James I. Kirkland

Over the past 30 years, exploration of the terrestrial Mesozoic section in Utah has resulted in a more than five-fold 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 geological, evolutionary, palaeoecological and palaeogeographic research. Local subsidence due to salt tectonics in the northern Paradox Basin is responsible for this region of eastern Utah preserving basal Cretaceous dinosaur faunas, known nowhere else in North America, that document Jurassic–Cretaceous faunal turnover palaeobiogeographic connections across the proto-North Atlantic with Europe. The more medial Cretaceous strata west of the San Rafael Swell, in central Utah, preserve a unique dinosaur assemblage on an isolated North America. These strata also record the first immigration of Asian dinosaurs into North America and the last occurrences of a number of endemic North American dinosaur lineages. Through the Late Cretaceous, extensive, fossiliferous floodplain deposits are exposed in the high plateaus of southern Utah within the Grand Canyon Bight on the western side of the Late Cretaceous Western Interior Seaway. Research on microvertebrate sites has resulted in a diverse record of vertebrate life substage by substage through most of the Upper Cretaceous sequence. Particularly, rich dinosaur-bearing beds through the Campanian have resulted in the discovery of many new dinosaur species distinct from the coeval dinosaur-bearing beds farther north along the western coast of the Western Interior Seaway in Montana and Alberta. The further development of these numerous rich dinosaur assemblages will provide the basis for considerable research in the future.

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-averostran neotheropod Dilophosaurus wetherilli from the Kayenta Formation were the dominant terrestrial predators. Theropods are virtually unknown from the intervening Rhaetian–Hettangian Moenave Formation, with the exception of two partial coelophysoid pelves from somewhere within the Dinosaur Canyon Member, which includes the Triassic–Jurassic boundary and end-Triassic mass extinction. Here we describe an anterior trunk vertebra from a non-coelophysoid, non-averostran neotheropod from the uppermost Whitmore Point Member of the Moenave Formation in southwestern Utah, which is Hettangian in age. The vertebra has prominent vertebral laminae and associated pneumatic fossae, and anterior and posterior ‘shoulders’ on the neural spine that are similar to those found in Dilophosaurus wetherilli. This vertebra belongs to a theropod that may be as many as 15 million years older than Dilophosaurus wetherilli from the middle of the Kayenta Formation in Arizona. This theropod is associated with Grallator, Eubrontes, and Characichnos theropod traces made on the shores of the Early Jurassic Lake Whitmore that are abundant in the Whitmore Point Member in southwestern Utah. Its occurrence in the Hettangian roughly coincides with the appearance of Eubrontes tracks in North America, indicating that not all contemporaneous theropod traces were made by coelophysoids.

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 chemostratigraphic correlations to the late Aptian–early Albian, hypothesized aridity during a positive carbon isotope excursion (CIE) and estimated p CO ₂ through this event. This study refines estimates using petrographical analyses, bulk geochemical proxies for mean annual precipitation (MAP) and clumped isotope palaeothermometry. MAP rates range from 736 to 1042 mm a ⁻¹ with a slight decrease during the hypothesized aridity event. We interpret warm-biased temperatures (with an average of 32.9°C) that do not vary significantly through the study section. Carbonate nodules are likely to have precipitated in highly evaporative conditions as indicated by the presence of dolomite. Utilizing a simple Rayleigh fractionation model and two estimates of δ ¹⁸ O of water, we suggest that evaporation of 2–57% is necessary to result in an enriched end member δ ¹⁸ O _w . These data suggest that an increase in aridity is a result of lower MAP rates and greater evaporation during seasonal extremes. Lastly, revised p CO ₂ calculations suggest overestimates but indicate a shift towards greater concentrations during the positive CIE.

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-developed and folded flat on the abdomen, oval abdomen shape, and the presence of a short pair of appendages. The taxonomic allocation close to members of the Nepomorpha is discussed. Morrisonnepa jurassica n. gen. et n. sp. was collected with abundant plants, spinicaudatan carapaces, and a small amphibian from a finely laminated shale that overlies a coarser plant debris bed, supporting the presence of a possible oxbow lake or pond, environments developed within the greater ecosystem of the Morrison Formation during the Late Jurassic. In this context, we analyse the taphonomic and palaeoecological implications of the presence of aquatic insects. Besides providing morphological information on Jurassic nepomorphs, the new fossil helps illustrate how the aquatic insect assemblage was integrated during the Jurassic in North America.

