A rare specimen of soft tissue preservation of a lizard from the Parachute Creek Member of the Eocene Green River Formation, Uinta Basin, Utah, is described. The preservation is unusual in that it is a miner¬alized body lacking the skeleton. This, and other small boneless vertebrate specimens also from the Para¬chute Creek, indicate occasional demineralizing conditions in Lake Uinta, but not apparently in the other two lakes of the Green River Formation—Fossil Lake and Lake Gosuite.
“The sauropod dinosaur genus Diplodocus Marsh, 1878, is currently typified by a morphologically undi¬agnosable type species, D. longus Marsh, 1878. Only two caudal vertebrae and an associated partial chev¬ron of its holotype (Yale Peabody Museum [YPM] VP.001920) remain reasonably complete, but more, fragmentary caudal vertebrae are available, and provide additional morphological information. YPM VP.001920 can be referred to Diplodocus generally, but cannot be distinguished from other Diplodocus spe¬cies based on autapomorphies. Thus, the genus Diplodocus would have to be considered a nomen dubium. In order to resolve this unsatisfactory taxonomic issue, Tschopp and Mateus (2016) proposed to designate a new type species for the genus Diplodocus: namely, the well-known D. carnegii Hatcher, 1901.
Herein, we expand upon historical and taxonomic issues concerning the holotype of D. longus, in order to: (1) provide additional imagery and information on the specimen and (2) to address comments against the replacement of D. longus by D. carnegii as the type species of Diplodocus as proposed by Tschopp and Mateus (2016).”
In 1878, Oramel Lucas shipped to E.D. Cope of the Academy of Natural Sciences of Philadelphia, a huge 1.5-m-tall neural spine from the dorsal vertebra of a sauropod (from the Upper Jurassic Morrison Formation) that Cope named and illustrated as Amphicoelis fragillimus.The holotype was lost and all that is known of the specimen is from Cope’s original publication. Reanalysis of Cope’s publication in light of other sauropods discovered since 1878 indicates that Amphicoelias fragillimus is a basal rebbachisaurid characterized by pneumatic neural spine and arch, and the unambiguous rebbachisaurid character of a festooned spinodiapophyseallamina. Because the specimen can no longer be referred to the basal diplodo coid Amphicoelias, the genus name is replaced with Maraapunisaurus n.g. As a rebbachisaurid, revised dimensions indicate a dorsal vertebra 2.4 m tall and a head-to-tail length for the animal of30.3 to 32m, significantly less than previous estimates.
Trace fossil assemblages in a fluvial-lacustrine sequence stratigraphic context hold significant poten-tial for expanding our understanding of environmental controls and continental basin-fill history. The succession of the Eocene Uinta Formation and four members of the Duchesne River Formation is ex¬tremely well-exposed in the Uinta Basin of northeastern Utah, revealing a robust stratigraphic framework to document broad-scale fluvial-lacustrine facies architectures and associated trace fossil assemblages. Greenish- and gray-colored mudstone beds with interbedded tabular sandstone representing lacustrine environments contain the trace fossils Arenicolites and Gordia (= Haplotichnus). In contrast, red mudstone beds with interbedded channelized sandstone representing upstream fluvial and alluvial environments contain a variety of insect trace fossils, including Scoyenia, Ancorichnus, and nest structures. Transitional, interfingering lithologies of wetland or shallow, short-lived lacustrine environments on the alluvial plain contain the trace fossil Steinichnus. Although there are many small-scale (bed-scale) physical sedimen¬tary structures and trace fossils from continental subenvironments, this study focuses on the large-scale (member-scale) change in trace fossil assemblages, with results indicating that the ichnofacies corroborate continental sequence stratigraphic interpretations in a fluvial-lacustrine setting.
