Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
Browse
21 results
Search Results
Item Understanding the Coprophilous fungus Sporormiella as a proxy for megaherbivores(Montana State University - Bozeman, College of Letters & Science, 2020) Ulrich, Barbara Carol; Chairperson, Graduate Committee: Cathy WhitlockIn many studies, the presence of the coprophilous fungus Sporormiella in Quaternary sediments has been interpreted as evidence of past megaherbivore activity. Despite its use as an ecological proxy, little is known about the taxonomy and life history of Sporormiella, and the taphonomic processes that lead to its preservation in lake sediments. This information underlies its utility to interpret past herbivore presence and abundance. Present-day bison (Bison bison) dung from Yellowstone National Park was examined to explore the production, dispersal, transportation, deposition, and preservation of Sporormiella there. While Sporormiella was found in dung samples, sediments from two lakes frequently visited by bison failed to yield Sporormiella spores. Laboratory preparation techniques were modified to increase the likelihood of Sporormiella spore survival, yet no spores were identified with the new treatment. Although the occurrence of spores in lake-sediment samples may indicate herbivore presence, our study suggests that spore absence does not necessarily indicate an absence of herbivores. We attribute the absence of spores in sediments to local climatic and seasonal factors that may affect production and transport in the watershed, sedimentary processes that may destroy spores after deposition, and harsh laboratory processing techniques that may damage or destroy spores. More research remains to be done to evaluate the importance of these factors before using Sporormiella as a reliable proxy of herbivore activity.Item Paleoecological utility of feeding traces at Egg Mountain, a rich terrestrial vertebrate locality of the upper Cretaceous Two Medicine Formation, Montana, U.S.A.(Montana State University - Bozeman, College of Letters & Science, 2020) Freimuth, William James; Chairperson, Graduate Committee: David Varricchio; David J. Varricchio, Alexandria L. Brannick, Lucas N. Weaver and Gregory P. Wilson were co-authors of the article, 'Mammal-bearing regurgitalites potentially attributable to Troodon formosus at the Egg Mountain locality, upper Cretaceous Two Medicine Formation, Montana, U.S.A.' submitted to the journal 'PLOS ONE' which is contained within this thesis.; David J. Varricchio, Karen Chin and Sara E. Oser were co-authors of the article, 'Paleoecological implications of invertebrate fecal pellets (Edaphichnium) at a rich terrestrial vertebrate locality, upper Cretaceous Two Medicine Formation, Montana, USA.' submitted to the journal 'Journal of paleontology' which is contained within this thesis.The Egg Mountain locality is a rich terrestrial vertebrate site from the Upper Cretaceous Two Medicine Formation of Montana. Numerous skeletal remains and nesting and dwelling traces of insects and other invertebrates, mammals, lizards, and carnivorous and herbivorous dinosaurs are known from the locality. Despite the diversity of different taxa and behaviors represented, little is known about their respective ecologies. To address this, I investigate a series of feeding traces, including regurgitalites (fossil gastric pellets) and invertebrate fecal pellets, and assess their potential trace-makers and paleoecological and paleoenvironmental implications for the site. Two amalgams of the metatherian Alphadon halleyi are identified as regurgitalites based on the presence of multiple individuals in a confined area, an abundance of paired and indigestible tooth-bearing cranial elements, extensive breakage and disarticulation, and periosteal corrosion patterns attributable to digestion. These are the first mammal-bearing regurgitalites from the Mesozoic. A third amalgam is composed of the multituberculate Filikomys primaevus and is represented by crushed skulls and abundant articulated postcrania, suggestive of a non-predatory origin. The available evidence favors Troodon formosus as the regurgitalite producer. The similar taphonomic features of these regurgitalites and the prey in regurgitates of diurnal raptors suggest Troodon may have manipulated prey during feeding. The ability to egest pellets in a large-bodied, non-volant troodontid supports previous hypotheses that avian-style pellet egestion may have evolved to accommodate increased physiological processes leading to modern birds. A series of unusual peloidal structures are interpreted as invertebrate fecal pellets and resemble the pellet-filled burrow trace Edaphichnium isp. Three morphotypes are identified, including linearly-arranged