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Andrew Milner

St. George Dinosaur Discovery Site at Johnson Farm, Paleontology, Site Paleontologist and Curator

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Phone: 435-574-3466, ext. 2
Address: St. George Dinosaur Discovery Site at Johnson Farm, 2180 E. Riverside Drive, St. George, Utah 84790 USA

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Matteo Belvedere

Università degli Studi di Firenze (University of Florence)

CSIRO

Abdalla Abu hamad

The University Of Jordan

Anthony Romilio

The University of Queensland, Australia

Universidade de Coimbra

Università degli Studi di Bari

National Museum of Wales

Utah Geological Survey

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Papers by Andrew Milner

TRACK RECOGNITION VIA ARTIFICIAL COGNITION (TRAC): PRELIMINARY REPORT ON THE APPLICATION OF MACHINE LEARNING TO IDENITFY DINOSAUR TRACKS

by Andrew Milner, Anthony Romilio, and Karen Houck

New Mexico Museum of Natural History and Science Bulletin, 2024

Despite the utilization of new technologies to objectively record and document dinosaur tracks in... more Despite the utilization of new technologies to objectively record and document dinosaur tracks in the field, the categorization and identification of dinosaur tracks remains a largely subjective process. Track Recognition via Artificial Cognition (TRAC) is a project that seeks to provide an objective method for categorizing and identifying dinosaur tracks using track surface photographs. TRAC will employ a combination of different iterations of supervised and unsupervised deep machine learning (ML) approaches to categorize track images drawing from a data set of over 1,000 digital photographs of dinosaur footprint images from around the world. Iterations and adjustments to the ML algorithms will identify natural clusters in the image data set, and our ultimate goal is to build a model capable of assigning an ichnotaxonomic identification to new images that TRAC analyzes. If successful, TRAC can be deployed as an application that can identify dinosaur footprints to ichnotaxon for use by professional paleontologists, citizen scientists, and land managers, with the potential of expanding the scope of the project to include more types of fossils. The TRAC Project is divided into two phases. This paper presents a preliminary report on Phase I, the preparation of the image data set.

FOLLOWING IN THE FOOTSTEPS OF DR. MARTIN G. LOCKLEY: ANOTHER 10 YEARS OF PALEONTOLOGICAL INVESTIGATIONS IN GLEN CANYON NATIONAL RECREATION AREA, UTAH AND ARIZONA

by Andrew Milner, James Kirkland, Amanda Charobee, and Erica Clites

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.

Possible eucynodont (Synapsida: Cynodontia) tracks from a lacustrine facies in the Lower Jurassic Moenave Formation of southwestern Utah

by Holly Hurtado, Jerald Harris, and Andrew Milner

PeerJ, 2024

Eight fossil tetrapod footprints from lake-shore deposits in the Lower Jurassic Moenave Formation... more Eight fossil tetrapod footprints from lake-shore deposits in the Lower Jurassic Moenave Formation at the St. George Dinosaur Discovery Site (SGDS) in southwestern Utah cannot be assigned to the prevalent dinosaurian (Anomoepus, Eubrontes, Gigandipus, Grallator, Kayentapus) or crocodyliform (Batrachopus) ichnotaxa at the site. The tridactyl and tetradactyl footprints are incomplete, consisting of digit-and digit-tiponly imprints. Seven of the eight are likely pes prints; the remaining specimen is a possible manus print. The pes prints have digit imprint morphologies and similar anterior projections and divarication angles to those of Brasilichnium, an ichnotaxon found primarily in eolian paleoenvironments attributed to eucynodont synapsids. Although their incompleteness prevents clear referral to Brasilichnium, the SGDS tracks nevertheless suggest a eucynodont track maker and thus represent a rare, Early Mesozoic occurrence of such tracks outside of an eolian paleoenvironment.

Tetrapod Tracksites from the Shinarump Formation (Chinle Group, Upper Triassic) of Southwestern Utah

New Mexico Museum of Natural History and Science Bulletin, 2006

Two unusual tetrapod tracksites are reported from the Upper Triassic Shinarump Formation, Chinle ... more Two unusual tetrapod tracksites are reported from the Upper Triassic Shinarump Formation, Chinle Group of the St. George area, Washington County, southwestern Utah. The occurrences represent the first reports of tetrapod tracks from this formation. One site, near Ivins, reveals the narrow trackway of a tridactyl biped, possibly attributable to a theropod dinosaur. The second site, near Harrisburg, reveals two sets of "swim tracks" made by a large vertebrate, possibly a phytosaur. Both track types have not previously been reported from the Chinle Group. As a result of preservational factors and a lack of comparative material, the ichnotaxonomic status of both track types is problematic.

