BRENT H. BREITHAUPT (1), ELIZABETH H. SOUTHWELL (1), THOMAS L. ADAMS (1),
AND NEFFRA A. MATTHEWS (2)
(1)Geological Museum, University of Wyoming, Laramie, WY 82071
(2)National Science and Technology Center, Bureau of Land Management, Denver, CO 80225
AbstractThe Red Gulch Dinosaur Tracksite (RGDT) UW V-98066 is a 1600 square meter area of public land administered by the Bureau of Land Management in the eastern Bighorn Basin of northern Wyoming. The most extensive dinosaur tracksite in the State, the RGDT preserves approximately 1000 tridactyl pes imprints in an oolitic limestone interval of the Bathonian (approximately 165 ma) Canyon Springs Member of the Lower Sundance Formation. Arranged into at least 125 discrete trackways, these footprints offer a unique glimpse of Middle Jurassic dinosaur evolution, ecology, and community development. In addition, the RGDT is a significant fossil site due to its extent, geologic age, geographic occurrence, educational opportunities, and public involvement.
To preserve the value of this unique paleontological resource, monitor erosion, and facilitate intensive scientific research of the tracks and trackways, extensive documentation and applications of innovative technologies have been conducted at the Red Gulch Dinosaur Tracksite. Established ichnological field methods consisting of hands-on track identification, ocation, measuring, and detailed recording of the tracks have been utilized over the past 4 years. This documentation is being synthesized with state-of-the-art data collection methodologies, resulting in one of the most precise approaches for the measuring, recording, and evaluating of fossil tracks. Global Positioning Systems data collecting, precision surveying, and photogrammetry were used to facilitate construction of a comprehensive database of information gathered on each track and provide a spatial framework for data analysis. Extensive photographic documentation (including standard format aerial photography, as well as 35-mm photos taken from tripod heights of 2-10 meters, a Low Altitude Remote Controlled plane, an Ultralight aircraft, and a blimp) are being georeferenced with the survey data. As state-of-the-art technology continues to be utilized at this site, the RGDT has gradually become one of the most extensively documented dinosaur tracksites in the world.
Over the past three years, investigations were conducted on a previously undescribed dinosaur tracksite found in the vicinity of Shell, Wyoming (Figure 1). This tracksite, hereafter referred to as the Red Gulch Dinosaur Tracksite (RGDT), is unique in the State of Wyoming and Represents a significant paleontological resource which will be developed for the educational benefit of the public. The initial tracksite discovery was made on land managed by the Bureau of Land Management (Section 20, T. 52 N., R. 91 W.) in the spring of 1997. Subsequent mapping has extended the tracked layer laterally onto adjacent sections.
|Figure 1. Location map of the Red Gulch Dinosaur Tracksite.|
After being invited and permitted by the BLM to undertake this study, the investigators devised a plan to study the vertebrate ichnology in this area and to coordinate our findings with those of other researchers working in the region. As this was a previously unrecorded site, the tracks were located, mapped, measured, described, surveyed, photographed and compared with other previously studied track assemblages. Analysis of these data is providing unique insights into individual and group behavior and dynamics, faunal diversity, community structure and habitat of Middle Jurassic dinosaurs in northern Wyoming, as well as the microenvironments of the substrate during track generation and track preservation/erosion. Ultimately, we will be able to tie the Red Gulch Dinosaur Tracksite into a geological and paleontological framework, which will allow comparison of its ichnofauna with other similar trace fossil assemblages worldwide, and to permit correlation of the tracked layer with beds of the same age in Wyoming and elsewhere in the western United States. The proximity of the site to an existing roadway allows for ready access for the public to view the tracks in situ. In a cooperative partnership with the BLM, the investigators have supported development of the site as a unique tool for public education. The investigators have worked with various parties to assist in the creation of interpretive displays and websites, as well as disseminating the information through the media.
