Paleoenvironments of Early Theropods, Chinle Formation (Late Triassic), Petrified Forest National Park, Arizona

Three localities in the Chinle Formation (Late Triassic), Petrified Forest National Park (PEFO), Arizona, provide insights into the paleoenvironments frequented by primitive North American theropods. At the Dinosaur Wash locality, an undetermined theropod is preserved in paleosols that indicate a transition from wet to dry conditions on the floodplain. Coelophysis bauri remains from the Dinosaur Hill locality are preserved in a filled channel scour. The paleosols at this locality contain carbonate nodules intimately associated with Fe and Mn oxides, indicative of alternating alkaline/acidic conditions around roots in response to a semi-arid climate with strong seasonal precipitation. At the Dinosaur Hollow locality, Chindesaurus bryansmalli is preserved in a setting similar to those encountered at Dinosaur Hill. The paleosols exhibit vertic features, such as pseudoanticlines, and are indicative of water-deficit periods during the year. The most complete theropod remains at PEFO are predominantly preserved in distinctive blue-colored paleosol horizons showing depletion in iron and aluminum, and exhibiting features such as localized Fe concentrations and mottling. These are interpreted as A-horizons of redoximorphic paleosols developed in wet areas of the floodplain where the degree of water saturation fluctuated. Preservational conditions of PEFO theropod localities indicate they are time-averaged attritional mortality assemblages representative of contemporaneous organisms. Comparison of these localities to the well-known Ghost Ranch, New Mexico, Coelophysis quarry reinforces the idea that the quarry represents unique preservational conditions

Trans-Atlantic Correlation of Upper Cretaceous Marine Sediments

Upper Cretaceous marine deposits from the Mid-Atlantic region of North America (Delaware, Maryland, and New Jersey) and the Maastricht area (southern Netherlands, and nearby Belgium and Gennany) are correlated across the Atlantic using a variety of macro invertebrates, nannofossils, and sequence stratigraphy. Four late Cretaceous Mid-Atlantic sequences, the Marshalltown, Englishtown, Merchantville, and Navesink, span the upper Santonian to lowennost Danian, and have direct correlatives in the Maastricht area. Correlations between the Mid-Atlantic and the Maastricht regions (respectively) are as follows: the upper Santonian to lower Campanian Merchantville and Matawan formations with the Achen and lower Vaals fonnations; the middle Campanian upper Englishtown F onnation with the upper Vaals F onnation; the uppermost middle Campanian to upper Campanian Marshalltown, Wenonah, and Mount Laurel fomlations with the lower Gulpen Fonnation; the Navesink and lower Severn fonnations with the middle Gulpen Fonnation; and the New Egypt and upper Severn fonnations with the upper Gulpen and Maastricht fonnations. Additionally, deposits of the Maastricht area also provide support for several proposed subdivisions in the Marshalltown and Navesink sequences. The correlations proposed here can serve to refine the biostratigraphy oflarge marine vertebrates known from both sides of the Atlantic

A Model for Integrating the Public into Scientific Research

Science progresses whenever new ways of explaining natural phenomena are revealed. New ideas can only be put to use after the results and significance of research have been brought to the attention of both the scientific and lay communities. The Milwaukee Public Museum Dig-A-Dinosaur Program is a model for scientists who want to conduct research as well as engage and educate the public in their field of study. An array of rewards is derived from including amateurs as members of a research team. Such collaborations strongly increase interest in and comprehension of science as a process. Active participation in scientific investigations promotes one\u27s ability to grasp the logic employed to construct scientific knowledge. Derivative to this, people who experience research enthusiastically share what they learn with diverse audiences. Moreover, the productivity of the scientist can be significantly increased, as exemplified in an extensive paleoecological research project conducted by the authors. In retrospect, the project provided an educational experience for the volunteers that should have been formalized. It would certainly be appropriate to earn college credit based on participation and formalization would validate this learning experience

A Floral Assemblage of the Upper Cretaceous El Gallo Formation, El Rosario, Baja California, Mexico