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 Cat Member yield youngest single-grain ages ranging from 142.5 ± 2.7 to 133.7 ± 2.7 Ma (Berriasian–late Valanginian); those from one mudstone palaeosol yield a robust Concordia Age of 136.3 ± 1.3 (Valanginian). Additionally, a new palynoflora – one of a few to be published from the Cedar Mountain Formation – is assigned to the middle Berriasian to early Hauterivian stages, based on the presence of Foraminisporis wonthaggiensis and Trilobosporites sp. cf. T. canadensis , and the absence of F . asymmetricus , Appendicisporites spp. and angiosperms. Furthermore, these chronostratigraphic data allow us to interpret part of the so-called ‘Weissert Event’ C-isotope excursion (Valanginian) in a new C-isotope profile through a palaeosol-bearing alluvial succession in the Yellow Cat Member. This research extends a firm understanding of the formation further back into the Early Cretaceous than was the case previously (except for ostracod biostratigraphy) and sets the stage for future advancements.

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 vertebrates. Four ostracode species, all belonging to the suborder Darwinulocopina, were recovered from these sediments:Suchonellina globosa,S. stricta,Whipplella? sp. 1, andW.? sp. 2. The diversity and composition of the Whitmore Point Member ostracode fauna agree with previous interpretations about Lake Dixie and nearby paleoenvironments as shallow lakes inhabited by darwinulocopine species that survived the effects of the Central Atlantic Magmatic Province and the subsequent end-Triassic extinction and quickly recolonized these areas, thanks to asexual reproduction by parthenogenesis. The Lake Dixie region, in its geographical isolation, could represent the last episode of darwinulocopine dominance in nonmarine environments before the Late Jurassic diversification of the cypridocopine/cytherocopine modern ostracodes.

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 from the lower Yellow Cat Member of Utah (USA) is also a member of this clade. This group of non-neosauropod eusauropods, which now includes five genera (Losillasaurus, Turiasaurus, Mierasaurus, Moabosaurus and Zby), was previously known only from the Jurassic of Europe. These recent discoveries in Utah suggest that turiasaurs as a lineage survived the Jurassic-Cretaceous extinction boundary and expanded their known range, at least, into western North America. The revised spatiotemporal distribution of turiasaurs is consistent with the presence of a land connection between North America and Europe sometime during the late Tithonian to Valanginian (c.147-133 Ma). Mierasaurus and Moabosaurus are the only non-neosauropod eusauropods known from North America, despite being younger than the classic neosauropods of the Morrison Formation (c.150 Ma).

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 Shinarump Member was largely confined to pre-Chinle paleovalleys and usually overprinted by mottled strata. From southeastern to southwestern Utah, the lower members of the Chinle Formation (Cameron Member and correlative Monitor Butte Member) thicken dramatically whereas the upper members of the Chinle Formation (the Moss Back, Petrified Forest, Owl Rock, and Church Rock Members) become erosionally truncated; south of Moab, the Kane Springs beds are laterally correlative with the Owl Rock Member and uppermost Petrified Forest Member. Prior to the erosional truncation of the upper members, the Chinle Formation was probably thickest in a southeast to northwest trend between Petrified Forest National Park and the Zion National Park, and thinned to the northeast due to the lower Chinle Formation lensing out against the flanks of the Ancestral Rocky Mountains, where the thickness of the Chinle is largely controlled by syndepositional salt tectonism. The Gartra and Stanaker Members of the Ankareh Formation are poorly understood Chinle Formation correlatives north of the San Rafael Swell. Osteichthyan fish, metoposaurid temnospondyls, phytosaurids, and crocodylomorphs are known throughout the Chinle Formation, although most remains are fragmentary. In the Cameron and Monitor Butte Members, metoposaurids are abundant and non-pseudopalatine phytosaurs are known, as is excellent material of the paracrocodylomorph Poposaurus; fragmentary specimens of the aetosaurs Calyptosuchus, Desmatosuchus, and indeterminate paratypothoracisins were probably also recovered from these beds. Osteichthyans, pseudopalatine phytosaurs, and the aetosaur Typothorax are especially abundant in the Kane Springs beds and Church Rock Member of Lisbon Valley, and Typothorax is also known from the Petrified Forest Member in Capitol Reef National Park. Procolophonids, doswelliids, and dinosaurs are known but extremely rare in the Chinle Formation of Utah. Body fossils and tracks of osteichthyans, therapsids, crocodylomorphs, and theropods are well known from the lowermost Wingate Sandstone and Moenave Formation, especially from the St. George Dinosaur Discovery Site at Johnson Farm.

Evan Johnson-Ransom, Kenshu Shimada, and James I. Kirkland (2016) The Late Cretaceous Lamniform Shark, Cretoxyrhina mantelli, from the Fairport Chalky Shale Member of the Carlile Shale in Northeastern Nebraska. Transactions of the Kansas Academy of Science: Vol. 119, No. 2, pp. 208-210. doi: http://dx.doi.org/10.1660/062.119.0212

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.