The initial discovery of the Red Gulch Dinosaur Tracksite was in a "dry wash" exposed along the Red Gulch/Alkali Backcountry Byway. The tracks are preserved in a limestone unit in the lower part of the Jurassic Sundance Formation. Although walked and driven over for decades, the dinosaur tracks were overlooked until recently, presumably because the Sundance Formation in the Bighorn Basin has historically been defined as open-water marine in character (Darton, 1899). However, this discovery and other recent work (Kilibarda and Loope, 1997; Schmude, 2000) now demonstrate episodes of subaerial exposure during the Middle Jurassic in this region during regressive phases of the Sundance Sea. In the vicinity of Shell, Wyoming, the lower Sundance strata were deposited on a broad, shallow shelf adjacent to the paleotectonic feature named the Sheridan Arch by Peterson (1957). Schmude (2000) identified another Jurassic paleotectonic feature in this region which he named the Black Mountain High. These local paleohighs created conditions that may have allowed creation and preservation of this paradoxical non-marine dinosaur ichnofauna in an otherwise marine depositional regime. The track-bearing limestone lies stratigraphically below the level of occurrence of the marine invertebrate fossil Gryphaea nebrascensis within the lower Sundance Formation. Geologic work in the area has assigned the track-bearing unit to the Middle Jurassic Bathonian age (approximately 165 million years old) Canyon Springs Member of the Sundance Formation (Schmude, 2000).
Any evidence of dinosaur activity from the Middle Jurassic is significant,
as this was a period which preserves little terrestrial deposition (particularly
in North America), and a very limited, vertebrate fossil record (Shubin and
Sues, 1991). Existing dinosaur bone assemblages are relatively sparse from this
time, but are known from localities in China, Morocco, Algeria, Madagascar,
England, France, Portugal, Argentina, Chile, Australia (Dodson, 1997; Weishampel,
1990) and Mexico (Clark et al., 1994; Fastovsky et al., 1995). The dinosaur
track record is also limited. In the New World, existing Middle Jurassic dinosaur
track records have been documented from Utah (Lockley and Hunt, 1995; Lockley
et al., 1998; Foster et al., 2000), Mexico (Ferrusquia-Villafranca et al., 1996),
and Chile (Weishampel, 1990). Worldwide, other Middle Jurassic tracks are reported
from England (Whyte and Romano, 1994; Lockley and Meyer, 2000), Scotland, Portugal,
Madagascar, Argentina, Morocco, China, and Iran (Lockley and Meyer, 2000), and
Australia (Weishampel, 1990). Clues on the existence and nature of dinosaur
communities in North America during the Middle Jurassic are especially important
and are needed to explain the apparent, sudden explosion of new and abundant
faunas that appeared here in the Late Jurassic (Gillette, 1996). The investigators
have previously noted that there should be more dinosaur tracks known in Wyoming
(Breithaupt, 1994) and have predicted that they would be found with deliberate
effort (Southwell and Lockley, 1996). Although vertebrate ichnology studies
are in their infancy in Wyoming, dinosaur tracks are known in a variety of units
throughout the state (Lockley et al., 1996; Southwell and Breithaupt, 1998;
Southwell, Breithaupt, Lockley, and Wright, in prep.). Theropod and sauropod
dinosaur tracks and pterosaur tracks have been documented in central Wyoming
in the Sundance Formation, and in Utah, Colorado, Oklahoma, Arizona in the Sundance
Formation equivalent Summerville Formation (Lockley et al., 1996). However,
these tracks are located in the upper part of the formation and are generally
considered to be Late Jurassic.
The Red Gulch Dinosaur Tracksite is a 1600 square meter area designated by the BLM in the eastern Bighorn Basin of northern Wyoming. The RGDT locality is UW V-98066 in the Scientific Collections Database of the Department of Geology and Geophysics at the University of Wyoming. The Smithsonian Institution locality number for the site is USNM Locality 41696. A major arroyo in the 1600 square meter area has been informally broken into 3 distinct areas (i.e., "Corridor," "Ballroom," and "Discovery Area"). Because of the density of tracks, degree of surface exposure, proximity to the road, and BLM development plans, this "dry wash" has been the area of emphasis of study and primary concentration during the past four field seasons.