The Early Jurassic (Hettangian) LDS Dinosaur Tracksite from the Moenave Formation in St. George, Utah

New Mexico Museum of Natural History and Science Bulletin, 2006

Early Jurassic (early Hettangian) dinosaur tracks, as well as invertebrate traces and bone materi... more Early Jurassic (early Hettangian) dinosaur tracks, as well as invertebrate traces and bone material, are preserved in marginal lacustrine deposits of the Whitmore Point Member of the Moenave Formation near the St. George Dinosaur Discovery Site at Johnson Farm (SGDS), within St. George city limits in southwestern Utah. A laterally extensive, 30 cm thick, fine-grain sandstone bed deposited along the shores of ancient Lake Dixie contains
hundreds of theropod dinosaur tracks, rare crocodylomorph tracks (cf. Batrachopus), Skolithos burrows, weathered bone fragments, and semionotid fish scales.

First report of "Chirotherium" lulli from the Upper Triassic Chinle Formation of San Juan County, Utah

New Mexico Museum of Natural History and Science Bulletin, 2021

We report the first occurrence of the track type &quot;Chirotherium&quot; lulli from west... more

3D model related to the publication: Morphology and distribution of scales, dermal ossifications, and other non-feather integumentary structures in non-avialan theropod dinosaurs

MorphoMuseuM, 2022

In this article, the remains of a nearly complete specimen of the enigmatic Sanmiguelia Brown pla... more In this article, the remains of a nearly complete specimen of the enigmatic Sanmiguelia Brown plant (narrow stem and attached palm-like leaves) are described from the Early Jurassic (Hettangian) in the uppermost part of the Whitmore Point Member of the Moenave Formation in southwestern Utah. Previously, the fossil was only known from Upper Triassic strata at ten localities found in all but the lowest members of the Chinle Formation of Late Triassic age and equivalent units in the American Southwest. A small isolated fragment of the palm-like leaf of the Sanmiguelia plant is also described here for the first time from the Church Rock Member of the Chinle Formation in Lisbon Valley, southeastern Utah. The twelve localities (counting those described here) extend from west Texas to Zion National Park in southwestern Utah and range in age from Late Triassic (Norian) to Early Jurassic (Hettangian).

Plant Fossils from the Owl Rock or Church Rock Members, Chinle Formation, San Juan County, Utah

Plant fossils from the Owl Rock or Church Rock members (middle Norian) of the Chinle Formation on... more Plant fossils from the Owl Rock or Church Rock members (middle Norian) of the Chinle Formation on the Colorado Plateau are uncommon, with few localities and specimens documented to date. Here I describe three new specimens consisting of a fragmentary cf. Neocalamites stem section, a fern frond identified as cf. Cynepteris, and a bennettitalean pinna (cf. Zamites powellii) from a new locality in east-central Utah. Unfortunately, the poor preservation of these plant fossils does not allow for a positive identification. These plant fossils aid in a better understanding of the paleoenvironmental conditions that existed in the region during the mid-Norian. These plants were found in very close association with a variety of reptilian tracks, fragmentary tetrapod body fossils, gastro- pods, bivalves, ostracodes, conchostracans and a rich fauna of fossil freshwater fishes.

The Ichnotaxonomy of Hopping Vertebrate Trackways from the Cenozoic of the Western USA

Tracks attributable to hopping vertebrates are rare in the fossil record. However, where they occ... more Tracks attributable to hopping vertebrates are rare in the fossil record. However, where they occur they are highly distinctive and easily differentiated from the tracks of other vertebrates that used different gaits. Among the groups of small extant vertebrates that hop, frogs, certain rodents, and some birds are well known. Trackways of two of these groups, frogs and rodents, occur in Cenozoic deposits of the western USA. However, despite highly distinctive and diagnostic morphologies, the material described here previously lacked any formal ichnotaxonomic designations. A well-preserved Eocene trackway of a frog from the Flagstaff Formation of Utah is here named Ranapes laci ichnogen. et ichnsp. nov. It is only the second example of frog footprints from the fossil record, and the first to show a clear trackway sequence with both manus and pes traces. Trackways of hopping, mouse-sized rodents occur quite abundantly in two Miocene deposits in the western USA (Colorado and Utah), whe...

