Dinosaur Tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas

Abstract

In 1940 R.T. Bird of the American Museum of Natural History collected segments of a sauropod and a theropod trackway from a site in the bed (Glen Rose Formation; Lower Cretaceous) of the Paluxy River, in what is now Dinosaur Valley State Park (Glen Rose, Texas, USA). However, Bird left undocumented thousands of other dinosaur footprints from this and other Paluxy tracksites. In 2008 and 2009 our international team carried out fieldwork to create detailed photomosaics of extant Paluxy tracksites, using GIS technology to combine these with historic maps and photographs. We also made photographs, tracings, LiDAR images, and measurements of individual footprints and trackways. Paluxy dinosaur tracksites occur in more than one tracklayer, but the largest and most spectacular footprints occur in the Main Tracklayer, a 20-30 cm thick, homogeneous dolomudstone that is thickly riddled with vertical invertebrate burrows (Skolithos). There are two dinosaur footprint morphotypes in the Main Tracklayer: spectacular sauropod trackways (Brontopodus) and the far more numerous tridactyl footprints, most or all of which were made by large theropods (possible ornithopod prints occur in a tracklayer stratigraphically higher than the Main Tracklayer). Tridactyl footprints are highly variable in quality; Paluxy tracksites collectively constitute a natural laboratory for investigating how trackmaker-substrate interactions create extensive extramorphological variability from a single foot morphology. Trackways of bipedal dinosaurs show a "mirror-image" distribution, suggesting movement of animals back and forth along a shoreline. In contrast, most sauropod trackways head in roughly the same direction, suggesting passage of a group of dinosaurs. The trackways collected by R.T. Bird suggest that at least one theropod was following a sauropod.

Full text

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Dinosaur Tracksites of the Paluxy River Valley (Glen Rose Formation,
Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
Rastros de dinosaurios del valle del río Paluxy (Formación Glen Rose,
Cretácico Inferior), Dinosaur Valley State Park, Condado de Somervell,
Tejas
J. O. Farlow
1
, M. O’Brien
2
, G. J. Kuban
3
, B. F. Dattilo
1
, K. T. Bates
4
, P. L.
Falkingham
5
, L. Piñuela
6
, A. Rose
1
, A. Freels
7
, C. Kumagai
1
, C. Libben
1
, J. Smith
1
and
J. Whitcraft
1
Recibido el 9 de diciembre de 2010, aceptado el 20 de mayo de 2011.
(1): Indiana-Purdue University, 2101 East Coliseum Boulevard, Fort Wayne, IN 46805 USA
(2): Texas Parks and Wildlife Department, 4200 Smith School Road, Austin, TX USA
(3): Strongsville, OH 44136 USA
(4): University of Liverpool, L69 3GE England
(5): University of Manchester, M13 9PL England
(6): Museo del Jurásico de Asturias, Colunga, Asturias, España
(7): Manchester College, North Manchester, IN 46962 USA
Actas de V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno,
Salas de los Infantes, Burgos
Abstract
In 1940 R.T. Bird of the American Museum of Natural History collected segments of a sauropod and a theropod
trackway from a site in the bed (Glen Rose Formation; Lower Cretaceous) of the Paluxy River, in what is now Dinosaur
Valley State Park (Glen Rose, Texas, USA). However, Bird left undocumented thousands of other dinosaur footprints
from this and other Paluxy tracksites. In 2008 and 2009 our international team carried out fieldwork to create detailed
photomosaics of extant Paluxy tracksites, using GIS technology to combine these with historic maps and photographs. We
also made photographs, tracings, LiDAR images, and measurements of individual footprints and trackways. Paluxy dinosaur
tracksites occur in more than one tracklayer, but the largest and most spectacular footprints occur in the Main Tracklayer,
a 20-30 cm thick, homogeneous dolomudstone that is thickly riddled with vertical invertebrate burrows (Skolithos). There
are two dinosaur footprint morphotypes in the Main Tracklayer: spectacular sauropod trackways (Brontopodus ) and the
far more numerous tridactyl footprints, most or all of which were made by large theropods (possible ornithopod prints
occur in a tracklayer stratigraphically higher than the Main Tracklayer). Tridactyl footprints are highly variable in quality;
Paluxy tracksites collectively constitute a natural laboratory for investigating how trackmaker-substrate interactions
create extensive extramorphological variability from a single foot morphology. Trackways of bipedal dinosaurs show a
“mirror-image” distribution, suggesting movement of animals back and forth along a shoreline. In contrast, most sauropod
trackways head in roughly the same direction, suggesting passage of a group of dinosaurs. The trackways collected by R.T.
Bird suggest that at least one theropod was following a sauropod.
Key words: dinosaurs, ichnology, Glen Rose Formation, Texas, Cretaceous