|Figure 2. Typical Red Gulch Dinosaur Tracksite footprints: phto and sketch. Track drawing by Thomas Adams.|
|Figure 3. Hypothetical Middle Jurassic dinosaur trackmaker for the Red Gulch Dinosaur Tracksite. Drawing by Thomas Adams.|
Dinosaur tracks are preserved as impressions in a gray, ripple-bedded, oolitic, peritidal limestone. This substrate also contains an interesting invertebrate trace fossil assemblage (e.g., Diplocraterion and Rhizocorallium) and various invertebrate body fossils (e.g., pelycypods, gastropods, and crinoids). The majority of tracks (Figure 2) have three distinct digits, a very faint "heel" imprint, sharp claws, and foot lengths greater than widths. This track morphology is consistent with those generally attributed to theropod dinosaurs (Thulborn, 1990). No other types of dinosaurs are currently recognized at the Red Gulch Dinosaur Tracksite based on the documented footprints. However, care must be taken in assigning a trackmaker due to "a rather blurred continuum" (Farlow, 1987) of features shared between theropod and ornithopod trackmakers. In general, assumptions about the identity of specific trackmakers must be approached with caution, unless direct bone evidence can be found and correlated with the tracks (Lockley, 1997). At the RGDT, all of the tracks are tridactyl pes impressions ranging in length from 8-30 cm. Most of the tracks are between 15-21 cm in length. From this evidence, it may be hypothesized that the tracks were created (Figure 3) by small- to medium-sized theropods (ranging in weight from only tens to hundreds of kilograms). Unfortunately, no Middle Jurassic dinosaur remains are currently known the United States.
|Figure 4. Red Gulch Dinosaur Tracksite "dry wash" (photo from Low Altitude Remote Controlled plane) with track points located from total station; "Discovery Area" (north), "Ballroom" (south).|
Over 1000 theropod tracks have been discovered at the Red Gulch Dinosaur Tracksite, making the RGDT the most extensive dinosaur tracksite known in Wyoming. Mapping efforts documented over 630 tracks (representing 40 trackways) from the Ballroom, approximately 280 tracks (representing 49 trackways) from the Discovery Area (Figure 4), and over 200 tracks (representing 36 trackways) from 23 outcrop outliers of the track-bearing Sundance Formation within the 1600 square meters of the RGDT. Arranged into at least 125 discrete trackways (ranging from 2 to 45 steps), these tracks offer a unique glimpse of dinosaurs walking in water-saturated, thixotropic sediments close to the shore of an inland seaway. A statistical analysis of 425 individual footprints, measured from mylar tracings, indicates that no distinct morphologic clustering is apparent, thus indicating that only one taxon of dinosaur is represented at the RGDT (Sizemore, 2000).
Because of the large population and areal extent, important morphological and preservational variations within and between trackways were analyzed. Irregular step lengths, variable straddle widths, and swerving trackway paths may be related to variations in substrate microenvironments or to intracommunity dynamics. The majority of the trackways show preferred orientations with two trends of parallel to subparallel groupings to the south and southwest, suggesting gregarious behavior. However, several solitary trackways trend in opposite and perpendicular directions; dispelling the existence of any confining barriers. Analysis of the various trackways with regard to time sequencing, origin, direction of travel, speed, and changes in morphology are currently in progress. Preliminary analyses indicate that the majority of dinosaurs were "walking" with an average speed of approximately 6 kilometers per hour.
Standard vertebrate ichnological field methods discussed by Thulborn (1990) and Lockley (1991) were incorporated during the study of the Red Gulch Dinosaur Tracksite. The first step in the study of dinosaur tracks was finding and discovering the extent of the track-bearing layer. Mapping and study focused on exposures within the RGDT, but continued prospecting of correlative beds was an ongoing process throughout the course of the investigation and will continue into the future.
|Figure 5. Red Gulch Dinosaur Tracksite footprint with toe and heel points marked and numbered.|
The track mapping process began with clearing the surface of covering debris. This entailed removing a thin veneer of unconsolidated material that had obscured the tracks and did not require the removal of thick deposits of overburden or disturbance of large, established vegetation. Because the area is so large, teams of well-supervised volunteers were utilized for the large and small scale sweeping. In addition, the surface was systematically sprayed with water via a portable water tank equipped with a gas-powered pump and a hose, allowing for the surface to be cleaned as necessary.