Over the past eight months, I have collaborated with paleontologists from the Universidad Nactional Autónoma de México to formally describe plant fossils they uncovered in Baja California between their 2013 and 2016 field seasons. We report the first floral assemblage of the dinosaur-aged El Gallo Formation, Baja California, Mexico, a small (82-specimen) collection of plant fossils from fossil soils contained within the 75.84 +/- 0.05 to 74.55 +/- 0.09 million-year-old El Disecado Member of the unit. A compound fruit belonging to the genus Operculifructus, previously reported from the 3.40 to 1.08 million year younger Cerro del Pueblo Formation, Coahuila, Mexico, dominates the flora, and displays an unusual suite of characters. We identify a fruit tissue seed cap that lies within a crown defined by distal extensions of the seed coat as a derived character unique to the taxon. Because this character has not yet been demonstrated in a grossly similar fossil reproductive structure from the younger El Cien Formation, Baja California, Mexico, we maintain that the unequivocal record of Operculifructus in Baja California is presently limited to the Mesozoic, or the age of dinosaurs. We also note a lack of characters diagnostic of family- and order-level groups within the fossils, and so consider their taxonomic position uncertain within flowering plants. Likewise, resulting from sparse character data, species-level referral is not yet possible. Temporal constraints on our analysis of relationships in the taxon suggest that character states represented by the El Gallo Operculifructus are the most primitive known within it

Cornalean affinities, phylogenetic significance, and biogeographic implications of Operculifructus infructescences from the Late Cretaceous (Campanian) of Mexico

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146566/1/ajb21179.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146566/2/ajb21179_am.pd

Cranial Growth and Variation in Edmontosaurs (Dinosauria: Hadrosauridae): Implications for Latest Cretaceous Megaherbivore Diversity in North America

The well-sampled Late Cretaceous fossil record of North America remains the only high-resolution dataset for evaluating patterns of dinosaur diversity leading up to the terminal Cretaceous extinction event. Hadrosaurine hadrosaurids (Dinosauria: Ornithopoda) closely related to Edmontosaurus are among the most common megaherbivores in latest Campanian and Maastrichtian deposits of western North America. However, interpretations of edmontosaur species richness and biostratigraphy have been in constant flux for almost three decades, although the clade is generally thought to have undergone a radiation in the late Maastrichtian. We address the issue of edmontosaur diversity for the first time using rigorous morphometric analyses of virtually all known complete edmontosaur skulls. Results suggest only two valid species, Edmontosaurus regalis from the late Campanian, and E. annectens from the late Maastrichtian, with previously named taxa, including the controversial Anatotitan copei, erected on hypothesized transitional morphologies associated with ontogenetic size increase and allometric growth. A revision of North American hadrosaurid taxa suggests a decrease in both hadrosaurid diversity and disparity from the early to late Maastrichtian, a pattern likely also present in ceratopsid dinosaurs. A decline in the disparity of dominant megaherbivores in the latest Maastrichtian interval supports the hypothesis that dinosaur diversity decreased immediately preceding the end Cretaceous extinction event

Rocks, resolution, and the record; A review of depositional constraints on fossil vertebrate assemblages at the terrestrial Cretaceous/Paleogene boundary, eastern Montana and western North Dakota

The spatial and temporal distributions of vertebrate fossil assemblages at the terrestrial Cretaceous/Paleogene (K/P) boundary in eastern Montana and western North Dakota are constrained by the meandering fluvial depositional system in which they are preserved. Vertebrate fossils are clasts within that system, and thus their positions within the sedimentary sequence are subject as much to hydrodynamics as to chronostratigraphy or evolution. Laterally discontinuous facies, incomplete stratigraphic sequences, facies-dependent fossil distributions, and reworking distort original patterns of faunal number and diversity through time. The sedimentary effects on vertebrate fossil distributions, however, can be assessed by the adoption of a facies-based biostratigraphy and the utilization of a chronostratigraphy that is concordant with the resolution afforded by the K/P rocks of eastern Montana and western North Dakota