Lithostratigraphy and biostratigraphy of the Chinle Formation (Upper Triassic) in southern Lisbon Valley, southeastern Utah

ABSTRACT We present here a detailed study of the lithostratigraphy and preliminary vertebrate bio... more ABSTRACT We present here a detailed study of the lithostratigraphy and preliminary vertebrate biostratigraphy of the Upper Triassic Chinle Formation in Lisbon Valley, southeastern Utah. Triassic salt tectonism resulted in a period of erosion and possibly non-deposition that removed the top of the Lower Permian Cutler Group, the Early-Middle Triassic Moenkopi Formation, and the Late Triassic (earliest Norian) Shinarump Member of the Chinle Formation. Chinle Formation deposition in Lisbon Valley began or resumed sometime during the middle-late Norian or Rhaetian and terminated before the end of the Rhaetian. Chinle Formation sediments are mostly siltstone to fine-grained sandstone dominated by planar cross-bedding and climbing ripple cross-lamination; these sediments generally exhibit poor paleosol development, with interbedded conglomerates dominated by clasts composed of reworked intrabasinal sediments and containing only minor extrabasinal silica. The regional climate during Chinle deposition was becoming increasingly arid, with fluctuating seasonal rainfall. Deposition by the braided and meandering rivers of the lower Kane Springs beds filled paleovalleys incised into the Cutler Group, and was followed by a poorly drained interval of poorly oxygenated swamps and lakes crisscrossed by small streams that produced the middle Kane Springs beds. These conditions transitioned back to the slowly aggrading braided and meandering rivers of the upper Kane Springs beds, probably by Rhaetian time. The Kane Springs paleoenvironment, probably at least partially syndepositional with that of the Owl Rock Member, was inhabited by conifers, freshwater ostracods, bivalves and gastropods, indeterminate phytosaurs, and the aetosaur Typothorax. The shift to the overlying Church Rock Member was gradational and probably involved only subtle shifts in the depositional system, largely related to better-drained sediments. Braided channels with seasonally variable discharge crossed well-drained, rapidly aggrading and well-oxygenated floodplains. Rare paleosols (including entisols, vertisols, and aridisols) indicate seasonal wetting and drying in a generally arid climate. Rivers and lakes were inhabited by the phytosaur taxon Machaeroprosopus (including the derived form “Redondasaurus”), rare metoposaurids, coelacanths, a diverse actinopterygian fish fauna, conchostracans, ostracods, bivalves, and gastropods. The flora included conifer trees, giant horsetails, Cynepteris (a fern), Zamites (a bennettitalean), the small shrub-like conifer Pelourdea, and the enigmatic Sanmiguelia. Terrestrial tetrapods included the aetosaur Typothorax (suggesting that the genus endured into the Rhaetian), paracrocodylomorphs, and small theropods. Eventually, wind-blown eolian deposits entered the region, and late in the Rhaetian, prior to 201.3 Ma, the eolian Wingate erg swamped small braided channels still inhabited by the phytosaur “Redondasaurus,” actinopterygian fishes, and small theropods.

The Story of the St. George Dinosaur Discovery Site at Johnson Farm: An Important New Lower Jurassic Dinosaur Tracksite from the Moenave Formation of Southwestern Utah

3 471 North 100 West, St. George, UT 84770 Abstract—Well-preserved theropod tracks from a newly d... more 3 471 North 100 West, St. George, UT 84770 Abstract—Well-preserved theropod tracks from a newly discovered Lower Jurassic, Moenave Formation site in St. George Utah, are mostly assigned to the dinosaurian ichnogenera Eubrontes and Grallator, with some assigned to cf. Gigandipus, cf. Kayentapus, and Anomoepus. The non-dinosaurian ichnogenera Batrachopus and cf. Selenichnus are also reported. The ichnofauna is very similar to others from the region of southern Utah and other classic ichnofaunas of the same age from the eastern United States and elsewhere. However, their excellent preservation as deep natural casts, some with skin impressions, sheds new light on the configuration of the metatarsus and hallux of the Eubrontes trackmaker. One dinosaurian trackway (cf. Gigandipus) also reveals tail and squatting traces. The deep tracks also shed light on the mode of foot emplacement and withdrawal of the Grallator trackmaker, and the potential for theropods to produce undertracks with unu...

A large collection of well-preserved theropod dinosaur swim tracks from the Lower Jurassic Moenave Formation, St. George, Utah

The Triassic-Jurassic Terrestrial Transition. NM Mus Nat Hist Sci Bull, 2006

Abstract—A large and exceptionally well-preserved collection of dinosaur swim tracks, attributabl... more Abstract—A large and exceptionally well-preserved collection of dinosaur swim tracks, attributable to the ichnogenus Characichnos, is preserved as natural casts and reported in detail for the first time from the St. George Dinosaur Discovery Site at Johnson Farm (SGDS) in southwestern Utah. Approximately 3200 individual claw marks, typically in sets of three and rarely singular or paired, were made predominantly by small theropod dinosaurs in a size range consistent with the ichnogenus Grallator. About 95% of all dinosaur footprints ...

