James I. Kirkland

Utah Geological Survey · GM&P

The Late Cretaceous of Western North America (Laramidia) supported a diverse dinosaur fauna, with duckbilled dinosaurs (Hadrosauridae) being among the most speciose and abundant members of this assemblage. Historically, collecting and preservational biases have meant that dinosaurs from Mexico and the American Southwest are poorly known compared to...

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...

The vertebrate assemblage of the Lower Jurassic Kayenta Formation is known for its preservation of post-end Triassic mass extinction lineages, including lissamphibians, lepidosaurs, turtles, mammaliamorphs, crocodylomorphs, pterosaurs, and ornithischian, theropod, and sauropodomorph dinosaurs. Most of the body fossils from the formation are known f...

Over the past thirty years, exploration of the terrestrial Mesozoic section in Utah has resulted in a more than fivefold increase in the known species of dinosaurs. A highly resolved temporal and sequence stratigraphic framework for these strata is facilitating the utility of these newly discovered dinosaur assemblages in geologic, evolutionary, pa...

The Early Cretaceous is an important time of transition in Earth history, marked by a succession of oceanic anoxic events and carbon cycle perturbations that drove changes on land and in the ocean. The need for more precise geochronologic constraints in terrestrial sediments of Early Cretaceous age that record faunal and floral transitions is espec...

The Early Cretaceous Yellow Cat Member of the terrestrial Cedar Mountain Formation in Utah, USA. has been interpreted as a “time-rich” unit because of its dinosaur fossils, prominent paleosols, and the results of preliminary chemostratigraphic and geochronologic studies. Herein, we refine prior interpretations with: (1) a new composite C-isotope ch...

A new specimen from a plant locality in the Morrison Formation of southeastern Utah exhibits characters suggestive of a small bromalite, possibly from a fish or semi-aquatic mammal. The specimen consists of a cluster of small bones, most referable to lissamphibians, including elements of at least one small frog (possibly a tadpole) and possibly the...

183-1 - VALANGINIAN CARBON-ISOTOPE EXCURSION IDENTIFIED AND DATED IN PALEOSOL-BEARING YELLOW CAT MEMBER, CEDAR MOUNTAIN FORMATION, EASTERN UTAH, USA • Tuesday, 11 October 2022 2:35 PM - 2:50 PM Colorado Convention Center - 207 Earlier work by some of us identified Aptian–Albian carbon-isotope excursions in chemostratigraphic profiles of the co...

Past environments of the Earth's surface may be deciphered and modelled using stable isotopes along with mineralogical, sedimentological, biological, palaeontological, chemical and climatological methodologies. This volume is devoted to studies investigating the distribution of stable isotopes in precipitation and groundwaters and their interaction...

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...

Previously published anomalous whole-rock stable isotopic values from the Poison Strip Sandstone Member of the Cretaceous Cedar Mountain Formation (CMF) of eastern Utah are of uncertain origins. This study investigated the diagenetic history and the processes responsible for these anomalous data. Accordingly, we integrated photomicroscopic techniqu...

In 2015, two fossil chimaeroid egg cases preserved as external molds were identified from the coastal facies of the middle Campanian (Late Cretaceous) Cliff House Sandstone at the top of the Mesaverde Group in Mesa Verde National Park, Colorado. The more complete specimen was unearthed earlier that year, while a fragmentary specimen containing only...

This paper reports a new assemblage of social insect ichnofossils from the Brushy Basin Member of the Upper Jurassic Morrison Formation near Green River, Utah. At least seven distinct nests are visible in the locality horizon, identifiable at the outcrop scale by loci of anastomosing, and orthogonally connected hor-izontal burrows and vertical shaf...

A multiproxy approach for evaluating palaeoclimate parameters in deep-time can result in improvements to inter-related factors affecting palaeohydrology. Here we utilize diverse geochemical tools to improve palaeoclimate estimates for the Cedar Mountain Formation (CMF). Prior research utilized stable carbon and oxygen isotopes to develop chemostrat...

In 2016 and 2017, the Utah Geological Survey partnered with the U.S. Bureau of Land Management to conduct a paleontological inventory of the Morrison Formation south and west of Blanding, Utah, along the eastern margin of the Bears Ears National Monument. The Morrison in this region is critical to understanding Upper Jurassic stratigraphy across th...