Bipedal ornithischian dinosaurs from the Upper Jurassic Morrison Formation are rare, forming only about 15% of the dinosaur specimens. Nevertheless, one of them was among the first dinosaurs named from what was then the ‘’Atlantosaurus Beds’’ of Colorado. Collecting and restudy for 140 years has increased the diversity from the initial 1877 discovery to the currently valid four genera and six species, viz., Fruitadens haagaroum, Nanosaurus agilis, Camptosaurus dispar, C. aphanoecetes, Dryosaurus altus, and D. elderae, which we briefly review. We demonstrate that the enigmatic Nanosaurus agilis is the senior name for Drinker nisti, Othnielosaurus consors, and Othnielia rex. In addition, a new species, Dryosaurus elderae is proposed for the Dryosaurus specimens from Dinosaur National Monument that are characterized by elongate cervical verebrae and a long, low ilium among other features.
Based on a methodic sedimentological analysis, the Late Jurassic (Oxfordian) Curtis Formation unravels the intricate facies variability which occurs in a tide-dominated, fluvially starved, low-gradient, semi-enclosed epicontinental basin. This unit crops out in east-central Utah, between the eolian deposits of the underlying Middle Jurassic (Callovian) Entrada Sandstone, from which it is separated by the J-3 unconformity, and the conformable overlying supratidal Summerville Formation of Oxfordian age. A high-resolution sedimentary analysis of the succession led to the recognition of eight facies associations (FA) with six sub-facies associa¬tions. Based on the specific three-dimensional arrangement of these eight facies associations, it is proposed to separate the Curtis Formation into three sub-units: the lower, middle and upper Curtis. The J-3 unconformity defines the base of the lower Curtis, which consists of upper shoreface to beach deposits (FA 2), mud-domi¬nated (FA 3a) and sand-dominated heterolithic subtidal flat (FA 3b), sand-rich sub- to supratidal flat (FA 4a) and correlative tidal channel infill (FA 4c). It is capped by the middle Curtis, which coincides with the sub- to intertidal channel-dune-flat complex of FA 5, and its lower boundary corresponds to a transgressive surface of regional extent, identified as the Major Transgressive Surface (MTS). This surface suggests a potential correla¬tion between the middle and the upper Curtis and the neighboring Todilto Member of the Wanakah Forma¬tion or Todilto Formation. The upper Curtis consists of the heterolithic upper sub- to intertidal flat (FA 6) and coastal dry eolian dunes belonging to the Moab Member of the Curtis Formation (FA 7), and it conformably overlies the middle Curtis.
The spatial distribution of these sub-units supports the distinction of three different sectors across the study area: sector 1 in the north, sector 2 in the south-southwest, and sector 3 in the east. In sector 1, the Curtis For¬mation is represented by its three sub-units, whereas sector 2 is dominated by the middle and upper Curtis, and sector 3 encompasses the extent of the Moab Member of the Curtis Formation.
This study also highlights the composite nature of the J-3 unconformity, which was impacted by various processes occurring before the Curtis Formation was deposited, as well as during the development of the lower and middle Curtis. Local collapse features within the lower and middle Curtis are linked to sand fluid over¬pressure within a remobilized sandy substratum, potentially triggered by seismic activity. Furthermore, the occurrence of a sub-regional angular relationship between the middle Curtis and substratum implies that the area of study was impacted by a regional deformational event during the Late Jurassic, before the deposition of the middle Curtis.
Most study of the Upper Jurassic Morrison Formation has focused on its spectacular and extensive outcrops on the southern Colorado Plateau. Nevertheless, outcrops of the Morrison Formation extend far off the Colorado Plateau, onto the southern High Plains as far east as western Oklahoma. Outcrops of the Morrison Formation east of and along the eastern flank of the Rio Grande rift in north-central New Mexico (Sandoval, Bernalillo, and Santa Fe Counties) are geographically intermediate between the Morrison Formation outcrops on the southeastern Colorado Plateau in northwestern New Mexico and on the southern High Plains of eastern New Mexico. Previous lithostratigraphic correlations between the Colorado Plateau and High Plains Morrison Formation outcrops using the north-central New Mexico sections encompassed a geographic gap in outcrop data of about 100 km. New data on previously unstudied Morrison Formation outcrops at Placitas in Sandoval County and south of Lamy in Santa Fe County reduce that gap and significantly add to stratigraphic coverage. At Placitas, the Morrison Formation is about 141 m thick, in the Lamy area it is about 232 m thick, and, at both locations, it consists of the (ascending) sandstone-dominated Salt Wash Member, mudstone-dominated Brushy Basin Member, and sandstone-dominated Jackpile Member. Correlation of Morrison strata across northern New Mexico documents the continuity of the Morrison depositional systems from the Colorado Plateau eastward onto the southern High Plains. Along this transect, there is significant stratigraphic relief on the base of the Salt Wash Member (J-5 unconformity), the base of the Jackpile Member, and the base of the Cretaceous strata that overlie the Morrison Formation (K unconformity). Salt Wash Member deposition was generally by easterly-flowing rivers, and this river system continued well east of the Colorado Plateau. The continuity of the Brushy Basin Member, and its characteristic zeolite-rich clay facies, onto the High Plains suggests that localized depositional models (e.g., “Lake T’oo’dichi’) need to be re-evaluated. Instead, envisioning Brushy Basin Member deposition on a vast muddy floodplain, with some localized lacustrine and palustrine depocenters, better interprets its distribution and facies.