A large arthropod trackway from the Gaspé Sandstone Group (Middle Devonian) of eastern Canada

Canadian Journal of Earth Sciences, 1998

A large arthropod trackway from the Cap-aux-Os Member of the Battery Point Formation (Gaspé Sands... more A large arthropod trackway from the Cap-aux-Os Member of the Battery Point Formation (Gaspé Sandstone Group, Middle Devonian), from the Baie de Gaspé, eastern Canada, is described and assigned to the ichnotaxon Palmichnium (= Paleohelcura) antarcticum (Gevers et al., 1971). A large stylonurid eurypterid or scorpion is considered the most likely producer. A shallow-water marginal fluvial environment is inferred as the setting, the animal making a transition from walking to swimming along the course of the trackway.

Annual Meeting of the Society of Vertebrate Paleontology

Field Trip Leaders

top: Dinosaur Canyon (red-brown ledges in foreground) and Whitmore Point (purplish, gray, and gre... more top: Dinosaur Canyon (red-brown ledges in foreground) and Whitmore Point (purplish, gray, and green slopes) members, Moenave Formation; Springdale Member of Kayenta Formation (yellowish sandstone at base and remainder of resistant ledge); and "silty facies " and "transition zone " of Kayenta Formation into the lower part of

Rock Formation of the Chinle Group. The approximate localities for tetrapod bones, fish plants, and vertebrate tracks are indicated. Modified afte

Lands in the area of Lisbon Valley (Figure 1.1) resulted in the collection of hundreds of specime... more Lands in the area of Lisbon Valley (Figure 1.1) resulted in the collection of hundreds of specimens, consisting of fish, mol-lusks, tetrapod remains, plants, invertebrate traces, and tetra-pod tracks, including coelophysoid theropod footprints. Explo-ration in the area was sparked by an interest in obtaining some of the well-preserved Late Triassic fossil fishes described by

Conference Edition

Morphology and distribution of scales, dermal ossifications, and other non‐feather integumentary structures in non‐avialan theropod dinosaurs

Biological Reviews, 2022

Modern birds are typified by the presence of feathers, complex evolutionary innovations that were... more Modern birds are typified by the presence of feathers, complex evolutionary innovations that were already widespread in the group of theropod dinosaurs (Maniraptoriformes) that include crown Aves. Squamous or scaly reptilian-like skin is, however, considered the plesiomorphic condition for theropods and dinosaurs more broadly. Here, we review the morphology and distribution of non-feathered integumentary structures in non-avialan theropods, covering squamous skin and naked skin as well as dermal ossifications. The integumentary record of non-averostran theropods is limited to tracks, which ubiquitously show a covering of tiny reticulate scales on the plantar surface of the pes. This is consistent also with younger averostran body fossils, which confirm an arthral arrangement of the digital pads. Among averostrans, squamous skin is confirmed in Ceratosauria (Carnotaurus), Allosauroidea (Allosaurus, Concavenator, Lourinhanosaurus), Compsognathidae (Juravenator), and Tyrannosauroidea (Santanaraptor, Albertosaurus, Daspletosaurus, Gorgosaurus, Tarbosaurus, Tyrannosaurus), whereas dermal ossifications consisting of sagittate and mosaic osteoderms are restricted to Ceratosaurus. Naked, non-scale bearing skin is found in the contentious tetanuran Sciurumimus, ornithomimosaurians (Ornithomimus) and possibly tyrannosauroids (Santanaraptor), and also on the patagia of scansoriopterygids (Ambopteryx, Yi). Scales are surprisingly conservative among non-avialan

A trace fossil made by a walking crayfish or crayfish-like arthropod from the Lower Jurassic Moenave Formation of southwestern Utah, USA

PeerJ, 2021

New invertebrate trace fossils from the Lower Jurassic Moenave Formation at the St. George Dinosa... more New invertebrate trace fossils from the Lower Jurassic Moenave Formation at the St. George Dinosaur Discovery Site at Johnson Farm (SGDS) continue to expand the ichnofauna at the site. A previously unstudied arthropod locomotory trace, SGDS 1290, comprises two widely spaced, thick, gently undulating paramedial impressions flanked externally by small, tapered to elongate tracks with a staggered to alternating arrangement. The specimen is not a variant of any existing ichnospecies, but bears a striking resemblance to modern, experimentally generated crayfish walking traces, suggesting a crayfish or crayfish-like maker for the fossil. Because of its uniqueness, we place it in a new ichnospecies, Siskemia eurypyge. It is the first fossil crayfish or crayfish-like locomotion trace ever recorded.

