In addition to being Utah's paleontological cheerleader, I'm focused on researching all aspects of Mesozoic geology and paleontology in the southwestern United States and Mexico. Supervisors: Erle Kauffman Phone: (801) 537-3307 Address: Utah Geological Survey
PO Box 146100
Salt Lake City, UT 84114-6100
A new mass death assemblage in Lower Cretaceous strata of east-central Utah contains well-preserv... more A new mass death assemblage in Lower Cretaceous strata of east-central Utah contains well-preserved skeletons representing an ontogenetic series of individuals of Utahraptor, and at minimum two iguanodont grade ornithischian skeletons. The dinosaurs were entombed in ovoid-lensoidal, fine-grained sandstone sills linked by sandstone pipes and/or dikes and another basal lensoidal mass with scattered and broken iguanodont and sauropod bones and to an underlying gravelly sandstone bed. Exposed in the excavation high-walls are syndepositional normal-faults bounding graded ripple strata. Multiphased fluid over-pressurization in an artesian setting creating the structures. Trapping, killing, and subsequent burial mechanism was generated by variations of pressure in a localized artesian spring system that breached the surface and is the first such mechanism documented with numerous dinosaur
Although only recognized as a discrete stratigraphic unit since 1949, the Cedar Mountain Formatio... more Although only recognized as a discrete stratigraphic unit since 1949, the Cedar Mountain Formation represents tens of millions of years of geological and biological history on the central Colorado Plateau. This guidebook represents an attempt to pull together the results of recent research on the lithostratigraphy, chronostratigraphy, sequence stratigraphy, chemostratigraphy, and biostratigraphy of these medial Mesozoic strata that document the dynamic and complex geological history of this region. Additionally, these data provide a framework by which to examine the history of terrestrial faunas during the final breakup of Pangaea. In fact, the medial Mesozoic faunal record of eastern Utah should be considered a keystone in understanding the history of life across the northern hemisphere. Following a period of erosion and sediment bypass spanning the Jurassic–Cretaceous boundary, sedimentation across the quiescent Colorado Plateau began during the Early Cretaceous. Thickening of these basal Cretaceous strata across the northern Paradox Basin indicate that salt tectonics may have been the predominant control on deposition in this region leading to the local preservation of fossiliferous strata, while sediment bypass continued elsewhere. Thickening of overlying Aptian strata west across the San Rafael Swell provides direct evidence of the earliest development of a foreland basin with Sevier thrusting that postdates geochemical evidence for the initial development of a rain shadow.
A new mass death assemblage in Lower Cretaceous strata of east-central Utah contains well-preserv... more A new mass death assemblage in Lower Cretaceous strata of east-central Utah contains well-preserved skeletons representing an ontogenetic series of individuals of Utahraptor, and at minimum two iguanodont grade ornithischian skeletons. The dinosaurs were entombed in ovoid-lensoidal, fine-grained sandstone sills linked by sandstone pipes and/or dikes and another basal lensoidal mass with scattered and broken iguanodont and sauropod bones and to an underlying gravelly sandstone bed. Exposed in the excavation high-walls are syndepositional normal-faults bounding graded ripple strata. Multiphased fluid over-pressurization in an artesian setting creating the structures. Trapping, killing, and subsequent burial mechanism was generated by variations of pressure in a localized artesian spring system that breached the surface and is the first such mechanism documented with numerous dinosaur victims.