The first fossil hemipteran from the Late Jurassic of North America, Morrisonnepa jurassica n. gen. et n. sp., is reported and described from the Morrison Formation, Jurassic Salad Bar locality, San Juan County, Utah, USA. The new specimen is characterised and illustrated, showing morphological characters similar to nepomorphs such as forewing well...

Along the western Cordillera of North America, there is an extensive temporal gap between the Jurassic and the base of the Cretaceous (JK gap) spanning some 25–30 million years. Intensive field research on the terrestrial faunas in the Lower Cretaceous Cedar Mountain Formation (CMF) of the central Colorado Plateau of Utah has succeeded in significa...

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...

This paper presents breakthroughs in the chronostratigraphy of the heretofore poorly constrained Yellow Cat Member of the Cedar Mountain Formation, which is an important record of terrestrial environments, ecosystems and global change in the ancient North American Cordilleran foreland. Zircon populations from 10 stratigraphic horizons in the Yellow...

Late Cretaceous dinosaur assemblages of North America—characterized by gigantic tyrannosaurid predators, and large-bodied herbivorous ceratopsids and hadrosaurids—were highly successful from around 80 million years ago (Ma) until the end of the ‘Age of Dinosaurs’ 66 Ma. However, the origin of these iconic faunas remains poorly understood because of...

The asterisked footnote to Extended Data Table 1 should state '*Including Thomasia and Haramiyavia'. This has been corrected online.

Haramiyida was a successful clade of mammaliaforms, spanning the Late Triassic period to at least the Late Jurassic period, but their fossils are scant outside Eurasia and Cretaceous records are controversial1-4. Here we report, to our knowledge, the first cranium of a large haramiyidan from the basal Cretaceous of North America. This cranium posse...

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...

Organic carbon (OC) isotope profiles from four sections of the Early Cretaceous continental Yellow Cat Member (YCM) of the Cedar Mountain Formation are presented to explore the constraints of studying and correlating continental sections. A significant body of research demonstrates that some continental chemostratigraphic profiles record global per...

Previous investigations document functional and phylogenetic signals in the histology of dinosaur teeth. In particular, incremental lines in dentin have been used to determine tooth growth and replacement rates in several dinosaurian clades. However, to date, few studies have investigated the dental microstructure of theropods in the omnivory/herbi...

In situ Falcarius utahensis dentary teeth UMNH VP 14527 (A–C) and UMNH VP 15259 (D, E) in labial (A, D), lingual (B, E) , and occlusal (C) views. Scale bar represents 1 mm.

Computed tomographic images of Falcarius utahensis dentary teeth (A) UMNH VP 14527 in transverse (labiolingual) cross-section. (B) UMNH VP 14529 in transverse cross-section. Crowns are not completely formed until they have begun erupting from the alveolus. Root lengths that equal or exceed crown height are indicative of fully erupted functional tee...

Location of transects on sectioned teeth Digital microscopy images of therizinosaurian teeth in longitudinal thin section. (A) UMNH VP 22857 maxillary tooth. (B) UMNH VP 15231 dentary tooth. (C) Suzhousaurus tooth. Red boxes indicate location of transects sampled in Figs. 2A–2C. Scale bar represents 500 µm.

Enamel apposition rates and enamel/crown volumes in therizinosauria Enamel Apposition Rates: calculated EAR in F. utahensis and S. megatherioides. EAR decreases by 52% in Suzhousaurus and LIG count is 85% greater than in Falcarius. However, enamel volume is 2.79 percentage points greater in the more derived taxon. Crown and Enamel Volumes: Calculat...

Crown volume, body mass, and dental microstructure raw data from sampled taxa Raw data from this study as well as Erickson (1996b) and D’Emic et al., 2013 on crown volumes, body masses, and dental microstructure in Archosauria. Body mass data from Benson et al., 2014. DDR vs. Replacement: No significant correlation was found between deposition rate...

von Ebner increment widths in Therinosauria Summary: Summary statistics for von Ebner line increment widths in thin sections of F. utahensis and S. megatherioides teeth. Raw: measured increment widths from histological thin sections of therizinosaurian teeth and distribution of thin VELs from EDJ to pulp cavity. Digital microscope images were taken...

A new, largely complete eusauropod dinosaur with cranial and postcranial elements from two skeletons, Mierasaurus bobyoungi gen. nov., sp. nov. from the lower Yellow Cat Member (Early Cretaceous) of Utah (USA), is the first recognized member of Turiasauria from North America. Moreover, according to our phylogenetic results, Moabosaurus utahensis fr...