Tracking Early Jurassic dinosaurs across southwestern Utah and the Triassic-Jurassic Transition

TRACK RECOGNITION VIA ARTIFICIAL COGNITION (TRAC): PRELIMINARY REPORT ON THE APPLICATION OF MACHINE LEARNING TO IDENITFY DINOSAUR TRACKS

by Andrew Milner, Anthony Romilio, and Karen Houck

New Mexico Museum of Natural History and Science Bulletin, 2024

Despite the utilization of new technologies to objectively record and document dinosaur tracks in... more Despite the utilization of new technologies to objectively record and document dinosaur tracks in the field, the categorization and identification of dinosaur tracks remains a largely subjective process. Track Recognition via Artificial Cognition (TRAC) is a project that seeks to provide an objective method for categorizing and identifying dinosaur tracks using track surface photographs. TRAC will employ a combination of different iterations of supervised and unsupervised deep machine learning (ML) approaches to categorize track images drawing from a data set of over 1,000 digital photographs of dinosaur footprint images from around the world. Iterations and adjustments to the ML algorithms will identify natural clusters in the image data set, and our ultimate goal is to build a model capable of assigning an ichnotaxonomic identification to new images that TRAC analyzes. If successful, TRAC can be deployed as an application that can identify dinosaur footprints to ichnotaxon for use by professional paleontologists, citizen scientists, and land managers, with the potential of expanding the scope of the project to include more types of fossils. The TRAC Project is divided into two phases. This paper presents a preliminary report on Phase I, the preparation of the image data set.

FOLLOWING IN THE FOOTSTEPS OF DR. MARTIN G. LOCKLEY: ANOTHER 10 YEARS OF PALEONTOLOGICAL INVESTIGATIONS IN GLEN CANYON NATIONAL RECREATION AREA, UTAH AND ARIZONA

by Andrew Milner, James Kirkland, Amanda Charobee, and Erica Clites

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.

Possible eucynodont (Synapsida: Cynodontia) tracks from a lacustrine facies in the Lower Jurassic Moenave Formation of southwestern Utah

by Holly Hurtado, Jerald Harris, and Andrew Milner

PeerJ, 2024

Eight fossil tetrapod footprints from lake-shore deposits in the Lower Jurassic Moenave Formation... more Eight fossil tetrapod footprints from lake-shore deposits in the Lower Jurassic Moenave Formation at the St. George Dinosaur Discovery Site (SGDS) in southwestern Utah cannot be assigned to the prevalent dinosaurian (Anomoepus, Eubrontes, Gigandipus, Grallator, Kayentapus) or crocodyliform (Batrachopus) ichnotaxa at the site. The tridactyl and tetradactyl footprints are incomplete, consisting of digit-and digit-tiponly imprints. Seven of the eight are likely pes prints; the remaining specimen is a possible manus print. The pes prints have digit imprint morphologies and similar anterior projections and divarication angles to those of Brasilichnium, an ichnotaxon found primarily in eolian paleoenvironments attributed to eucynodont synapsids. Although their incompleteness prevents clear referral to Brasilichnium, the SGDS tracks nevertheless suggest a eucynodont track maker and thus represent a rare, Early Mesozoic occurrence of such tracks outside of an eolian paleoenvironment.

Tetrapod Tracksites from the Shinarump Formation (Chinle Group, Upper Triassic) of Southwestern Utah

New Mexico Museum of Natural History and Science Bulletin, 2006

Two unusual tetrapod tracksites are reported from the Upper Triassic Shinarump Formation, Chinle ... more Two unusual tetrapod tracksites are reported from the Upper Triassic Shinarump Formation, Chinle Group of the St. George area, Washington County, southwestern Utah. The occurrences represent the first reports of tetrapod tracks from this formation. One site, near Ivins, reveals the narrow trackway of a tridactyl biped, possibly attributable to a theropod dinosaur. The second site, near Harrisburg, reveals two sets of "swim tracks" made by a large vertebrate, possibly a phytosaur. Both track types have not previously been reported from the Chinle Group. As a result of preservational factors and a lack of comparative material, the ichnotaxonomic status of both track types is problematic.

The Early Jurassic (Hettangian) LDS Dinosaur Tracksite from the Moenave Formation in St. George, Utah

New Mexico Museum of Natural History and Science Bulletin, 2006

Early Jurassic (early Hettangian) dinosaur tracks, as well as invertebrate traces and bone materi... more Early Jurassic (early Hettangian) dinosaur tracks, as well as invertebrate traces and bone material, are preserved in marginal lacustrine deposits of the Whitmore Point Member of the Moenave Formation near the St. George Dinosaur Discovery Site at Johnson Farm (SGDS), within St. George city limits in southwestern Utah. A laterally extensive, 30 cm thick, fine-grain sandstone bed deposited along the shores of ancient Lake Dixie contains
hundreds of theropod dinosaur tracks, rare crocodylomorph tracks (cf. Batrachopus), Skolithos burrows, weathered bone fragments, and semionotid fish scales.

