Timothy Myers
I am currently a Research Assistant Professor in the Huffington Department of Earth Sciences at Southern Methodist University in Dallas. In addition to my research in vertebrate paleontology, I use stable isotope geochemistry to address questions related to ancient terrestrial ecosystems.
My primary research interests are paleoclimatology and paleoecology. Using sedimentological and geochemical techniques, I reconstruct terrestrial paleoenvironments and provide detailed paleoclimatic information for comparison with faunal data. My current research involves (1) determination of the effect of paleoclimate on primary productivity and faunal richness in Mesozoic terrestrial ecosystems and (2) refinement of geochemical techniques to estimate soil CO2 concentrations in ancient environments. I emphasize the importance of connections between the biosphere, atmosphere, and geosphere in deep-time paleoenvironments, and use the sedimentary and faunal records to reconstruct the details of ecological interactions.
Phone: 214-768-2901
Address: Department of Earth Sciences
Southern Methodist University
3225 Daniel Ave
Dallas, TX 75275-0395
My primary research interests are paleoclimatology and paleoecology. Using sedimentological and geochemical techniques, I reconstruct terrestrial paleoenvironments and provide detailed paleoclimatic information for comparison with faunal data. My current research involves (1) determination of the effect of paleoclimate on primary productivity and faunal richness in Mesozoic terrestrial ecosystems and (2) refinement of geochemical techniques to estimate soil CO2 concentrations in ancient environments. I emphasize the importance of connections between the biosphere, atmosphere, and geosphere in deep-time paleoenvironments, and use the sedimentary and faunal records to reconstruct the details of ecological interactions.
Phone: 214-768-2901
Address: Department of Earth Sciences
Southern Methodist University
3225 Daniel Ave
Dallas, TX 75275-0395
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minimum of 26 upper teeth and bears a thin premaxillary crest that begins above the fourth pair of alveoli. The rostrum,
characterized by a slight lateral flare, lacks the pronounced lateral expansion found in ornithocheirids and anhanguerids. The tip of the snout is small and blunt, and the anterior face of the rostrum is oriented posteroventrally, forming an approximately 45 angle with the anterior portion of the palate. The anteroventrally oriented first pair of alveoli is directed more ventrally than anteriorly. Phylogenetic analysis suggests that Cimoliopterus dunni and Cimoliopterus cuvieri, from the Cenomanian Grey Chalk Subgroup in Kent, England, are basal pteranodontoids that are closely related to Aetodactylus halli from the middle Cenomanian Tarrant Formation of north Texas. Cimoliopterus dunni marks only the second known occurrence of Cimoliopterus, extending its geographic range from Europe to North America. In conjunction with Coloborhynchus wadleighi from the upper Albian Pawpaw Formation, Cimoliopterus dunni provides unambiguous evidence of biogeographic linkages between the pterosaur faunas of North America and Europe in the middle Cretaceous.
stratigraphic architecture and basin evolution. Recent paleosol research has introduced semiquantitative and quantitative measures for environmental and chronometric reconstructions that provide insight intomajor regional to global changes in temperature, precipitation, and atmospheric pCO2. These
new proxies focus on morphological and chemical transfer functions and stable isotope geochemistry to provide estimates of precipitation, temperature, pCO2, and productivity, as well as chronometric estimates of mineral crystallization in deep-time pedogenic systems. Looking forward, consensus must be reached on terminology that most effectively communicates paleosol characteristics and implies important processes. Proxy development will continue to improve as data sets become available across greater ranges of environments and timescales.
values calculated for paleosols without shrink-swell (vertic) features correspond to MAP estimates between 800 and 1100 mm yr–1, with an average of 1000 mm yr–1. CALMAG values, calculated for vertic paleosols, correspond to MAP estimates between 50 and 1200 mm yr–1, with an average of 700 mm yr–1. MAP estimates from the older New Mexico strata indicate that early Morrison environments were relatively arid. MAP estimates from the younger Wyoming and Montana deposits reflect wetter conditions in the
northernmost part of the Morrison Formation, but the transition from arid interior environments was abrupt. Humidity provinces inferred from geochemical proxy-based estimates of evapotranspiration and energy influx from precipitation range from semiarid to superhumid, suggesting wetter conditions than the MAP estimates, but supporting the relative differences in moisture among the
three study areas. Paleoprecipitation patterns within the Morrison depositional basin do not match the modern latitudinal distribution of rainfall that arises from zonal atmospheric circulation. Comparison with the Upper Jurassic
Lourinhã Formation in Portugal and the Vega Formation in Spain reveals that MAP in Late Jurassic Portuguese environments was similar to that in the wet northern
part of the Morrison Formation, although more arid conditions prevailed in some areas of Portugal. Inferred humidity regimes for the Lourinhã Formation, which range from semiarid to superhumid, also indicate small scale
geographic variability in climate, although less pronounced than that observed in the Morrison Formation. Paleoenvironments in northern Spain were similar to the drier Morrison environments in the continental interior.