42
Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno
INTRODUCTION
Although Native Americans (cf. Mayor, 2005), Spanish
explorers, and early Anglo-American settlers may have
observed them, the first person known to have seen
dinosaur footprints in the carbonate bedrock of the Paluxy
River or its tributary streams was a truant schoolboy,
George Adams, at the beginning of the 20th Century
(Farlow, 1987; Jasinski, 2009). Young Adams called the
tridactyl footprints to the attention of his teacher, who
recognized them as dinosaur tracks. Brief descriptions of
these trace fossils were published by Ellis W. Shuler (1917,
1935, 1937), who created two ichnotaxa, Eubrontes (?)
glenrosensis and E. titanopelopatidus, to accommodate them
(regrettably, the type specimen of Eubrontes (?) glenrosensis
was incorporated into the wall of an outdoor bandstand,
where it has suffered due to weathering; Adams et al.,
2010). Subsequently tridactyl tracks were found to be
common throughout the area of outcrop of the Glen Rose
Formation and other Lower Cretaceous units across central
Texas (Wrather, 1922; Gould, 1929; Albritton, 1942;
Langston, 1974, 1979; Skinner and Blome, 1975; Farlow,
1981; 1987; Sams, 1982; Pittman, 1989; Hawthorne et al.,
2002; Rogers, 2002; Farlow et al., 2006).
But the Paluxy hid even bigger ichnological secrets. By
the mid-1930s local residents were aware of enormous
footprints of quadrupedal animals that their discoverers
assumed were elephants (Jasinski, 2009). These ichnites
were made known to Science by Roland T. Bird, a fossil
collecter for Barnum Brown of New York’s American
Museum of Natural History (AMNH) (Bird, 1985).
Visiting an Indian trading post in Gallup, New Mexico on
his way home from the field, Bird saw putative footprints
of a tridactyl dinosaur and a gigantic human in loose
slabs of rock. Upon inquiry he learned that they had
come from Glen Rose, Texas, and so he stopped there for
a look. Although the “tracks” Bird had seen in Gallup
turned out to be forgeries carved by a local entrepreneur
(George Adams himself) for sale to unsuspecting tourists,
Bird discovered that the tridactyl footprints were based on
authentic originals in the bed of the Paluxy River. He was
also shown indistinct, elongate, “mystery” prints in the
riverbed that the locals called “man tracks” or “moccasin
tracks.” Most importantly, Bird learned of the huge
“elephant” footprints, which he immediately recognized
as having been made by sauropods.
Bird described the tridactyl and sauropod footprints in
a brief popular article (Bird, 1939), in which he also
talked about the mysterious “man tracks.” The last were
mentioned in the hope of amusing oil magnate Harry
Sinclair, an important patron of Barnum Brown’s dinosaur-
hunting forays (Farlow, 1985).
Bird returned to Texas in 1940, with federal support
in the form of a Works Progress Administration work
crew, to collect portions of trackways of a sauropod and
an apparently following theropod (Bird, 1941, 1944,
1954, 1985). The footprints and the surrounding rock
were quarried out in pieces, and eventually reassembled
behind the skeleton of an Apatosaurus at the AMNH. A
second segment of the two trackways was assembled in an
Resumen
En 1940 R.T. Aves del Museo Americano de Historia Natural extrajo los rastros de un saurópodo y de un terópodo
de un yacimiento situado río Paluxy (Formación Glen Rose, Cretácico Inferior), en lo que hoy es Dinosaur Valley State
Park (Glen Rose, Texas, EE.UU.). Sin embargo, dejó sin documentar miles de icnitas de dinosaurios de éste y de otros
yacimientos del Río Paluxy. En 2008 y 2009, nuestro equipo internacional llevó a cabo el trabajo de campo para crear
fotomosaicos detalladas de los yacimientos del río Paluxy. Se utilizó la tecnología SIG para combinar los fotomosaicos con
los mapas históricos y fotografías. También hicimos fotografías, calcos, imágenes LiDAR y las mediciones de las huellas
individuales y de los rastros.
Las icnitas de dinosaurios del río Paluxy se encuentran en más de una capa, pero las huellas más grandes y más
espectaculares se han conservado en una sola capa de unos 20-30 cm de espesor. Litológicamente se trata de un carbonato
bioturbado de madrigueras verticales de invertebrados (Skolithos). Hay dos morfotipos de icnitas de dinosaurios en esta
capa: espectaculares rastros de saurópodos (Brontopodus) y huellas tridáctilas, mucho más numerosos, la mayor parte o
la totalidad de las cuales fueron realizadas por grandes terópodos (impresiones posibles de ornitópodos se encuentran en
una capa estratigráficamente más alta). La conservación de las icnitas tridáctilas es muy variable. Los yacimientos del río
Paluxy en su conjunto, constituyen un laboratorio natural para investigar cómo se producen interacciones entre el sustrato
y los miembros de los dinosaurios. Un solo dinosaurio produce una gran variedad de morfotipos distintos de la morfología
de su pie. Los rastros de los dinosaurios bípedos tienen una distribución que sugieren el movimiento de los animales de un
lado a otro a lo largo de la costa. En contraste, la mayoría de rastros de los saurópodos van en la misma dirección, lo que
sugiere el paso de un grupo de dinosaurios. Los rastros recogidos por R.T. Bird sugieren que al menos un terópodo paso
después de un saurópodo.
Palabras clave: Dinosaurios, icnología, Formación Glen Rose, Tejas, Cretácico

43
Salas de los Infantes, Burgos
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
outbuilding of the Texas Memorial Museum (TMM) in
Austin, and individual footprints were collected for other
institutions.
Unfortunately, Bird’s 1939 exercise in grantsmanship
resulted in dramatic “blowback.” Religious fundamentalists
who literally interpreted the events of the biblical book of
Genesis concluded that Bird’s “man tracks” were genuine,
particularly large examples of which had been made by the
giants (Nephilim) of Genesis 6:1-4 (Attridge, 2006). The co-
occurrence of human and dinosaur footprints in the Glen
Rose Formation was further cited as evidence against both
the antiquity of the earth and scientific descriptions of
the evolution of life (Numbers, 2006). The “man tracks”
figured prominently in creationist publications, most
notably Stanley Taylor’s 1970 film Footprints in Stone and
Morris’ (1980) book. However, some creationists were
skeptical of the “man track” claims (Neufeld, 1975), and
in the 1980s, the scientific community also responded,
providing evidence that those human prints that were
not out-and-out fakes or the caprices of weathering
were in fact preservational variants of tridactyl dinosaur
footprints, particularly of prints made during an unusual
style of locomotion for the huge reptiles (see Milne and
Schafersman, 1983; Cole and Godfrey 1985; Hastings,
1986, 1987; Kuban, 1986, 1989a, b; Farlow, 1987 and
references cited therein), an interpretation that will be
further documented in this paper.
At the same time, interest in the dinosaur footprints of
the Glen Rose Formation in and of themselves, and
not in the context of the “man track” controversy, was
renewed (Farlow, 1987, 1993; Farlow and Hawthorne,
1989; Pittman, 1989; Hawthorne et al., 2002; Rogers, 2002;
Farlow et al., 2006), as part of revived worldwide interest
in dinosaur trace fossils more generally (e.g. Gillette and
Lockley, 1989; Thulborn, 1990; Lockley, 1991; Leonardi,
1994; Lockley et al., 1994b; Gierlinski, 1995; Lockley
and Hunt, 1995; Sanz et al., 1997; Leonardi and Mietto,
2000; Lockley and Meyer, 2000; Fuentes Vidarte y Torcida
Fernández-Baldor (Eds.), 2001; Pérez-Lorente et al.,
2001; Lockley, 2002; Moreno and Pino, 2002; Huh et al.,
2003; Pérez-Lorente (Ed.), 2003; García-Ramos et al.,
2004; Torcida Fernández-Baldor and Huerta Hurtado
(Eds.), 2006, 2009; Moratalla, 2009; Whyte et al., 2010).
The Paluxy River sauropod tracks were formally named
Brontopodus birdi by Farlow et al. (1989), and recognized as
the prime example of “wide-gauge” sauropod trackways
(Farlow, 1992b; Wilson and Carrano, 1999; Romano et al.,
2007; Marty et al., 2010).
Dinosaur Valley State Park (DVSP) was created in 1970
to protect the dinosaur tracks of the Paluxy River and
surrounding natural areas (Jasinski, 2009). Although the
park hosts thousands of visitors each year, paleontologists
who have not seen the park may not be aware that Bird’s
collecting activities merely scratched the surface of
DVSP’s ichnological riches. During the 1980s and 1990s
Kuban(sometimes working with one or more associates)
mapped dozens of trackways at several sites. In the same
period Farlow repeatedly visited the park to carry out field
work, but was overwhelmed by the enormity of the task that
adequate documentation of the Paluxy’s tracksites would
entail. In 2008 and 2009, however, a serendipitous coming
together of financial support, technological resources,
and manpower made possible intensive documentation of
several major tracksites exposed in the bed of the Paluxy
in DVSP by an international team of workers. The present
paper summarizes the goals of this work, describes our
field and laboratory activities, and presents our preliminary
findings.
METHODS AND GOALS
Supported by grants from funding agencies in the U.S.,
Spain, and the U.K., we assembled an international team
to document thoroughly dinosaur tracksites within the
boundaries of DVSP that still preserved significant footprint
assemblages, and that also were not covered by gravel and
sand river deposits so large as to be impossible, or too
disruptive to the park’s aquatic and riparian ecosystems,
to clean. Additional Paluxy tracksites than those described
here are known to exist or have existed (Kuban, 1986;
Farlow, 1987; Hawthorne, 1990), but will not be discussed
in this paper.
Our project has several long-term goals, which have only
partly been accomplished thus far:
1) to create an updatable database of footprint and tracksite
information;
2) to determine the number of kinds of footprint
morphotypes and the number of individual animals
responsible for the tracksites;
3) to document the range of variability of footprint
shapes within each morphotype, and the sediment factors
responsible for that variability;
4) to determine the appropriate nomenclature to apply to
the tridactyl footprints;
5) if possible, to determine the interval of time over which
tracklayers accumulated footprints;
6) to determine what the animals were doing as they made
the tracks.
Our efforts were aided by drought conditions in 2008
and 2009 that either exposed tracksites that are normally
underwater, or at least lowered water levels covering the
footprints enough to make photography possible. Even so,
working conditions were not always ideal. By late morning
breezes usually became strong enough to create ripples
in the water surface, reducing visibility of submerged
footprints. In 2009 a strong thunderstorm moved along
the valley of the Paluxy, dumping enough rain onto the
watershed to create a river rise high and powerful enough
to shut us down for a few days, and submerging for the
duration of our fieldwork some important sites that
had hitherto been R.T. Bird (1985) experienced similar
frustrations.