First report of "Chirotherium" lulli from the Upper Triassic Chinle Formation of San Juan County, Utah

New Mexico Museum of Natural History and Science Bulletin, 2021

We report the first occurrence of the track type &quot;Chirotherium&quot; lulli from west... more

3D model related to the publication: Morphology and distribution of scales, dermal ossifications, and other non-feather integumentary structures in non-avialan theropod dinosaurs

MorphoMuseuM, 2022

In this article, the remains of a nearly complete specimen of the enigmatic Sanmiguelia Brown pla... more In this article, the remains of a nearly complete specimen of the enigmatic Sanmiguelia Brown plant (narrow stem and attached palm-like leaves) are described from the Early Jurassic (Hettangian) in the uppermost part of the Whitmore Point Member of the Moenave Formation in southwestern Utah. Previously, the fossil was only known from Upper Triassic strata at ten localities found in all but the lowest members of the Chinle Formation of Late Triassic age and equivalent units in the American Southwest. A small isolated fragment of the palm-like leaf of the Sanmiguelia plant is also described here for the first time from the Church Rock Member of the Chinle Formation in Lisbon Valley, southeastern Utah. The twelve localities (counting those described here) extend from west Texas to Zion National Park in southwestern Utah and range in age from Late Triassic (Norian) to Early Jurassic (Hettangian).

Plant Fossils from the Owl Rock or Church Rock Members, Chinle Formation, San Juan County, Utah

Plant fossils from the Owl Rock or Church Rock members (middle Norian) of the Chinle Formation on... more Plant fossils from the Owl Rock or Church Rock members (middle Norian) of the Chinle Formation on the Colorado Plateau are uncommon, with few localities and specimens documented to date. Here I describe three new specimens consisting of a fragmentary cf. Neocalamites stem section, a fern frond identified as cf. Cynepteris, and a bennettitalean pinna (cf. Zamites powellii) from a new locality in east-central Utah. Unfortunately, the poor preservation of these plant fossils does not allow for a positive identification. These plant fossils aid in a better understanding of the paleoenvironmental conditions that existed in the region during the mid-Norian. These plants were found in very close association with a variety of reptilian tracks, fragmentary tetrapod body fossils, gastro- pods, bivalves, ostracodes, conchostracans and a rich fauna of fossil freshwater fishes.

The Ichnotaxonomy of Hopping Vertebrate Trackways from the Cenozoic of the Western USA

Tracks attributable to hopping vertebrates are rare in the fossil record. However, where they occ... more Tracks attributable to hopping vertebrates are rare in the fossil record. However, where they occur they are highly distinctive and easily differentiated from the tracks of other vertebrates that used different gaits. Among the groups of small extant vertebrates that hop, frogs, certain rodents, and some birds are well known. Trackways of two of these groups, frogs and rodents, occur in Cenozoic deposits of the western USA. However, despite highly distinctive and diagnostic morphologies, the material described here previously lacked any formal ichnotaxonomic designations. A well-preserved Eocene trackway of a frog from the Flagstaff Formation of Utah is here named Ranapes laci ichnogen. et ichnsp. nov. It is only the second example of frog footprints from the fossil record, and the first to show a clear trackway sequence with both manus and pes traces. Trackways of hopping, mouse-sized rodents occur quite abundantly in two Miocene deposits in the western USA (Colorado and Utah), whe...

Lithostratigraphy and biostratigraphy of the Chinle Formation (Upper Triassic) in southern Lisbon Valley, southeastern Utah

