Dave Lovelace - Academia.edu (original) (raw)

Papers by Dave Lovelace

Diversity

New discoveries in the lower Popo Agie Formation (lower carbonate unit) of central Wyoming necess... more New discoveries in the lower Popo Agie Formation (lower carbonate unit) of central Wyoming necessitated a reevaluation of USNM 494329 from the same unit, the only known hyperodapedontine rhynchosaur in western North America. Well known from Gondwanan deposits, hyperodapedontines appear to be restricted to the Carnian age (Late Triassic), with the exception of Teyumbaita in the earliest Norian age (Late Triassic) of Brazil. Initially assigned to c.f. ‘Hyperodapedon’ sanjuanensis, our phylogenetic analyses reject this hypothesis, in support of a sister relationship between USNM 494329 (Beesiiwo cooowuse, gen. et. sp. nov.) and Oryctorhynchus bairdi forming an early-diverging clade that is only distantly related to ‘H.’ sanjuanensis. Five additional specimens recovered from the lower Popo Agie are described. Three are referred to B. cooowuse, and another two are placed closer to Hyperodapedon and the remainder of Hyperodapedontinae. Our analysis demonstrates potential temporal distinct...

Implications for a Northern Pangean Early-Late Triassic (Carnian) Fauna.

There were a variety of datasets used in the stratigraphic study including: unpublished observati... more There were a variety of datasets used in the stratigraphic study including: unpublished observations and reports, Bureau of Land Management Reports, field notes and field reports, LiDAR survey raw data,

Quaternary International, 2021

We employed the widely-tested biophysiological modeling software, Niche Mapper™ to investigate th... more We employed the widely-tested biophysiological modeling software, Niche Mapper™ to investigate the metabolic function of Late Triassic dinosaurs Plateosaurus and Coelophysis during global greenhouse conditions. We tested them under a variety of assumptions about resting metabolic rate, evaluated within six microclimate models that bound paleoenvironmental conditions at 12° N paleolatitude, as determined by sedimentological and isotopic proxies for climate within the Chinle Formation of the southwestern United States. Sensitivity testing of metabolic variables and simulated “metabolic chamber” analyses support elevated “ratite-like” metabolic rates and intermediate “monotreme-like” core temperature ranges in these species of early saurischian dinosaur. Our results suggest small theropods may have needed partial to full epidermal insulation in temperate environments, while fully grown prosauropods would have likely been heat stressed in open, hot environments and should have been rest...

PeerJ, 2019

The last two decades have seen a remarkable increase in the known diversity of basal avialans and... more The last two decades have seen a remarkable increase in the known diversity of basal avialans and their paravian relatives. The lack of resolution in the relationships of these groups combined with attributing the behavior of specialized taxa to the base of Paraves has clouded interpretations of the origin of avialan flight. Here, we describe Hesperornithoides miessleri gen. et sp. nov., a new paravian theropod from the Morrison Formation (Late Jurassic) of Wyoming, USA, represented by a single adult or subadult specimen comprising a partial, well-preserved skull and postcranial skeleton. Limb proportions firmly establish Hesperornithoides as occupying a terrestrial, non-volant lifestyle. Our phylogenetic analysis emphasizes extensive taxonomic sampling and robust character construction, recovering the new taxon most parsimoniously as a troodontid close to Daliansaurus, Xixiasaurus, and Sinusonasus. Multiple alternative paravian topologies have similar degrees of support, but propos...

Historical Biology, 2017

Turtle (Testudines) tracks, Chelonipus torquatus, reported from the early Middle Triassic (Anisia... more Turtle (Testudines) tracks, Chelonipus torquatus, reported from the early Middle Triassic (Anisian) of Germany, and Chelonipus isp. from the late Early Triassic (Spathian) of Wyoming and Utah, are the oldest fossil evidence of turtles, but have been omitted in recent discussions of turtle origins. These tracks provide significant clues as to how early the turtle Bauplan originated. Turtle trackways are quite distinctive: the manus and pes form tracks nearly parallel to the midline and indicate an unusually wide gait in which the trackway width is nearly equal to the stride length. These tracks do not fit what would be expected to be made by Triassic Pappochelys or Odontochelys, a supposed prototurtle and an early turtle, respectively. In contrast, these tracks are consistent with what would be expected from the Triassic turtles Proganochelys and Palaeochersis. The features inferred to be present in Triassic turtle tracks support the notion that Odontochelys is a derived aquatic branch of the turtle stem lineage rather than the ancestral state of all turtles. Chelonipus also resembles the Permian track Pachypes dolomiticus, generally assigned to a pareiasaur trackmaker. These revelations highlight the need to consider all available evidence regarding turtle origins, rather than just the body fossils.