44
Field methods included both low-tech and high-tech
approaches. Often assisted by volunteers from across the
state of Texas, we began by cleaning sediment off tracksites,
using brushes, push brooms, power hoses, shovels, and
wheelbarrows. Once a site was cleaned, if the tracksite
surface was above water we drew a meter-square chalk
grid over it. We then used a Trimble GeoXh GPS system
with Trimble Hurricane antenna to georeference footprints
and other features of tracksite surfaces, and photographed
overlapping sections of tracksites that were then stitched
together using Arcview 9.3 to create photomosaics of
tracksite surfaces. We also took thousands of photographs
of individual footprints and trackways, both at ground level
and from an elevated platform. Where possible, we traced
the surface outlines of individual footprints or trackways
on sheets of plastic, and directly measured footprint and
step lengths and individual footprint bearings. Casts were
made of some of the better preserved tridactyl dinosaur
footprints. In order to characterize vertical burrows in the
Main Tracklayer, an oriented sample, about 20 cm thick
and 40 cm by 30 cm wide, was collected in place as it
was in the process of eroding from the edge of the Main
Tracklayer in the Blue Hole Parlor site. This sample was cut
into two perpendicular vertical slabs and into 8 horizontal
slabs, each 2 cm thick, with the exception of the bottom
and top slab, which were cut a little thicker.
For comparison with previous stratigraphic studies (e.g.
Hawthorne, 1990), a stratigraphic section was measured
along the river bank outside the eastern boundaries of the
park. It was measured to centimeter precision by marking
10 cm intervals on the exposure. Beds were observed,
photographed, described, and sketched in the field from
this framework.
To document the AMNH-TMM footprint slabs, the fully
portable RIEGL LMS-Z420i 3D laser scanner was chosen
for its ability to rapidly acquire spatial data (12,000 x,
y, z and intensity points per second). A 6.1 megapixel
Nikon D100 digital camera was mounted on the scanner
and, once calibrated, provided images that were used to
extract an RGB colour channel and reflection intensity
information for the point cloud, to texture map the final
model, and to produce a photorealistic representation of
the track blocks (e.g. Bates et al., 2008). Both track blocks
were scanned from multiple perspectives to provide more
detailed 3D shape information by eliminating “shadows”
(areas not visible to the laser) caused by irregularities in
the exposure surface. Both perpendicular and oblique scan
perspectives were necessary to eliminate shadows occurring
FIGURE 1. Digital elevation map of the Paluxy River valley in and around Dinosaur Valley State Park (Somervell County, Texas), in-
dicating the major tracksites documented in this study, other track occurrences known to have existed (unlabeled), and a test excavation
dug in 1974, away from exposures in the river bed, through overlying strata, to reach the Main Tracklayer.
Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno

