Andrew Milner

St. George Dinosaur Discovery Site at Johnson Farm

Fossil tracks made by non-avian theropod dinosaurs commonly reflect the habitual bipedal stance retained in living birds. Only rarely-captured behaviors, such as crouching, might create impressions made by the hands. Such tracks provide valuable information concerning the often poorly understood functional morphology of the early theropod forelimb....

The Lower Jurassic Whitmore Point Member is a widespread lacustrine unit at the top of the Moenave Formation that can be traced across southwestern Utah and northeastern Arizona. The shoreline to the northeast of the outcrop belt trends northwest to southeast, and the central part of the lake is interpreted to be southwest of the outcrop belt. The...

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 Moenkop...

The Chinle Formation and the lower part of the overlying Wingate Sandstone and Moenave Formation were deposited in fluvial, lacustrine, paludal, and eolian environments during the Norian and Rhaetian stages of the Late Triassic (~230 to 201.3 Ma), during which time the climate shifted from subtropical to increasingly arid. In southern Utah, the Shi...

The Jurassic period was crucial for continental ecosystems, with dinosaurs rising to dominance and many key vertebrate groups emerging. In the Early Jurassic, theropod tracks were dominant, alongside those of crocodylomorphs, synapsids, ornithischians, and sauropodomorphs. The Middle Jurassic saw a shift to more diverse ichnofaunas, with new tracks...

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...

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 fo...

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 tetr...

This poster is part of an undergraduate research project and presents a measured section of the Late Triassic Chinle Formation in Cedar City, Utah, USA and preliminary correlations between units that section and the Chinle Formation as it crops out in nearby Zion National Park. It also describes fossil vertebrate material collected at the site and...

A large fallen block of Early Jurassic Navajo Sandstone located at Lake Powell, within Glen Canyon National Recreation Area, south-central Utah, displays natural casts of vertebrate tracks. The footprints occur on at least three track-bearing horizons preserved on and between stromatolitic sandstone beds. Two large, parallel trackways, plus a third...

During the Late Triassic, the Pangaean monsoonal circulation is considered to have been at maximum strength, and western Pangaea began to shift from extremely humid to wet-and-dry seasonal climatic conditions (Lucas & Tanner, 2018; Nordt et al., 2015). Although these climatic changes are interpreted to have been documented in fluvial and lacustrine...

In November 2018, a team of researchers from the National Park Service and the St. George Dinosaur Discovery Site documented fossil vertebrate tracks at the Andre’s Alcove Tracksite (AAT) in the Lower Jurassic (?190–185 Ma) Navajo Sandstone in Glen Canyon National Recreation Area, Utah. The tracks at the AAT were photo-documented for photogrammetri...

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 m...

Wupatki National Monument (WUPA) in north-central Arizona preserves extensive exposures of the Moenkopi Formation, coastal plain and fluvial deposits that record Early–Middle Triassic time in western Pangea. A diverse, reptile-dominated vertebrate ichnofossil assemblage has been documented in the Moenkopi Formation throughout southwestern North Ame...

Theropod dinosaurs are minor components of Late Triassic ecosystems in North America, comprising coelophysoids and various non-neotheropods from the Chinle Formation of Arizona, Utah, Colorado, and New Mexico and the Dockum Group of western Texas. By the Sinemurian (Early Jurassic), the coelophysoid “Syntarsus” kayentakatae and the large-bodied non...

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 smal...

Structure-from-motion (SfM) photogrammetry is an increasingly common component of paleontological research and fossil resources management. The three-dimensional (3D) data and the derived products allow for novel and useful avenues to engage and problem-solve with park resource managers and stakeholders. The National Park Service (NPS) is developin...

We report the first occurrence of the track type “Chirotherium” lulli from western North America. Three specimens were discovered at the “Feather Ridge Tracksite” in the Owl Rock Member of the Chinle Formation within Bears Ears National Monument of San Juan County, Utah. The ichnospecies occurs in association with Grallator isp., Brachychirotherium...

Two types of unusual concretions with similar biotic contents but markedly different shapes and distributions were found in close stratigraphic proximity within the Lower Jurassic Whitmore Point Member of the Moenave Formation in St. George, Utah. Both types of concretions formed in lacustrine sediments and contain abundant ganoid fish scales, nume...

In the summer of 2016, field crews from the Museums of Western Colorado (MWC) discovered a laterally extensive bone bed in the Upper Triassic Chinle Formation. The site lay within the initial boundaries of Bears Ears National Monument but was excluded following a Presidential Proclamation in late 2017. Preliminary excavations of the site began in S...