New Mexico Museum of Natural History and Science Bulletin, 2024
Dr. Martin G. Lockley explored and published extensively on vertebrate ichnological resources at ... more Dr. Martin G. Lockley explored and published extensively on vertebrate ichnological resources at Glen Canyon National Recreation Area (GLCA), primarily from the shores of Lake Powell in Utah and Arizona. Since 2010, a team from the St. George Dinosaur Discovery Site, working in conjunction with GLCA and National Park Service paleontologists, has focused research primarily on specific vertebrate tracksites in the Lower Jurassic Glen Canyon Group, especially in the Kayenta Formation and Navajo Sandstone. In the process, several significant body fossil sites have been discovered in the Upper Triassic Chinle Formation that have produced plants, fishes, and archosaurian reptiles. Additionally, two tritylodont bonebeds have been discovered, one each in the uppermost Kayenta Formation and lower Navajo Sandstone. As recognized by Lockley, GLCA, and NPS, the paleontological resources within GLCA park boundaries are extensive, ranging from the Pennsylvanian to Late Cretaceous, and the Pleistocene. Here, we summarize the major fossil localities studied at GLCA in the last decade and also report on the first occurrences of these trace fossils from GLCA (in geologic order): cf. Psammichnites from the lower Cutler beds; cf. Oravaichnium, Scoyenia, and cf. Gwyneddichnium from the Shinarump Member of the Chinle Formation; Evazoum gatewayensis, cf. Evazoum, and Brachychirotherium from the lower Wingate Sandstone; Undichna, cf. Ameghinichnus, and cf. Rhynchosauroides from the Kayenta Formation; a large Eubrontes crouching trace with possible manus prints from the Kayenta–Navajo transition, the ninth known example worldwide and second from GLCA; and Navahopus tracks from the Navajo Sandstone. We also report on locally abundant Grallator tracks in the upper part of the Navajo Sandstone.
<p>(A) General Lower Cretaceous stratigraphy in the area of the Oliete sub-basin with the r... more <p>(A) General Lower Cretaceous stratigraphy in the area of the Oliete sub-basin with the relative distribution of thyreophoran dinosaurs in Spain and southern England indicated. (B) General stratigraphy of the Escucha Fm. in the area around Ariño, Aragón, Spain showing approximate position of dinosaur locality AR-1. Stratigraphic nomenclature following Rodríguez-López and others <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080405#pone.0080405-RodrguezLpez2" target="_blank">[53]</a>.</p
The Iron Springs Formation represents a braidplain consisting of sediments shed from the eastward... more The Iron Springs Formation represents a braidplain consisting of sediments shed from the eastward advancing Sevier orogenic belt, and the fauna it contains is the most proximal, relative to the orogenic belt, of those recovered from the Cretaceous of southern Utah. The fauna spans the Cenomanian into Santonian (and possibly the early Campanian). Among the taxa of fishes, the fauna includes four elasmobranch, one rhinobatoid, two neopterygian, two teleost, and one dipnoan. The lissamphibians are quite diverse and include anurans (at least 1 taxon), urodeles (at least 6 taxa), and albanerpetontids (at least 1 taxon). The squamates are of surprising low diversity, represented by only three taxa. Theropod dinosaurs are present including two taxa of dromaeosaurs, two taxa of coelurosaurs, and an unknown taxon. Among ornithiscians, an ankylosaur, an ornithopod, and possibly a ceratopsian are present. Sixteen mammalian taxa including multituberculates, marsupials, a spalacotheriid, and a symmetrodont are present. This is a relatively high diversity fauna from a small sample suggesting that the upland fauna was not greatly different from those recovered from adjacent plateaus (Markagunt, Paunsaugunt, and Kaiparowits) to the east. The diversity represented by this small sample suggests the potential for more extensive research in the Iron Springs Formation.
Spectacular rocks exposed in Utah's national parks include many fossiliferous intervals. In ... more Spectacular rocks exposed in Utah's national parks include many fossiliferous intervals. In cooperation with the Utah Geological Survey, National Park Service interns have been conducting comprehensive inventories of paleontological resources located within Utah's national parks. The goal of this work is to identify new fossil localities and to assess the distribution of fossils within formations to establish baseline paleontological resource data to support the management and protection of non-renewable fossils. Because of the vast ...