45
FIGURE 2. Stratigraphic section of the lower Glen Rose For-
mation in and around Dinosaur Valley State Park, based on our
observations, and comparisons with Hawthorne (1990); also see
Pittman (1989). Bed lithologies are labeled by shading / pattern,
and (particularly for different kinds of limestone [wackestone /
packstone / grainstone]) by horizontal distance to the right of
the vertical axis of the section. Most of the park’s tracksites are
in the Main Tracklayer, a dolomitic wackestone. The Taylor Site
is stratigraphically higher. Hawthorne (1990) identified two ad-
ditional track horizons in the Paluxy River section.
in the tracks themselves. Point clouds captured from
different perspectives were aligned using PolyWorks (Bates
et al., 2008) to form a merged network of scans aligned to
extremely high precision (standard deviation less than 10
7
).
Merged point clouds of the two separate track blocks were
then surfaced using Geomagic to produce high-resolution
triangulated meshes, which were contoured and shaded
according to topography. The polygonal meshes of the
AMNH and TMM blocks were imported into Maya (a
CAD package) and rotated until they matched R.T. Bird’s
1940 maps and photographs of the two dinosaur trackways.
GEOGRAPHIC AND GEOLOGIC SETTING OF
TRACKSITES
The dinosaur tracksites described in this study (Fig. 1) occur
within DVSP, where the Paluxy River flows to the north
before making a hairpin turn southward. The river has cut
its way through overlying strata to expose track-bearing
layers in and just above its bed. The local stratigraphic
section comprises the lower and middle (Thorp Spring)
members of the Glen Rose Formation (Nagle, 1968;
Perkins et al., 1987; Pittman, 1989; Winkler et al., 1989;
Hawthorne, 1990). Detailed stratigraphic sections (Fig. 2
and Hawthorne, 1990) indicate that tracklayers occur at
four horizons, two of which are described in this paper.
Most of the dinosaur tracksites in the park (Figs. 3-12)
occur in the Main Tracklayer, a ca. 20-30 cm thick, sandy,
homogeneous dolomitic wackestone (cf. Shelton et al.,
1993). In addition to containing dinosaur footprints,
the Main Tracklayer is thickly riddled with openings for
vertical invertebrate burrows (Fig. 13A-C). Similar long,
unbranched, tubular trace fossils are commonly assigned
to the ichnogenus Skolithos (cf. Alpert, 1974; Droser, 1991;
Schlirf and Uchman, 2005), and indicate an intertidal to
shallow subtidal depositional environment (Seilacher,
1967; Curran, 1984; Droser, 1991; Vossler and Pemberton,
1988; Skoog et al., 1994), consistent with the presence of
dinosaur tracks. Skolithos is also associated with dinosaur
footprints in a shallow-water, carbonate setting in the
Middle Jurassic Sundance Formation of Wyoming (Kvale
et al., 2001).
A second kind of possible trace fossil (or tool mark?) was
observed only once in the Main Tracklayer, at the Blue
Hole Ballroom. This was a large, horizontal, somewhat
linear feature in the surface of the bed, composed of
repeated shallow depressions separated by short gaps (Fig.
13D). Similar features were observed at another site in the
Glen Rose Formation (Farlow et al., 2006), where they
were provisionally attributed to large gastropods.
With only one or two trace types, the diversity of
invertebrate traces in the Main Tracklayer is quite low.
However, we have observed at least two other distinct
invertebrate trace fossil morphotypes (cf. Thalassinoides
and cf. Diplocraterion) in exposures along the river between
the Blue Hole Ballroom and the Taylor Site (Fig. 1), and
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
Salas de los Infantes, Burgos

46
Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno
FIGURE 3. Denio Branch Mouth Tracksite. A) View from an elevated platform across the site, looking upstream (northward). Most of
the site was under shallow water at the time this photograph was taken, but a dry portion of the site, containing several tridactyl prints,
is visible at the top of the photograph. A sauropod trackway (black arrow) marked only by poorly preserved pes prints heads southward
(?) across the site, while a trackway composed mainly of “elongate” footprints (white arrow) heads in the opposite direction. B) Photo-
mosaic detail of the northmost edge of the site; one of several tridactyl footprints is indicated by an arrow.

47
Salas de los Infantes, Burgos
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
FIGURE 4. The Main Tracksite (so named because it contains the footprint exposures most easily seen by the casual observer). A)
Aerial view, looking northward. Exposures of the Main Tracklayer (1, 2, 3) peek out from beneath an overlying hard limestone shelf. B)
Footprints in the three exposures of the Main Tracklayer; north to the top of the map. Extensive change in the footprint surface, due to
erosion of previously exposed tracks, and uncovering of new tracks, has occurred over the last two decades; note the changing position
of the shelf layer in exposure area 1 between the 1980s (small arrow) and the present (large arrow). The final footprint in the trackway
of a small sauropod in exposure area 2 is indicated by a heavy black arrow. Exposure area 3 is contiguous with the West Bank of the
Bird Site. Additional theropod footprints that do not appear in the map were documented here in 2008. The locations of the beginnings
of two of the sauropod trackways mapped by Bird in 1940 (S1 and S2) are plotted on the map. C) Photomosaic (1-m grid) of exposure
area 2. South to the top of the image. Note the well-preserved sauropod trackway (S0; Main Site Trail of Farlow et al. [1989: Table 42.2])
from panel B; a white arrow labels the final exposed footprint in this trackway. Tridactyl prints are also scattered across this exposure.

48
Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno
FIGURE 5. The Bird Site. A) Aerial view of the Bird Site and the Main Tracksite (left edge of photograph), with Bird’s and our track-
way maps superimposed. Sauropod trackways S1 - S5 numbered according to Farlow et al. (1989: Figure 42.1). Note erosional destruc-
tion of a significant part of the Main Tracklayer between 1940 and 2009-2010. B) Oblique view of East Bank sauropod trackways S7 - S9
from an elevated platform on the West Bank.
probably stratigraphically between them as well (Fig. 2),
but these localities require further documentation (cf.
Hawthorne, 1990).
Dinosaur tracks in the Main Tracklayer are preserved as
concave epireliefs with distinct outlines. They are often
quite deep, with sauropod prints sometimes punching
through the bed to reach the underlying silt layer. Tridactyl
footprints nearly always show some collapse or roofing over
of toe marks, or other features suggestive of rather plastic
substrate conditions at the time footprints were emplaced.
The Taylor Site (Figs. 2, 14) Tracklayer is a grainstone,
strongly laminated at its base and bioturbated at its top.
Preservation of tracks is very different from that in the Main
Tracklayer. The Taylor Site contains numerous trackways
of elongate footprints with metatarsal impressions, most of
which are largely filled in with a bluish-gray sedimentary
rock. This reduces their topographic relief with respect to
the surrounding rock, and contributes to the human-like
shapes that creationists have identified as human tracks.
However, when well cleaned the infilled prints clearly
show tridactyl digital patterns. Cores taken at the margin
of the fillings show that the original footprints were several
centimeters deep before sediment filled them. Moreover,
with repeated exposure due to low river levels during
droughts, the iron-rich infilling sediment has in places
oxidized to a reddish-brown color, making print outlines
even more distinct (Kuban, 1986, 1989b; Farlow, 1987).
Some of the Taylor Site prints presently occur as convex
epireliefs that are topographically somewhat higher than
the surrounding rock. One of the Taylor site trackways
contains more than two hundred individual footprints.
DINOSAUR FOOTPRINT MORPHOTYPES
Remarkably, despite the large areal extent of tracksite
exposures along the Paluxy, only two distinct dinosaur
footprint morphotypes have been recognized, making this
a low-diversity vertebrate ichnological assemblage.
Sauropods (Figs. 3A, 4B, C, 5-8, 12A, B, 15)
The sauropod footprints are of course what captured R.T.
Bird’s attention, and are among the world’s best-preserved
sauropod trace fossils (Farlow et al., 1989). Well-preserved
manus prints (Fig. 15F) are rather horseshoe-shaped, being
deepest along the anterior margin and shallowest at the
center and rear of the print. Digits II-IV seem to have been
bound together and separated from digits I and V. There is
no indication of a claw on digit I. However, manus prints
are often squashed from the rear, or even obliterated by pes
prints (Figs. 3A, 4C, 12A-B).
Sauropod pes prints are much larger (commonly about
a meter in length) than manus prints, and somewhat
triangular in shape. Well-preserved pes prints (Figs. 7,
15F) show three large, laterally directed claw marks, and
sometimes additional nail or callosity marks lateral to the
large claw marks. The footprint is deepest along its medial
margin, particularly at the front and rear edges of the print,
and shallowest toward its lateral margin. Pes prints are as
deep as, or deeper than, associated manus prints.