Anatomical record (Hoboken, N.J. : 2007), 2014

A vertebral element assigned to an Apatosaurus cf. ajax from the Late Jurassic Morrison Formation... more A vertebral element assigned to an Apatosaurus cf. ajax from the Late Jurassic Morrison Formation is described. The specimen exhibits an unusual morphology where two vertebrae are nearly seamlessly fused together, including the haemal arch that spans them. This morphology is thought be the result of a developmental abnormality. CT scans of the specimen reveal a thin zone of dorsoventral thickening between the two neural arches consistent with cortical bone. Contrast in internal morphology differentiates the anterior and posterior vertebral bodies with the anterior expressing greater porosity, which increased accommodation for barite-rich calcite precipitation. No vacuities are observed to suggest the former presence of an intervertebral disk or intervertebral joints: the absence of an intervertebral disc or intervertebral joints is indicative of a condition known as block vertebra. Block vertebrae occur with the loss, or inhibition, of somitocoele mesenchyme early in embyogenesis (i...

Sedimentary Geology, 2011

Small lakes are excellent records of environmental changes and are sensitive to local climate flu... more Small lakes are excellent records of environmental changes and are sensitive to local climate fluctuations. Large lacustrine systems record larger-scale climate events. Wetland deposits also provide high-resolution paleoclimatic and paleoenvironmental data. Although wetland deposits are typically associated with wet climatic conditions, they actually occur in a wide variety of climates. Whereas lakes and wetlands are very sensitive to changes in climate, high-resolution data in these archives are lost unless it is possible to differentiate these deposits from other "floodplain" deposits. Synthesis of micromorphological and geochemical data with facies relationships is critical to accurate interpretations of ancient wetland-lacustrine deposits. This study illustrates how micromorphology and geochemistry, combined with facies relationships, provide a viable method for differentiating complex, ancient wetland-lacustrine subenvironments. A hydrogeomorphological classification is proposed to provide appropriate genetic terminology that is useful in the rock record. Eight Morrison Formation subenvironments within lacustrine depositional successions from north central Wyoming were delineated using this interdisciplinary approach. Subenvironments include shallow-water wetlands, marsh, lacustrine fringe, and fen basin and fringe deposits. Synthesized data indicate that an overall basinal infilling succession was punctuated by 3 major lake contraction events, which were followed by extended periods of landscape stability. Initially balance-filled conditions dominated the shallowing-upward lacustrine deposits such that sediment and water supply, and accommodation space were relatively equal. As the lake basin filled, shallower water, underfilled lake conditions prevailed. The distribution of wetland pedotypes indicates that evapotranspiration remained high, suggesting that a stable, semi-arid to arid climate dominated in this area throughout Morrison time. Also supporting a semi-arid to arid climate are more positive carbon isotopes compared to values for disseminated organic material in the surrounding area, abundant barite nodules, gypsum pseudomorphs, and zeolites. Although major fluctuations in lake level may have resulted from punctuated wetter episodes, synthesized data suggest that overall the climate remained relatively arid to semiarid and the lake basin remained closed throughout most of Morrison time. Fluctuations in lake level likely resulted from a significant increase in recharge in the source area, possibly related to volcanic events rather than a change in climate.

Journal of Colloid and Interface Science, 2006

The interaction of metalloproteins with oxides has implications not only for bioanalytical system... more The interaction of metalloproteins with oxides has implications not only for bioanalytical systems and biosensors but also in the areas of biomimetic photovoltaic devices, bioremediation, and bacterial metal reduction. Here, we investigate mitochondrial ferricytochrome c (Cyt c) co-sorption with 0.01 and 0.1 M phosphate on hematite (α-Fe 2 O 3) surfaces as a function of pH (2-11). Although Cyt c sorption to hematite in the presence of phosphate is consistent with electrostatic attraction, other forces act upon Cyt c as well. The occurrence of multilayer adsorption, and our AFM observations, suggest that Cyt c aggregates as the pH approaches the Cyt c isoelectric point. In solution, methionine coordination of heme Fe occurs only between pH 3 and 7, but in the presence of phosphate this coordination is retained up to pH 10. Electrochemical evidence for the presence of native Cyt c occurs down to pH 3 and up to pH 10 in the absence of phosphate, and this range is extended to pH 2 and 11 in the presence of phosphate. Cyt c that initially adsorbs to a hematite surface may undergo conformation change and coat the surface with unfolded protein such that subsequently adsorbing protein is more likely to retain the native conformational state. AFM provides evidence for rapid sorption kinetics for Cyt c co-sorbed with 0.01 or 0.1 M phosphate. Cyt c co-sorbed with 0.01 M phosphate appears to unfold on the surface of hematite while Cyt c co-sorbed with 0.1 M phosphate possibly retains native conformation due to aggregation.