ABSTRACT We present here a detailed study of the lithostratigraphy and preliminary vertebrate bio... more ABSTRACT We present here a detailed study of the lithostratigraphy and preliminary vertebrate biostratigraphy of the Upper Triassic Chinle Formation in Lisbon Valley, southeastern Utah. Triassic salt tectonism resulted in a period of erosion and possibly non-deposition that removed the top of the Lower Permian Cutler Group, the Early-Middle Triassic Moenkopi Formation, and the Late Triassic (earliest Norian) Shinarump Member of the Chinle Formation. Chinle Formation deposition in Lisbon Valley began or resumed sometime during the middle-late Norian or Rhaetian and terminated before the end of the Rhaetian. Chinle Formation sediments are mostly siltstone to fine-grained sandstone dominated by planar cross-bedding and climbing ripple cross-lamination; these sediments generally exhibit poor paleosol development, with interbedded conglomerates dominated by clasts composed of reworked intrabasinal sediments and containing only minor extrabasinal silica. The regional climate during Chinle deposition was becoming increasingly arid, with fluctuating seasonal rainfall. Deposition by the braided and meandering rivers of the lower Kane Springs beds filled paleovalleys incised into the Cutler Group, and was followed by a poorly drained interval of poorly oxygenated swamps and lakes crisscrossed by small streams that produced the middle Kane Springs beds. These conditions transitioned back to the slowly aggrading braided and meandering rivers of the upper Kane Springs beds, probably by Rhaetian time. The Kane Springs paleoenvironment, probably at least partially syndepositional with that of the Owl Rock Member, was inhabited by conifers, freshwater ostracods, bivalves and gastropods, indeterminate phytosaurs, and the aetosaur Typothorax. The shift to the overlying Church Rock Member was gradational and probably involved only subtle shifts in the depositional system, largely related to better-drained sediments. Braided channels with seasonally variable discharge crossed well-drained, rapidly aggrading and well-oxygenated floodplains. Rare paleosols (including entisols, vertisols, and aridisols) indicate seasonal wetting and drying in a generally arid climate. Rivers and lakes were inhabited by the phytosaur taxon Machaeroprosopus (including the derived form “Redondasaurus”), rare metoposaurids, coelacanths, a diverse actinopterygian fish fauna, conchostracans, ostracods, bivalves, and gastropods. The flora included conifer trees, giant horsetails, Cynepteris (a fern), Zamites (a bennettitalean), the small shrub-like conifer Pelourdea, and the enigmatic Sanmiguelia. Terrestrial tetrapods included the aetosaur Typothorax (suggesting that the genus endured into the Rhaetian), paracrocodylomorphs, and small theropods. Eventually, wind-blown eolian deposits entered the region, and late in the Rhaetian, prior to 201.3 Ma, the eolian Wingate erg swamped small braided channels still inhabited by the phytosaur “Redondasaurus,” actinopterygian fishes, and small theropods.

The Story of the St. George Dinosaur Discovery Site at Johnson Farm: An Important New Lower Jurassic Dinosaur Tracksite from the Moenave Formation of Southwestern Utah

3 471 North 100 West, St. George, UT 84770 Abstract—Well-preserved theropod tracks from a newly d... more 3 471 North 100 West, St. George, UT 84770 Abstract—Well-preserved theropod tracks from a newly discovered Lower Jurassic, Moenave Formation site in St. George Utah, are mostly assigned to the dinosaurian ichnogenera Eubrontes and Grallator, with some assigned to cf. Gigandipus, cf. Kayentapus, and Anomoepus. The non-dinosaurian ichnogenera Batrachopus and cf. Selenichnus are also reported. The ichnofauna is very similar to others from the region of southern Utah and other classic ichnofaunas of the same age from the eastern United States and elsewhere. However, their excellent preservation as deep natural casts, some with skin impressions, sheds new light on the configuration of the metatarsus and hallux of the Eubrontes trackmaker. One dinosaurian trackway (cf. Gigandipus) also reveals tail and squatting traces. The deep tracks also shed light on the mode of foot emplacement and withdrawal of the Grallator trackmaker, and the potential for theropods to produce undertracks with unu...

A large collection of well-preserved theropod dinosaur swim tracks from the Lower Jurassic Moenave Formation, St. George, Utah

The Triassic-Jurassic Terrestrial Transition. NM Mus Nat Hist Sci Bull, 2006

Abstract—A large and exceptionally well-preserved collection of dinosaur swim tracks, attributabl... more Abstract—A large and exceptionally well-preserved collection of dinosaur swim tracks, attributable to the ichnogenus Characichnos, is preserved as natural casts and reported in detail for the first time from the St. George Dinosaur Discovery Site at Johnson Farm (SGDS) in southwestern Utah. Approximately 3200 individual claw marks, typically in sets of three and rarely singular or paired, were made predominantly by small theropod dinosaurs in a size range consistent with the ichnogenus Grallator. About 95% of all dinosaur footprints ...

A large arthropod trackway from the Gaspé Sandstone Group (Middle Devonian) of eastern Canada

Canadian Journal of Earth Sciences, 1998

A large arthropod trackway from the Cap-aux-Os Member of the Battery Point Formation (Gaspé Sands... more A large arthropod trackway from the Cap-aux-Os Member of the Battery Point Formation (Gaspé Sandstone Group, Middle Devonian), from the Baie de Gaspé, eastern Canada, is described and assigned to the ichnotaxon Palmichnium (= Paleohelcura) antarcticum (Gevers et al., 1971). A large stylonurid eurypterid or scorpion is considered the most likely producer. A shallow-water marginal fluvial environment is inferred as the setting, the animal making a transition from walking to swimming along the course of the trackway.