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Salas de los Infantes, Burgos
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
FIGURE 6. West Bank of the Bird Site. A) Photomosaic of the tracksite surface. Many individual sauropod and theropod footprints
are outlined in black. North (N) at the top of the image; BC marks the site from which the Brooklyn College (New York) manus-pes
set (Fig. 7) was collected. B) Ground-level oblique view of a sauropod trackway; the animal was moving southward and away from the
viewer. Tape measure exposes 1 m of tape. C) Sauropod footprint with a theropod print impressed into its margin; scale in photograph
marked in cm and inches.

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Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno
FIGURE 7. Well-preserved left sauropod manus-pes set collected by R.T. Bird for Brooklyn College. A) Photograph of the manus-pes
set (courtesy of John Chamberlain); scale bar marked off in 10-cm increments. B) Detail of the photomosaic of the West Bank of the
Bird Site (Fig. 6A; the image is here rotated 180 degrees from its position in Fig. 6A, with south here toward the top of the image) show-
ing the Brooklyn College manus-pes set as originally located in sauropod trackway S4 (BC); also see Bird (1985: 179).

51
Salas de los Infantes, Burgos
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
FIGURE 8. Footprints discovered during a 1974 test excavation in a field well away from the river bed. A) Digging the pit. B-D) Foot-
prints exposed, probably in the Main Tracklayer. B) Map and C) photograph of the uncovered track surface. Several footprints are identi-
fied by number in both panels. D) Tridactyl footprint (print 6 in panels B and C).

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Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno
FIGURE 9. The Opossum Branch tracksite, exposed in the bed of a small tributary of the Paluxy River. The tracklayer is either the
Main Tracklayer itself, or stratigraphically very close to it. A) Photomosaic of much of the tracksite surface. B) Map of footprints su-
perimposed on the photomosaic.
Both manus and pes prints are usually well offset from
the trackway midline (Figs. 3A, 4C, 6B, 15A, B, D, E),
pes impressions being more so than manus impressions,
making Brontopodus the paradigm of “wide-gauge”
sauropod trackways (Farlow, et al., 1989; Farlow, 1992b;
Wilson and Carrano, 1999; Wright, 2005; cf. Romano et
al., 2007; Marty et al., 2010). Both manus and pes prints are
rotated outward with respect to the trackmaker’s direction
of travel. The pace angulation of pes prints is about 100-
120o.
A plausible candidate for the Brontopodus-maker is
Paluxysaurus (previously assigned to Pleurocoelus), known
from skeletal (including pedal) material from stratigraphic
units of about the same age, from the same region
(Langston, 1974; Gallup, 1989; Rose, 2007). Another
candidate is Sauroposeidon (Wedel et al., 2000), but nothing
is known of its pedal skeleton.
Tridactyl Footprints (Figs. 4C, 8D, 9, 10C, 12C, 14, 16-18)
With regard to three-toed footprints of bipedal dinosaurs,
Paluxy River tracksites collectively constitute a natural
laboratory for investigating extramorphological effects
of substrate conditions and trackmaker movements in
creating a variety of footprint shapes from a uniform
foot shape. Although some tridactyl prints in the Main
Tracklayer are beautifully preserved, even showing traces
of digital pads in the toemarks (Fig. 16B, F), most show
some toe tip pinching, toemark collapse, or other plastic
deformation. Toemarks are often roofed over, such that
their lengths in surface expression are considerably less

53
Salas de los Infantes, Burgos
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
FIGURE 10. The Blue Hole, a popular swimming area at DVSP. A) Aerial photograph; upstream (south) toward the viewer. Black
arrow indicates a ledge exposing the Main Tracklayer along the downstream side of the Blue Hole. B) Photomosaic and map (north to
the top) of several dinosaur tracks exposed in the Main Tracklayer indicated by the arrow in panel A. C) Ground level oblique view of
several typical Blue Hole Site tridactyl footprints.

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Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno
than their lengths as toe tunnels beneath the rock surface
(Fig. 17J; when the river level is up, it is amusing to watch
small fishes swim in and out of such dinosaur toe tunnels).
Sometimes toemarks are indicated by little more than
gashes extending forward from the footprint (Figs. 17,
18E). In some trackways the animal impressed portions
of the metatarsal region of the foot (Figs. 17E, F, K; 18),
either deliberately or inadvertently as the foot interacted
with substrate conditions, making “elongate” footprints
(Kuban 1986, 1989a; cf. Pérez-Lorente, 1993; Lockley et
al., 2003; Romero-Molina et al., 2003; Romano and Whyte,
2003; Boutakiout et al., 2009; Gierlinski et al., 2009).
These extramorphological features complicate anatomical
interpretation of tridactyl prints. For example, toemark
pinching, collapse, and/or roofing make toe marks in
surface expression look shorter and blunter than they really
are (Fig. 17H, L).
Those of the alleged Paluxy River “man tracks” that are
not erosional markings or human carvings are elongate
metatarsal tracks in which the digit impressions are
subdued by one or more factors (infilling, erosion, toemark
collapse), causing the remaining metatarsal portion to
appear more human-like (Kuban, 1986,1989a, b; Hastings,
1987); arguably such prints might be considered to be a
footprint morphotype different from the more typical
tridactyl prints. Although topographic expression of
the toemarks is nearly lost in the “man tracks”, they
nonetheless show triangular distal ends that suggest a
tridactyl shape (Fig. 18C). Furthermore, as already noted,
the toemarks of some Taylor Site prints are accentuated
by color differences between infilling material and the
surrounding rock (Kuban, 1989b). Some color-delimited
tridactyl prints at this site have positive relief relative to
the surrounding rock (Fig. 17M; also see Fig. 16A, B for
color differences between a well-preserved footprint and
surrounding rock in the Main Tracklayer).
The best-preserved Paluxy tridactyls have long, narrow,
pointed toemarks, with a slightly S-shaped digit III
impression whose terminal end is medially directed (Fig.
16B, C, F). Typically they are 45-60 cm in total length.
FIGURE 11. Aerial photograph showing location of the Blue Hole Ballroom and Blue Hole Parlor, two extensive exposures of the
Main Tracklayer.