Geochimica et Cosmochimica Acta, 2006

clays and clay minerals, 2005

Late Cretaceous Vertebrates from the Western Interior. edited by Lucas SG, Sullivan R M. New Mexico Museum of Natural History & Science Bulletin, 2006

Abstract—Duckbill dinosaur chin skin (DCS) has been discovered in direct association with the und... more Abstract—Duckbill dinosaur chin skin (DCS) has been discovered in direct association with the underside of a dinosaurjaw from the" This Side ofHell Wyoming"(TSOH) quarry. The quarry is located on United States Depart ment ofthe Interior Bureau ofLand Management administered lands in northwestern Wyoming. The dinosaur re mains are preserved within regionally laterally continuous, very fine-grained sheet sandstone beds ofthe Upper Cre taceous (Maastrichtian) Lance Formation. Well-preserved dinosaur elements that were at ...

ABSTRACTAlmost a half-century ago excavations at Natural Trap Cave (NTC) began to yield evidence ... more ABSTRACTAlmost a half-century ago excavations at Natural Trap Cave (NTC) began to yield evidence of the steppe paleoecology along the western slope of the Bighorn Mountains in north central Wyoming. The first decade of fieldwork led to the discovery of a diverse fauna that existed at the end of the Last Glacial Maximum. Stratigraphic deposits below the entrance of the cave were studied soon after excavations began, but never formally published. Although stratigraphy, taphonomy, and depositional circumstances were briefly discussed over the following years, little has been done to correlate the numerous stratigraphic schemes used by various authors. In this study, four stratigraphic sections were measured and analysed to establish an easily modifiable lithostratigraphic system of nomenclature. We provide the first correlations of all stratigraphic nomenclature used throughout excavations at NTC to facilitate comparisons with current and previous collections and publications. By lever...

Small lakes are excellent records of environmental changes and are sensitive to local climate flu... more Small lakes are excellent records of environmental changes and are sensitive to local climate fluctuations. Large lacustrine systems record larger-scale climate events. Wetland deposits also provide high-resolution paleoclimatic and paleoenvironmental data. Although wetland deposits are typically associated with wet climatic conditions, they actually occur in a wide variety of climates. Whereas lakes and wetlands are very sensitive to changes in climate, high-resolution data in these archives are lost unless it is possible to differentiate these deposits from other “floodplain” deposits. Synthesis of micromorphological and geochemical data with facies relationships is critical to accurate interpretations of ancient wetland–lacustrine deposits. This study illustrates how micromorphology and geochemistry, combined with facies relationships, provide a viable method for differentiating complex, ancient wetland–lacustrine subenvironments. A hydrogeomorphological classification is propose...

PLOS ONE, 2020

We employed the widely-tested biophysiological modeling software, Niche Mapper™ to investigate th... more We employed the widely-tested biophysiological modeling software, Niche Mapper™ to investigate the metabolic function of the Late Triassic dinosaurs Plateosaurus and Coelophysis during global greenhouse conditions. We tested a variety of assumptions about resting metabolic rate, each evaluated within six microclimate models that bound paleoenvironmental conditions at 12˚N paleolatitude, as determined by sedimentological and isotopic proxies for climate within the Chinle Formation of the southwestern United States. Sensitivity testing of metabolic variables and simulated "metabolic chamber" analyses support elevated "ratite-like" metabolic rates and intermediate "monotreme-like" core temperature ranges in these species of early saurischian dinosaur. Our results suggest small theropods may have needed partial to full epidermal insulation in temperate environments, while fully grown prosauropods would have likely been heat stressed in open, hot environments and should have been restricted to cooler microclimates such as dense forests or higher latitudes and elevations. This is in agreement with the Late Triassic fossil record and may have contributed to the latitudinal gap in the Triassic prosauropod record.