Annual Meeting of the Society of Vertebrate Paleontology

Field Trip Leaders

top: Dinosaur Canyon (red-brown ledges in foreground) and Whitmore Point (purplish, gray, and gre... more top: Dinosaur Canyon (red-brown ledges in foreground) and Whitmore Point (purplish, gray, and green slopes) members, Moenave Formation; Springdale Member of Kayenta Formation (yellowish sandstone at base and remainder of resistant ledge); and "silty facies " and "transition zone " of Kayenta Formation into the lower part of

Rock Formation of the Chinle Group. The approximate localities for tetrapod bones, fish plants, and vertebrate tracks are indicated. Modified afte

Lands in the area of Lisbon Valley (Figure 1.1) resulted in the collection of hundreds of specime... more Lands in the area of Lisbon Valley (Figure 1.1) resulted in the collection of hundreds of specimens, consisting of fish, mol-lusks, tetrapod remains, plants, invertebrate traces, and tetra-pod tracks, including coelophysoid theropod footprints. Explo-ration in the area was sparked by an interest in obtaining some of the well-preserved Late Triassic fossil fishes described by

Conference Edition

Morphology and distribution of scales, dermal ossifications, and other non‐feather integumentary structures in non‐avialan theropod dinosaurs

Biological Reviews, 2022

Modern birds are typified by the presence of feathers, complex evolutionary innovations that were... more Modern birds are typified by the presence of feathers, complex evolutionary innovations that were already widespread in the group of theropod dinosaurs (Maniraptoriformes) that include crown Aves. Squamous or scaly reptilian-like skin is, however, considered the plesiomorphic condition for theropods and dinosaurs more broadly. Here, we review the morphology and distribution of non-feathered integumentary structures in non-avialan theropods, covering squamous skin and naked skin as well as dermal ossifications. The integumentary record of non-averostran theropods is limited to tracks, which ubiquitously show a covering of tiny reticulate scales on the plantar surface of the pes. This is consistent also with younger averostran body fossils, which confirm an arthral arrangement of the digital pads. Among averostrans, squamous skin is confirmed in Ceratosauria (Carnotaurus), Allosauroidea (Allosaurus, Concavenator, Lourinhanosaurus), Compsognathidae (Juravenator), and Tyrannosauroidea (Santanaraptor, Albertosaurus, Daspletosaurus, Gorgosaurus, Tarbosaurus, Tyrannosaurus), whereas dermal ossifications consisting of sagittate and mosaic osteoderms are restricted to Ceratosaurus. Naked, non-scale bearing skin is found in the contentious tetanuran Sciurumimus, ornithomimosaurians (Ornithomimus) and possibly tyrannosauroids (Santanaraptor), and also on the patagia of scansoriopterygids (Ambopteryx, Yi). Scales are surprisingly conservative among non-avialan

A trace fossil made by a walking crayfish or crayfish-like arthropod from the Lower Jurassic Moenave Formation of southwestern Utah, USA

PeerJ, 2021

New invertebrate trace fossils from the Lower Jurassic Moenave Formation at the St. George Dinosa... more New invertebrate trace fossils from the Lower Jurassic Moenave Formation at the St. George Dinosaur Discovery Site at Johnson Farm (SGDS) continue to expand the ichnofauna at the site. A previously unstudied arthropod locomotory trace, SGDS 1290, comprises two widely spaced, thick, gently undulating paramedial impressions flanked externally by small, tapered to elongate tracks with a staggered to alternating arrangement. The specimen is not a variant of any existing ichnospecies, but bears a striking resemblance to modern, experimentally generated crayfish walking traces, suggesting a crayfish or crayfish-like maker for the fossil. Because of its uniqueness, we place it in a new ichnospecies, Siskemia eurypyge. It is the first fossil crayfish or crayfish-like locomotion trace ever recorded.

Tracking Early Jurassic dinosaurs across southwestern Utah and the Triassic-Jurassic Transition

SIGNIFICANT VERTEBRATE FOSSIL LOCALITIES DISCOVERED DURING CONTINUING PALEONTOLOGICAL RESOURCE INVENTORY AND MONITORING OF THE LATE TRIASSIC CHINLE FORMATION AT CAPITOL REEF NATIONAL PARK, UTAH

by Don DeBlieux, James Kirkland, and Andrew Milner

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.