New perspectives on horned dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium. Indiana University Press, Bloomington, Jun 17, 2010
Zuniceratops christopheri Wolfe and Kirkland 1998 is a neoceratopsian dinosaur from the middle Tu... more Zuniceratops christopheri Wolfe and Kirkland 1998 is a neoceratopsian dinosaur from the middle Turonian Moreno Hill Formation of west-central New Mexico. The holotype is a partial skeleton (MSM P2101), with additional bonebed material comprising at least seven partial skeletons. The bonebed has yielded numerous disarticulated cranial and postcranial elements, expanding our osteological knowledge of Zuniceratops and allowing execution of a full skeletal mount and reconstruction.
The occipital braincase of Nothronychus mckinleyi Kirkland and Wolfe 2001 from the lower middle T... more The occipital braincase of Nothronychus mckinleyi Kirkland and Wolfe 2001 from the lower middle Turonian Moreno Hill Formation of west-central New Mexico is that of an advanced therizinosaurid. It is ventrally expanded and highly pneumatic, as is the braincase of Erlicosaurus andrewsi Perle from Mongolia, the only other described therizinosaurid braincase; this similarity supports the close relationship of these two taxa.
A new mass death assemblage in Lower Cretaceous strata of east-central Utah contains well-preserv... more A new mass death assemblage in Lower Cretaceous strata of east-central Utah contains well-preserved skeletons representing an ontogenetic series of individuals of Utahraptor, and at minimum two iguanodont grade ornithischian skeletons. The dinosaurs were entombed in ovoid-lensoidal, fine-grained sandstone sills linked by sandstone pipes and/or dikes and another basal lensoidal mass with scattered and broken iguanodont and sauropod bones and to an underlying gravelly sandstone bed. Exposed in the excavation high-walls are syndepositional normal-faults bounding graded ripple strata. Multiphased fluid over-pressurization in an artesian setting creating the structures. Trapping, killing, and subsequent burial mechanism was generated by variations of pressure in a localized artesian spring system that breached the surface and is the first such mechanism documented with numerous dinosaur
Although only recognized as a discrete stratigraphic unit since 1949, the Cedar Mountain Formatio... more Although only recognized as a discrete stratigraphic unit since 1949, the Cedar Mountain Formation represents tens of millions of years of geological and biological history on the central Colorado Plateau. This guidebook represents an attempt to pull together the results of recent research on the lithostratigraphy, chronostratigraphy, sequence stratigraphy, chemostratigraphy, and biostratigraphy of these medial Mesozoic strata that document the dynamic and complex geological history of this region. Additionally, these data provide a framework by which to examine the history of terrestrial faunas during the final breakup of Pangaea. In fact, the medial Mesozoic faunal record of eastern Utah should be considered a keystone in understanding the history of life across the northern hemisphere. Following a period of erosion and sediment bypass spanning the Jurassic–Cretaceous boundary, sedimentation across the quiescent Colorado Plateau began during the Early Cretaceous. Thickening of these basal Cretaceous strata across the northern Paradox Basin indicate that salt tectonics may have been the predominant control on deposition in this region leading to the local preservation of fossiliferous strata, while sediment bypass continued elsewhere. Thickening of overlying Aptian strata west across the San Rafael Swell provides direct evidence of the earliest development of a foreland basin with Sevier thrusting that postdates geochemical evidence for the initial development of a rain shadow.
A new mass death assemblage in Lower Cretaceous strata of east-central Utah contains well-preserv... more A new mass death assemblage in Lower Cretaceous strata of east-central Utah contains well-preserved skeletons representing an ontogenetic series of individuals of Utahraptor, and at minimum two iguanodont grade ornithischian skeletons. The dinosaurs were entombed in ovoid-lensoidal, fine-grained sandstone sills linked by sandstone pipes and/or dikes and another basal lensoidal mass with scattered and broken iguanodont and sauropod bones and to an underlying gravelly sandstone bed. Exposed in the excavation high-walls are syndepositional normal-faults bounding graded ripple strata. Multiphased fluid over-pressurization in an artesian setting creating the structures. Trapping, killing, and subsequent burial mechanism was generated by variations of pressure in a localized artesian spring system that breached the surface and is the first such mechanism documented with numerous dinosaur victims.