An ostracode fauna is described from lacustrine sediments of the Hettangian, Lower Jurassic, Whitmore Point Member of the Moenave Formation. The Moenave is well known for its rich, Late Triassic?–Early Jurassic fossil record, which includes fossil fishes, stromatolites, ostracodes, spinicaudatans, and a diverse ichnofauna of invertebrates and verte...

The Late Triassic is a period of abrupt climate change associated with a disruption to the global carbon cycle usually ascribed to the emplacement of the Central Atlantic Magmatic Province (CAMP). Geochronologic, paleontologic, and geochemical studies have shown that the CAMP was likely the major factor for the end-Triassic extinction (ETE), howeve...

A macrophotography technique coupled with focus stacking was used to produce source images for photogrammetry of two isolated fossil teeth from the Lower Jurassic Kayenta Formation of southwest Utah. The crown heights of the teeth are approximately 4 mm and 9 mm. The macrophotography was conducted using a Canon digital camera body with a 24-megapix...

The Chinle Formation and the lower part of the overlying Wingate Sandstone and Moenave Formation were deposited in fluvial, lacustrine, paludal, and eolian environments during the Norian and Rhaetian stages of the Late Triassic (~230 to 201.3 Ma), during which time the climate shifted from subtropical to increasingly arid. In southern Utah, the Shi...

New Triassic bonebed consisting of articulated individuals.

The end-Permian extinction was the largest such event in earth history and resulted in the ecologic restructuring of both terrestrial and marine environments. The dynamics and timing of marine ecologic recovery following this event has been the subject of numerous studies incorporating body and trace fossils. We report a relatively low diversity ic...

In February 2000, while excavating his property in St. George, Utah, Sheldon Johnson turned over a piece of ground and discovered a fully preserved dinosaur footprint. That track was the first of many fossils to be uncovered. Five years later, the St. George Dinosaur Discovery Site at Johnson Farm was established to preserve one of the richest and...

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 ve...

The Kayenta Formation has yielded numerous tetrapod fossils, including, amphibians, theropods, prosauropods, ornithischians, crocodylomorphs, sphenodonts, tritylodonts, pterosaurs, turtles, and rare mammals. Despite the phylogenetic diversity of the preserved animals, virtually all of the vertebrate fossils have come from the Ward Terrace area of n...

The Kayenta Formation has yielded numerous tetrapod fossils, including, amphibians, theropods, prosauropods, ornithischians, crocodylomorphs, sphenodonts, tritylodonts, pterosaurs, turtles, and rare mammals. Despite the phylogenetic diversity of the preserved animals, virtually all of the vertebrate fossils have come from the Ward Terrace area of n...

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...

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 th...

The Lower-Middle Triassic Moenkopi Formation of the Colorado Plateau preserves a high-diversity track assemblage (e.g., Chirotherium, Rotodactylus, Rhynchosauroides) produced by a variety of reptilian trackmakers. Many of these trackmakers are not represented by skeletal remains and therefore they are an important record of Early Triassic reptilian...

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 pro...

Description of characters used in the phylogenetic analysis of Iguanodontia. (0.07 MB DOC)

List of the references cited in the character and specimen lists. (0.05 MB DOC)

Data matrix used in the phylogenetic analysis of Iguanodontia. (0.12 MB XLS)

List of the fossil specimens examined firsthand and references used to code the 61 taxa in the phylogenetic analysis of Iguanodontia. (0.03 MB XLS)

Basal iguanodontian dinosaurs were extremely successful animals, found in great abundance and diversity almost worldwide during the Early Cretaceous. In contrast to Europe and Asia, the North American record of Early Cretaceous basal iguanodonts has until recently been limited largely to skulls and skeletons of Tenontosaurus tilletti. Herein we des...

The name Timpoweap Member of the Moenkopi Formation has long been applied to the lowermost stratigraphic interval (mostly limestone and shale of marine origin) of the Moenkopi Formation in southwestern Utah. We describe in detail a section (lectostratotype) of the Timpoweap Member in Timpoweap Canyon near Hurricane, Utah. At this section, the Timpo...

Bird and mammal tracks from the White Narrows Formation (early Pliocene) in the Moapa area, near Glendale, Nevada, have been known and collected for several decades, furnishing at least four museums with representative specimens. This easily accessible site contains the best Nevadan examples of early Pliocene ungulate and carnivore tracks. One carn...

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 pinn...

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 Batrach...

The purpose of this field trip is to familiarize participants with the faunas and floras that have been recognized along the northwestern shores of the Champlain Sea during the late glacial (Late Wisconsinan-Early Holocene) within the Ottawa region.