pellets, pellets in condensed masses, and pellets in dispersed masses. Potential trace-makers include coleopterans, millipedes, and possibly earthworms. The abundance of Edaphichnium isp. and other traces at specific horizons throughout the locality suggest buildup of organic material in the substrate, likely induced by depositional hiatuses. Some Edaphichnium isp. are associated with Maiasaura egg clutches, suggesting invertebrate communities scavenged the decaying nest materials. Taken together, these studies provide ecological and depositional context to the abundance of dinosaur nesting and the diversity of taxa and behaviors represented at the Egg Mountain locality.Item Nest site taphonomy of modern archosaurs(Montana State University - Bozeman, College of Letters & Science, 2016) Ferguson, Ashley Lynn; Chairperson, Graduate Committee: David Varricchio; David J. Varricchio, Carlos I. Piña and Frankie D. Jackson were co-authors of the article, 'From eggs to hatchlings: nest site taphonomy of American crocodile (Crocodylus acutus) and broad snouted caiman (Caiman latirostris)' submitted to the journal 'Palaios' which is contained within this thesis.; David J. Varricchio and Alex J. Ferguson were co-authors of the article, 'Nest site taphonomy of colonial ground nesting birds at Bowdoin National Wildlife Refuge' submitted to the journal 'Palaios' which is contained within this thesis.The goal of this thesis is to investigate the taphonomic processes that affect crocodylian and modern bird nesting localities in the hope that they would shed light into the identification of fossil nesting grounds and the interpretation of juvenile developmental stage. This project in particular observed nests of American crocodiles (Crocodylus acutus) at the Turkey Point Power Plant in Homestead, Florida, broad snouted caiman (Caiman latirostris) nests in the Northern Santa Fe and Chaco Provinces of Argentina, and colonial ground nesting birds (American white pelicans, double-crested cormorants, ring-billed and California gulls) at Bowdoin National Wildlife Refuge (BNWR) east of Malta, Montana. A major component of this project is the documentation of potentially preservable components, i.e., specimens (bones, eggshell, etc.) and structures (e.g. nesting traces) that might be represented in the fossil record. This thesis documents the agents and processes influencing bone and egg accumulations and nesting trace preservation across diverse biologies and environments.Item Osteology, phylogeny, taphonomy, and ontogenetic histology of Oryctodromeus cubicularis, from the middle Cretaceous (Albian-Cenomanian) of Montana and Idaho(Montana State University - Bozeman, College of Letters & Science, 2017) Krumenacker, L. J.; Chairperson, Graduate Committee: David Varricchio; David J. Varricchio, Chris Organ, Clint Boyd and Brooks Britt were co-authors of the article, 'Osteology and phylogeny of the neornithischian dinosaur Oryctodromeus cubicularis from the middle Cretaceous (Albian-Cenomanian) of Montana and Idaho' submitted to the journal 'Journal of vertebrate paleontology' which is contained within this thesis.; David J. Varricchio, John Wilson and Ashley Ferguson were co-authors of the article, 'Taphonomy of Oryctodromeus cubicularis from the mid-Cretaceous (Albian-Cenomanian) of Idaho, and additional Oryctodromeus burrows from Idaho and Montana' submitted to the journal 'Palaeogeography, palaeoclimatology, palaeoecology' which is contained within this thesis.; David J. Varricchio, John R. Horner and Kelli Taddy were co-authors of the article, 'Ontogenetic histology and growth of the neornithischian dinosaur Oryctodromeus cubicularis from the middle Cretaceous (Albian-Cenomanian) of Montana and Idaho' submitted to the journal 'Journal of vertebrate paleontology' which is contained within this thesis.Oryctodromeus is a small bipedal dinosaur known from middle Cretaceous (95-100 My) Wayan Formation of Idaho and the Vaughn Member of the Blackleaf Formation of Montana. This taxon is hypothesized to be a burrowing dinosaur, which cared for its young within these burrows. This dissertation is a broad three-part treatment of this taxon, and excepting the introductory and concluding chapters this dissertation consists of three main chapters. Chapter two describes the osteology and phylogenetic relationships of this animal. Notable features of the Oryctodromeus skeleton described include a network of ossified tendons along the vertebral column that completely ensheath the tail, a long tail that forms more than half the length of the animal, and unusual femoral heads whose morphology may be related to burrowing behavior. The first full skeletal and skull reconstructions of this animal are presented. Chapter three investigates