PeerJ, 2019

The last two decades have seen a remarkable increase in the known diversity of basal avialans and... more The last two decades have seen a remarkable increase in the known diversity of basal avialans and their paravian relatives. The lack of resolution in the relationships of these groups combined with attributing the behavior of specialized taxa to the base of Paraves has clouded interpretations of the origin of avialan flight. Here, we describe Hesperornithoides miessleri gen. et sp. nov., a new paravian theropod from the Morrison Formation (Late Jurassic) of Wyoming, USA, represented by a single adult or subadult specimen comprising a partial, well-preserved skull and postcranial skeleton. Limb proportions firmly establish Hesperornithoides as occupying a terrestrial, non-volant lifestyle. Our phylogenetic analysis emphasizes extensive taxonomic sampling and robust character construction, recovering the new taxon most parsimoniously as a troodontid close to Daliansaurus, Xixiasaurus, and Sinusonasus. Multiple alternative paravian topologies have similar degrees of support, but proposals of basal paravian archaeopterygids, avialan microraptorians, and Rahonavis being closer to Pygostylia than archaeopterygids or unenlagiines are strongly rejected. All parsimonious results support the hypothesis that each early paravian clade was plesiomorphically flightless, raising the possibility that avian flight originated as late as the Late Jurassic or Early Cretaceous.

Turtle (Testudines) tracks, Chelonipus torquatus, reported from the early Middle Triassic ... more Turtle (Testudines) tracks, Chelonipus torquatus, reported from the early Middle Triassic (Anisian) of Germany, and Chelonipus isp. from the late Early Triassic (Spathian) of Wyoming and Utah, are the oldest fossil evidence of turtles, but have been omitted in recent discussions of turtle origins. These tracks provide significant clues as to how early the turtle Bauplan originated. Turtle trackways are quite distinctive: the manus and pes form tracks nearly parallel to the midline and indicate an unusually wide gait in which the trackway width is nearly equal to the stride length. These tracks do not fit what would be expected to be made by Triassic Pappochelys or Odontochelys, a supposed prototurtle and an early turtle, respectively. In contrast, these tracks are consistent with what would be expected from the Triassic turtles Proganochelys and Palaeochersis. The features inferred to be present in Triassic turtle tracks support the notion that Odontochelys is a derived aquatic branch of the turtle stem lineage rather than the ancestral state of all turtles. Chelonipus also resembles the Permian track Pachypes dolomiticus, generally assigned to a pareiasaur trackmaker. These revelations highlight the need to consider all available evidence regarding turtle origins, rather than just the body fossils.

A vertebral element assigned to an Apatosaurus cf. ajax from the Late Jurassic Morrison Formation... more A vertebral element assigned to an Apatosaurus cf. ajax from the Late Jurassic Morrison Formation is described. The specimen exhibits an unusual morphology where two vertebrae are nearly seamlessly fused together, including the haemal arch that spans them. This morphology is thought be the result of a developmental abnormality. CT scans of the specimen reveal a thin zone of dorsoventral thickening between the two neural arches consistent with cortical bone. Contrast in internal morphology differentiates the anterior and posterior vertebral bodies with the anterior expressing greater porosity, which increased accommodation for barite-rich calcite precipitation. No vacuities are observed to suggest the former presence of an intervertebral disk or intervertebral joints: the absence of an intervertebral disc or intervertebral joints is indicative of a condition known as block vertebra. Block vertebrae occur with the loss, or inhibition, of somitocoele mesenchyme early in embyogenesis (i.e., during resegmentation of the somites responsible for the formation of the affected vertebra). The derivatives of somitocoele mesenchyme include the intervertebral disc and joints. Although vertebral paleopathologies are not uncommon in the fossil record, this specimen is the first recognized congenital malformation within Sauropoda. Anat Rec, 00:000-000, 2014. V C 2014 Wiley Periodicals, Inc.

Diversity

New discoveries in the lower Popo Agie Formation (lower carbonate unit) of central Wyoming necess... more New discoveries in the lower Popo Agie Formation (lower carbonate unit) of central Wyoming necessitated a reevaluation of USNM 494329 from the same unit, the only known hyperodapedontine rhynchosaur in western North America. Well known from Gondwanan deposits, hyperodapedontines appear to be restricted to the Carnian age (Late Triassic), with the exception of Teyumbaita in the earliest Norian age (Late Triassic) of Brazil. Initially assigned to c.f. ‘Hyperodapedon’ sanjuanensis, our phylogenetic analyses reject this hypothesis, in support of a sister relationship between USNM 494329 (Beesiiwo cooowuse, gen. et. sp. nov.) and Oryctorhynchus bairdi forming an early-diverging clade that is only distantly related to ‘H.’ sanjuanensis. Five additional specimens recovered from the lower Popo Agie are described. Three are referred to B. cooowuse, and another two are placed closer to Hyperodapedon and the remainder of Hyperodapedontinae. Our analysis demonstrates potential temporal distinct...