Each track located was marked (Figure 5) and numbered in chalk on the outcrop and sketched onto a map with a scale of 1 inch = 1 meter. This map was continually updated and redrafted. The one square meter grids for this map were laid out on the outcrop surface utilizing a Topcon standard total station (Figure 6) or a Geodimeter System 4000 one-man total station with a robotic unit and data collector (Figure 7). Grid corners were marked on the limestone surface with a permanent black marker circle no more than 2 cm in diameter. This practice did not permanently mar the track surface, as the grid points resemble the lichen that occur naturally on the surface. The ink weathered away over the course of a year or two. In addition, the locations of toe and heel points were captured using the Geodimeter System 4000 total station. Global Positioning Systems coordinate data were used to bring the surveyed points into a real world coordinate system.
Figure 7. Ty Naus (South Dakota School of Mines and Technology student) surveying "Ballroom" with Geodimeter total station.
|Figure 6. Volunteer Susan Horn (Kentucky teacher) surveying
in the "Discovery Area".
By the end of 2000, approximately 900 grids within the dry wash were mapped, measured and photodocumented. All grids of the Ballroom and Discovery Area containing tracks were photographed with a metric camera. Track density varied throughout the Red Gulch Dinosaur Tracksite, ranging from 0-8 tracks per square meter. In addition, each track was documented. Description and measurements taken on individual tracks included: identification number, location, size, shape and arrangements of digits, with special attention to the presence of claw marks, digital pads, and other distinctive track features. The lengths of individual digits were measured, as well as the overall pes length, width and depth (Figure 8). The angles between each digit were noted with the orientation direction of the foot midline, to note direction of rotation of each print. Over 20,000 track attributes were recorded at the RGDT and entered into an Excel spreadsheet.
|Figure 8. Beth Southwell mapping tracks at the Red Gulch Dinosaur Tracksite.|
Trackway segments were also noted. Measurements of adjacent steps, stride lengths, and pace angles were used for gait and speed analysis. Length of trackways and distance between adjacent trackways were also analyzed. Select miscellaneous biogenic (e.g., invertebrate trace fossils) and inorganic features (e.g., salt casts, ripple marks) associated with the tracks were noted, measured and photographed. Mylar tracings were made of significant, individual tracks and trackways. Information on variation in the degree of track preservation throughout the exposure was noted and time-sequencing of tracks (overprinting) analyzed. Throughout the project, variations in surveying, mapping, photographing, and describing the tracks were noted when different individuals were involved. To maintain consistency, one individual was selected to do all track measurements and others were each delegated their own specific tasks. We strongly recommend assignment of select duties to single individuals for consistency in documentation and information dissemination.
It was planned that few tracks would be permanently removed from the Red Gulch Dinosaur Tracksite for study purposes, as this would detract from the overall aesthetic value of the site (Thulborn, 1990; Lockley, 1991). However, those tracks in danger of destruction or theft were noted and some outside of the dry wash were removed for microscopic study. Castings of select tracks and trackways were made for publication photography/drawing, interpretive displays, and as teaching tools. Liquid latex is the least destructive casting medium, but high grade silicone may be used for its superior detail resolution and mold reusability, if the individual track surface is competent enough to withstand the stronger stresses involved. Both compounds were used at the RGDT. As the track-bearing limestone is fractured and highly fissile, hard casting media should not be used. Unfortunately, plaster and resin casts taken at the RGDT by unpermitted individuals irreparably damaged some of the tracks (Milstein, 1998).
|Figure 9. Low Altitude Remote Controlled plane with mounted 35mm camera flying over the Red Gulch Dinosaur Tracksite.|
To preserve the data of this unique paleontological resource, monitor weathering, and facilitate the scientific research of the tracks, the Red Gulch Dinosaur Tracksite was intensively photodocumented. A variety of photographic methods have been used to document the tracks at the RGDT. Imagery of the tracksite ranges from 30-meter resolution satellite data to close-range photogrammetric images of a single track. Large format (9"x9") natural color aerial photography was flown in the fall of 1998 at scales of 1:12,000, 1:3000, and 1:1800 with an endlap of 60% to ensure stereoscopic coverage. The large format aerial photography, while suitable for developing management and recreation plans for the RGDT, did not provide the level of detail needed to illustrate track and trackway relationships. To fill the gap, a 35-mm camera was mounted on a Low Altitude Remote Controlled plane (Figure 9) and used to photograph the main track-bearing surface (i.e., "dry wash"). The resulting photographs were scanned, mosaicked, and registered to the digital orthophoto. These images were georeferenced with the survey data for use in Geographic Information Systems (GIS) technology. In addition, the "Ballroom" was photographed and videoed from an Ultralight aircraft. However, camera motion was a noticeable problem for all pictures taken from planes. Aerial cameras take still pictures while the plane is moving, resulting in blurred images. For most aerial photography this is not a problem, as the resolution of extremely high levels of detail is not necessary. To rectify this problem a tethered blimp with a 50x70 mm. format camera and light-weight video camera was used at the RGDT (Figures 10 and 11).