patterns of preservation of Oryctodromeus. Data suggests that preservation of single to multiple individuals of this taxon typically occurred in burrows that may be difficult to impossible to recognize in the fossil record. New examples of burrows from Oryctodromeus from the Vaughn and Wayan, as well as additional evidence for social behavior, are also described. A third chapter details the ontogenetic histology, growth rates and patterns of skeletal fusion based on seven limb elements (femora and tibiae) from different individuals. Based on the data in this dissertation, three growth stages can be recognized in Oryctodromeus based on bone histology. Juveniles are defined by more rapidly growing fibrolamellar tissue, sub-adults are defined by a cortex of inner fibrolamellar tissue and outer zonal parallel fibered tissue, and near-adult individuals have tissue similar to sub adults with dense avascular bone in the outermost cortex that signals a decrease in growth rate. LAG's suggest a minimum age of six to seven years for more mature individuals. Patterns of neurocentral fusion in Oryctodromeus appear similar to those of crocodylians and some other small ornithischians, while the growth rates of Oryctodromeus appear slower than those of some dinosaurs, but similar to taxa such as Orodromeus and Tenontosaurus.Item Histovariability and growth in the basal ceratopsian dinosaur Psittacosaurus mongoliensis from the lower Cretaceous Khulsangol Formation, central Mongolia(Montana State University - Bozeman, College of Letters & Science, 2016) Zorigt, Badamkhatan; Chairperson, Graduate Committee: David Varricchio; John R. Horner (co-chair); John R. Horner and Khatanbaatar Purevdorj were co-authors of the article, 'Taphonomy and depositional environment of a monodominant Psittacosaurus bonebed from the lower Cretaceous Khulsangol Formation of central Mongolia' submitted to the journal 'Journal of vertebrate paleontology ' which is contained within this dissertation.; John R. Horner was a co-author of the article, 'Intraskeletal histovariability in the hind limb of Psittacosaurus mongoliensis' submitted to the journal 'Journal of vertebrate paleontology' which is contained within this dissertation.; John R. Horner was a co-author of the article, 'Ontogenetic histovariability in a population of Psittacosaurus mongoliensis from the lower Cretaceous Khulsangol Formation, Uvurkhangai Province, Mongolia' submitted to the journal 'Journal of vertebrate paleontology' which is contained within this dissertation.Large datasets are required in order to study the details of growth in non-avian dinosaurs. The Cretaceous dinosaur sites in Mongolia offer tremendous opportunities to collect a sufficient data for such study. This dissertation introduces a brief history of dinosaur research in Mongolia. As a result of many expeditions since the 1920s, numerous new dinosaurs were named and many new dinosaur localities have been discovered. Whereas the majority of studies of Mongolian dinosaurs have focused on the fossils of Late Cretaceous taxa, dinosaur fossils are also abundant in the Early Cretaceous dinosaur sites. One of the richest Early Cretaceous dinosaur sites is Builst Khudag (BLK) in central Mongolia. Sedimentologic and taphonomic studies of the BLK site suggest that the depositional environment of the locality indicates the occurrence of a debris flow and sheet-flood in an alluvial setting. The fossils of the parrot-beaked, herbivorous dinosaur Psittacosaurus is the most common taxon from the BLK site. A Psittacosaurus aggregation consisting of juveniles reflects a catastrophic mortality event. Previously, the humerus, femur, tibia, and fibula were suggested to represent the ideal bones for growth determination studies. Since various elements grow in different developmental regimes, it is necessary to further determine an ideal element for Psittacosaurus growth assessment. Associated femora, tibiae, and fibulae from four individuals were examined. The femur and tibia show comparable bone tissues in all individuals; the tibia and fibula present comparable numbers of growth lines. Based on this finding, the tibia appears to provide the most comprehensive view of growth in Psittacosaurus. The Psittacosaurus growth strategy was further assessed using 58 tibiae collected from the BLK site. The Psittacosaurus growth rate reaches its peak (3.19 microns/day) after passing the threshold size at the age of two. During the ages of 10-13, the body size reaches 170.3 cm in length and the growth rate is considerably slowed down. This study confirms that Psittacosaurus growth fits in a sigmoidal shaped curve.Item Taphonomy of arboreal nesting in great blue herons(Montana State University - Bozeman, Graduate School, 2014) McGrath, Ashley