving them. Later, the peat became coal and has been
removed, allowing an examination of the natural casts of these
footprints and other fossils which were on the swamp surface (Parker
and Balsley 1989 and in prep.).
other Blackhawk mine roof surfaces, there are abundant fossil leaves,
horizontal logs and trees in growth position which are directly
associated with dinosaur footprint casts (Parker and Balsley in prep.).
Recently, Rowley has collected several ferns, dicot leaves, petrified
tree stumps, pelecypods and gastropods from the roof of the Price River
mine, all of which made up a portion of the swamp flora and fauna at
the time the footprints were made.
Removal of Tracks from the Roof Surface
As the coal is being mined it normally separates easily from the roof
rock, exposing sedimentary features and fossils which might be present.
Footprints can be removed where the roof rock is carbonaceous shale or
siltstone; sometimes these specimens are loose and are easily pried
down. The best tracks for removal are those which extend down from the
roof surface at least 10 cm and have a carbonaceous layer above them.
Because they are heavy and positioned slightly above head height, it is
impossible for one or two persons to safely hold or catch them when
they separate from the roof. Therefore, it is necessary to prepare a
cushion under them and allow them to fall on it. Mine "brattice", a
yellow plastic-impregnated fabric used in mines as a fire retardant and
as a drape for directing ventilating air, has been effectively used for
sedimentary matrix around the track is chiselled away with hand tools
until a groove or channel is formed around it. Eventually, horizontal
chiseling, up behind the track, will loosen it and allow it to drop
from the roof. Specimens as large as 140 kg have been obtained in this
manner without damage to the tracks. An average weight of the tracks
after removal is about 45 kg. Outside the mine, extraneous coal and
rock matrix can be cleaned away. Sandstone preserves footprints less
frequently, but, because it makes a much harder surrounding matrix,
sandstone tracks have been impossible to remove intact.
Dinosaur Tracks and Mine Safety
the removal process it is important to consider the structural
integrity of the surrounding roof to insure that large blocks of rocks
do not fall. In addition, the presence of "black damp" (a deficiency of
oxygen, including the build-up of carbon dioxide and carbon monoxide)
and methane must continually be checked, since these gases can
accumulate very quickly at certain times in a working mine.
footprint casts which extend down from the roof several inches are a
nuisance where the coal seam is thin, causing the roof to be low; mine
workers continually bump their heads on them. More serious problems
have existed with them since mining began in the area in the early part
of the century, because they fall and kill or seriously injure mine
workers. Therefore, loose footprints are bolted to the roof with a
vertical drill designed to drive a 1 to 3 m long steel bolt upward into
the roof rock and prevent tracks and blocks of rock from falling (Figs.
1-3). We are unaware of other lethal trace fossils, nor do we know of
other circumstances where dinosaur activity has contributed to the
possible death of human beings.
Morphology of the Footprints
The natural footprint casts collected from the Price River Mine seem to
have been produced by several animal taxa. A few of the casts we
illustrate here (Figs. 9-23) have similar morphologies, suggesting that
they may have been made by the same dinosaur species, depending on age
of the animal or activities at the time the footprints were made.
However, it should be emphasized that all those 14 morphotypes
illustrated are represented in the collection by at least four similar
specimens. The only exception is the specimen shown as Figure 22, which
is unique in the collection. Certain track types are represented by as
many as 12 specimens including distinct left and right pes. In
addition, it is clear from examinations of primary sedimentary features
in the roof surface that all footprints had been pressed into peat;
none were made in clastic sediment. Therefore, the morphological
consistency of all specimens of each track type, each produced on the
same kind of surface, suggests that the dinosaur fauna included at
least 14 taxa. Most Price River specimens are three-toed; only two
types are four-toed. No five-toed tracks have been observed in this
mine, but they are known in other Blackhawk Formation coal mines. These
tracks range in length from 28 to 87.5 cm. With a few exceptions, the
foot prints, which are mostly pedes, have short toes on wide,
apparently flat feet (Figs. 1, 3, 7-20, 23). This broad foot structure
seems to have been adapted for walking on the soft peat of the swamp
surface, similar to a snowshoe. Tracks with narrow toes occur but they
are rare, both in the collection and in the actual mine roof (Figs. 2,
(Strevell 1932) gave Latin binomials to eight ichnospecies of the
ichnogenus "Dinosauropodes" collected from a coal in the now-abandoned
Standard mine (Blackhawk Formation, Castlegate A and B Coals, Doelling
1972), although Lockley and Jennings (1987) indicated that these names
are not valid. Three of the species collected in the Price River mine
are similar in size and shape to those in the Standard mine: D.
bransfordii (Fig. 7); D. magrawii (although our specimens are not as
large; Fig. 9); and D. osborni (Fig. 23). In addition, at least six
species from the Price River mine have been seen in a Kenilworth mine
(Blackhawk Formation, Kenilworth Coal, Parker and Balsley in prep.).
These have not been described nor given Latin binomials, but include
those shown here as Figures 1, 4, 7, 10, 16, and 18.
that certain of these track types occur in three stratigraphically
different coals in the Blackhawk Formation indicates that the animals
which produced them were part of the Cretaceous swamp fauna for a great
length of time. Other types, collected in only one coal bed, may be
restricted in time and may prove useful as stratigraphic or
Diagnostic skeletal material is rarely collected in the Blackhawk
Formation. What has been collected includes a carnosaur tooth (Steven
F. Robison pers. comm. 1984) and the skull of Albertosaurus sp. (James
H. Madsen, Jr., pers. comm. 1985; Parker and Balsley in prep.). It is
thought that many of the large, flat footprint types were made by
unidentified hadrosaurian species (Figs. 1, 3, 7-9, 11-20) (Strevell
1932, Parker and Balsley in prep.), certain of the narrow-toed forms
were probably made by theropods like Albertosaurus (Figs. 2, 4-6, 10,
21), and a ceratopsian probably produced the four-toed specimen (Fig.
23, cf. Lockley 1986, Lockley and Jennings 1987).