New Mexico Museum of Natural History and Science Bulletin, 2024
Dr. Martin G. Lockley explored and published extensively on vertebrate ichnological resources at ... more Dr. Martin G. Lockley explored and published extensively on vertebrate ichnological resources at Glen Canyon National Recreation Area (GLCA), primarily from the shores of Lake Powell in Utah and Arizona. Since 2010, a team from the St. George Dinosaur Discovery Site, working in conjunction with GLCA and National Park Service paleontologists, has focused research primarily on specific vertebrate tracksites in the Lower Jurassic Glen Canyon Group, especially in the Kayenta Formation and Navajo Sandstone. In the process, several significant body fossil sites have been discovered in the Upper Triassic Chinle Formation that have produced plants, fishes, and archosaurian reptiles. Additionally, two tritylodont bonebeds have been discovered, one each in the uppermost Kayenta Formation and lower Navajo Sandstone. As recognized by Lockley, GLCA, and NPS, the paleontological resources within GLCA park boundaries are extensive, ranging from the Pennsylvanian to Late Cretaceous, and the Pleistocene. Here, we summarize the major fossil localities studied at GLCA in the last decade and also report on the first occurrences of these trace fossils from GLCA (in geologic order): cf. Psammichnites from the lower Cutler beds; cf. Oravaichnium, Scoyenia, and cf. Gwyneddichnium from the Shinarump Member of the Chinle Formation; Evazoum gatewayensis, cf. Evazoum, and Brachychirotherium from the lower Wingate Sandstone; Undichna, cf. Ameghinichnus, and cf. Rhynchosauroides from the Kayenta Formation; a large Eubrontes crouching trace with possible manus prints from the Kayenta–Navajo transition, the ninth known example worldwide and second from GLCA; and Navahopus tracks from the Navajo Sandstone. We also report on locally abundant Grallator tracks in the upper part of the Navajo Sandstone.
<p>(A) General Lower Cretaceous stratigraphy in the area of the Oliete sub-basin with the r... more <p>(A) General Lower Cretaceous stratigraphy in the area of the Oliete sub-basin with the relative distribution of thyreophoran dinosaurs in Spain and southern England indicated. (B) General stratigraphy of the Escucha Fm. in the area around Ariño, Aragón, Spain showing approximate position of dinosaur locality AR-1. Stratigraphic nomenclature following Rodríguez-López and others <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0080405#pone.0080405-RodrguezLpez2" target="_blank">[53]</a>.</p
The Iron Springs Formation represents a braidplain consisting of sediments shed from the eastward... more The Iron Springs Formation represents a braidplain consisting of sediments shed from the eastward advancing Sevier orogenic belt, and the fauna it contains is the most proximal, relative to the orogenic belt, of those recovered from the Cretaceous of southern Utah. The fauna spans the Cenomanian into Santonian (and possibly the early Campanian). Among the taxa of fishes, the fauna includes four elasmobranch, one rhinobatoid, two neopterygian, two teleost, and one dipnoan. The lissamphibians are quite diverse and include anurans (at least 1 taxon), urodeles (at least 6 taxa), and albanerpetontids (at least 1 taxon). The squamates are of surprising low diversity, represented by only three taxa. Theropod dinosaurs are present including two taxa of dromaeosaurs, two taxa of coelurosaurs, and an unknown taxon. Among ornithiscians, an ankylosaur, an ornithopod, and possibly a ceratopsian are present. Sixteen mammalian taxa including multituberculates, marsupials, a spalacotheriid, and a symmetrodont are present. This is a relatively high diversity fauna from a small sample suggesting that the upland fauna was not greatly different from those recovered from adjacent plateaus (Markagunt, Paunsaugunt, and Kaiparowits) to the east. The diversity represented by this small sample suggests the potential for more extensive research in the Iron Springs Formation.