Cathryn; Chairperson, Graduate Committee: Peggy Taylor.This research supports the growing number of modern bird taphonomic studies and furthers our understanding of the taphonomy of birds and non-avian dinosaurs. The purpose was to broaden modern taphonomic models available for the interpretation of fossil localities of both dinosaurs and birds through examination of the taphonomy of great blue heron (Ardea herodias) nesting materials found below their arboreal nests. Investigations took place during the 2012 and 2013 breeding season where heron generated materials were described within the colony and compared to Controls outside of the colony. The Cascade Heron Colony located along the Missouri River in central Montana produced heron eggshells, heron nests, heron prey, and heron bones. The heron diet greatly consisted of fish, small mammals, and crayfish. Of the 1,788 elements discovered, great blue herons made up 52% (N=934), of which at least 83% (N=776) were considered juvenile. Broken, disarticulated juvenile heron bones dominated the heron skeletal assemblage. The heron bone assemblage exhibited a strong and statistically significant bias for hindlimb elements (74.09%) in comparison to wing elements (25.91%). Of the bone assemblage, nearly 40% (N=702) of the materials were found in the subsurface survey. I compared the surface sample versus subsurface sample and found herons largely dominated both samples, but more mammal remains and fish remains made up the taxon-specific subsurface sample. All data were compiled for taphonomic interpretation, reporting and testing for significance. Using a 2x2 Fisher's exact test significant difference between the abundance of materials between surface and subsurface was found. Using a X superscript 2 for independence there was difference between plot types (sparsely vegetated, densely vegetated and controls). In the heron eggshell assemblage, ample eggshell was found (N= 947), but little was buried in the subsurface (N=31). Eggshells were described as small eggshell fragments (>1cm but <1/4 of an egg) and large eggshells (>1/4 of an egg). For small and large eggshells, a X superscript 2 test was used to compare against the null 1:1 'concave up'(CU): concave down'(CD) (CU: CD), and further against the alternative hypotheses for hatched (60:40) and predated eggs (70:30) (Hayward et al, 2011). Outside of plots the large eggshells were found in CU (77:23) positions and small eggshell fragments were found in CD (30:70) orientations. Inside plots small eggshells were found in CU (58:42) orientations. Eggshell orientations significantly differed from the null prediction and for large hatched eggshells (N=106) favored CU at 77.40%. Tree-based nesting relative to ground nesting localities had similar nesting material inputs as studied in ground-nesting birds (Hypothesis 1). Controls outside the colony provided the materials described her were generated by heron nesting activities. Hatched large eggshells preferred CU orientations above the hatched 60:40 expected ratio (Hypothesis 2). This work showed burial features of heron materials through the subsurface survey (Hypothesis 4). Tree-based nesting relative to ground nesting showed herons had a higher representations of leg elements than forelimb elements (Hypothesis 5), and the findings from this study showed that vegetation and pH did not influence the density of biological materials below heron nests (Hypothesis 6). Future work into tree-based nesting should examine fallen nest orientation trends and quantify the spatial patterns of juvenile carcasses in proximity to tree bases, tree-based nesting (Hypothesis 3). This works supports great blue herons as plausible models for past-life nesting locale reconstructions.Item Paleoenvironment and taphonomy of the fauna of the Tullock Formation (early Paleocene), McGuire Creek area, McCone County, Montana(Montana State University - Bozeman, College of Letters & Science, 1992) Katsura, YoshihiroItem Sedimentology and taphonomy of a shell bed assemblage from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of eastern Montana(Montana State University - Bozeman, College of Letters & Science, 2001) Shoup, Bentley EdwardItem Fluvial systems of the Upper Jurassic Morrison Formation, northern Beartooth and Gallatin Ranges, southwest Montana(Montana State University - Bozeman, College of Letters & Science, 1993) Cooley, Jonathan Todd; Chairperson, Graduate Committee: James G. Schmitt; John R. Horner (co-chair)Item Sedimentology and taphonomy of a dinosaur bonebed from the Upper Cretaceous (Campanian) Judith River Formation of north central Montana(Montana State University - Bozeman, College of Letters & Science, 2000) LaRock, Jeffrey William
- «
- 1 (current)
- 2
- 3
- »