Implications for a Northern Pangean Early-Late Triassic (Carnian) Fauna.

There were a variety of datasets used in the stratigraphic study including: unpublished observati... more There were a variety of datasets used in the stratigraphic study including: unpublished observations and reports, Bureau of Land Management Reports, field notes and field reports, LiDAR survey raw data,

Quaternary International, 2021

We employed the widely-tested biophysiological modeling software, Niche Mapper™ to investigate th... more We employed the widely-tested biophysiological modeling software, Niche Mapper™ to investigate the metabolic function of Late Triassic dinosaurs Plateosaurus and Coelophysis during global greenhouse conditions. We tested them under a variety of assumptions about resting metabolic rate, evaluated within six microclimate models that bound paleoenvironmental conditions at 12° N paleolatitude, as determined by sedimentological and isotopic proxies for climate within the Chinle Formation of the southwestern United States. Sensitivity testing of metabolic variables and simulated “metabolic chamber” analyses support elevated “ratite-like” metabolic rates and intermediate “monotreme-like” core temperature ranges in these species of early saurischian dinosaur. Our results suggest small theropods may have needed partial to full epidermal insulation in temperate environments, while fully grown prosauropods would have likely been heat stressed in open, hot environments and should have been rest...

PeerJ, 2019

The last two decades have seen a remarkable increase in the known diversity of basal avialans and... more The last two decades have seen a remarkable increase in the known diversity of basal avialans and their paravian relatives. The lack of resolution in the relationships of these groups combined with attributing the behavior of specialized taxa to the base of Paraves has clouded interpretations of the origin of avialan flight. Here, we describe Hesperornithoides miessleri gen. et sp. nov., a new paravian theropod from the Morrison Formation (Late Jurassic) of Wyoming, USA, represented by a single adult or subadult specimen comprising a partial, well-preserved skull and postcranial skeleton. Limb proportions firmly establish Hesperornithoides as occupying a terrestrial, non-volant lifestyle. Our phylogenetic analysis emphasizes extensive taxonomic sampling and robust character construction, recovering the new taxon most parsimoniously as a troodontid close to Daliansaurus, Xixiasaurus, and Sinusonasus. Multiple alternative paravian topologies have similar degrees of support, but propos...

Historical Biology, 2017

Turtle (Testudines) tracks, Chelonipus torquatus, reported from the early Middle Triassic (Anisia... more Turtle (Testudines) tracks, Chelonipus torquatus, reported from the early Middle Triassic (Anisian) of Germany, and Chelonipus isp. from the late Early Triassic (Spathian) of Wyoming and Utah, are the oldest fossil evidence of turtles, but have been omitted in recent discussions of turtle origins. These tracks provide significant clues as to how early the turtle Bauplan originated. Turtle trackways are quite distinctive: the manus and pes form tracks nearly parallel to the midline and indicate an unusually wide gait in which the trackway width is nearly equal to the stride length. These tracks do not fit what would be expected to be made by Triassic Pappochelys or Odontochelys, a supposed prototurtle and an early turtle, respectively. In contrast, these tracks are consistent with what would be expected from the Triassic turtles Proganochelys and Palaeochersis. The features inferred to be present in Triassic turtle tracks support the notion that Odontochelys is a derived aquatic branch of the turtle stem lineage rather than the ancestral state of all turtles. Chelonipus also resembles the Permian track Pachypes dolomiticus, generally assigned to a pareiasaur trackmaker. These revelations highlight the need to consider all available evidence regarding turtle origins, rather than just the body fossils.

Anatomical record (Hoboken, N.J. : 2007), 2014

A vertebral element assigned to an Apatosaurus cf. ajax from the Late Jurassic Morrison Formation... more A vertebral element assigned to an Apatosaurus cf. ajax from the Late Jurassic Morrison Formation is described. The specimen exhibits an unusual morphology where two vertebrae are nearly seamlessly fused together, including the haemal arch that spans them. This morphology is thought be the result of a developmental abnormality. CT scans of the specimen reveal a thin zone of dorsoventral thickening between the two neural arches consistent with cortical bone. Contrast in internal morphology differentiates the anterior and posterior vertebral bodies with the anterior expressing greater porosity, which increased accommodation for barite-rich calcite precipitation. No vacuities are observed to suggest the former presence of an intervertebral disk or intervertebral joints: the absence of an intervertebral disc or intervertebral joints is indicative of a condition known as block vertebra. Block vertebrae occur with the loss, or inhibition, of somitocoele mesenchyme early in embyogenesis (i...