Spectacular rocks exposed in Utah's national parks include many fossiliferous intervals. In ... more Spectacular rocks exposed in Utah's national parks include many fossiliferous intervals. In cooperation with the Utah Geological Survey, National Park Service interns have been conducting comprehensive inventories of paleontological resources located within Utah's national parks. The goal of this work is to identify new fossil localities and to assess the distribution of fossils within formations to establish baseline paleontological resource data to support the management and protection of non-renewable fossils. Because of the vast ...
New perspectives on horned dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium. Indiana University Press, Bloomington, Jun 17, 2010
Zuniceratops christopheri Wolfe and Kirkland 1998 is a neoceratopsian dinosaur from the middle Tu... more Zuniceratops christopheri Wolfe and Kirkland 1998 is a neoceratopsian dinosaur from the middle Turonian Moreno Hill Formation of west-central New Mexico. The holotype is a partial skeleton (MSM P2101), with additional bonebed material comprising at least seven partial skeletons. The bonebed has yielded numerous disarticulated cranial and postcranial elements, expanding our osteological knowledge of Zuniceratops and allowing execution of a full skeletal mount and reconstruction.
The occipital braincase of Nothronychus mckinleyi Kirkland and Wolfe 2001 from the lower middle T... more The occipital braincase of Nothronychus mckinleyi Kirkland and Wolfe 2001 from the lower middle Turonian Moreno Hill Formation of west-central New Mexico is that of an advanced therizinosaurid. It is ventrally expanded and highly pneumatic, as is the braincase of Erlicosaurus andrewsi Perle from Mongolia, the only other described therizinosaurid braincase; this similarity supports the close relationship of these two taxa.
Transactions of the Kansas Academy of Science, Apr 1, 2016
The Blue Hill Shale Member of the Carlile Shale is a Middle Turonian (ca. 90 Ma) nearshore deposi... more The Blue Hill Shale Member of the Carlile Shale is a Middle Turonian (ca. 90 Ma) nearshore deposit formed during the regressive phase of the Late Cretaceous Western Interior Seaway of North America. Over 900 identifiable specimens of fossil vertebrates were recovered from a locality in northeastern Nebraska that include at least 40 taxa, comprising a minimum of 23 chondrichthyan fishes, 16 osteichthyan fishes, and one aquatic squamate reptile. The fauna includes taxa such as Meristodonoides, Cantioscyllium, Scapanorhynchus, Cretodus, Protoplatyrhina, Pseudohypolophus, and Ptychotrygon, that are commonly represented in Middle Turonian nearshore deposits of North America. The vertebrate fauna described here is composed of nearly 50% non-durophagous and 50% durophagous fishes by number of taxa. Among the nondurophagous fishes are a large carnivorous Cretodus crassidens and medium-sized scavengers Squalicorax spp., but others are primarily piscivores.
Pterosaur tracks (cf. Pteraichnus) from the Summerville Formation of the Ferron area of central U... more Pterosaur tracks (cf. Pteraichnus) from the Summerville Formation of the Ferron area of central Utah add to the growing record of Pteraichnus tracksites in the Late Jurassic Summerville Formation and time-equivalent, or near time-equivalent, deposits. The site is typical in revealing high pterosaur track densities, but low ichnodiversity suggesting congregations or “flocks” of many individuals. Footprint length varies from 2.0 to 7.0 cms. The ratio of well-preserved pes: manus tracks is about 1: 3.4. This reflects a bias in favor of ...
Recent studies (eg, Winkler et al., 1995; Archibald, 1996; Eaton et al., 1997) have suggested rel... more Recent studies (eg, Winkler et al., 1995; Archibald, 1996; Eaton et al., 1997) have suggested relationships between eustasy during specific intervals within the Cretaceous and early Tertiary (Albian-Aptian, Cenomanian-Turonian, Maastrichtian-Tertiary, respectively) and the evolution of vertebrate faunas. Predictions based on the studies of relatively narrow time intervals (4 million years or less) have not been tested as part of a consistent pattern over long-term eustatic fluctuations. This paper represents a preliminary attempt at compiling ...