55
Salas de los Infantes, Burgos
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
FIGURE 12. The Blue Hole Ballroom. A) Map of the tracksite; north to the top of the page. Black arrow indicates the beginning of the
trackway of a large sauropod. A distinct trackway of a smaller sauropod (dark fill) crosses the trail of the bigger dinosaur near the end
of the latter trackway, moving from east to west across the site. A second, less distinct trackway of a small sauropod crosses the trail
of the large sauropod about midway along the latter’s length. B and C) Details from a site photomosaic, marked off in a meter grid. B)
Portion of the tracksite emphasizing the trail of the large sauropod. C) Southwest portion of the tracksite featuring numerous tridactyl
footprints.

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Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno
FIGURE 13. Sedimentary features associated with the Main Tracklayer. A and B) Vertical invertebrate burrows (cf. Skolithos). A)
Tracklayer surface densely marked by burrow openings adjacent to tridactyl footprints, Bird Site; scale marked in cm. B) Vertical section
through a sample of the Main Tracklayer (top of the layer upward), Blue Hole Parlor; 1-cm bar indicated in the lower right-hand portion
of the photograph. Numerous vertical burrows (darker than the surrounding sediment) snake in and out of the plane of the cut. The
left-hand portion of the section shows some distortion of bedding, possibly due to a dinosaur footprint. C) Contact between the Main
Tracklayer and overlying beds, Main Tracksite; scale marked in cm. A tridactyl print is emerging from the riverbank. Note numerous
pinprick vertical burrow openings dotting the tracklayer surface. D) Horizontal surface trace of a large invertebrate, or possibly a tool
mark, Blue Hole Ballroom; a meter stick provides the scale.
Footprints of this size and shape are consistent with
having been made by a large theropod (Langston, 1974;
Farlow, 1987, 2001; Pittman, 1989; Farlow et al., 2006).
A plausible candidate is Acrocanthosaurus, known from
Lower Cretaceous rocks of Oklahoma and Texas (Stovall
and Langston, 1950; Harris, 1998; Currie and Carpenter,
2000).
The skeletal fauna of the Trinity Group includes other
bipedal dinosaurs (Winkler et al., 1989). Conceivably some
of the smallest Paluxy tridactyls could have been made
by gracile ornithopods. Although some large tridactyls
in the Main Tracklayer look ornithopod-like in surface
expression (Fig. 17H), the complicating effects of sediment-
foot interactions mean that at present there are no Main
Tracklayer prints that can unambiguously be identified
as having been made by large ornithopods. However, the
A Trackway of the Taylor Site (Fig. 14A), preserved at a
higher stratigraphic level than the Main Tracklayer, shows

57
Salas de los Infantes, Burgos
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
FIGURE 14. The Taylor Site, a footprint exposure stratigraphically several meters higher than the Main Tracklayer. A) Map of the site
by Glen Kuban, with labels for individual footprints. B) Photomosaic of that portion of the tracksite recognized in 2009; numerous
footprints mapped by Kuban in previous years were not seen. Some individual prints beyond the limits of the 2009 exposure, mapped by
Kuban, are superimposed on the image. Footprint labels from Kuban’s map are added to the photomosaic, which in this view is rotated
about 30 degrees counterclockwise from Kuban’s map.

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Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno
FIGURE 15. Sauropod footprints and trackways. A) Trackway of the large sauropod, Blue Hole Ballroom; meter stick provides scale.
The animal was moving from left to right, with pes prints obliterating manus prints. B, C) Portions of the more distinct small sauropod
trackway from the Blue Hole Ballroom; meter stick provides scale. B) Ground-level oblique view of the last several footprints in the
sequence. C) Overhead view of the final right pes print (and possible deformed manus impression ahead of it?). D) View from an
elevated platform of three sauropod trackways in the East Bank of the Bird Site (Fig. 5). White arrows indicate direction of travel of
trackmakers. From left to right these are the “East” (S9; mean pes print length 76.5 cm), “Middle” (S8; mean pes print length 62.0 cm),
and “Wet” (S7; mean pes print length 90.0 cm) sauropod trackways of Farlow et al. (1989: Table 42.2). Manus prints occur in trackways
S8 and S9, but not trackway S7. E) Overhead view of left manus-pes set, West Bank Bird Site; tape exposes 1 m. F) Overhead and
oblique LiDAR images of right manus-pes set S2M (trackway S2) from the American Museum trackway slab collected by R.T. Bird; pes
print length about 87 cm. Shading indicates print depth, with darker shading indicating greater depth.

59
Salas de los Infantes, Burgos
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
FIGURE 16. Well-preserved tridactyl footprints. A, B) Particularly well-preserved trackway, Blue Hole Ballroom A) Ground-level
oblique view; meter stick provides scale. B) Overhead view of the splendid left print seen in the foreground of panel A; meter stick
marked in 1-cm intervals. Note distinctly darker color of rock inside than outside the print. C) Print from Opossum Branch; scale
marked in centimeter and inch intervals. D) Footprint with distinct hallux impression, south end of exposure area 2 of Main Tracksite.
E) Large tridactyl, Blue Hole. F) Two very nice tridactyls, Opossum Branch. G, H) Somewhat distorted tridactyls, West Bank Bird Site.