Sedimentary Geology, 2011

Small lakes are excellent records of environmental changes and are sensitive to local climate flu... more Small lakes are excellent records of environmental changes and are sensitive to local climate fluctuations. Large lacustrine systems record larger-scale climate events. Wetland deposits also provide high-resolution paleoclimatic and paleoenvironmental data. Although wetland deposits are typically associated with wet climatic conditions, they actually occur in a wide variety of climates. Whereas lakes and wetlands are very sensitive to changes in climate, high-resolution data in these archives are lost unless it is possible to differentiate these deposits from other "floodplain" deposits. Synthesis of micromorphological and geochemical data with facies relationships is critical to accurate interpretations of ancient wetland-lacustrine deposits. This study illustrates how micromorphology and geochemistry, combined with facies relationships, provide a viable method for differentiating complex, ancient wetland-lacustrine subenvironments. A hydrogeomorphological classification is proposed to provide appropriate genetic terminology that is useful in the rock record. Eight Morrison Formation subenvironments within lacustrine depositional successions from north central Wyoming were delineated using this interdisciplinary approach. Subenvironments include shallow-water wetlands, marsh, lacustrine fringe, and fen basin and fringe deposits. Synthesized data indicate that an overall basinal infilling succession was punctuated by 3 major lake contraction events, which were followed by extended periods of landscape stability. Initially balance-filled conditions dominated the shallowing-upward lacustrine deposits such that sediment and water supply, and accommodation space were relatively equal. As the lake basin filled, shallower water, underfilled lake conditions prevailed. The distribution of wetland pedotypes indicates that evapotranspiration remained high, suggesting that a stable, semi-arid to arid climate dominated in this area throughout Morrison time. Also supporting a semi-arid to arid climate are more positive carbon isotopes compared to values for disseminated organic material in the surrounding area, abundant barite nodules, gypsum pseudomorphs, and zeolites. Although major fluctuations in lake level may have resulted from punctuated wetter episodes, synthesized data suggest that overall the climate remained relatively arid to semiarid and the lake basin remained closed throughout most of Morrison time. Fluctuations in lake level likely resulted from a significant increase in recharge in the source area, possibly related to volcanic events rather than a change in climate.

Journal of Colloid and Interface Science, 2006

The interaction of metalloproteins with oxides has implications not only for bioanalytical system... more The interaction of metalloproteins with oxides has implications not only for bioanalytical systems and biosensors but also in the areas of biomimetic photovoltaic devices, bioremediation, and bacterial metal reduction. Here, we investigate mitochondrial ferricytochrome c (Cyt c) co-sorption with 0.01 and 0.1 M phosphate on hematite (α-Fe 2 O 3) surfaces as a function of pH (2-11). Although Cyt c sorption to hematite in the presence of phosphate is consistent with electrostatic attraction, other forces act upon Cyt c as well. The occurrence of multilayer adsorption, and our AFM observations, suggest that Cyt c aggregates as the pH approaches the Cyt c isoelectric point. In solution, methionine coordination of heme Fe occurs only between pH 3 and 7, but in the presence of phosphate this coordination is retained up to pH 10. Electrochemical evidence for the presence of native Cyt c occurs down to pH 3 and up to pH 10 in the absence of phosphate, and this range is extended to pH 2 and 11 in the presence of phosphate. Cyt c that initially adsorbs to a hematite surface may undergo conformation change and coat the surface with unfolded protein such that subsequently adsorbing protein is more likely to retain the native conformational state. AFM provides evidence for rapid sorption kinetics for Cyt c co-sorbed with 0.01 or 0.1 M phosphate. Cyt c co-sorbed with 0.01 M phosphate appears to unfold on the surface of hematite while Cyt c co-sorbed with 0.1 M phosphate possibly retains native conformation due to aggregation.

Geochimica et Cosmochimica Acta, 2006

clays and clay minerals, 2005

Late Cretaceous Vertebrates from the Western Interior. edited by Lucas SG, Sullivan R M. New Mexico Museum of Natural History & Science Bulletin, 2006

Abstract—Duckbill dinosaur chin skin (DCS) has been discovered in direct association with the und... more Abstract—Duckbill dinosaur chin skin (DCS) has been discovered in direct association with the underside of a dinosaurjaw from the" This Side ofHell Wyoming"(TSOH) quarry. The quarry is located on United States Depart ment ofthe Interior Bureau ofLand Management administered lands in northwestern Wyoming. The dinosaur re mains are preserved within regionally laterally continuous, very fine-grained sheet sandstone beds ofthe Upper Cre taceous (Maastrichtian) Lance Formation. Well-preserved dinosaur elements that were at ...