Little is known about the growth trends of dromaeosaurid taxa due to the lack of unambiguous onto... more Little is known about the growth trends of dromaeosaurid taxa due to the lack of unambiguous ontogenetic series like those available for other theropods (e.g., Allosaurus). However, ongoing preparation of a nine-ton field jacket excavated by the Utah Geological Survey (UGS) has produced skeletal material from at least 7 Utahraptor individuals representing multiple ontogenetic stages. Juvenile elements thus far recovered from this field jacket allow for a preliminary investigation of growth trends in this large-bodied dromaeosaurid. We investigated growth trends in the tibia and the pedal digit II ungual by comparing the adult holotype from the Utah State University Eastern Prehistoric Museum (CEUM) with juvenile material currently housed at the UGS. Measurements from each element were log transformed to improve normality then plotted on bivariate plots and the slopes checked for allometry. A measure of claw curvature was obtained by fitting a circle to its outer edge and recording the degrees of arc scribed by the claw. The proximal width, diaphyseal circumference, and distal width of the tibia show positive allometry when compared to overall length with line slope values of 1.85, 2.33, and 2.80, respectively. These slopes reflect a relative increase in tibia robustness through ontogeny. General increases in hind limb robustness associated with relative shortening of the limb through ontogeny have been observed in the other theropods and is well-documented in Allosaurus. In contrast, the pedal digit II ungual of Utahraptor displays more isometric-like growth. Articular surface height, total claw height, and flexor tubercle width all have line slope values closer to 1 (1.22, 1.17, and 0.92, respectively) when compared to claw length. Interestingly, the flexor tubercle width/articular surface height ratio is higher in the juvenile (0.41) than it is in the adult (0.29) suggesting that juveniles may have had a relatively enlarged flexor tubercle compared to adults. Claw curvature is smaller in the juvenile (118 degrees) compared to the adult (127 degrees). The growth trends reported here are only preliminary. As preparation of the UGS field jacket continues more elements and ontogenetic stages will be sampled and additional methods (e.g., histology) will be employed to analyze growth trends. However, the initial trends reported here incite intriguing questions for ongoing research such as how much allometry may be ascribed to body size increase and how much may be explained by functional differences between juvenile and adult Utahraptors.
Map of Capitol Reef National Park showing location of our measured sections (red dots). Section n... more Map of Capitol Reef National Park showing location of our measured sections (red dots). Section names with a U prefix were measured by Stewart and others (1972), section names with a number were measured by Beer (2005). Sections designated by red dots and capital letters were measured as part of this study. Modified from the CARE brochure map.