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Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno
et al., 2003; Pérez-Lorente (Ed.), 2003; Weems, 2003; Day
et al., 2004; Farlow et al., 2006; Rainforth, 2007; Lockley
et al., 2008). Shuler (1935, 1937) tentatively assigned the
Paluxy River tridactyls to two species of the Early Jurassic
Connecticut Valley ichnogenus Eubrontes; Langston
(1974) suggested that the Early Cretaceous ichnogenus
Irenesauripus might be more appropriate. Evaluating the
ichnotaxonomy of Glen Rose Formation tridactyls is one
of the long-term goals of the present project.
WHAT WERE THE DINOSAURS DOING?
PALEOECOLOGICAL AND BEHAVIORAL
INTERPRETATIONS
The joint occurrence of sauropod and theropod footprints,
particularly in coastal carbonate rocks, is a recurrent
feature of dinosaur trace fossil assemblages (cf. Lockley
et al., 1994b; Pittman and Lockley, 1994; Dalla Vecchia
et al., 2000, 2001; Moreno and Pino, 2002; Marty et al.,
2003; Hunt and Lucas, 2007; Lockley, 2007; Marty, 2008;
Petti et al., 2008). However, given the huge sizes of the
trackmakers, and the carnivorous diet of the theropod, it
is unlikely that any of Paluxy trackmakers was restricted
to the shoreline habitat in which their prints are preserved
(Farlow, 1992b, 2001; Meyer and Pittman, 1994; cf. Dalla
Vecchia et al., 2000), and skeletal fossils of the likely
trackmakers are known from more inland clastic facies
(Stovall and Langston, 1950; Harris, 1998; Currie and
Carpenter, 2000; Rose, 2007; cf. Wright, 2005; Mannion
and Upchurch, 2010).
The homogeneous character of the Main Tracklayer
suggests that it was deposited in a single event. The density
of Skolithos burrows might provide a clue as to how long
the muddy deposit that became the Main Tracklayer was
FIGURE 17. A-L), Moderately to greatly distorted tridactyl footprints, Main Tracklayer; scale in most panels provided by portions of a
meter stick or tape marked in 1-cm intervals, or by a small scale marked in centimeter and inch, or only in centimeter, intervals. In all of
these prints there is at least some pinching off or collapse of toe impressions. Some of the prints also show probable impressions of the
metatarsal region of the trackmaker’s foot. Footprints from Denio Branch (A, B, E, F, K), the Blue Hole (C, D, H, L), Opossum Branch
(G), West Bank Bird Site (I), Main Tracksite (J). M). Tridactyl print from the Taylor Site. In contrast to prints from the Main Tracklayer,
which are preserved as concave epireliefs, this print is preserved as a convex epirelief delimited from surrounding rock by darker color.

61
Salas de los Infantes, Burgos
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
FIGURE 18. Trackways of “elongate” footprints. A-D) Trackway IIS, Taylor Site (Fig. 14). A) Photomosaic of the trackway; black
arrow indicates print IIS,-3). B) Ground-level oblique view of print IIS,-3 and the following footprint in sequence, IIS,-2; meter stick pro-
vides scale. C) Overhead view of print IIS,-3. D) Ground-level oblique view further along the IIS trackway (IIS,-1 and following prints);
the 2 m of exposed tape are adjacent to print IIS,+1). E) Print from the Blue Hole Ballroom. F) Final portion of elongate trackway from
Denio Branch Site (Fig. 3A); human figure provides scale. Most of the footprints in this trackway show little indication of toe marks in
the prints, but the final print (black arrow) is clearly tridactyl, as seen (inset) in the photograph from an elevated platform.

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Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno
FIGURE 19. Direction of travel of sauropods, Main Tracksite and Bird Site (Figs. 4-6, 15D). A) Composite map of
sauropod movements from Bird’s 1942 Rye Chart (Farlow et al., 1989) and our observations. Main Tracksite trackways
are at the top, the West Bank of the Bird Site is in the middle, and the East Bank of the Bird Site is at the lower right. B)
Sauropod movements summarized as arrows. Information is provided for the sauropod trackways illustrated in panel
A, and also for trackways further to the south (upstream). Note the strong preference for southward movement by the
sauropods. C) View of the Bird site, looking south (upstream). Location of Bird’s 1940 trackway quarry in the immediate
foreground.

63
Salas de los Infantes, Burgos
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
FIGURE 20. The AMNH-TMM theropod-sauropod chase sequence. A) Portion of the 1942 Rye chart showing the chase sequence, the
two main trackway blocks collected for the AMNH and the TMM, and individual prints collected for other institutions. Selected key
footprints of theropod C1 and sauropod S2 are labeled for comparison with other panels of this figure. B) One of Bird’s photographs of
the chase sequence; image used by permission of the AMNH. C) Composite LiDAR image of the American Museum (AMNH FARB
3065; cf. Bates et al., 2009a) and Texas Memorial Museum (TMM 40638-1) trackway blocks.