Several shark teeth have been collected from limestones in the marine-nonmarine transitional zone of the lower Cutler beds in the Shafer Basin near Moab, Utah. The shark teeth include the Pennsylvanian petalodontiform Petalodus ohioensis, which is the first described from the state, and the Permo-Carboniferous cladodontomorph Cladodus sp. The Petalodus specimens are compared with the holotype P. hastingsae Owen, P. acuminatus (Agassiz), P. ohioensis (Shafer), and P. alleghaniensis (Leidy). Several of these key taxa are illustrated with photographs for the first time.
Two tooth-bearing snout fragments from a diplodocid sauropod from the Brushy Basin Member of the Morrison Formation (Upper Jurassic) excavated from the Mygatt-Moore Quarry in Rabbit Valley, Colorado are described. The Mygatt-Moore Quarry has produced thousands of vertebrate fossils from the Brushy Basin Member, with the diplodocid Apatosaurus cf. louisae and the tetanuran Allosaurus fragilis dominating the assemblage. Additionally, remains of another diplodocid, Diplodocus sp., have been found near the quarry within Rabbit Valley. Both specimens in this study preserve eight teeth per alveolar position, as observed through broken surfaces at the gross anatomical level and also through computed tomography (CT) scans. This is inconsistent with the genus Diplodocus sp., which has been previously shown to have a maximum of six teeth per alveolus. The presence of eight replacement teeth per alveolus has previously only been reported in the Cretaceous rebbachisaurid Nigersaurus taqueti, which has been interpreted to have occupied a similar ground-height browsing feeding strategy to both Diplodocus and Apatosaurus. This is the first report of this type of high-count replacement teeth in a diplodocid sauropod from the Morrison Formation. The high number of replacement teeth in a close relative to the contemporaneous Diplodocus provides evidence for niche partitioning among the contemporary ground-height browsing diplodocid sauropods of the Late Jurassic Period in North America.
The Mygatt-Moore Quarry is a deposit of several thousand dinosaur bones in the Brushy Basin Member of the Morrison Formation in western Colorado. The site has been worked for more than 30 years and nearly 2400 mapped specimens have been collected. This study gathered data about the quarry from many sources to investigate the origin of the deposit. The Mygatt-Moore Quarry appears to be an attritional deposit of a relatively restricted diversity of dinosaurs, with few other non-dinosaurian taxa, that accumulated in a vernal pool deposit in an overbank setting. Bone modification was mostly by corrosion and breakage by trampling; scavenging was abundant. The paleofauna is dominated by Allosaurus and Apatosaurus (MNI and NIS), with the polacanthid ankylosaur Mymoorapelta less common. The matrix of the main quarry layer includes abundant carbonized fragments of plant material, and the mud during the time of deposition may have been often at least damp and occasionally acidic and dysoxic. The Cleveland-Lloyd Dinosaur Quarry is a close correlate of the Mygatt-Moore Quarry in terms of lithology and taphonomy, but demonstrates significant differences upon close inspection of matrix details and bone modification. Large quarries of fine-grained facies in the Morrison Formation possess a very different preservation mode as well as different taxon and relative abundance profiles from those in coarser sediments, which suggests that more may be learned in the future from taphofacies study of large quarries in mudstone beds.