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...

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 Yellow Cat Member of the Cedar Mountain Formation in Poison Strip, Utah, USA, consists of stacked, erosionally bounded alluvial sequences dominated by massive mudstones (lithofacies Fm) with paleo-Vertisols. Sediment bodies within these sequences grade vertically and laterally into each other at pedogenic boundaries, across which color, texture...

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...

Although only recognized as a discrete stratigraphic unit since 1944, the Cedar Mountain Formation represents tens of millions of years of geological and biological history on the central Colorado Plateau. This field guide represents an attempt to pull together the results of recent research on the lithostratigraphy, chronostratigraphy, sequence st...

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 repre...

Utahraptor Ontogeny

During an internship at Mesa Verde National Park (MEVE), Colorado, the senior author recovered two chimaera egg cases preserved as external molds from the coastal facies of the middle Campanian Cliff House Sandstone at the top of the Mesaverde Group in the park. The most complete specimen was 20 cm in length and 7.5 cm at its widest point. The ribb...

Background Bothremydidae is a clade of extinct pleurodiran turtles known from the Cretaceous to Paleogene of Africa, Europe, India, Madagascar, and North and South America. The group is most diverse during the Late Cretaceous to Paleogene of Africa. Little is known, however, about the early evolution of the group. Methods We here figure and descri...

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 dike...

Although only recognized as a discrete stratigraphic unit since 1944, the Cedar Mountain Formation represents tens of millions of years of geological and biological history on the central Colorado Plateau. This field guide represents an attempt to pull together the results of recent research on the lithostratigraphy, chronostratigraphy, sequence st...

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...

The body fossil record of insects and other arthropods in the Morrison Formation is poorly known, thus the studies of trace fossils are vital for faunal reconstruction. A newly recognized social insect trace has been recovered in the upper Morrision Formation. The depositional environment of this trace fossil assemblage is interpreted as a distal f...

Although only recognized as a discrete stratigraphic unit since 1944, the Cedar Mountain Formation represents tens of millions of years of geological and biological history on the central Colorado Plateau. This field guide represents an attempt to pull together the results of recent research on the lithostratigraphy, chronostratigraphy, sequence st...

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...

For symposium “Advances in Mid-Cretaceous Paleoecology: Understanding a Major Terrestrial Transition” A NEAR-CONTINUOUS, WELL-DATED SEQUENCE OF CRETACEOUS TERRESTRIAL FAUNAS: MID-CRETACEOUS FAUNAL CHANGE IN THE NORTHERN HEMISPHEREAS VIEWED FROM UTAH James I. Kirkland Utah Geological Survey PO Box 146100 Salt Lake City, UT USA 84114-6100 jameskirkl...

The newly discovered White Mesa tracksite in the Burro Canyon Formation represents a snapshot of a diverse, Lower Cretaceous dinosaur fauna from south-eastern Utah. The tracks were found at a construction site where the sandstone had been bulldozed and broken up. All tracks were found as deep, well-preserved natural casts on the underside of the sa...

More than 130 footprints representing ~ 43 trackways of birds (avian theropods) and two non-avian theropods occur as seven separate assemblages on loose blocks recovered from the Poison Strip Member of the Cedar Mountain Formation, near the Stikes Quarry locality in eastern Utah. Six of assemblages, four with bird tracks and two with small non avia...

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...

The Wahweap Formation preserves the most di-verse middle Campanian terrestrial fauna in North America, based largely on information gained by the study of micro-vertebrate fossils collected by wet screen washing. These studies have documented a minimum of fi ve freshwater shark species, three freshwater ray species, eight bony fi sh species, 11 amp...

Ornithopod dinosaurs were bipedal, herbivorous dinosaurs represented in the Late Cretaceous of North Amer-ica by basal ornithopods ("hypsilophodontids") and a clade of derived iguanodontians containing, in part, hadrosaurids. Recent research focused on the Cretaceous macrovertebrates of Grand Staircase–Escalante National Monument and sur-rounding a...

An examination of freshwater euselachian fossils from the Maastrichtian lower and upper Hell Creek Formation, and the Bug Creek Anthills (Cretaceous-Paleogene boundary), and the early Paleocene (Puercan) Tullock Member of the Fort Union Formation of Montana, USA, revealed seven taxa: Lonchidion selachos, Protoginglymostoma estesi, Chiloscyllium, Re...