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Dinosaur tracksites of the Paluxy River Valley (Glen Rose Formation, Lower Cretaceous), Dinosaur Valley State Park, Somervell County, Texas
V Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno
exposed before burial. If the ichnofabric proves to have
little sign of second-generation burrowing (e.g. vertical
burrows that cut across older burrows), this will support
the interpretation that the dinosaur track-making event(s)
occurred over a relatively short time interval. In that event,
the number of dinosaur trackways as a function of the size
of tracklayer exposures might serve as a proxy for the local
abundance of dinosaurs on the landscape (cf. Farlow et al.,
2010).
The Paluxy tridactyl prints and trackways show a mirror-
image pattern of arrangement, with most heading generally
northward or southward, in approximately equal numbers
(Farlow, 1987), a commonly observed dinosaur tracksite
pattern that suggests that trackmakers were moving back
and forth along the local coastline (Lockley, 1991; Farlow
et al., 2006). This pattern provides no information about
whether the theropod trackmakers were travelling singly
or in groups. In marked contrast, the Paluxy sauropod
trackways show a strong preference for moving southward
(Fig. 19). This suggests that the sauropods were moving
through the area as a herd (Farlow, 1987). The total number
of animals in the hypothetical herd would have been greater
than the number of sauropod trackways exposed in the
riverbed, because modern lateral river erosion continually
exposes new trackways, and how far away from the river
valley dinosaur trackways occur in the Main Tracklayer
(cf. Fig. 8) is unknown. If the sauropods were travelling
in a group, at least some of them were not walking side-
by-side, with one animal right beside its neighbor, because
some of the. sauropod trackways cross each other (Figs.
5, 12, 15D, 19). R.T. Bird (1954, 1985) believed that one
or more of the large theropods was pursuing the sauropod
herd, and that the theropod in the AMNH-TMM trackway
slab actually attacked the fleeing sauropod (Farlow, 1987;
Thomas and Farlow, 1997). The theropod clearly walked
across the site after the sauropod did, because the big
carnivore’s footprints are repeatedly impressed into the
margins of the sauropod tracks (Fig. 20), as also occurs
in other sauropod-theropod footprint associations at the
Bird Site (Fig. 6C). Equally interesting, over much of the
exposure of the two trackways, both the sauropod and the
theropod trackway follow the same curving path, with the
theropod trackway hugging the left edge of the sauropod
trackway (Fig. 20).
Bird’s imagination was captured by a missing left footprint
(which would have borne the label C1K) of the theropod
that coincides with the shortest stride involving the
right feet (from C1J [whose toemarks are only partially
impressed in the front margin of sauropod pes print S2R]
to C1L; Fig. 20) of the big carnivore. Bird concluded-and
the late paleoartist David Thomas concurred-that at this
point in the trackway the theropod had actually attacked
the sauropod, only to be dragged off its feet by the forward
motion of the much bigger herbivore (Bird, 1985:173;
Thomas and Farlow, 1997). As the meat-eater took an
involuntary forward hop, its left foot was unable to touch
the ground, and so print C1K was never made.
Although we think it quite possible that the theropod was
indeed closely following the sauropod, we are skeptical that
Bird’s putative hop actually occurred. Had the carnivore
been pulled off its feet after partly impressing right print
C1J, to come down on the same right foot to make print
C1L, we would expect footprint C1L to be very unusual.
There might be a spectacular skid mark as the theropod’s
right foot contacted the substrate as it swung forward.
Given the weight of the theropod (Bates et al., 2009b), print
C1L would likely have been particularly deep, probably
passing completely through the Main Tracklayer as many
of the sauropod footprints do. Unfortunately, there seems
to be nothing unusual about footprint C1L.
FOOTPRINT CONSERVATION
Once uncovered by the river, the footprints are ephemeral
features. Exposures of the Main Tracklayer adjacent to
Bird’s 1940 quarry have been greatly reduced in size (Fig.
5); this and routine erosion have blurred or destroyed many
of the footprints that Bird saw. Footprints that O’Brien,
Kuban, and Farlow saw at the Main Tracksite in the 1980s
have been lost (Fig. 4B). The Park Overlook site (which was
positioned along the river between the Main Tracksite and
Denio Branch Mouth Site), which in the 1980s contained a
beautiful theropod trackway, is essentially gone.
Although river erosion contributes to footprint destruction,
an even greater threat is freezing of the rock surface during
the winter time, if water levels are so low that the prints
are exposed. At such times, the footprints shatter (Farlow,
1992a). As long as the river flows freely, there is a rough
balance between the rate at which “old” tracks are effaced
by erosion, and “new” tracks are exposed by river action.
A proposal in the 1980s to dam the Paluxy upstream
from DVSP would have threatened this balance (Farlow,
1992a), but fortunately came to naught. For now, then, the
dinosaur footprint resource at DVSP seems safe. However,
the continued erosional loss of presently exposed footprints
adds impetus to our goal of creating a database of tracksite
information that can continually be updated.
Ironically, even some of the footprints collected by Bird
are under threat. The portion of the “chase sequence” that
Bird collected for the TMM (part of the type trackway of
Brontopodus birdi; Farlow et al., 1989) was not assembled
inside the museum, but rather inside a small outbuilding
on the museum grounds. The rock slabs were placed over
a sand layer atop a concrete slab lying on the ground,
with the building built around them. Since Bird’s time the
porous rock of the Main Tracklayer has allowed moisture
to seep up from below, causing weathering of the tracklayer
surface, and gradual effacement of the footprints (Shelton
et al., 1993). Indeed, some of the footprints in this specimen
that were still clear in the 1980s (Farlow, 1987) have now
become indistinct. The cost of moving the huge specimen

65
Salas de los Infantes, Burgos
JAMES O. FARLOW, MIKE O’BRIEN, GLEN J, KUBAN, BENJAMIN F. DATTILO, KARL T. BATES, PETER L. FALKINGHAM, LAURA PIÑUELA,
AMANDA ROSE, AUSTIN FREELS, CORY KUMAGAI, COURTNEY LIBBEN, JUSTIN SMITH, AND JAMES WHITCRAFT
indoors is great enough to have made the TMM reluctant to
do this. Furthermore, the little outbuilding has itself been
designated a national historic landmark, causing some to
regard the building as more significant than the dinosaur
tracks it was erected to protect. Discussions are presently
underway that may, however, lead to better conservation of
the remaining footprints in this slab.
ACKNOWLEDGMENTS
We thank the U.S. National Natural Landmarks
Program, Texas Parks and Wildlife, Indiana University,
the University of Oviedo (Protocolo CN-040226,
Principado de Asturias, Spain), the Jurassic Foundation,
the Palaeontological Association Sylvester-Bradley
Award (UK), and the National Environmental Research
Council doctoral dissertation grants (UK) for financial
support of our field work. The Basins Studies Group of
the University of Manchester is thanked for use of laser
scanner equipment. John Chamberlain provided us with
a photograph of the Brooklyn College sauropod manus-
pes track set. The AMNH permitted us to reproduce an
archival photograph, and the AMNH and TMM kindly
allowed LiDAR scanning of the chase sequence trackway
slabs. Collis Park provided aerial photos of DVSP. Park
staff Jason Sanchez, Shannon Blalock, Michael Hale, Nate
Gold, Kathy Lenz, Jim Bader, and Yvette Vaughn assisted
our field work in innumerable ways. Faculty and students
of Baylor University, and volunteers Laurie and Larry
Jasinski, helped with site preparation and other aspects of
field work. This paper is dedicated to the memory of Billy
Paul Baker, long-time Superintendent of Dinosaur Valley
State Park (Appendix), for his friendship, support and
encouragement of this project.
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APPENDIX
Billy Paul Baker. An Appreciation
Billy Baker was born on 6 July 1949, and died 4 November
2010. He is remembered for an exceptionally meritorious
career with the Texas Parks and Wildlife Department as
Park Superintendent at Dinosaur Valley State Park in
Glen Rose. Billy’s service of more than 37 years included
respected roles in law enforcement, search and rescue, and
numerous community organizations. Throughout this
time, Billy was always intensely interested in the dinosaur
tracks of the park, and was unstintingly generous of time
and resources to further the research that made this paper
possible. He will be missed by all who had the opportunity
to know him.