ABSTRACTAlmost a half-century ago excavations at Natural Trap Cave (NTC) began to yield evidence ... more ABSTRACTAlmost a half-century ago excavations at Natural Trap Cave (NTC) began to yield evidence of the steppe paleoecology along the western slope of the Bighorn Mountains in north central Wyoming. The first decade of fieldwork led to the discovery of a diverse fauna that existed at the end of the Last Glacial Maximum. Stratigraphic deposits below the entrance of the cave were studied soon after excavations began, but never formally published. Although stratigraphy, taphonomy, and depositional circumstances were briefly discussed over the following years, little has been done to correlate the numerous stratigraphic schemes used by various authors. In this study, four stratigraphic sections were measured and analysed to establish an easily modifiable lithostratigraphic system of nomenclature. We provide the first correlations of all stratigraphic nomenclature used throughout excavations at NTC to facilitate comparisons with current and previous collections and publications. By lever...

Small lakes are excellent records of environmental changes and are sensitive to local climate flu... more Small lakes are excellent records of environmental changes and are sensitive to local climate fluctuations. Large lacustrine systems record larger-scale climate events. Wetland deposits also provide high-resolution paleoclimatic and paleoenvironmental data. Although wetland deposits are typically associated with wet climatic conditions, they actually occur in a wide variety of climates. Whereas lakes and wetlands are very sensitive to changes in climate, high-resolution data in these archives are lost unless it is possible to differentiate these deposits from other “floodplain” deposits. Synthesis of micromorphological and geochemical data with facies relationships is critical to accurate interpretations of ancient wetland–lacustrine deposits. This study illustrates how micromorphology and geochemistry, combined with facies relationships, provide a viable method for differentiating complex, ancient wetland–lacustrine subenvironments. A hydrogeomorphological classification is propose...

PLOS ONE, 2020

We employed the widely-tested biophysiological modeling software, Niche Mapper™ to investigate th... more We employed the widely-tested biophysiological modeling software, Niche Mapper™ to investigate the metabolic function of the Late Triassic dinosaurs Plateosaurus and Coelophysis during global greenhouse conditions. We tested a variety of assumptions about resting metabolic rate, each evaluated within six microclimate models that bound paleoenvironmental conditions at 12˚N paleolatitude, as determined by sedimentological and isotopic proxies for climate within the Chinle Formation of the southwestern United States. Sensitivity testing of metabolic variables and simulated "metabolic chamber" analyses support elevated "ratite-like" metabolic rates and intermediate "monotreme-like" core temperature ranges in these species of early saurischian dinosaur. Our results suggest small theropods may have needed partial to full epidermal insulation in temperate environments, while fully grown prosauropods would have likely been heat stressed in open, hot environments and should have been restricted to cooler microclimates such as dense forests or higher latitudes and elevations. This is in agreement with the Late Triassic fossil record and may have contributed to the latitudinal gap in the Triassic prosauropod record.

PeerJ, 2019

The last two decades have seen a remarkable increase in the known diversity of basal avialans and... more The last two decades have seen a remarkable increase in the known diversity of basal avialans and their paravian relatives. The lack of resolution in the relationships of these groups combined with attributing the behavior of specialized taxa to the base of Paraves has clouded interpretations of the origin of avialan flight. Here, we describe Hesperornithoides miessleri gen. et sp. nov., a new paravian theropod from the Morrison Formation (Late Jurassic) of Wyoming, USA, represented by a single adult or subadult specimen comprising a partial, well-preserved skull and postcranial skeleton. Limb proportions firmly establish Hesperornithoides as occupying a terrestrial, non-volant lifestyle. Our phylogenetic analysis emphasizes extensive taxonomic sampling and robust character construction, recovering the new taxon most parsimoniously as a troodontid close to Daliansaurus, Xixiasaurus, and Sinusonasus. Multiple alternative paravian topologies have similar degrees of support, but proposals of basal paravian archaeopterygids, avialan microraptorians, and Rahonavis being closer to Pygostylia than archaeopterygids or unenlagiines are strongly rejected. All parsimonious results support the hypothesis that each early paravian clade was plesiomorphically flightless, raising the possibility that avian flight originated as late as the Late Jurassic or Early Cretaceous.