The Nugget Sandstone of northern Utah, along with the Navajo and Aztec sandstones to the south, w... more The Nugget Sandstone of northern Utah, along with the Navajo and Aztec sandstones to the south, was deposited as part of a vast sand sea. Although these Triassic-Jurassic erg deposits generally lack body fossils, vertebrate and invertebrate trace fossils are more common and can be locally abundant. In northern Utah the Nugget preserves a diverse vertebrate and invertebrate ichnoassemblage. The diversity and associations of these trace fossils provide unique insights for understanding this arid terrestrial ecosystem. A slab preserving five large arthropod trackways and was recently recovered from a flagstone quarry in the Nugget Sandstone near Heber, Utah and donated to the Natural History Museum of Utah by Marshall McFarland. Two trackways belong to the ichnogenus Paleohelcura sp., two to Octopodichnus tridactylus, and one is cf. Octopodichnus raymondi. Both ichnogenera are attributed to arachnids, either spiders (Octopodichnus) or scorpions (Paleohelcura). The largest trackway on the slab is a well-defined Paleohelcura sp. with a maximum external width of 12 cm and an average stride length of 6.2 cm. The smallest is a faint Octopodichnus tridactylus with a maximum external width of 5 cm and an average stride length of 6.5 cm. All the trackways run subparallel, with trackway orientations within 25 degrees of one another. Differences in the degree of preservation of detail between trackways are likely due to factors such as tracemaker size, differences in the moisture content of the substrate, or undertrack fallout. The two best preserved trackways, a large Paleohelcura and a large Octopodichnus, were probably made on the same depositional surface, and show well developed sediment displacement rims and tic traces which indicate the tracemakers were traveling in the same direction either on flat ground or upslope. Although this particular slab only contains invertebrate surface traces, Octopodichnus and Paleohelcura are associated elsewhere in the Nugget with the small tetrapod surface trace Brasilichnium (often all traveling in the same direction) and the burrowing arthropod trace Entradichnus. These associations are typical of the Chelichnus vertebrate ichnofacies, which correlates with the Octopodichnus invertebrate ichnofacies, and represents an eolian dune lower slipface environment.
Uploads
Books by James Kirkland
Following a period of erosion and sediment bypass spanning the Jurassic–Cretaceous boundary, sedimentation across the quiescent Colorado Plateau began during the Early Cretaceous. Thickening of these basal Cretaceous strata across the northern Paradox Basin indicate that salt tectonics may have been the predominant control on deposition in this region leading to the local preservation of fossiliferous strata, while sediment bypass continued elsewhere. Thickening of overlying Aptian strata west across the San Rafael Swell provides direct evidence of the earliest development of a foreland basin with Sevier thrusting that postdates geochemical evidence for the initial development of a rain shadow.
Papers by James Kirkland
Here, we summarize the major fossil localities studied at GLCA in the last decade and also report on the first occurrences of these trace fossils from GLCA (in geologic order): cf. Psammichnites from the lower Cutler beds; cf. Oravaichnium, Scoyenia, and cf. Gwyneddichnium from the Shinarump Member of the Chinle Formation; Evazoum gatewayensis, cf. Evazoum, and Brachychirotherium from the lower Wingate Sandstone; Undichna, cf. Ameghinichnus, and cf. Rhynchosauroides from the Kayenta Formation; a large Eubrontes crouching trace with possible manus prints from the Kayenta–Navajo transition, the ninth known example worldwide and second from GLCA; and Navahopus tracks from the Navajo Sandstone. We also report on locally abundant Grallator tracks in the upper part of the Navajo Sandstone.
Following a period of erosion and sediment bypass spanning the Jurassic–Cretaceous boundary, sedimentation across the quiescent Colorado Plateau began during the Early Cretaceous. Thickening of these basal Cretaceous strata across the northern Paradox Basin indicate that salt tectonics may have been the predominant control on deposition in this region leading to the local preservation of fossiliferous strata, while sediment bypass continued elsewhere. Thickening of overlying Aptian strata west across the San Rafael Swell provides direct evidence of the earliest development of a foreland basin with Sevier thrusting that postdates geochemical evidence for the initial development of a rain shadow.
Here, we summarize the major fossil localities studied at GLCA in the last decade and also report on the first occurrences of these trace fossils from GLCA (in geologic order): cf. Psammichnites from the lower Cutler beds; cf. Oravaichnium, Scoyenia, and cf. Gwyneddichnium from the Shinarump Member of the Chinle Formation; Evazoum gatewayensis, cf. Evazoum, and Brachychirotherium from the lower Wingate Sandstone; Undichna, cf. Ameghinichnus, and cf. Rhynchosauroides from the Kayenta Formation; a large Eubrontes crouching trace with possible manus prints from the Kayenta–Navajo transition, the ninth known example worldwide and second from GLCA; and Navahopus tracks from the Navajo Sandstone. We also report on locally abundant Grallator tracks in the upper part of the Navajo Sandstone.