Figure 10. Tethered blimp with mounted camera over the balloon.
|Figure 11. Low-level aerial photos of tracks in the "Balloon" from the blimp.|
|Figure 12. Brent Breithaupt and Neffra Matthews photographing a meter grid in the "Balloon".|
Photogrammetry, which involves making precise measurements from photographs, was used as a noninvasive strategy for collecting three-dimensional data above the track surface (Matthews and Breithaupt, 2001). Tracks and grids were photographed from three different tripod heights ranging from roughly 2-10 meters. Close-range photogrammetry at 174 cm above the surface was used to document the track surface on a meter by meter basis, with the camera angle positioned parallel to outcrop dip (Figure 12). To increase the accuracy of the measurements a metric camera is required.
The advantages obtained by using a metric or calibrated camera are that the lens distortions have been measured and that a system of fiducials whose coordinates are known to the nearest micron are imprinted on each frame. A Rollieflex 3003 metric 35-mm surveying camera was used at the Red Gulch Dinosaur Tracksite. To further preserve and record the paleontological resources on the main track-bearing surface, each one-meter grid in the "dry wash," which contained a track, was photographed using the metric camera and a 1.05 meter square grid, which provided internal horizontal and vertical control. These photographs were scanned, rectified, mosaicked, and georeferenced using the total station coordinates.
The close-range photographs, as well as other scientific observations, are being integrated into a real-world, rectangular coordinate system that provide the framework for a Geographic Information System of the Red Gulch Dinosaur Tracksite. The GIS will be used to analyze the relationships of the scientific data in 3-D space, and eventually be used to build 3-D models of select tracks found at the site. Detailed measurements, such as digital terrain models and topographic contours, can be produced for the individual tracks (Figure 13) utilizing a Zeiss P3 Analytical Stereoplotter. These models preserve information about the footprints which may be lost through time as the result of illegal collection, vandalism, erosion, and human interaction and can be used to monitor and manage the site in the future.
|Figure 13. Photo of Red Gulch Dinosaur Tracksite footprint (upper left); digital contour of track (upper right); Digital Terrain Model of track, planar view (lower left); and Digital Terrain Model of track, oblique view (lower right).|
Incorporating Geographic Information Systems documentation methodologies with traditional ichnology research methods in the course of the study at the Red Gulch Dinosaur Tracksite, have resulted in one of the most precise approaches for the measuring, recording, and evaluating of fossil tracks. In addition, various track documentation methodologies are being compared as to their utility. State-of-the-art technology utilized at this site, has resulted in the RGDT gradually becoming one of the most extensively documented dinosaur tracksites in the world.
|Figure 14. School group "walking like a dinosaur" along dinosaur tracks in the "Balloon".|
Dinosaurs have always excited the public's interest and with the recent spate of dinosaur films, that interest level is higher than ever. The Red Gulch Dinosaur Tracksite has the potential to become a popular, paleontological interpretive site. The RGDT is a unique, North American, dinosaur fossil site located on public land and is readily accessible for educational opportunities and public involvement. To this end, investigators coordinated their work with the BLM to accurately disseminate vertebrate ichnology data from the RGDT. We have worked closely with the BLM to develop plans that have accommodated the needs of the general public and media, without negatively impacting the scientific research. Because of this coordinated effort the public and media could visit the site without the research being impeded. Proximity the site to the existing Red Gulch/Alkali National Back Country Byway allows ready access for the public to view the tracks in situ.
Figure 15. Student looking for dinosaur footprints at the Red Gulch Dinosaur Tracksite.