Turtle (Testudines) tracks, Chelonipus torquatus, reported from the early Middle Triassic ... more Turtle (Testudines) tracks, Chelonipus torquatus, reported from the early Middle Triassic (Anisian) of Germany, and Chelonipus isp. from the late Early Triassic (Spathian) of Wyoming and Utah, are the oldest fossil evidence of turtles, but have been omitted in recent discussions of turtle origins. These tracks provide significant clues as to how early the turtle Bauplan originated. Turtle trackways are quite distinctive: the manus and pes form tracks nearly parallel to the midline and indicate an unusually wide gait in which the trackway width is nearly equal to the stride length. These tracks do not fit what would be expected to be made by Triassic Pappochelys or Odontochelys, a supposed prototurtle and an early turtle, respectively. In contrast, these tracks are consistent with what would be expected from the Triassic turtles Proganochelys and Palaeochersis. The features inferred to be present in Triassic turtle tracks support the notion that Odontochelys is a derived aquatic branch of the turtle stem lineage rather than the ancestral state of all turtles. Chelonipus also resembles the Permian track Pachypes dolomiticus, generally assigned to a pareiasaur trackmaker. These revelations highlight the need to consider all available evidence regarding turtle origins, rather than just the body fossils.

A vertebral element assigned to an Apatosaurus cf. ajax from the Late Jurassic Morrison Formation... more A vertebral element assigned to an Apatosaurus cf. ajax from the Late Jurassic Morrison Formation is described. The specimen exhibits an unusual morphology where two vertebrae are nearly seamlessly fused together, including the haemal arch that spans them. This morphology is thought be the result of a developmental abnormality. CT scans of the specimen reveal a thin zone of dorsoventral thickening between the two neural arches consistent with cortical bone. Contrast in internal morphology differentiates the anterior and posterior vertebral bodies with the anterior expressing greater porosity, which increased accommodation for barite-rich calcite precipitation. No vacuities are observed to suggest the former presence of an intervertebral disk or intervertebral joints: the absence of an intervertebral disc or intervertebral joints is indicative of a condition known as block vertebra. Block vertebrae occur with the loss, or inhibition, of somitocoele mesenchyme early in embyogenesis (i.e., during resegmentation of the somites responsible for the formation of the affected vertebra). The derivatives of somitocoele mesenchyme include the intervertebral disc and joints. Although vertebral paleopathologies are not uncommon in the fossil record, this specimen is the first recognized congenital malformation within Sauropoda. Anat Rec, 00:000-000, 2014. V C 2014 Wiley Periodicals, Inc.

BioRxiv, 2021

Almost a half-century ago excavations at Natural Trap Cave (NTC) began to yield evidence of the s... more Almost a half-century ago excavations at Natural Trap Cave (NTC) began to yield evidence of the steppe paleoecology along the western slope of the Bighorn Mountains in north central Wyoming. The first decade of fieldwork led to the discovery of a diverse fauna that existed at the end of the Last Glacial Maximum. Stratigraphic deposits below the entrance of the cave were studied soon after excavations began, but never formally published. Although stratigraphy, taphonomy, and depositional circumstances were briefly discussed over the following years, little has been done to correlate the numerous stratigraphic schemes used by various authors. In this study, four stratigraphic sections were measured and analysed to establish an easily modifiable lithostratigraphic system of nomenclature. We provide the first correlations of all stratigraphic nomenclature used throughout excavations at NTC to facilitate comparisons with current and previous collections and publications. By leveraging more than 100 radioisotopic dates we developed an age-depth model and chronostratigraphic framework to further interrogate spatiotemporal relationships between strata, paleoenvironmental proxies, and fossil assemblages. Deposition is shown to be discontinuous; sediment accumulation in the study area is restricted to the buildup through peak penultimate and Last Glacial maxima. More recent (<10 ka) Holocene deposits unconformably cover the eroded surface of underlying Pleistocene strata. There is active reworking of sediments with transport and deposition of reactivated sediments within the Lower Chamber. We note that the two hiatuses coincide with interglacial periods and may reflect changing depositional circumstances within the cave such as extended periods of non-deposition, erosion, or bypass (possibly leading to deposition in the Lower Chamber). Contrary to previous reports, we demonstrate that it is unlikely a prominent snow cone existed or contributed to the pattern of sediment and fossil distribution within the study area, furthermore, we do not observe a continuous Pleistocene-Holocene transition in the study area. Further stratigraphic work will be needed to better understand the interrelationship between Main and Lower chamber deposits and the evolution of sediment accumulation in NTC.