Given the abrupt climatic transitions inferred here for the Morrison Formation, paleoprecipitation estimates derived from a geographically restricted sample may reflect only local conditions and should not necessarily be extrapolated to larger areas.
values, D13Ccc-om, is smaller in profiles affected by groundwater saturation as well as most Vertisols and may be a product of waterlogging. The larger D13Ccc-om values in soils with gravity-driven flow are consistent with open-system mixing of tropospheric CO2 and CO2 derived from in situ oxidation of soil organic matter with mean soil PCO2 values potentially in excess of ~20,000 ppmV at the time of calcite crystallization. There is a correlation between estimates of soil PCO2 and a value termed ‘‘EPPT-U’’ (kJm2/yr) among the soil profiles characterized by gravity-driven flow. EPPT-U is the energy flux through the soil during periods of soil moisture utilization, and it is the product of water mass and temperature in the profile during the growing season. Thus, soils with high water-holding capacity/storage and/or low/high growing season temperature may form soil calcite in the presence of high soil PCO2, and vice versa. The results of this research have important implications for reconstructions of paleoclimate from stable carbon isotopes of
calcareous paleosol profiles.
minimum of 26 upper teeth and bears a thin premaxillary crest that begins above the fourth pair of alveoli. The rostrum,
characterized by a slight lateral flare, lacks the pronounced lateral expansion found in ornithocheirids and anhanguerids. The tip of the snout is small and blunt, and the anterior face of the rostrum is oriented posteroventrally, forming an approximately 45 angle with the anterior portion of the palate. The anteroventrally oriented first pair of alveoli is directed more ventrally than anteriorly. Phylogenetic analysis suggests that Cimoliopterus dunni and Cimoliopterus cuvieri, from the Cenomanian Grey Chalk Subgroup in Kent, England, are basal pteranodontoids that are closely related to Aetodactylus halli from the middle Cenomanian Tarrant Formation of north Texas. Cimoliopterus dunni marks only the second known occurrence of Cimoliopterus, extending its geographic range from Europe to North America. In conjunction with Coloborhynchus wadleighi from the upper Albian Pawpaw Formation, Cimoliopterus dunni provides unambiguous evidence of biogeographic linkages between the pterosaur faunas of North America and Europe in the middle Cretaceous.
stratigraphic architecture and basin evolution. Recent paleosol research has introduced semiquantitative and quantitative measures for environmental and chronometric reconstructions that provide insight intomajor regional to global changes in temperature, precipitation, and atmospheric pCO2. These
new proxies focus on morphological and chemical transfer functions and stable isotope geochemistry to provide estimates of precipitation, temperature, pCO2, and productivity, as well as chronometric estimates of mineral crystallization in deep-time pedogenic systems. Looking forward, consensus must be reached on terminology that most effectively communicates paleosol characteristics and implies important processes. Proxy development will continue to improve as data sets become available across greater ranges of environments and timescales.
values calculated for paleosols without shrink-swell (vertic) features correspond to MAP estimates between 800 and 1100 mm yr–1, with an average of 1000 mm yr–1. CALMAG values, calculated for vertic paleosols, correspond to MAP estimates between 50 and 1200 mm yr–1, with an average of 700 mm yr–1. MAP estimates from the older New Mexico strata indicate that early Morrison environments were relatively arid. MAP estimates from the younger Wyoming and Montana deposits reflect wetter conditions in the
northernmost part of the Morrison Formation, but the transition from arid interior environments was abrupt. Humidity provinces inferred from geochemical proxy-based estimates of evapotranspiration and energy influx from precipitation range from semiarid to superhumid, suggesting wetter conditions than the MAP estimates, but supporting the relative differences in moisture among the
three study areas. Paleoprecipitation patterns within the Morrison depositional basin do not match the modern latitudinal distribution of rainfall that arises from zonal atmospheric circulation. Comparison with the Upper Jurassic
Lourinhã Formation in Portugal and the Vega Formation in Spain reveals that MAP in Late Jurassic Portuguese environments was similar to that in the wet northern
part of the Morrison Formation, although more arid conditions prevailed in some areas of Portugal. Inferred humidity regimes for the Lourinhã Formation, which range from semiarid to superhumid, also indicate small scale
geographic variability in climate, although less pronounced than that observed in the Morrison Formation. Paleoenvironments in northern Spain were similar to the drier Morrison environments in the continental interior.
Given the abrupt climatic transitions inferred here for the Morrison Formation, paleoprecipitation estimates derived from a geographically restricted sample may reflect only local conditions and should not necessarily be extrapolated to larger areas.
values, D13Ccc-om, is smaller in profiles affected by groundwater saturation as well as most Vertisols and may be a product of waterlogging. The larger D13Ccc-om values in soils with gravity-driven flow are consistent with open-system mixing of tropospheric CO2 and CO2 derived from in situ oxidation of soil organic matter with mean soil PCO2 values potentially in excess of ~20,000 ppmV at the time of calcite crystallization. There is a correlation between estimates of soil PCO2 and a value termed ‘‘EPPT-U’’ (kJm2/yr) among the soil profiles characterized by gravity-driven flow. EPPT-U is the energy flux through the soil during periods of soil moisture utilization, and it is the product of water mass and temperature in the profile during the growing season. Thus, soils with high water-holding capacity/storage and/or low/high growing season temperature may form soil calcite in the presence of high soil PCO2, and vice versa. The results of this research have important implications for reconstructions of paleoclimate from stable carbon isotopes of
calcareous paleosol profiles.