In addition, we are assisting the BLM in the development of the site as a unique tool for public education by aiding in the development of interpretive displays, tour materials and guidebooks, K-12 classroom materials, and websites. We have successfully disseminated information about the site to the general public through newspaper and magazine stories, as well as television productions. Additionally, building on suggestions and ideas presented by other science educators (Munsart, 1993; Zike, 1994; Munsart and Van Gundy, 1995), we plan to provide some exciting interactive teaching exercises (Figure 14), which will utilize the track information available at the Red Gulch Dinosaur Tracksite and allow students (Figure 15) to do their own "footprint sleuthing" (Bakker, 1996). The size and complexity of the site presents an opportunity for students of all ages to practice their observational skills, descriptive techniques, critical thinking and mathematical skills. It has been our ongoing interest (Breithaupt, 1992; Leite and Breithaupt, 1993; Breithaupt, 1996) to utilize the unique fascination people have with dinosaurs and their world to teach science in a fun and intellectually stimulating way.
Appreciation is extended to all of the students and volunteers who made this project so enjoyable. Thanks to BLM paleontologist Laurie Bryant for her assistance in the project. Gratitude is extended to various BLM representatives, especially those of the Worland Office, for their help in arranging and participating in this project. Various anonymous reviewers provided valuable suggestions on this manuscript. Finally, thanks goes out to the BLM for assistance in funding this program.
Bakker, R.T., 1996. Dr. Bob's guide to teaching dinosaur science: World Book, Inc., Chattanooga, 16 pp.
Breithaupt, B.H., 1992. The use of fossils in interpreting past environments: in: Goldman, C.A. (ed.), Tested studies for laboratory teaching: 13th Workshop/Conference,Association for Biology Laboratory Education, Proceedings, v. 13, p. 147-158.
_______, 1994. Wyoming's dinosaur diversity: in Nelson, G.E. (ed.), The dinosaurs of Wyoming: Wyoming Geological Association, 44th annual Field Conference Guidebook, Casper, p. 101-104.
_______, 1996. Fossilization and adaptation: Activities in paleontology: in Scotchmoor, J. and McKinney, F.K. (eds.), Learning from the fossil record, The Paleontology Society Papers, v. 2, p. 157-165.
Clark, J.M., J.M. Montellano, J.A. Hopson, R. Hernandez, and D.E. Fastovsky, 1994. An Early or Middle Jurassic tetrapod assemblage from the La Boca Formation, northeastern Mexico: in Fraser, N.C. and Sues, H.D. (eds.), In the shadow of the dinosaurs, Early Mesozoic tetrapods, Cambridge University Press, Cambridge, U.K., p. 295-302.
Darton, N.H., 1899. Jurassic formations of the Black Hills of South Dakota: Geological Society of America Bulletin, v. 10, p. 383-396.
Dodson, P., 1997. Jurassic Period: in Currie, P.J. and Padian, K. (eds.), Encyclopedia of dinosaurs, Academic Press, San Diego, CA, p. 387-388.
Farlow, J.O., 1987. A guide to Lower Cretaceous dinosaur footprints and tracksites of the Paluxy River Valley, Somervell County: Field Trip Guidebook, 21st Annual Meeting, south-central section, Geological Society of America, Waco, Texas, 50 p.
Fastovsky, D.E., J.M. Clark, N.H. Strater, M. Montellano, R. Hernandez, and J.A. Hopson, 1995. Depositional environments of a Middle Jurassic terrestrial vertebrate assemblage, Huizachal Canyon, Mexico: Journal of Vertebrate Paleontology, v. 15(3), p. 561-575.
Ferrusquia-Villafranca, I., E. Jimenez-Hidalgo, and V.M. Bravo-Cuevas, 1996. Footprints of small sauropods from the Middle Jurassic of Oaxaca, southeastern Mexico: in Morales, M., The continental Jurassic, Museum of Northern Arizona Bulletin 60, p. 119-126.
Foster, J.R., A.H. Hamblin, and M.G. Lockley, 2000. The oldest evidence of a sauropod dinosaur in the western United States and other important vertebrate trackways from Grand Staircase-Escalante National Monument, Utah: Ichnos, v. 73, p. 169-181.
Gillette, D.D., 1996. Stratigraphic position of the sauropod Dystrophaeus viamalae Cope 1877 and its evolutionary implications: in Morales, M., The continental Jurassic, Museum of Northern Arizona Bulletin 60, p. 59-68.
Kilibarda, Z. and D.B. Loope, 1997. Jurassic aeolian oolite on a Paleohigh in the Sundance Sea, Bighorn Basin, Wyoming: Sedimentology, v. 44, p.391-404.
Leite, M.B. and B.H. Breithaupt, 1993. Teaching paleontology in the National Parks and Monuments: A curriculum guide for teachers of the second and third grade levels: National Park Service, Department of the Interior, 105 p.
Lockley, M., 1991. Tracking dinosaurs: Cambridge University Press, Cambridge,
______, 1997. Footprints and trackways: in, Currie, P.J. and Padian, K. (eds.), Encyclopedia of dinosaurs, Academic Press, San Diego, CA, p. 242-245.
Lockley, M. and A.P. Hunt, 1995. Dinosaur tracks and other fossil footprints of the western United States: Columbia University Press, 338 p.
Lockley, M., A.P. Hunt, and S.G. Lucas, 1996. Vertebrate track assemblages from the Jurassic Summerville formation and correlative deposits: in Morales, M. (ed.), The continental Jurassic, Museum of Northern Arizona Bulletin 60, p. 249-254.
Lockley, M., A.P. Hunt, M. Paquette, S.A. Bilbey, and A. Hamblin, 1998. Dinosaur tracks from the Carmel Formation, northeastern Utah: implications for Middle Jurassic paleoecology, Ichnos, v. 5, p. 255-267.
Lockley, M. and C. Meyer, 2000. Dinosaur tracks and other fossil footprints of Europe, Columbia University Press, New York, 323 p.
Matthews, N.A. and B.H. Breithaupt, 2001. Close-range photogrammetric experiments at Dinosaur Ridge, Mountain Geologist, v. 38 (3), p. 147-153.
Milstein, M., 1998. Popularity threatens dino traces. Billings Gazette, September 27.
Munsart, C.A., 1993, Investigating science with dinosaurs: Teacher Ideas Press, Englewood, CO, 248 p.
Munsart, C.A. and K.A. Van Gundy, 1995. Primary dinosaur investigations: Teacher Idea Press, Englewood, CO, 292 p.
Peterson, J.A., 1957. Marine Jurassic of Northern Rocky Mountains and Williston Basin: A.A.P.G. Bulletin, v. 41(3), p. 399-440.
Schmude, D.E., 2000. Interplay of paleostructure, sedimentation and preservation of Middle Jurassic Rocks, Bighorn Basin, Wyoming, The Mountain Geologist, v. 37 (4), p. 145-155.
Shubin, N. and H.D. Sues, 1991. Biogeography of early Mesozoic continental tetrapods: patterns and implications: Paleobiology, v. 17, p. 214-230.
Sizemore, J.A., 2000. Analysis of tridactyl dinosaur footprints from the Middle Jurassic Sundance Formation of Wyoming, Senior Thesis, Butler University, 59 p.
Southwell, E.H. and B.H. Breithaupt, 1998. Wyoming's vertebrate tracks: 130 years of discovery: Journal of Vertebrate Paleontology, v. 18 (3), p. 79A.
Southwell, E.H. and M.G. Lockley, 1996. First reports of dinosaur tracks from the Morrison Formation, Como Bluff, Wyoming: in Hunter, R.A. (ed.), Paleoenvironments of the Jurassic, Tate Geological Museum Guidebook no. 1, Casper College, Casper, WY, p. 81-87.
Thulborn, T., 1990. Dinosaur tracks: Chapman and Hall, New York, 410 p.
Weishampel, D.B., 1990. Dinosaur distribution: in Weishampel, D.B., Dodson, P. and Osmolska, H. (eds.), The Dinosauria, University of California Press, Berkeley, p. 63-139.
Whyte, M.A. and M. Romano, 1994. Probable sauropod footprints from the Middle Jurassic of Yorkshire, England: Gaia: Revista de geociencias, Museau Nacional de Historia Natural, Lisbon, Portugal, 10, p. 15-26.
Zike, D., 1994. Dinosaur studies in the pre-K through junior high curriculum: in Rosenberg, G.D. and Wolberg, D.L. (eds.), Dinofest, The Paleontological Society Special Publication no. 7, p. 109-116.